ABSTRACT:

The effects of climate change on corals are not uniform. Some corals tolerate greater rises in temperature, even across an individual reef and others thrive in naturally acidified waters. This phenomenon is present on Ofu Island, in American Samoa, where we conducted a field experiment. Identifying these resilient corals and prioritizing their protection may be the best strategy for long-term conservation of coral ecosystems. Although it is not fully understood what makes certain reefs more resilient to coral bleaching than others, emerging evidence suggests that reefs living in areas with naturally variable thermal environments may have higher temperature tolerance. By deploying DTS technology in the back-reef of Ofu Island, we can produce maps of environmental heterogeneity of unprecedented spatiotemporal resolution.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

In collaboration with Christa Kelleher (Syracuse University) and Julianne Davis (Syracuse University), AirCTEMPs is examining the impacts of beaver dam analogues (fake beaver dams) on deposition and erosion, vegetation greenness, and groundwater-surface water interactions. Ongoing data collection of stitched visual RGB imagery (left) and NDVI (right) is helping to reveal how these restoration structures impact the exchange of sediment, energy, and water across this landscape. Annual imagery collection (since 2017) will continue to benchmark how Red Canyon Creek and the surrounding floodplain are transformed by beaver dam analogue structures.

Davis, J., Lautz, L., Kelleher, C., Russoniello, C., and Vidon, P., 2019, Assessing the effects of beaver dam analogues on channel morphology using high-resolution imagery from unoccupied aerial vehicles (UAVs): Abstract H53M-1962, presented at 2019 AGU Fall Meeting, San Francisco, California, 9-13 December.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Groundwater-surface water (GW-SW) flux measurement techniques, such as reach mass-balance, seepage meters, Darcian flux and temperature sensing can be applied simultaneously to provide multiple lines of evidence (e.g., Gonzalez et al. 2015, Schmadel et al. 2014, Kennedy et al. 2009, Gilmore et al. 2016b), but challenges remain for directly linking results from different spatial and temporal scales of measurement. For smaller streams where groundwater discharge is a significant percentage of stream discharge into the reach (typically ≥10%), the integrated groundwater flux from point measurements can be compared to a larger-scale (i.e. 10^2-10^3 m reach length) approach to confirm results. But for reaches in larger stream (river) systems, the stream-groundwater discharge ratio is usually much too large to use reach mass balance as a direct point of comparison (Gilmore et al. 2016b, Schmadel et al. 2010, Jain, 2000). A promising approach for linking point measurements and testing interpolation techniques in large river systems is fiber-optic distributed temperature sensing (FO-DTS) (Briggs et al. 2012a, Briggs et al. 2012b, Tyler et al. 2009). FO-DTS uses a fiber-optic cable to detect groundwater discharge through the streambed along the length of the cable (typically ≤1km). This may be an effective way to “connect the dots” between point measurements of groundwater discharge in large systems (Krause et al. 2012), when other techniques like reach mass balance, are not feasible. The overall goal of this research is to develop an optimal approach to link point measurements of groundwater-surface water fluxes in large river systems. The specific objectives are to: (1) test the combined DTS and point-measurement approach in a small stream, where interpolated results can be confirmed using a reach mass-balance approach, and (2) apply the technique in larger river systems to characterize spatial distributions and temporal variability of groundwater fluxes at existing groundwater-surface water monitoring stations on larger rivers. This project will improve techniques for multi-scale measurement of groundwater-surface water interactions, give critical insight into temporal and spatial variability of water fluxes in larger river systems, and improve our understanding of the value of existing groundwater-surface water monitoring stations.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Recent research has demonstrated the use of in-well heat tracer tests monitored by a fiber optic distributed temperature sensing (DTS) system to characterize borehole flow conditions in open bedrock boreholes. However, the accuracy of borehole flow rates determined from in-well heat tracer tests has not been evaluated. The purpose of the research presented here is to determine whether borehole flow rates obtained using DTS-monitored in-well heat tracer tests are reasonable, and to evaluate the range of flow rates measureable with this method. To accomplish this, borehole flow rates measured using in-well heat tracer tests are compared to borehole flow rates measured in the same boreholes using an impeller or heat pulse flowmeter. A comparison of flow rates measured using in-well heat tracer tests to flow rates measured with an impeller flowmeter under the same conditions showed good agreement. A comparison of in-well heat tracer test flow rate measurements to previously-collected heat pulse flowmeter measurements indicates that the heat tracer test results produced borehole flow rates and flow profiles similar to those measured with the heat pulse flowmeter. The results of this study indicate that borehole flow rates determined from DTS-monitored in-well heat tracer tests are reasonable estimates of actual borehole flow rates. In addition, the range of borehole flow rates measurable by in-well heat tracer tests spans from less than 10−1 m/min to approximately 101 m/min, overlapping the ranges typically measurable with an impeller flowmeter or a heat pulse flowmeter, making in-well heat tracer testing a versatile boreholeflow logging tool.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

The question: ‘how does a streambed change over a minor flood?’ does not have a clear answer due to lack of measurement methods during high flows. We investigate bedload transport and disentrainment during a 1.5-year flood by linking field measurements using fiber optic distributed temperature sensing (DTS) cable with sediment transport theory and an existing explicit analytical solution to predict depth of sediment deposition from amplitude and phase changes of the diurnal near-bed pore-water temperature. The method facilitates the study of gravel transport by using near-bed temperature time series to estimate rates of sediment deposition continuously over the duration of a high flow event coinciding with bar formation. The observations indicate that all gravel and cobble particles present were transported along the riffle at a relatively low Shields Number for the median particle size, and were re-deposited on the lee side of the bar at rates that varied over time during a constant flow. Approximately 1–6% of the bed was predicted to be mobile during the 1.5-year flood, indicating that large inactive regions of the bed, particularly between riffles, persist between years despite field observations of narrow zones of local transport and bar growth on the order ~3–5 times the median particle size. In contrast, during a seven-year flood approximately 8–55% of the bed was predicted to become mobile, indicating that the continuous along-stream mobility required to mobilize coarse gravel through long pools and downstream to the next riffle is infrequent. Copyright © 2017 John Wiley & Sons, Ltd.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

This dissertation seeks to characterize the cave atmospheres and dynamics of fumarolic ice caves. The introduction presents a broad framework for understanding the caves and describes the historical and conservation context into which the work fits. This framework provides the motivation for five investigations which are presented as Chapters 2 through 6. Chapter 2 details a fiber-optic distributed temperature sensing (FODTS) experiment in which 438m of fiber-optic cable was deployed along the main passages of Warren Cave on Erebus Volcano, Antarctica. Point sources of warm gas flowing into the cave manifested as multi-degree C temperature anomalies and persisted throughout the weeklong experiment. Observed temperatures were anti-correlated with local atmospheric pressure, indicating barometric pumping of the gas vents. Chapter 3 extends the FODTS technique used in Chapter 2 to three dimensions for volumetric imaging of the temperature field inside a fumarolic ice cave chamber. Using terrestrial laser scanning (TLS) and automatic pointcloud classification techniques, I precisely located each virtual temperature sensor along the fiber optic cable. Interpolation and analysis of spatial patterns revealed a strong, upward-positive temperature gradient which averaged 0.265C m-1 over the 7 day experiment. I used satellite data and a permafrost model to assess potential Holocene volcano ice interaction globally, finding that 19.8% of known Holocene volcanic centers host glaciers or areas of permanent snow. The results, presented in Chapter 4, suggest that fumarolic ice caves are globally widespread and largely undiscovered. Fumarolic ice caves are expected to form when degassing begins beneath any volcano with moderate ice overburden. In Chapter 5, I present six years of morphological observations using TLS, structure from motion (SfM), and traditional cave survey, revealing that fumarolic ice caves change on the scale of tens of centimeters annually, and that the topography above the caves responds to enlargement of chambers through melting. I find that the cave wall icehas passed the pore-closeoff density, and conclude that densification is accelerated by heat from the cave. The rapid passage enlargement observed means that fresh rock substrate regularly becomes available to the cave microbial communities. For theoretical context, I developed two “toy” models. A computational fluid dynamics (CFD) simulation of cave melt is presented which represents a cave during initiation of growth.A simple flow model based on Glen's flow law, gives a first estimate of expected passage closure rates due to ice creep. Chapter 6 represents a collaborative effort to characterize the isotopic and chemical composition (δ2H and δ18O) of Erebus' snow and ice mantle which hosts the fumarolic ice caves. We found that snow samples from the entire summit caldera area, including ice cores collected through fumarolic ice tower walls, fall far outside an Antarctic Meteoric Water Field which encompasses all other available Antarctic snow isotope data. This suggests a magmatic component in the snow, which may be supplied by the plume emanating from Erebus' main crater. Several cross-cutting themes are addressed in multiple chapters. I discuss how fumarolic ice caves provide important indicators of volcanic unrest, analogues of extraterrestrial systems, and critical habitats for microbes. Going forward, this dissertation should be a foundation on which to plan the further exploration of fumarolic ice caves on Earth and elsewhere in the solar system. Keywords: distributed temperature sensing, LiDAR, isotopes, glaciovolcanism, flank degassing, Erebus, Antarctica.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

The cost effective maintenance of underwater pressure pipes for sewage disposal in Austria requires the detection and localization of leakages. Extrusion of wastewater in lakes can heavily influence the water and bathing quality of surrounding waters. The Distributed Temperature Sensing (DTS) technology is a widely used technique for oil and gas pipeline leakage detection. While in pipeline leakage detection, fiber optic cables are installed permanently at the outside or within the protective sheathing of the pipe; this paper aims at testing the feasibility of detecting leakages with temporary introduced fiber optic cable inside the pipe. The detection and localization were tested in a laboratory experiment. The intrusion of water from leakages into the pipe, producing a local temperature drop, served as indicator for leakages. Measurements were taken under varying measurement conditions, including the number of leakages as well as the positioning of the fiber optic cable. Experiments showed that leakages could be detected accurately with the proposed methodology, when measuring resolution, temperature gradient and measurement time were properly selected. Despite the successful application of DTS for leakage detection in this lab environment, challenges in real system applications may arise from temperature gradients within the pipe system over longer distances and the placement of the cable into the real pipe system.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

In recent years, the spatial resolution of fiber-optic distributed temperature sensing (DTS) has been enhanced in various studies by helically coiling the fiber around a support structure. While solid polyvinyl chloride tubes are an appropriate support structure under water, they can produce considerable errors in aerial deployments due to the radiative heating or cooling. We used meshed reinforcing fabric as a novel support structure to measure high-resolution vertical temperature profiles with a height of several meters above a meadow and within and above a small lake. This study aimed at quantifying the radiation error for the coiled DTS system and the contribution caused by the novel support structure via heat conduction. A quantitative and comprehensive energy balance model is proposed and tested, which includes the shortwave radiative, longwave radiative, convective, and conductive heat transfers and allows for modeling fiber temperatures as well as quantifying the radiation error. The sensitivity of the energy balance model to the conduction error caused by the reinforcing fabric is discussed in terms of its albedo, emissivity, and thermal conductivity. Modeled radiation errors amounted to −1.0 and 1.3 K at 2 m height but ranged up to 2.8 K for very high incoming shortwave radiation (1000 J s−1 m−2) and very weak winds (0.1 m s−1). After correcting for the radiation error by means of the presented energy balance, the root mean square error between DTS and reference air temperatures from an aspirated resistance thermometer or an ultrasonic anemometer was 0.42 and 0.26 K above the meadow and the lake, respectively. Conduction between reinforcing fabric and fiber cable had a small effect on fiber temperatures (< 0.18 K). Only for locations where the plastic rings that supported the reinforcing fabric touched the fiber-optic cable were significant temperature artifacts of up to 2.5 K observed. Overall, the reinforcing fabric offers several advantages over conventional support structures published to date in the literature as it minimizes both radiation and conduction errors.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Taylors' frozen turbulence hypothesis suggests that all turbulent eddies are advected by the mean streamwise velocity, without changes in their properties. This hypothesis has been widely invoked to compute Reynolds averaging using temporal turbulence data measured at a single point in space. However, in the atmospheric surface layer, the exact relationship between convection velocity and wave number k has not been fully revealed since previous observations were limited by either their spatial resolution or by the sampling length. Using Distributed Temperature Sensing (DTS), acquiring turbulent temperature fluctuations at high temporal and spatial frequencies, we computed convection velocities across wave numbers using a phase spectrum method. We found that convection velocity decreases as k−1/3 at the higher wave numbers of the inertial subrange instead of being independent of wave number as suggested by Taylor's hypothesis. We further corroborated this result using large eddy simulations. Applying Taylor's hypothesis thus systematically underestimates turbulent spectrum in the inertial subrange. A correction is proposed for point-based eddy-covariance measurements, which can improve surface energy budget closure and estimates of CO2 fluxes.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

The need to identify groundwater seepage locations is of great importance for managing both stream water quality and groundwater sourced ecosystems due to their dependency on groundwater-borne nutrients and temperatures. Although several reconnaissance methods using temperature as tracer exist, these are subjected to limitations related to mainly the spatial and temporal resolution and/or mixing of groundwater and surface water leading to dilution of the temperature differences. Further, some methods, for example, thermal imagery and fiber optic distributed temperature sensing, although relative efficient in detecting temperature differences over larger distances, these are labor-intensive and costly. Therefore, there is a need for additional cost-effective methods identifying substantial groundwater seepage locations. We present a method expanding the linear regression of air and stream temperatures by measuring the temperatures in dual-depth; in the stream column and at the streambed-water interface (SWI). By doing so, we apply metrics from linear regression analysis of temperatures between air/stream and air/SWI (linear regression slope, intercept, and coefficient of determination), and the daily water temperature cycle (daily mean temperatures, temperature variance, and the mean diel temperature fluctuation). We show that using metrics from only single-depth stream temperature measurements are insufficient to identify substantial groundwater seepage locations in a head-water stream. Conversely, comparing the metrics from dual-depth temperatures show significant differences; at groundwater seepage locations, temperatures at the SWI merely explain 43–75% of the variation opposed to ⩾ 91% at the corresponding stream column temperatures. In general, at these locations at the SWI, the slopes ( < 0.25) and intercepts ( > 6.5 °C) are substantially lower and higher, respectively, while the mean diel temperature fluctuations ( < 0.98 °C) are decreased compared to remaining locations. The dual-depth approach was applied in a post-glacial fluvial setting, where metrics analyses overall corroborated with field measurements of groundwater fluxes and stream flow accretions. Thus, we propose a method reliably identifying groundwater seepage locations along streambeds in such settings.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Multicomponent groundwater tracer tests were conducted in a well-characterized field site in Altona, NY using inert carbon-cored nanoparticles and a thermally degrading phenolic compound. Experiments were conducted in a mesoscale reservoir consisting of a single subhorizontal bedding plane fracture located 7.6 m below ground surface contained between two wells separated by 14.1 m. The reservoir rock, initially at 11.7°C, was heated using 74°C water. During the heating process, a series of tracer tests using thermally degrading tracers were used to characterize the progressive in situ heating of the fracture. Fiber-Optic Distributed Temperature Sensing (FODTS) was used to measure temperature rise orthogonal to the fracture surface at 10 locations. Recovery of the thermally degrading tracer's product was increased as the reservoir was progressively heated indicating that the advancement of the thermal front was proportional to the mass fraction of the thermally degrading tracer recovered. Both GPR imaging and FODTS measurements reveal that flow was reduced to a narrow channel which directly connected the two wells and led to rapid thermal breakthrough. Computational modeling of inert tracer and heat transport in a two-dimensional discrete fracture demonstrate that subsurface characterization using inert tracers alone could not uniquely characterize the Altona field site. However, the inclusion of a thermally degrading tracer may permit accurate subsurface temperature monitoring. At the Altona field site, however, fluid-rock interactions appear to have increased reaction rates relative to laboratory-based measurements made in the absence of rock surfaces.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

We investigate nocturnal flow dynamics and temperature behaviour near the surface of a 170-m long gentle slope in a mid-range mountain valley. In contrast to many existing studies focusing on locations with significant topographic variations, gentle slopes cover a greater spatial extent of the Earth’s surface. Air temperatures were measured using the high-resolution distributed-temperature-sensing method within a two-dimensional fibre-optic array in the lowest metre above the surface. The main objectives are to characterize the spatio-temporal patterns in the near-surface temperature and flow dynamics, and quantify their responses to the microtopography and land cover. For the duration of the experiment, including even clear-sky nights with weak winds and strong radiative forcing, the classical cold-air drainage predicted by theory could not be detected. In contrast, we show that the airflow for the two dominant flow modes originates non-locally. The most abundant flow mode is characterized by vertically-decoupled layers featuring a near-surface flow perpendicular to the slope and strong stable stratification, which contradicts the expectation of a gravity-driven downslope flow of locally produced cold air. Differences in microtopography and land cover clearly affect spatio-temporal temperature perturbations. The second most abundant flow mode is characterized by strong mixing, leading to vertical coupling with airflow directed down the local slope. Here variations of microtopography and land cover lead to negligible near-surface temperature perturbations. We conclude that spatio-temporal temperature perturbations, but not flow dynamics, can be predicted by microtopography, which complicates the prediction of advective-heat components and the existence and dynamics of cold-air pools in gently sloped terrain in the absence of observations.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

We observed polymictic behaviour in stream pools in Long Meadow, Sequoia National Park, California—part of the Southern Sierra Critical Zone Observatory. Stream pools stratified thermally during the day time and were isothermal at night—this pattern persists from the middle of summer into the fall. We found that four characteristics typical of a mountain meadow environment—low stream flow, open sky, cold groundwater discharge, and elevated organic carbon concentrations—are particularly conducive to pool stratification. Incoming shortwave radiation was the dominant energy input to heat pool water while nighttime emitted longwave radiation was the major cooling mechanism. Relatively cold groundwater discharge into the pool bottom increased density stratification within the pool. Elevated DOC concentrations increased the capacity of the pool to absorb photosynthetically active radiation and also promoted stratification. Stream velocities in the meadow were generally insufficient to meet threshold Richardson numbers and mix the pools during the daytime; smaller stream cross sectional areas would have potential for destabilizing pools in the daytime. We propose a conceptual model for describing polymictic stream pools and assessing the potential for polymictic pools to occur.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

A prototype temperature-sensing pair of waders is introduced and tested. The water temperature at the streambed is interesting both for scientists studying the hyporheic zone and for, e.g., fishers spotting good fishing locations. A temperature sensor incorporated into waders worn by members of the public can give scientists an additional source of information on stream-water–groundwater interaction. A pair of waders was equipped with a thermistor and calibrated in the lab. Tests with both the waders and a reference thermometer in a deep polder ditch with a known localized groundwater contribution (i.e., boil) showed that the temperature-sensing waders are capable of identifying the boil location. However, the temperature-sensing waders showed a less pronounced response to changing water temperature compared to the reference thermometer, most likely due to the heat capacity of the person in the waders. This research showed that data from temperature-sensing waders worn by the public and shared with scientists can be used to decide where the most interesting places are to do more detailed and more expensive research.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

To better understand the groundwater resources of southern Nye County, Nevada, a multipart distributed thermal perturbation sensing (DTPS) test was performed on a complex of three wells. These wells penetrate an alluvial aquifer that drains the Nevada National Security Site, and characterizing the hydraulic properties and flow paths of the regional groundwater flow system has proven very difficult. The well complex comprised one pumping well and two observation wells, both located 18 m from the pumping well. Using fiber-optic cables and line heaters, DTPS tests were performed under both stressed and unstressed conditions. Each test injects heat into the water column over a period of one to two days, and observes the rising temperature during heat injection and falling temperatures after heating ceases. Aquifer thermal properties are inferred from temperature patterns in the cased section of the wells, and fluxes through the 30-m screened section are estimated based on a model that incorporates conductive and advective heat fluxes. Vertical variations in flux are examined on a scale of tens of cm. The actively flowing zones of the aquifer change between the stressed and unstressed test, and anisotropy in the aquifer permeability is apparent from the changing fluxes between tests. The fluxes inferred from the DTPS tests are compared to solute tracer tests previously performed on the same site. The DTPS-based fluxes are consistent with the fastest solute transport observed in the tracer test, but appear to overestimate the mean flux through the system.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

The purpose of this project was to examine the transport of momentum, scalars, and heavy particles like fungal spores in a trellised agricultural canopy. To study these interactions, particle dispersion experiments were performed Sept 2-4, 2014 at Lone Star Vineyard (138 acres of wine grapes, 44 deg 4′ 8′′ N, 123 deg 5′ 48′′ W) near Amity, Oregon while high frequency wind and temperature data were collected.

Instruments:
-* Distributed Temperature Sensor fiber optic
- Sensornet Oryx: 1 m sampling resolution
- 900 micron AFL simplex fiber strung horizontally along _101 m_ vine at 6" vertical spacing at Tower 1
- 12 horizontal lengths looping through the baths (one cold, one ambient) at one end each time for the turn around
- DTS data starts at 11:28 on August 28th and ends at 12 on September 5, 2014. Up until 10:07 on September 1, only the first 898m of the fiber was captured, which corresponds to 7 lengths of fiber across the trellis. After 10:56, the DTS was reconfigured to write out data for the entire fiber length, corresponding to 12 fiber lengths.

- 3 Meteorological Towers
- 6 LEMS Towers
- Radiation Sensors (CNR1, LI200) at T1
- Soil sensors (HFP01, CS616, & TCAV) at T1
- 7 PAR sensors. 3 in canopy, 3 below at T1
- 18 Leaf surface temperature thermocouples

For more information on other aspects of the project:
Miller, N.E., Stoll, R., Mahaffee, W.F., Neill, T.M. and Pardyjak, E.R., 2015. An experimental study of momentum and heavy particle transport in a trellised agricultural canopy. Agricultural and forest meteorology, 211, 100-114. https://www.sciencedirect.com/science/article/pii/S0168192315001823
Miller, N.E., Stoll, R., Mahaffee, W.F. and Pardyjak, E.R., 2017. Mean and turbulent flow statistics in a trellised agricultural canopy. Boundary-Layer Meteorology, 165(1), pp.113-143. https://link.springer.com/article/10.1007/s10546-017-0265-y

Raw DTS project data is available by contacting ctemps@unr.edu

ABSTRACT:

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Aquatic habitats have a boundary layer near the air–water interface (AWI) that governs mass transport. Little is known about temperature profiles and boundary layers at the AWI. We used a high-resolution distributed temperature sensing (HR-DTS) system onboard an unmanned surface vehicle (USV) to resolve temperature profiles from about 1 m above and 1 m below the surface of the water. Our USV–HR-DTS system resolved a temperature differential of about 5.5 °C at the AWI, spanning a distance of approximately 13 cm. DTS profiles were similar for stationary holds and forward and reverse transects in the water. There was a significant change in temperature as a function of height, with an exponential decrease in temperature starting around 13 cm down to the AWI (P = 2 × 10−16). This is the first application of a HR-DTS onboard a USV to examine temperature profiles across the AWI. To our knowledge, these are the first high-resolution temperature profiles of the AWI captured from a mobile platform. Because our USV–HR-DTS system is mobile, it could be used to profile temperatures at the AWI at multiple locations in a large body of water. This technology could also find unique applications in the measurement of meteorological drivers of hazardous agent dispersal for source localization efforts.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

The Dead Sea is a hypersaline terminal lake, experiencing negative water balance, increasing salinity, and NaCl (halite) crystallization. We observed atypical evolution of the thermohaline stratification in comparison to most lakes due to the role of salt crystallization and diapycnal fluxes across lake layers. We characterized the dynamics of the thermohaline properties of the lake strata through high‐resolution continuous measurements of temperature profiles, novel water sampling methods, and observation of vertical profiles of salt crystallization. The diapycnal fluxes across the metalimnion were explained by Double Diffusion (DD) salt fingering driven by instability between warmer saltier water above cooler less salty water. The DD flux is associated with: (1) sharpening of the metalimnion from a 20 m wide transition in early summer, to staircase, ultimately merging to a single sharp sub‐meter step, (2) salinity decline from the epilimnion starting from mid‐summer synchronous with increasing salinity and temperature of the hypolimnion, and (3) active halite crystallization in the hypolimnion. We hypnotize that the salt fingering mechanism in saturated brines reveals a unique asymmetry; i.e., the descending cooling fingers become supersaturated and crystallize halite, whereas the ascending warming fingers becomes undersaturated. The DD flux in the Dead Sea is shown to be fundamental in the dynamics of stratification, providing a framework for general understanding DD flux in hypersaline environments. The finding that the epilimnion experiences seasonal halite undersaturation whereas the hypolimnion continuously precipitates salt by DD flux, has wide implications on the understanding of the dynamics of deposition of evaporitic rocks.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

The heat pulse probe method can be implemented with actively heated fiber optics (AHFO) to obtain distributed measurements of soil water content (θ) by using reported soil thermal responses measured by Distributed Temperature Sensing (DTS) and with a soil‐specific calibration relationship. However, most reported applications have been calibrated to homogeneous soils in a laboratory, while inexpensive efficient in situ calibration procedures useful in heterogeneous soils are lacking. Here we employed the Hydrus 2‐D/3‐D code to define a soil‐specific calibration curve. We define a 2‐D geometry of the fiber optic cable and the surrounding soil media, and simulate heat pulses to capture the soil thermal response at different soil water contents. The model was validated in an irrigated field using DTS data from two locations along the FO deployment in which reference moisture sensors were installed. Results indicate that θ was measured with the model‐based calibration with accuracy better than 0.022 m3 m−3.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Distributed Temperature Sensing (DTS) technology enables downhole temperature monitoring to study hydrogeological processes at unprecedentedly high frequency and spatial resolution. DTS has been widely applied in passive mode in site investigations of groundwater flow, in‐well flow, and subsurface thermal property estimation. However, recent years have seen the further development of the use of DTS in an active mode (A‐DTS) for which heat sources are deployed. A suite of recent studies using A‐DTS downhole in hydrogeological investigations illustrate the wide range of different approaches and creativity in designing methodologies. The purpose of this review is to outline and discuss the various applications and limitations of DTS in downhole investigations for hydrogeological conditions and aquifer geological properties. To this end, we first review examples where passive DTS has been used to study hydrogeology via downhole applications. Secondly, we discuss and categorize current A‐DTS borehole methods into three types. These are thermal advection tests, hybrid cable flow logging, and heat pulse tests. We explore the various options with regards to cable installation, heating approach, duration, and spatial extent in order to improve their applicability in a range of settings. These determine the extent to which each method is sensitive to thermal properties, vertical in‐well flow, or natural gradient flow. Our review confirms that the application of DTS has significant advantages over discrete point temperature measurements, particularly in deep wells, and highlights the potential for further method developments in conjunction with other emerging hydrogeophysical tools.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

In situ soil moisture monitoring networks are critical to the development of soil moisture remote sensing missions as well as agricultural and environmental management, weather forecasting, and many other endeavors. These in situ networks utilize a variety of sensors and installation practices, which confounds the development of a unified reference database for satellite calibration and validation programs. As part of the Soil Moisture Active Passive Mission, the Marena, Oklahoma, In Situ Sensor Testbed (SMAP-MOISST) was initiated to perform inter-comparisons and study sensor limitations. Soil moisture sensors that are deployed in major monitoring networks were included in the study, along with new and emerging technologies, such as the Cosmic Ray Soil Moisture Observing System (COSMOS), passive/active distributed temperature sensing (DTS), and global positioning system reflectometers (GPSR). Four profile stations were installed in May of 2010, and soil moisture was monitored to a depth of 1 m on an hourly basis. The four stations were distributed within a circular domain of approximately 600 m diameter, adequate to encompass the sensing range of COSMOS. The sensors included in the base station configuration included the Stevens Water Hydra Probe, Campbell Scientific 616 and 229, Decagon EC-TM, Delta-T Theta Probe, Acclima, and Sentek EnviroSMART capacitance system. In addition, the Pico TRIME system and additional time-domain reflectometry (TDR) systems were deployed when available. It was necessary to apply site-specific calibration to most sensors to reach an RMSE below 0.04 m3 m−3. For most sensor types, a single near surface sensor could be scaled to represent the areal-average of a field domain by simple linear regression, resulting in RMSE values around 0.03 m3 m−3.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Fiber-optic distributed temperature sensing (DTS) makes it possible to observe temperatures on spatial scales as fine as centimeters and at frequencies up to 1 Hz. Over the past decade, fiber-optic DTS instruments have increasingly been employed to monitor environmental temperatures, from oceans to atmospheric monitoring. Because of the nature of environmental deployments, optical fibers deployed for research purposes often encounter step losses in the Raman spectra signal. Whether these phenomena occur due to cable damage or impingements, sharp bends in the deployed cable, or connections and splices, the step losses are usually not adequately addressed by the calibration routines provided by instrument manufacturers and can be overlooked in postprocessing calibration routines as well. Here we provide a method to identify and correct for the effects of step losses in raw Raman spectra data. The utility of the correction is demonstrated with case studies, including synthetic and laboratory data sets.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Meso-scale field testing of thermally reactive tracers was conducted at the Altona field site in a well-characterized, single subhorizontal bedding plane fracture roughly 100 m2 in active area located 8 meters below ground surface. The spatial distribution of subsurface groundwater flow was previously characterized using ground penetrating radar (GPR) measurements. The reservoir rock, initially at 11.7 °C, was heated using 74 °C hot water injection in a two-spot pattern using an injection to production well separation of 14 m. During the heating process, a series of thermally degrading tracer experiments were used to characterize the progressive in situ heating of the fracture. In addition, a conservative, carbon-cored engineered nanoparticle tracer was used to measure the residence time distribution (RTD) of fluid flowing from injector to producer. Fiber Optic Distributed Temperature Sensing (FODTS) was used to continuously measure the spatial distribution of heat exchange at ten locations spread out between the injection and production well. The experiments revealed reduced recovery of the thermally degrading tracer as the reservoir was progressively heated indicating that the advancement of the thermal front was proportional to the mass fraction recovered of the thermally degrading tracer. Both GPR imaging and FODTS measurements reveal that flow was reduced to a narrow channel which directly connected the two flowing wells and led to early and rapid thermal breakthrough. Computational modeling of conservative/reactive tracer and heat transport in a two-dimensional discrete fracture demonstrate that subsurface characterization using conservative tracers alone could not uniquely characterize the Altona field site. The inclusion of the thermally reactive tracer, however, provided improved resolution of the spatial distribution of flow after 1 day of hot water injection.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Understanding the spatial and temporal characteristics of water flux into or out of shallow aquifers is imperative for water resources management and eco‐environmental conservation. In this study, the spatial variability in the vertical specific fluxes and hydraulic conductivities in a streambed were evaluated by integrating distributed temperature sensing (DTS) data and vertical hydraulic gradients into an ensemble Kalman filter (EnKF) and smoother (EnKS) and an empirical thermal‐mixing model. The formulation of the EnKF/EnKS assimilation scheme is based on a discretized 1D advection‐conduction equation of heat transfer in the streambed. We first systematically tested a synthetic case and performed quantitative and statistical analyses to evaluate the performance of the assimilation schemes. Then a real‐world case was evaluated to calculate assimilated specific flux. An initial estimate of the spatial distributions of the vertical hydraulic gradients was obtained from an empirical thermal‐mixing model under steady‐state conditions using a constant vertical hydraulic conductivity. Then, this initial estimate was updated by repeatedly dividing the assimilated specific flux by estimates of the vertical hydraulic gradients to obtain a refined spatial distribution of vertical hydraulic gradients and vertical hydraulic conductivities. Our results indicate that optimal parameters can be derived with fewer iterations but greater simulation effort using the EnKS compared with the EnKF. For the field application in a stream segment of the Heihe River Basin in northwest China, the average vertical hydraulic conductivities in the streambed varied over three orders of magnitude (5 × 10−1 to 5 × 102 m/d). The specific fluxes ranged from near zero (qz < ±0.05 m/d) to ±1.0 m/d, while the vertical hydraulic gradients were within the range of −0.2 to 0.15 m/m. The highest and most variable fluxes occurred adjacent to a debris‐dam and bridge pier. This phenomenon is very likely the result of heterogeneous streambed hydraulic characteristics in these areas. Our results have significant implications for hyporheic micro‐habitats, fish spawning and other wildlife incubation, regional flow and hyporheic solute transport models in the Heihe River Basin, as well as in other similar hydrologic settings.

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ABSTRACT:

In recent years, wireline temperature profiling methods have evolved to offer new insight into fractured rock hydrogeology. Important advances in wireline temperature logging in boreholes make use of active line source heating alone and then in combination with temporary borehole sealing with flexible impervious fabric liners to eliminate the effects of borehole cross-connection and recreate natural flow conditions. Here, a characterization technique was developed based on combining fiber optic distributed temperature sensing (DTS) with active heating within boreholes sealed with flexible borehole liners. DTS systems provide a temperature profiling method that offers significantly enhanced temporal resolution when compared with conventional wireline trolling-based techniques that obtain a temperature–depth profile every few hours. The ability to rapidly and continuously collect temperature profiles can better our understanding of transient processes, allowing for improved identification of hydraulically active fractures and determination of relative rates of groundwater flow. The advantage of a sealed borehole environment for DTS-based investigations is demonstrated through a comparison of DTS data from open and lined conditions for the same borehole. Evidence for many depth-discrete active groundwater flow features under natural gradient conditions using active DTS heat pulse testing is presented along with high resolution geologic and geophysical logging and hydraulic datasets. Implications for field implementation are discussed.

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ABSTRACT:

Emerging application areas such as air pollution in megacities, wind energy, urban security, and operation of unmanned aerial vehicles have intensified scientific and societal interest in mountain meteorology. To address scientific needs and help improve the prediction of mountain weather, the U.S. Department of Defense has funded a research effort—the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program—that draws the expertise of a multidisciplinary, multi-institutional, and multinational group of researchers. The program has four principal thrusts, encompassing modeling, experimental, technology, and parameterization components, directed at diagnosing model deficiencies and critical knowledge gaps, conducting experimental studies, and developing tools for model improvements. The access to the Granite Mountain Atmospheric Sciences Testbed of the U.S. Army Dugway Proving Ground, as well as to a suite of conventional and novel high-end airborne and surface measurement platforms, has provided an unprecedented opportunity to investigate phenomena of time scales from a few seconds to a few days, covering spatial extents of tens of kilometers down to millimeters. This article provides an overview of the MATERHORN and a glimpse at its initial findings. Orographic forcing creates a multitude of time-dependent submesoscale phenomena that contribute to the variability of mountain weather at mesoscale. The nexus of predictions by mesoscale model ensembles and observations are described, identifying opportunities for further improvements in mountain weather forecasting.

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ABSTRACT:

The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow, and mass balance of ice sheets, but measurements of this parameter are difficult to make in ice-covered regions. We report the first direct measurement of geothermal heat flux into the base of the West Antarctic Ice Sheet (WAIS), below Subglacial Lake Whillans, determined from the thermal gradient and the thermal conductivity of sediment under the lake. The heat flux at this site is 285 ± 80 mW/m2, significantly higher than the continental and regional averages estimated for this site using regional geophysical and glaciological models. Independent temperature measurements in the ice indicate an upward heat flux through the WAIS of 105 ± 13 mW/m2. The difference between these heat flux values could contribute to basal melting and/or be advected from Subglacial Lake Whillans by flowing water. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region.

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ABSTRACT:

AbstractGroundwater–surface-water (GW-SW) interactions in streams are difficult to quantify because of heterogeneity in hydraulic and reactive processes across a range of spatial and temporal scales. The challenge of quantifying these interactions has led to the development of several techniques, from centimeter-scale probes to whole-system tracers, including chemical, thermal, and electrical methods. We co-applied conservative and smart reactive solute-tracer tests, measurement of hydraulic heads, distributed temperature sensing, vertical profiles of solute tracer and temperature in the stream bed, and electrical resistivity imaging in a 450-m reach of a 3rd-order stream. GW-SW interactions were not spatially expansive, but were high in flux through a shallow hyporheic zone surrounding the reach. NaCl and resazurin tracers suggested different surface–subsurface exchange patterns in the upper ⅔ and lower ⅓ of the reach. Subsurface sampling of tracers and vertical thermal profiles quantified relatively high fluxes through a 10- to 20-cm deep hyporheic zone with chemical reactivity of the resazurin tracer indicated at 3-, 6-, and 9-cm sampling depths. Monitoring of hydraulic gradients along transects with MINIPOINT streambed samplers starting ∼40 m from the stream indicated that groundwater discharge prevented development of a larger hyporheic zone, which progressively decreased from the stream thalweg toward the banks. Distributed temperature sensing did not detect extensive inflow of ground water to the stream, and electrical resistivity imaging showed limited large-scale hyporheic exchange. We recommend choosing technique(s) based on: 1) clear definition of the questions to be addressed (physical, biological, or chemical processes), 2) explicit identification of the spatial and temporal scales to be covered and those required to provide an appropriate context for interpretation, and 3) maximizing generation of mechanistic understanding and reducing costs of implementing multiple techniques through collaborative research.

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ABSTRACT:

Technological advances in environmental sensing have increased our awareness of the complexity of spatial patterns and temporal dynamics of ecohydrological processes and their interactions. Improving the basis of knowledge of dynamically interacting processes is crucial for advancing our understanding of how ecosystems function under the influence of, and their resilience to, environmental change. Capturing the often fast changing and nonlinear behaviour of ecosystems represents a challenge for current observational networks, particularly when studying system interfaces and coupled ecological, hydrological, geomorphological and biogeochemical processes, demanding novel, adaptive approaches in real‐time monitoring and research. This paper discusses conceptual, technological and methodological challenges and resulting requirements for real‐time ecohydrological research by reviewing current approaches of capturing nonlinear behaviour with high‐frequency, high‐resolution monitoring and develops strategies for transforming ecohydrological research by including real‐time analysis of highly dynamic processes that are currently understudied. Examples of highly dynamic processes include rapid system changes, hot spots and hot moment behaviour.

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ABSTRACT:

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Error in distributed temperature sensing (DTS) water temperature measurements may be introduced by contact of the fiber optic cable sensor with bed materials (e.g., seafloor, lakebed, streambed). Heat conduction from the bed materials can affect cable temperature and the resulting DTS measurements. In the Middle Fork John Day River, apparent water temperature measurements were influenced by cable sensor contact with aquatic vegetation and fine sediment bed materials. Affected cable segments measured a diurnal temperature range reduced by 10% and lagged by 20–40 min relative to that of ambient stream temperature. The diurnal temperature range deeper within the vegetation–sediment bed material was reduced 70% and lagged 240 min relative to ambient stream temperature. These site-specific results illustrate the potential magnitude of bed-conduction impacts with buried DTS measurements. Researchers who deploy DTS for water temperature monitoring should understand the importance of the environment into which the cable is placed on the range and phase of temperature measurements.

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ABSTRACT:

We present a novel technique to simultaneously measure wind speed (U) at thousands of locations continuously in time based on measurement of velocity‐dependent heat transfer from a heated surface. Measuring temperature differences between paired passive and actively heated fiber‐optic (AHFO) cables with a distributed temperature sensing system allowed estimation of U at over 2000 sections along the 230 m transect (resolution of 0.375 m and 5.5 s). The underlying concept is similar to that of a hot wire anemometer extended in space. The correlation coefficient between U measured by two colocated sonic anemometers and the AHFO were 0.91 during the day and 0.87 at night. The combination of classical passive and novel AHFO provides unprecedented dynamic observations of both air temperature and wind speed spanning 4 orders of magnitude in spatial scale (0.1–1000 m) while resolving individual turbulent motions, opening new opportunities for testing basic theories for near‐surface geophysical flows.

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ABSTRACT:

Recent research has demonstrated the use of in‐well heat tracer tests monitored by a fiber optic distributed temperature sensing (DTS) system to characterize borehole flow conditions in open bedrock boreholes. However, the accuracy of borehole flow rates determined from in‐well heat tracer tests has not been evaluated. The purpose of the research presented here is to determine whether borehole flow rates obtained using DTS‐monitored in‐well heat tracer tests are reasonable, and to evaluate the range of flow rates measureable with this method. To accomplish this, borehole flow rates measured using in‐well heat tracer tests are compared to borehole flow rates measured in the same boreholes using an impeller or heat pulse flowmeter. A comparison of flow rates measured using in‐well heat tracer tests to flow rates measured with an impeller flowmeter under the same conditions showed good agreement. A comparison of in‐well heat tracer test flow rate measurements to previously‐collected heat pulse flowmeter measurements indicates that the heat tracer test results produced borehole flow rates and flow profiles similar to those measured with the heat pulse flowmeter. The results of this study indicate that borehole flow rates determined from DTS‐monitored in‐well heat tracer tests are reasonable estimates of actual borehole flow rates. In addition, the range of borehole flow rates measurable by in‐well heat tracer tests spans from less than 10−1 m/min to approximately 101 m/min, overlapping the ranges typically measurable with an impeller flowmeter or a heat pulse flowmeter, making in‐well heat tracer testing a versatile borehole flow logging tool.

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ABSTRACT:

AbstractThe effect of proglacial groundwater systems on surface hydrology and ecology in cold regions often is neglected when assessing the ecohydrological implications of climate change. We present a novel approach in which we combined 2 temperature-tracing techniques to assess the spatial patterns and short-term temporal dynamics of groundwater–surface-water exchange in the proglacial zone of Skaftafellsjökull, a retreating glacier in southeastern Iceland. Our study focuses on localized groundwater discharge to a surface-water environment, where high temporal- and spatial-resolution mapping of sediment surface and subsurface temperatures (10–15 cm depth) were obtained by Fiber-Optic Distributed Temperature Sensing (FO-DTS). The FO-DTS survey identified temporally consistent locations of temperature anomalies at the sediment–water interface, indicating distinct zones of cooler groundwater upwelling. The high-resolution FO-DTS surveys were combined with calculations of 1-dimensional groundwater seepage fluxes based on 3 vertical sediment temperature profiles, covering depths of 10, 25, and 40 cm below the lake bed. The calculated groundwater seepage rates ranged between 1.02 to 6.10 m/d. We used the combined techniques successfully to identify substantial temporal and spatial heterogeneities in groundwater–surface exchange fluxes that have relevance for the ecohydrological functioning of the investigated system and its potential resilience to environmental change.

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ABSTRACT:

The evolution of cold air layers near the surface was investigated for a night with stable conditions near the surface. Spatial air temperature observations at 276 co-located vertical profiles were made using high-resolution fibre-optic based distributed temperature sensing (DTS) in a quasi three-dimensional geometry oriented along a shallow depression in the landscape and analysed for patterns in near-surface flow. Temperature stratification was observed to be interrupted by transient temperature structures on the scale of metres for which the flow direction and velocity could be quantified. The high spatial resolution and large spatial domain of the DTS revealed temperature structures in a level of detail that exceeded the capability of traditional point observations of air temperature at low wind speeds. Further, composition techniques were applied to describe wave-like motions in the opposite direction of the mean flow, at intervals of approximately 200 s (5 mHz). The DTS technique delivered tomography on a scale of tens of metres. The spatial observations at high spatial (fractions of a metre) and temporal (sec) resolution provided new opportunities for detection and quantification of surface-flow features and description of complicated scale interactions. High-resolution DTS is therefore a valuable addition to experimental research on stable and weak-wind boundary layers near the surface.

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ABSTRACT:

Geophysical and geochemical surveys were conducted to understand groundwater discharge to Great Salt Lake (GSL) and assess the potential significance of groundwater discharge as a source of selenium (Se). Continuous resistivity profiling (CRP) focusing below the sediment/water interface and fiber-optic distributed temperature sensing (FO-DTS) surveys were conducted along the south shore of GSL. FO-DTS surveys identified persistent cold-water temperature anomalies at 10 separate locations. Seepage measurements were conducted at 17 sites (mean seepage rate = 0.8 cm/day). High resistivity anomalies identified by the CRP survey were likely a mirabilite (Na2SO4·10H2O) salt layer acting as a semi-confining layer for the shallow groundwater below the south shore of the lake. Positive seepage rates measured along the near-shore areas of GSL indicate that a ∼1-m thick oolitic sand overlying the mirabilite layer is likely acting as a shallow, unconfined aquifer. Using the average seepage rate of 0.8 cm/day over an area of 1.6 km2, an annual Se mass loading to GSL of 23.5 kg was estimated. Determination of R/Ra values (calculated 3He/4He ratio over the present-day atmospheric 3He/4He ratio) <1 and tritium activities of 1.2–2.0 tritium units in groundwater within and below the mirabilite layer indicates a convergence of regional and local groundwater flow paths discharging into GSL. Groundwater within and below the mirabilite layer obtains its high sulfate salinity from the dissolution of mirabilite. The δ34S and δ18O isotopic values in samples of dissolved sulfate from the shallow groundwater below the mirabilite are almost identical to the isotopic signature of the mirabilite core material. The saturation index calculated for groundwater samples using PHREEQC indicates the water is at equilibrium with mirabilite. Water samples collected from GSL immediately off shore contained Se concentrations that were 3–4 times higher than other sampling sites >25 km offshore from the study site and may be originating from less saline groundwater seeps mixing with the more saline water from GSL. Additional evidence for mixing with near shore seeps is found in the δD and δ18O isotopic values and Br:Cl ratios. Geochemical modeling for a water sample collected in the vicinity of the study area indicates that under chemically reducing conditions, arsenic- (As) bearing minerals could dissolve while Se-bearing minerals will likely precipitate out of solution, possibly explaining why the shallow groundwater below and within the mirabilite salt layer contains low concentrations of Se (0.9–2.3 μg/L).

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ABSTRACT:

Techniques for characterizing the hydraulic properties and groundwater flow processes of aquifers are essential to design hydrogeologic conceptual models. In this study, rapid time series temperature profiles within open‐groundwater wells in fractured rock were measured using fiber optic distributed temperature sensing (FO‐DTS). To identify zones of active groundwater flow, two continuous electrical heating cables were installed alongside a FO‐DTS cable to heat the column of water within the well and to create a temperature difference between the ambient temperature of the groundwater in the aquifer and that within the well. Additional tests were performed to examine the effects of pumping on hydraulic fracture interconnectivity around the well and to identify zones of increased groundwater flow. High‐ and low‐resolution FO‐DTS cable configurations were examined to test the sensitivities of the technique and compared with downhole video footage and geophysical logging to confirm the zones of active groundwater flow. Two examples are presented to demonstrate the usefulness of this new technique for rapid characterization of fracture zones in open boreholes. The combination of the FO‐DTS and heating cable has excellent scope as a rapid appraisal tool for borehole construction design and improving hydrogeologic conceptual models.

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ABSTRACT:

The Devils Hole pupfish (Cyprinodon diabolis) is a federally listed endangered species living solely within the confines of Devils Hole, a geothermal pool ecosystem in the Mojave Desert of the American Southwest. This unique species has suffered a significant, yet unexplained, population decline in the past two decades, with a record low survey of 35 individuals in early 2013. The species survives on a highly variable seasonal input of nutrients and has evolved in a thermal regime lethal to other pupfish species. The short lifespan of the species (approximately 1 year) makes annual recruitment in Devils Hole critical to the persistence of the species, and elevated temperatures on the shallow shelf that comprises the optimal spawning habitat in the ecosystem can significantly reduce egg viability and increase larval mortality. Here we combine computational fluid dynamic modeling and ecological analysis to investigate the timing of thresholds in the seasonal cycles of food supply and temperature. Numerical results indicate a warming climate most impacts the heat loss from the water column, resulting in warming temperatures and reduced buoyancy‐driven circulation. Observed climate change is shown to have already warmed the shallow shelf, and climate change by 2050 is shown to shorten the window of optimum conditions for recruitment by as much as 2 weeks. While there are many possible reasons for the precipitous decline of this species, the changing climate of the Mojave region is shown to produce thermal and nutrient conditions likely to reduce the success of annual recruitment of young C. diabolis in the future, leading to continued threats to the survival of this unique and enigmatic species.

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ABSTRACT:

Supraglacial channel networks link time varying melt production and meltwater routing on temperate glaciers. Such channel networks often include components of both surface transport in streams and subsurface porous flow through near-surface ice, firn or snowpack. Although subsurface transport if present will likely control network transport efficacy, it is the most poorly characterized component of the system. We present measurements of supraglacial channel spacing and network properties on the Juneau Icefield, subsurface water table height, and time variation of hydraulic characteristics including diurnal variability in water temperature. We combine these data with modeling of porous flow in weathered ice to infer near-surface permeability. Estimates are based on an observed phase lag between diurnal water temperature variations and discharge, and independently on measurement of water table surface elevation away from a stream. Both methods predict ice permeability on a 1–10 m scale in the range of 10−10–10−11 m2. These estimates are considerably smaller than common parameterizations of surface water flow on bare ice in the literature, as well as smaller than most estimates of snowpack permeability. For supraglacial environments in which porosity/permeability creation in the subsurface is balanced by porous flow of meltwater, our methods provide an estimate of microscale hydraulic properties from observations of supraglacial channel spacing.

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ABSTRACT:

This paper introduces the special section on “new modeling approaches and novel experimental technologies for improved understanding of process dynamics at aquifer‐surface water interfaces.” It is contextualizing the framework for the 27 research papers of the special section by firth identifying research gaps and imminent challenges for ecohydrological research at aquifer‐surface water interfaces and then discussing the specific paper contributions on (i) new developments in temperature/heat tracing at GW‐SW interfaces, (ii) new methods to capture the temporal and spatial variability of groundwater—surface water exchange, (iii) new approaches in modeling aquifer‐river exchange flow, and (iv) new concepts and advanced theory of groundwater—surface water exchange.

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ABSTRACT:

We thank J. S. Selker et al. (Comment on “Capabilities and limitations of tracing spatial temperature 1 patterns by fiber‐optic distributed temperature sensing” by Liliana Rose et al., hereinafter cited as “Selker et al. [2014]”) for their insightful comment on the Rose et al. [2013] technical note, which provides a helpful perspective on some instrumental performance aspects of Fiber‐optic Distributed Sensing (FO‐DTS).

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ABSTRACT:

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Studies of surface water–groundwater interactions using fiber optic distributed temperature sensing (FO-DTS) has increased in recent years. However, only a few studies to date have explored the limitations of FO-DTS in detecting groundwater discharge to 5 streams. A FO_DTS system was therefore tested in a flume under controlled laboratory conditions for its ability to accurately measure the discharge of hot or cold groundwater into a simulated surface water flow. In the experiment the surface water (SW) and groundwater (GW) velocities, expressed as ratios (vgw/vsw), were varied from 0.21 % to 61.7 %; temperature difference between SW-GW were varied from 2 to 10 ◦C; the 10 direction of temperature gradient were varied with both cold and-hot water injection; and two different bed materials were used to investigate their effects on FO_DTS’s detection limit of groundwater discharge. The ability of the FO_DTS system to detect the discharge of groundwater of a different temperature in the laboratory environment was found to be mainly dependent upon the surface and groundwater flow velocities and 15 their temperature difference. A correlation was proposed to estimate the groundwater discharge from temperature. The correlation is valid when the ratio of the apparent temperature response to the source temperature difference is above 0.02

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ABSTRACT:

This study employed Distributed Temperature Sensing (DTS) and Heat Source modeling to quantify the thermal regime of a one-kilometer section of the North Fork of the Salmon River, a tributary of the Klamath River, northern California, USA. The study collected eight days of temperature data using DTS at one-meter, 15-minute intervals during July 2012. The research aimed to: 1) investigate the geomorphic and thermal conditions of the study reach and their impact on native Salmonids. 2) identify and quantify groundwater seeps; and 3) employ and calibrate Heat Source to predict effects of riparian management, channel geometry, and climate change on stream temperature over the study reach. DTS observations revealed nearly uniform warming over the study reach, a diel heating cycle of 5 °C, a small groundwater spring (7 % of mainstem flow), and a Maximum Weekly Maximum Temperature (MWMT) of 23.00 °C. Statistical modeling of salmonid distribution field observations with AICc found that depth was the most explanatory parameter. Habitat inventory of the study reach indicated poor salmonid habitat quality with low habitat complexity with no large woody debris or instream cover. Heat Source model performance (Bias, RMSE, MARE, and NSE), compared to DTS iii observations, were all within the range of previous Heat Source applications. Heat Source modeling of reforestation of denuded legacy gravel bars from historic gold mining and areas of low vegetation in the study reach indicated that reforestation buffered daily maximum stream temperatures. Modeled channel restoration scenarios reduced the rate of heating (ºC /90 m) in the treatment area by a maximum of 34 %. Climate changescenarios were simulated with a uniform increase of air temperature by 2 °C, 4 °C, and 6 °C which warmed stream temperatures by 0.09 ºC / km per 2 ºC air temperature increase. Warming predicted by climate change was ameliorated with reforestation (0.11 ºC /km and 0.26 ºC per 2 ºC /km air temperature increase for partial and fully forested respectively).

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ABSTRACT:

Distributed Temperature Sensing (DTS) technology can collect abundant high resolution river temperature data over space and time to improve development and performance of modeled river temperatures. These data can also identify and quantify ther5 mal variability of micro-habitat that temperature modeling and standard temperature sampling do not capture. This allows researchers and practitioners to bracket uncertainty of daily maximum and minimum temperature that occurs in pools, side channels, or as a result of cool or warm inflows. This is demonstrated in a reach of the Shasta River in Northern California that receives irrigation runoff and inflow from small ground10 water seeps. This approach highlights the influence of air temperature on stream temperatures, and indicates that physically-based numerical models may under-represent this important stream temperature driver. This work suggests DTS datasets improve efforts to simulate stream temperatures and demonstrates the utility of DTS to improve model performance and enhance detailed evaluation of hydrologic processes.

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ABSTRACT:

The rate of groundwater flow has long been recognized as a critical control on solute transport in the subsurface. However, information about groundwater flux and its variability in space is rarely available, especially at the resolution required for investigations at sites of groundwater contamination. Recently, high‐resolution information about vertical variations in groundwater flux was obtained using fiber‐optic distributed temperature sensing technology to monitor the temperature response to active heating in a well. A series of vertical thermal profiles were acquired at a 1.4 cm resolution in a sand and gravel aquifer. These high‐resolution profiles, which display many of the same general features as hydraulic conductivity (K) profiles obtained using multiple techniques at the same well, provide new insights into site hydrostratigraphy. In particular, the near‐continuous profiles reveal the existence of thin zones of relatively high or low velocity that would be difficult to detect using other methods. These profiles also demonstrate that vertical variations in K may not be an accurate indicator of vertical variability in groundwater flux in highly heterogeneous aquifers.

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ABSTRACT:

Thermal diffusivity of snow is an important thermodynamic property associated with key hydrological phenomena such as snow melt and heat and water vapor exchange with the atmosphere. Direct determination of snow thermal diffusivity requires coupled point measurements of thermal conductivity and density, which continually change due to snow metamorphism. Traditional methods for determining these two quantities are generally limited by temporal resolution. In this study we present a method to determine the thermal diffusivity of snow with high temporal resolution using snow temperature profile measurements. High resolution (between 2.5 and 10 cm at 1 min) temperature measurements from the seasonal snow pack at the Plaine-Morte glacier in Switzerland are used as initial conditions and Neumann (heat flux) boundary conditions to numerically solve the one-dimensional heat equation and iteratively optimize for thermal diffusivity. The implementation of Neumann boundary conditions and a t-test, ensuring statistical significance between solutions of varied thermal diffusivity, are important to help constrain thermal diffusivity such that spurious high and low values as seen with Dirichlet (temperature) boundary conditions are reduced. The results show that time resolved thermal diffusivity can be determined from temperature measurements of seasonal snow and support density-based empirical parameterizations for thermal conductivity.

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ABSTRACT:

We show how fully distributed space‐time measurements with Fiber‐Optic Distributed Temperature Sensing (FO‐DTS) can be used to investigate groundwater flow and heat transport in fractured media. Heat injection experiments are combined with temperature measurements along fiber‐optic cables installed in boreholes. Thermal dilution tests are shown to enable detection of cross‐flowing fractures and quantification of the cross flow rate. A cross borehole thermal tracer test is then analyzed to identify fracture zones that are in hydraulic connection between boreholes and to estimate spatially distributed temperature breakthrough in each fracture zone. This provides a significant improvement compared to classical tracer tests, for which concentration data are usually integrated over the whole abstraction borehole. However, despite providing some complementary results, we find that the main contributive fracture for heat transport is different to that for a solute tracer.

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ABSTRACT:

A 6 month temperature record collected below McMurdo Ice Shelf in 2011–2012 shows the temporal and spatial structure of the summertime warm water signal that penetrates beneath the ice shelf. The strength and duration of the warm water intrusion suggest an annual melt rate at Windless Bight of 0.71 m/yr. A Ross Sea numerical model demonstrates a seasonal warm water pathway leading from the west side of the Ross Sea Polynya (RSP) toward McMurdo Sound. The warm water enters McMurdo Sound, subducts beneath the ice shelf and causes accelerated summer melting. Temperature data were recorded using Distributed Temperature Sensing fiber optics, which gives a vertical temperature profile at a 1 m vertical resolution. This study constitutes one of the first successful implementations of this technology in Polar Regions.

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ABSTRACT:

Surface and groundwater discharges and contaminant fluxes can vary with time and space depending upon the hydrogeological processes and geological setting of the area of interest. This study examined a ~300-m-long, channelized reach of a first-order perennial stream, Little Bayou Creek, in the Coastal Plain of far western Kentucky during the period October 2010–February 2012. Along the study reach, springs discharge groundwater contaminated by the chlorinated organic compound trichloroethene (TCE) and radionuclide technetium-99 (99Tc) released as a result of past activities at the U.S. Department of Energy’s Paducah Gaseous Diffusion Plant. The study addressed variability in groundwater discharge patterns and contaminant concentrations at various timescales (seasonal, annual, and decadal) and the extent to which the discharge sites are spatially persistent. Understanding patterns of groundwater discharge along a stream can be important for assessing the fate and transport of aqueous contaminants.

Groundwater discharge was estimated during baseflow conditions using different mass-balance approaches, including velocity-area and dye-dilution gauging. Discharge fluctuated seasonally but typically increased downstream, indicating the entire study reach to be gaining throughout the year. Discharge rates of individual springs also fluctuated seasonally. Tracer test data were utilized to model flow and transient storage along the reach using the USGS software OTIS-P. Cross-sectional area determined from OTIS-P was similar to that measured by velocity-area gauging. Reach area-normalized discharge fluxes were comparable to values determined by Darcy’s law calculations from a pair of monitoring wells at the downstream end of the study reach. Temperature data acquired from probing along grids in winter and summer, from fiber-optic sensing along the reach in autumn, and from data-loggers and manual measurements in springs were used to delineate focused discharge locations. Comparison of temperature-probing results with prior studies indicated that locations of some springs persisted over a decade, whereas other springs emerged and disappeared. Because the stream is located in unlithified sediments, discharge rates of springs appear to fluctuate with soil piping and collapse along joints in fractured clay. Contaminant concentrations in springs decreased downstream along the reach and were lower than observed during September 1999 – May 2001. The continued occurrence of dissolved oxygen and the absence of TCE daughter products in springs suggest that the decrease in TCE concentrations resulted from the installation of upgradient extraction wells, rather than from intrinsic reductive degradation.

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ABSTRACT:

Devils Hole, a groundwater-filled fracture in the carbonate aquifer of the southern Nevada Mojave Desert, represents a unique ecohydrological setting, as home to the only extant population of Cyprinodon diabolis, the endangered Devils Hole pupfish. Using water column temperatures collected with a fiber-optic distributed temperature sensor (DTS) during four field campaigns in 2009, evidence of deep circulation and nutrient export are, for the first time, documented. The DTS was deployed to measure vertical temperature profiles in the system, and the raw data returned were postprocessed to refine the calibration beyond the precision of the instrument’s native calibration routines. Calibrated temperature data serve as a tracer for water movement and reveal a seasonal pattern of convective mixing that is supported by numerical simulations of the system. The periodic presence of divers in the water is considered, and their impacts on the temperature profiles are examined and found to be minimal. The seasonal mixing cycle may deplete the pupfish’s food supplies when nutrients are at their scarcest. The spatial and temporal scales of the DTS observations make it possible to observe temperature gradients on the order of 0.001C m1 , revealing phenomena that would have been lost in instrument noise and uncertainty.

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ABSTRACT:

Subsurface heterogeneity in hydraulic properties and processes is a fundamental challenge in hydrogeology. We have developed an improved method of borehole dilution testing for hydrostratigraphic characterization, in which distributed temperature sensing (DTS) is used to monitor advective heat movement. DTS offers many advantages over conventional technologies including response times in the order of seconds rather than minutes, the ability to profile temperature synoptically in a well without disturbing the fluid column, sensitivity to a wider range of flow rates than conventional spinner and heat pulse flow meters, and the ease of interpretation. Open‐well thermal dilution tests in two multiaquifer wells near Madison, Wisconsin, provided detailed information on the borehole flow regimes, including flow rates and the locations of inflows from both fractures and porous media. The results led to an enhanced understanding of flow in a hydrostratigraphic unit previously conceptualized as homogenous and isotropic.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Characterizing both spatial and temporal soil moisture (θ) dynamics at site scales is difficult with existing technologies. To address this shortcoming, we developed a distributed soil moisture sensing system that employs a distributed temperature sensing system to monitor thermal response at 2 m intervals along the length of a buried cable which is subjected to heat pulses. The cable temperature response to heating, which is strongly dependent on soil moisture, was empirically related to colocated, dielectric-based θ measurements at three locations. Spatially distributed, and temporally continuous estimates of θ were obtained in dry conditions (θ ≤ 0.31) using this technology (root mean square error [RMSE] = 0.016), but insensitivity of the instrument response curve adversely affected accuracy under wet conditions (RMSE = 0.050).

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

We present a novel approach based on fibre-optic distributed temperature sensing (DTS) to measure the two-dimensional thermal structure of the surface layer at high resolution (0.25m, ≈0.5 Hz). Air temperature observations obtained from a vertically-oriented fibre-optics array of approximate dimensions 8m×8m and sonic anemometer data from two levels were collected over a short grass field located in the flat bottom of a wide valley with moderate surface heterogeneity. The objectives of the study were to evaluate the potential of the DTS technique to study small-scale processes in the surface layer over a wide range of atmospheric stability, and to analyze the space–time dynamics of transient cold-air pools in the calm boundary layer. The time response and precision of the fibre-based temperatures were adequate to resolve individual sub-metre sized turbulent and non-turbulent structures, of time scales of seconds, in the convective, neutral, and stable surface layer. Meaningful sensible heat fluxes were computed using the eddy-covariance technique when combined with vertical wind observations. We present a framework that determines the optimal environmental conditions for applying the fibre-optics technique in the surface layer and identifies areas for potentially significant improvements of the DTS performance. The top of the transient cold-air pool was highly non-stationary indicating a superposition of perturbations of different time and length scales. Vertical eddy scales in the strongly stratified transient cold-air pool derived from the DTS data agreed well with the buoyancy length scale computed using the vertical velocity variance and the Brunt–Vaisala frequency, while scales for weak stratification disagreed. The high-resolution DTS technique opens a new window into spatially sampling geophysical fluid flows including turbulent energy exchange.

Raw project data will be available in 2020 by contacting ctemps@unr.edu

ABSTRACT:

Over the past five years, Distributed Temperature Sensing (DTS) along fiber optic cables using Raman backscattering has become an important tool in the environmental sciences. Many environmental applications of DTS demand very accurate temperature measurements, with typical RMSE < 0.1 K. The aim of this paper is to describe and clarify the advantages and disadvantages of double-ended calibration to achieve such accuracy under field conditions. By measuring backscatter from both ends of the fiber optic cable, one can redress the effects of differential attenuation, as caused by bends, splices, and connectors. The methodological principles behind the double-ended calibration are presented, together with a set of practical considerations for field deployment. The results from a field experiment are presented, which show that with double-ended calibration good accuracies can be attained in the field.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Degassing of CO2 on the flanks of the active Erebus volcano is thought to occur mainly through fumarolic ice caves (FIC) and associated fumarolic ice towers. There is alsom minor CO2 degassing from isolated areas of warm ground. The mechanism supplying heat and CO2 gas into the FIC is poorly understood. To investigate this system, a fiber optic distributed temperature sensing (DTS) system was deployed in a FIC to obtain temperature measurements every meter. The DTS data reveal that localized gas vents (GV) supply heat to the FIC air mass and are an important component of the FIC microclimate. FIC temperature is anti‐correlated with local atmospheric pressure, indicating barometric pumping of the GV. These results enable the use of FIC temperature as a proxy for flank degassing rate on Erebus, and represent the first application of DTS for monitoring an active volcano.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Hydrologic research is a very demanding application of fiber-optic distributed temperature sensing (DTS) in terms of precision, accuracy and calibration. The physics behind the most frequently used DTS instruments are considered as they apply to four calibration methods for single-ended DTS installations. The new methods presented are more accurate than the instrument-calibrated data, achieving accuracies on the order of tenths of a degree root mean square error (RMSE) and mean bias. Effects of localized non-uniformities that violate the assumptions of single-ended calibration data are explored and quantified. Experimental design considerations such as selection of integration times or selection of the length of the reference sections are discussed, and the impacts of these considerations on calibrated temperatures are explored in two case studies.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

In lentic water bodies, such as lakes, the water temperature near the surface typically increases during the day, and decreases during the night as a consequence of the diurnal radiative forcing (solar and infrared radiation). These temperature variations penetrate vertically into the water, transported mainly by heat conduction enhanced by eddy diffusion, which may vary due to atmospheric conditions, surface wave breaking, and internal dynamics of the water body. These two processes can be described in terms of an effective thermal diffusivity, which can be experimentally estimated. However, the transparency of the water (depending on turbidity) also allows solar radiation to penetrate below the surface into the water body, where it is locally absorbed (either by the water or by the deployed sensors). This process makes the estimation of effective thermal diffusivity from experimental water temperature profiles more difficult. In this study, we analyze water temperature profiles in a lake with the aim of showing that assessment of the role played by radiative forcing is necessary to estimate the effective thermal diffusivity. To this end we investigate diurnal water temperature fluctuations with depth. We try to quantify the effect of locally absorbed radiation and assess the impact of atmospheric conditions (wind speed, net radiation) on the estimation of the thermal diffusivity. The whole analysis is based on the results of fiber optic
distributed temperature sensing, which allows unprecedented high spatial resolution measurements (4 mm) of the temperature profile in the water and near the water surface.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Through its role in the energy and water balances at the land surface, soil moisture is a key state variable in surface hydrology and land‐atmosphere interactions. Point observations of soil moisture are easy to make using established methods such as time domain reflectometry and gravimetric sampling. However, monitoring large‐scale variability with these techniques is logistically and economically infeasible. Here passive soil distributed temperature sensing (DTS) will be introduced as an experimental method of measuring soil moisture on the basis of DTS. Several fiber‐optic cables in a vertical profile are used as thermal sensors, measuring propagation of temperature changes due to the diurnal cycle. Current technology allows these cables to be in excess of 10 km in length, and DTS equipment allows measurement of temperatures every 1 m. The passive soil DTS concept is based on the fact that soil moisture influences soil thermal properties. Therefore, observing temperature dynamics can yield information on changes in soil moisture content. Results from this preliminary study demonstrate that passive soil DTS can detect changes in thermal properties. Deriving soil moisture is complicated by the uncertainty and nonuniqueness in the relationship between thermal conductivity and soil moisture. A numerical simulation indicates that the accuracy could be improved if the depth of the cables was known with greater certainty.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

The structural integrity of deep, large underground facilities such as tunnels, mines, pumped storage facilities, and physics laboratories requires the ability to predict rock mass stability under loading to ensure the safety of human occupants and the longevity of the underground space. Deformation occurs over time scales that range from milliseconds to decades and spatial scales that range from millimeters to facility scale. Beginning with design, prediction is typically based on finite element models using available or estimated properties. As with most geotechnical problems, much of the difficulty of prediction lies in the inability to sufficiently characterize the rock properties, especially discontinuities. As a consequence, semi-quantitative measures, such as Rock Mass Rating (RMR) or the Hoek-Brown Geological Structure Index (GSI) [1], are used to characterize the rock mass together with empirical charts for design criteria such as rock bolt spacing for ground control. During and following construction, validating model predictions is necessary to assess their performance. Parameter adjustment, or even the physics incorporated within the model, can be made using back analysis. This monitoring should be a continuous or periodic process over the life of the facility. For civil structures, the post-construction era will be measured in decades. With the inherent uncertainties and high stresses associated with the deep underground environment, the potential for rock failure must always be borne in mind. Mitigating the risk is prudent, but formal cost-benefit analysis may be precluded by the uncertainties. Keeping abreast of the condition of the facility through Structural Health Monitoring (SHM) is gaining acceptance for underground construction [2]. One reason for the growth in research in monitoring is that maturing technologies, like fiber-optic sensors and associated instrumentation, can collect data that were not previously achievable. They are robust and geometrically flexible, possess long-term stability, are cost effective, and extend coverage in spatial extent with improved resolution or provide data at a higher sampling rate. In addition to fiber-optic technology, a host of new technologies with potential for underground geotechnical applications exist, including LIDAR, wireless “smart dust”, piezoelectric sensors, and high resolution electrical and seismic imaging [3; 4; 5; 6; 7]. The subject of this paper is mainly to describe preliminary experiments, future needs, and instrumentation and monitoring plans of the authors' research activities in the 2400-meter Deep Underground Science and Engineering Laboratory (DUSEL) in the Black Hills of South Dakota, USA, where fiber-optic sensors and water-level tiltmeter arrays have been installed.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

The exchange of groundwater and surface water (GW‐SW), including dissolved constituents and energy, represents a critical yet challenging characterization problem for hydrogeologists and stream ecologists. Here we describe the use of a suite of high spatial resolution remote sensing techniques, collected using a small unmanned aircraft system (sUAS), to provide novel and complementary data to analyze GW‐SW exchange. sUAS provided centimeter‐scale resolution topography and water surface elevations, which are often drivers of exchange along the river corridor. Additionally, sUAS‐based vegetation imagery, vegetation‐top elevation, and normalized difference vegetation index mapping indicated GW‐SW exchange patterns that are difficult to characterize from the land surface and may not be resolved from coarser satellite‐based imagery. We combined these data with estimates of sediment hydraulic conductivity to provide a direct estimate of GW “shortcutting” through meander necks, which was corroborated by temperature data at the riverbed interface.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Detect and Avoid (DAA) systems are complex communication and locational technologies comprising multiple independent components. DAA technologies support communications between ground-based and space-based operations with aircraft. Both manned and unmanned aircraft systems (UAS) rely on DAA communication and location technologies for safe flight operations. We examined the occurrence and duration of communication losses between radar and automatic dependent surveillance–broadcast (ADS-B) systems with aircraft operating in proximate airspace using data collected during actual flight operations. Our objectives were to identify the number and duration of communication losses for both radar and ADS-B systems that occurred within a discrete time period. We also investigated whether other unique communication behavior and anomalies were occurring, such as reported elevation deviations. We found that loss of communication with both radar and ADS-B systems does occur, with variation in the length of communication losses. We also discovered that other unexpected behaviors were occurring with communications. Although our data were gathered from manned aircraft, there are also implications for UAS that are operating within active airspaces. We are unaware of any previously published work on occurrence and duration of communication losses between radar and ADS-B systems.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Identifying where groundwater-surface water exchange occurs along the lower 8 miles of river bed of the Passaic River, NJ utilizing armoured fiber optic cable and Silixa XT-DTS from June 11 - August 8, 2018.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

The current scope involves three FO-DTS deployments, each 1km in length and for 5 days each. The site we are working on would like to evaluate groundwater discharge from the site into the river downgrade to facilitate discrete porewater sampling and evaluate potential plume migration. Previous GSI studies have been conducted here; however, due to recent landscape changes a comprehensive seepage survey is desired.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

We are performing an Aquifer Storage and Recovery injection test in a newly installed test well. A nearby well with a relatively long well screen interval will be used to sample recovered groundwater to assess water quality. The DTS cable will be installed in the nearby observation to determine the best depth to place a sampling pump for performing the water quality tests and to better evaluate potential vertical variations in relative aquifer transmissivity during the test. The DTS cable will be deployed in a locked environment at the City of Sonoma wellsite.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

The use of tile drainage is documented as far back as 200 B. C. and continues to be used in poorly drained agricultural regions throughout the world. Recent increases in annual precipitation throughout the mid-western United States, the potential for future regulation of tile, and more efficient installation methods for plastic tile have accelerated tile installation across the region. While good for crop production, the eco-hydrologic impacts of this modification have been shown to adversely affect natural drainage networks. Knowing the location of tile drain networks is essential to developing groundwater and surface water models. The geometry of tile networks installed decades ago has often been lost with time or was never well documented in the first place. Previous work has recognized that tiles can be observed for certain soil types in visible remote sensing data due to changes in soil albedo. The soil surface directly above the tile appears to have a lower soil moisture content due to strong water table gradients adjacent to tiles, causing a detectable color contrast at the surface. In this work, small Unmanned Aerial Systems (sUAS) were used to collect high resolution visible and thermal data to map tile drain patterns. Within less than 96 hours of a 12 mm rain event, a total of approximately 60 hectares of sUAS thermal and RGB data were acquired at two different locations at the Intensively Managed Lands Critical Zone Observatory in Illinois. Selected thermal images were co-registered with RGB images at known tile locations. The thermal imagery showed limited evidence of thermal contrast related to the tile, however, it is possible that a contrast could have been detected sooner after the rain event when greater thermal contrasts due to lower soil moisture proximal to tile would be expected. The RGB data, however, elucidated the tile entirely at one site and provided traces of the tile at the other site. These results illustrate the importance of the timing of sUAS data collection with respect to the precipitation event. Ongoing related work focusing on laboratory and numerical experiments to better quantify feedbacks between albedo, soil moisture, and heat transfer will help predict the optimal timing of data collection for applications such as tile mapping.

Raw project data is available by contacting ctemps@unr.edu

ABSTRACT:

Stable boundary layers are still a relatively problematic component of atmospheric modeling, despite their frequent occurrence. While general agreement exists that MO similarity is not applicable in the SBL due to the non-homogeneous, non-stationary flow, no universal organizing theory for the surface SBL has been presented. This poses a problem when examining aerosol movement as a function of atmospheric dynamics. It is known that stable air stratification results in katabatic downslope winds, even in very shallow topographic airsheds. These downslope winds can converge with background flow, and it is hypothesized that this convergence provides a starting point for specific events, such as internal gravity waves. Even though the stable boundary layer is normally shallow, internal gravity waves can propagate at an angle from the horizontal plane, and modify local shear, thus generating periodic turbulent mixing in space. Some studies have measured converging background and drainage flows in mountain areas, however, few studies have examined this in less dramatic, but more common, topographic areas. We are conducting a measurement campaign to address these open issues.

Raw DTS project data will be available in 2020 by contacting ctemps@unr.edu

ABSTRACT:

Near-surface wind speed is typically only measured by point observations. The so-called Actively Heated Fiber-Optic (AHFO) technique, however, has the potential to provide high-resolution distributed observations, allowing for better understanding of different processes. However, before it can be widely used, its performance needs to be tested in a range of settings. Therefore, in this work, experimental results on this novel observational wind-probing technique are presented. We utilized a controlled wind-tunnel setup to assess both the accuracy and the precision of AHFO as well as its potential for outdoor atmospheric operation. The technique allows for wind speed characterization with a spatial resolution of 0.3 m on a 1 s time scale. The flow in the wind tunnel is varied in a controlled manner, such that the mean wind, ranges between 1 and 17 m/s. Comparison of the AHFO measurements with observations from a sonic anemometer shows a high overall correlation, ranging from 0.94-0.99. Also, both precision and accuracy are greater than 95 %. As such, it is concluded that the AHFO has potential to be employed as an outdoor observational technique in addition to existing techniques. In particular, it allows for characterization of spatial varying fields of mean wind in complex terrain, such as in canopy flows or in sloping terrain. In the future the technique could be combined with regular Distributed Temperature Sensing (DTS) for turbulent heat flux estimation in micrometeorological/hydrological applications.

Raw DTS project data will be available in 2020 by contacting ctemps@unr.edu.

ABSTRACT:

Goal: Develop techniques for observing 3D, high resolution atmospheric motions during stably stratified
conditions.
Missing Physics: The need for a full 3D sensor
1) Fundamental mismatch between scales of variability in wind and temperature break observation assumptions
2) Stability and wind speed alone can not describe the strength of mixing during weak wind conditions
3) Spatial heterogeneity in both temperature and wind fields at varying scales

Raw DTS project data will be available in 2020 from ctemps@unr.edu

ABSTRACT:

The purpose of this part of the project is to compare hyporheic exchange measurement methods and evaluate feasibility of using fiber optic DTS in a small stream (East Fork Poplar Creek) in Tennessee. CTEMPS stand-alone high resolution temperature loggers and fiber optic DTS were used to measure temperature gradients between stream-bed sediments and a stream to estimate groundwater discharge to surface water across a small hyporheic zone. There are also in-stream piezometer, electrical resistivity, and in-stream tracer test data to compare with the temperature method.

Data will be available upon in September 2021.

ABSTRACT:

A tethered-balloon system (TBS) has been developed and is being operated by Sandia National Laboratories (SNL) on behalf of the U.S. Department of Energy’s (DOE) Atmospheric Radiation Measurement (ARM) User Facility in order to collect in situ atmospheric measurements within mixed-phase Arctic clouds. Periodic tethered-balloon flights have been conducted since 2015 within restricted airspace at ARM’s Advanced Mobile Facility 3 (AMF3) in Oliktok Point, Alaska, as part of the AALCO (Aerial Assessment of Liquid in Clouds at Oliktok), ERASMUS (Evaluation of Routine Atmospheric Sounding Measurements using Unmanned Systems), and POPEYE (Profiling at Oliktok Point to Enhance YOPP Experiments) field campaigns. The tethered-balloon system uses helium-filled 34 m3 helikites and 79 and 104 m3 aerostats to suspend instrumentation that is used to measure aerosol particle size distributions, temperature, horizontal wind, pressure, relative humidity, turbulence, and cloud particle properties and to calibrate ground-based remote sensing instruments. Supercooled liquid water content (SLWC) sondes using the vibrating-wire principle, developed by Anasphere Inc., were operated at Oliktok Point at multiple altitudes on the TBS within mixed-phase clouds for over 200 h. Sondecollected SLWC data were compared with liquid water content derived from a microwave radiometer, Ka-band ARM zenith radar, and ceilometer at the AMF3, as well as liquid water content derived from AMF3 radiosonde flights. The in situ data collected by the Anasphere sensors were also compared with data collected simultaneously by an alternative SLWC sensor developed at the University of Reading, UK; both vibrating-wire instruments were typically observed to shed their ice quickly upon exiting the cloud or reaching maximum ice loading. Temperature sensing measurements distributed with fiber optic tethered balloons were also compared with AMF3 radiosonde temperature measurements. Combined, the results indicate that TBSdistributed temperature sensing and supercooled liquid water measurements are in reasonably good agreement with remote sensing and radiosonde-based measurements of both properties. From these measurements and sensor evaluations, tethered-balloon flights are shown to offer an effective method of collecting data to inform and constrain numerical models, calibrate and validate remote sensing instruments, and characterize the flight environment of unmanned aircraft, circumventing the difficulties of in-cloud unmanned aircraft flights such as limited flight time and inflight icing.

Data collected with CTEMPs DTS available upon request from ctemps@unr.edu.

ABSTRACT:

Deployment of DTS in bottom of small lake bed. Effort is geared towards finding underwater springs/seepage.

Data available by contacting ctemps@unr.edu in September 2021.

ABSTRACT:

This project is focused on measuring turbulence over an aerodynamically homogeneous playa surface that has heterogeneity in surface moisture and temperature. A large horizontal array of sonic anemometers will be deployed with an array of hot-wire probes covering a scales from 1-km down below 1-cm at the salt playa in Utah's west desert (SLTEST). We deployed a DTS to measure surface temperature and air temperature just above the surface (less than 1 m above the surface) covering an area of several hundred meters.

Data available in August 2021 by contacting ctemps@unr.edu.

ABSTRACT:

We present a new method for using temperature to infer bathymetric change of an artificial beach placed in the O.H. Hinsdale Wave Research Laboratory Large Wave Flume at Oregon State University. The temperature latency technique compares recorded temperature measured within the sediment with modeled temperatures expected to result from surface water temperature changes through time. Because surface-driven temperature changes are attenuated and lagged in time with deeper burial, we can estimate depth of burial by examining the time series of temperatures measured within the sediment relative to surface temperatures. Temperatures are recorded at more than 900 cross-shore locations across two depths using a fiber optic distributed temperature system (DTS) and at 2 cross-shore locations at two depths using stacked point thermocouples for DTS verification.

Data will be available in October 2021 by request from ctemps@unr.edu.

ABSTRACT:

The recent discovery of resurgent brook trout populations – brook trout present in 68% of southeastern Minnesota streams compared to only 3% in the early 1970s - has led to an increased interest in documenting and improving critical habitat for this native species - the most temperature-sensitive of southeastern Minnesota’s trout population. Many of the brook trout analyzed were not associated with known hatchery sources, leading investigators at the Minnesota DNR and University of Minnesota to focus on potentially remnant lineages that have proven their ability to sustain themselves in this region (Hoxmeier, Dieterman and Miller, 2015). Brook trout often display distinct distributions along stream reaches, thought to be caused by stream temperature, discharge, competition with brown trout, or a combination of all three. Previous groundwater and geologic investigations, funded in part by the LCCMR, have shown that specific layers within the bedrock provide greater groundwater flow. Stream reaches that cross these layers are subject to greater groundwater inputs, increased base flow and lower temperature along and downstream from these reaches thus providing habitat conditions supportive to brook trout.

The goal of this project is develop a workable temperature sensing methodology and apply the methodology to candidate trout stream reaches to quantify the changes in temperature, flow, and trout distributions that occur along them. Advances in temperature measurements using fiber optic cables (distributed temperature sensing, DTS) allow temperature to be recorded through time at regularly spaced intervals, over distances of 1 to 2 kilometers. Stream reaches to be measured will be chosen based on geologic mapping by the Minnesota Geological Survey, focusing in areas where different geologic conditions exist and information on trout distribution and abundance are available. To date, DTS installation, temperature data collection and fish population sampling have been completed at East Indian Creek in Wabasha County.

Data available by contacting ctemps@unr.edu

ABSTRACT:

Find raw data here: https://nevada.app.box.com/folder/118092693469

ABSTRACT:

Determine the Thermal Conductivity of the soil at different "layers" down to 500'. See attachments for more information.

RAW DTS data are available here: https://nevada.app.box.com/folder/118087363227

ABSTRACT:

At a New York study area 1.2 acres of sediment were monitored for evidence of groundwater seeps using a fiber optic distributed temperature sensor (DTS). A fiber optic cable was installed and monitored, providing 1.0 kilometers of cable laid out in six transects, each approximately 140 m in length and separated by 5-8 m. The DTS system recorded sediment temperatures at half-meter intervals every 20 minutes in September, 2019, yielding approximately 1.5 million temperature measurements during the study. Temperature data was analyzed through a suite of analytical methods to identify potential groundwater discharge locations.

Data available by contacting ctemps@unr.edu

ABSTRACT:

Short term deployment of DTS in Oxbow feature of Johnson Creek, Portland, OR.

Data available in August 2021 by contacting ctemps@unr.edu.

ABSTRACT:

Weathering and transport of potentially acid generating material (PAGM) at abandoned
mines can degrade downstream environments and contaminate water resources. Monitoring the
thousands of abandoned mine lands (AMLs) for exposed PAGM using field surveys is time intensive.
Here, we explore the use of Remotely Piloted Aerial Systems (RPASs) as a complementary remote
sensing platform to map the spatial and temporal changes of PAGM across a mine waste rock pile on
an AML. We focus on testing the ability of established supervised and unsupervised classification
algorithms to map PAGM on imagery with very high spatial resolution, but low spectral sampling.
At the Perry Canyon, NV, USA AML, we carried out six flights over a 29-month period, using
a RPAS equipped with a 5-band multispectral sensor measuring in the visible to near infrared
(400–1000 nm). We built six different 3 cm resolution orthorectified reflectance maps, and our tests
using supervised and unsupervised classifications revealed benefits to each approach. Supervised
classification schemes allowed accurate mapping of classes that lacked published spectral libraries,
such as acid mine drainage (AMD) and efflorescent mineral salts (EMS). The unsupervised method
produced similar maps of PAGM, as compared to supervised schemes, but with little user input.
Our classified multi-temporal maps, validated with multiple field and lab-based methods, revealed
persistent and slowly growing ‘hotspots’ of jarosite on the mine waste rock pile, whereas EMS
exhibit more rapid fluctuations in extent. The mapping methods we detail for a RPAS carrying a
broadband multispectral sensor can be applied extensively to AMLs. Our methods show promise to
increase the spatial and temporal coverage of accurate maps critical for environmental monitoring
and reclamation efforts over AMLs.

ABSTRACT:

A 9.4 mm armored cable with two single mode and two multimode fibers was deployed in the cross shore coastal ocean from Duck, NC. DAS and DTS were used to measure bottom temperature and strain and connect those measurements to surface signatures of coastal hydrodynamics measured by camera and radar.

DTS data available via Box: https://oregonstate.box.com/s/4ugltcd8ud54ovf8oif9gsys40dpo30w.

ABSTRACT:

This project focused on identifying groundwater seep locations and estimating flux rates of groundwater emerging into a 0.5 km reach of a naturally-bedded culvert confining a stream channel in an industrial area. Two steel-reinforced 1-cm diameter fiber optic cables were installed approximately 20 cm into streambed sediment in 4 transects along the length of the tunnel (See layout figure). The two fibers were connected a Silixa Ultima DTS Interrogator in a double-ended fashion, which collected temperature data from each of the four channels at 10 minute intervals. Data was collected Aug 18 – 31, 2020 and again January 9, 2021 to March 12, 2021.

Raw DTS data files available via Box: https://oregonstate.box.com/s/u6lnraus2ae9sehvkm5vkx6dz2sqs4va

ABSTRACT:

We acquired temperature profile measurements on two ice shelves in the Antarctica Peninsula : The Wilkins and the George VI. This work was achieved with a Silixa XT Distributed Temperature Sensing (DTS).

RAW DTS data can be found here: https://nevada.app.box.com/folder/172079674577

ABSTRACT:

The spread of invasive plant species severely alters wildfire regimes, degrades critical habitat for native species, and has detrimental impacts upon ecosystem function, rangeland productivity, and dynamics of long-term carbon storage. Remote sensing technology has greatly improved our understanding of invasive plant ecology, and hence our ability to manage invasive species. Imagery obtained from airborne or space-borne platforms can provide spatially explicit estimates of plant population size, extent, and spread. However, it has proved quite challenging to remotely detect and monitor weed invasions at the species level, as even the most detailed satellite imagery is commonly greater than one meter in resolution and is too coarse to identify isolated individuals or small patches of invasion. There is a growing need to map the spread of invasive grasses at the species level to facilitate precision management of invasive weeds. Controlling emerging and individual infestations is critical for slowing the rate of invasion and promoting rangeland biodiversity in regions that are potentially at risk.

By capitalizing on species-specific differences in plant phenology and using high resolution Unmanned Aerial Vehicle (UAV) imagery we are able to collect detailed data emphasizing the spectral differences between invasive plants at the species level, even where different species co-occur in a fine-grained mosaic. UAVs can produce images at the centimeter scale, avoiding the 'mixed-pixel problem' where larger pixels encompass multiple cover types and plant species, confounding classification efforts. Pixel-based landcover classifications at this scale frequently contain excessive spatial detail caused by variations in features such as shadows and canopy gaps, often resulting in misclassification, inaccuracy, and a “salt-and-pepper” effect. This study addresses this challenge and refines a novel combination of spectral, textural, contextual, object-based, and multitemporal plant phenology-based classification techniques that employs the full range of available information to differentiate invasive annual plants to the species level. A detailed vegetation classification can be used to train classifications at larger resolutions, identifying invasion patterns at landscape and regional scales. By comparing classifications across spatial resolutions, we can better characterize the landscape context of annual grass invasions. Our approach distinguishes invasive plant species from one another and from the dominant species of native vegetation within which they are embedded, increasing the utility of remote sensing data in invasive species management. Analyzing alternative resolutions contributes to the management of invasive species and deepens our understanding of invaded plant communities at multiple scales.

ABSTRACT:

Determine the Thermal Conductivity of the soil at different "layers" down to 500'

RAW DTS data can be found here: https://nevada.app.box.com/folder/118087363227

ABSTRACT:

Install fiber optic cable to detect groundwater upwelling in small section of Newtown Creek Canal in New York City. The site has DNAPL contaminants.

ABSTRACT:

Design, construction and laboratory testing (prior to testing in Madison) of a melt
probe with cabling to enable deployment of Raman DTS, as well as injection of ethanol
at 0 C above the descending probe, in collaboration with Collaborative Research
partners at the University of Nevada - Reno (Scott Tyler, PI) and Oregon State
University (J. Selker, PI). The University of Nevada/OSU focus is on the integration of
the DTS system into the melt probe design to provide both real time feedback on the
thermal condition of the probe, and most importantly, the entire borehole from the ice
surface to the probe. This aspect is critical as the system design relies upon a small
diameter unfroze portion of the borehole to remain open throughout the descent
phase.

Deployment in February 2019 to Madison, WI Ice Drilling Program testing facility,
equipment testing, and return to Seattle (see Supporting Files 1 and 2 for
photographs). The new trials tested our approaches to melt-hole control and probe
recovery in the taller column, as well as cable and cable-tension-management methods
more nearly approximating those needed to work on ice sheets. Following the Madison
field trial, we conducted extensive discussion and review of data and lessons
learned. Post audit analysis of the test indicated weaknesses in the heater designs as
well as the cable feed system, weaknesses that the testing was designed to probe. We
then carried out modifications to the melt probe, changing the heater mountings and
control system and redesigning the DTS fiber termination system to allow for a more
seamless integration of other telemetry and ethanol.

Numerical modeling of melt-hole refreezing with and without injection of anti-freeze,
to understand quantitatively conditions where slush formation in a melt-hole filled with
ethanol/water solution and thus to guide equipment design and experimental
procedures (see Supporting Files 3 and 4 for explanatory figures). This work resulted in
a publication currently under review for a special issue of the Annals of Glaciology.

RAW DTS data can be found here: https://nevada.app.box.com/folder/118092693469

ABSTRACT:

Uncooled thermal infrared (TIR) imagers, commonly used on aircraft and small unmanned aircraft systems (UAS, “drones”), can provide high‐resolution surface temperature maps, but their accuracy is dependent on reliable calibration sources. A novel method for correcting surface temperature observations made by uncooled TIR imagers uses observations over melting snow, which provides a constant 0 °C reference temperature. This bias correction method is applied to remotely sensed surface
temperature observations of forests and snow over two mountain study sites: Laret, Davos, Switzerland (27 March 2017) in the Alps, and Sagehen Creek, California, USA (21 April 2017) in the Sierra Nevada. Surface temperature retrieval errors that arise from temperature‐induced instrument bias, differences in image resolution, retrieval of mixed pixels, and variable view angles were evaluated for these forest snow scenes. Applying the melting snow‐based bias correction decreased the root‐mean‐square error by about 1 °C for retrieving snow, water, and forest canopy temperatures from airborne TIR observations. The influence of mixed pixels on surface temperature retrievals over forest snow scenes was found to depend on
image resolution and the spatial distribution of forest stands. Airborne observations over the forests at Sagehen showed that near the edges of TIR images, at more than 20° from nadir, the snow surface within forest gaps smaller than 10 m was obscured by the surrounding trees. These off‐nadir views, with fewer mixed pixels, could allow more accurate airborne and satellite‐based observations of canopy surface temperatures.

RAW and processed data can be found here: https://nevada.app.box.com/folder/172808842498

ABSTRACT:

The Automated Meteorology - Ice - Geophysics – Ocean observing System, (AMIGOS-III) is an autonomous multi-sensor station designed to support investigations of ice-ocean-atmosphere interactions in polar environments. It consists of a microprocessor running a simplified Linux operating system, with weather, GPS, accumulation, and surface melt, and includes a set of ocean and ice measurement sensors (CTD, doppler current flow, and DTS thermal profiler). Two stations are installed on the Thwaites Eastern Ice Shelf as of January 2020 and are still transmitting GPS data at this time.

RAW DTS and DAS data can be found here: https://nevada.app.box.com/folder/172261197639

ABSTRACT:

UAS Structure from Motion data were acquired at Palisades Ranch on the Mojave River for riparian restoration work being done by Mojave Desert Land Trust.

https://www.mdlt.org/palisadesranch/

Processed data can be found here: https://nevada.app.box.com/folder/173333914150

ABSTRACT:

Single-pass thermal and RGB Sfm imaging along eight, 1 km long segments of the Snoqualmie River near North Bend. Images were acquired with a 20 MP Sony RGB camera and and ICI 8640 thermal camera.

RAW and processed data can be found here: https://nevada.app.box.com/folder/22332682706

ABSTRACT:

If infrared mapping results are not definitive in identifying groundwater discharge locations, we will deploy another ground-based temperature measurement tool, a fiber optic distributed temperature sensor (FO-DTS), along specific areas of interest that have high potential for contaminated groundwater discharge. FO-DTS can be deployed directly on nearshore sediments along a 1 km stretch of shoreline and left in place for a few weeks to capture temperature changes over ranges of tidal cycles and sun/weather conditions (Henderson and others, 2009). FO-DTS measures temperature continuously along the length of the deployed fiber at a specified frequency, for example, every 15 minutes, so it provides highly refined temporal data along a transect, albeit not two-dimensional spatial data such as the infrared camera can provide. This work is conducted by Selker Metrics.

RAW DTS data can be found here: https://nevada.app.box.com/folder/172251130008

ABSTRACT:

We plan to evaluate the response of a near-surface horizontal geothermal exchange system improved with soil amendments. Soil amendments increase the thermal conductivity of background soils and therefore facilitate the transfer of heat from the thermal exchange pipe to the soil formation. During testing, we will be using distributed temperature sensing (DTS) arrays to monitoring the heat transfer response by heat flow from the thermal exchange pipe. We will measure the circumferential temperature field around the thermal exchange pipe at radial distances of 0.375 m and 0.75 m at 30-degree separations.

The model will be built on a 3 m by 3 m by 3 m soil pit, where 1.5 m of the thermal exchange pipe will be tested with background soil, and the other 1.5 m of the thermal exchange pipe will be tested with the amended soils. We will monitor the heat load and then the recovery of the system. Numerical models indicate that the testing will be a month-long. Additionally, to the temperature of the field, we will measure the flow in the geothermal exchange pipe and changes in the soil moisture during testing. The use of DTS will allow us having a density of measurements no afforded with other measurement systems. In this way, we will be able to calibrate numerical models that will include heterogeneity in the material and the heat transfer process and assess the response of amended soils in the design of more efficient geothermal exchange systems.

ABSTRACT:

Tethered balloon deployment to obtain data for atmospheric science research.

RAW DTS data can be found here: https://nevada.app.box.com/folder/172595215279

ABSTRACT:

This dataset presents physical parameters (temperature, Stokes and anti-Stokes Raman scattering signals) measured during the emplacement of bare single-mode optical fiber within the Greenland Ice Sheet using the Ice Diver melt probe at Summit Station, Greenland (specifically, at 72.5817 N, 38.4578 W). In addition to Stokes and Anti-Stokes signals, the dataset includes englacial temperature profiles derived via Raman distributed temperature sensing (DTS) at 1 m resolution, from ice depths -50 – 355 m (with 0 m representing the top of the borehole). The Raman backscatter signals (Stokes and Anti-Stokes) were captured by the ULTIMA Single Mode Distributed Temperature System (Silixa Ultima Single Mode interrogator) operating at a source wavelength of 1550 nm. Temperature data represent the first 108 hours of cooling (from June 7 – June 12, 2024) following melt probe entrapment in the ice at a depth of ~350 m. Temperature data were calibrated using a section of 25 m of the unreinforced fiber placed in an insulated controlled temperature bath during deployment. Two external PT-100 temperature probes were placed within the bath above and below the spool of fiber optic cable to monitor calibration bath temperatures. External temperature probes were an average of 1.5±0.2 °C warmer than the fiber optic cable. Data records are contained in three Excel spreadsheets (ice_diver_temperatures, Stokes_ice_diver and Anti_Stokes_ice_diver). The first column represents depth below the ice surface, with time in both standard and Matlab datenum format across the top of the spreadsheet.

For additional information contact: Scott Tyler styler@unr.edu; Dale Weinbrenner dpw@apl.washington.edu; Sophie Wensman Sophia.Wensman@dri.edu

ABSTRACT:

A transect using micrometeorological
instrumentation will be deploy over an almond orchard surrounded by dry
grasslands and urban landscape in Vacaville, California. The experiment
aims to quantify the role of heat sources from drylands driving higher ET
demands from agricultural orchards. The DTS would allow to better
understand the temperature transition in between the edge of these adjacent
landscapes, which it can lead to a better understanding of the magnitude
and scale of the interaction between these two landscapes.

ABSTRACT:

Experiment description: This project will collect and analyze spatially and
temporally detailed summer stream temperature data using a distributed
temperature sensing system in three sub-basins of the Tualatin river basin
for two summers where stream restoration and beaver dams are located.
Additionally, we will analyze basinwide stream temperature collected by
multiple agencies and collect riparian landscape variables that are likely
to be associated with the variation of stream temperature in order to
assess the effectiveness of restoration and beaver activities on stream
temperature in the study reaches. We will also create an interactive
website for visualizing spatial and temporal variation of stream
temperature for wide dissemination of the project findings.

ABSTRACT:

Little Bayou Creek is an 11-km long, first-order
stream in the lower Ohio River valley in McCracken County, Kentucky. The
creek’s ~ 24-km2 watershed includes part of the US Department of Energy’s
Paducah Gaseous Diffusion Plant (PGDP), which enriched uranium for use in
nuclear reactors; the Tennessee Valley Authority’s Shawnee Plant (a
coal-fired generating station); the state-run West Kentucky Wildlife
Management Area; and several small farms. Little Bayou Creek was originally
a tributary of the Ohio River, but between 1953 and 1971, the creek was
rerouted around ash ponds at the Shawnee Plant. Thereby, Little Bayou Creek
was channelized along its lower 2.5 km and connected to Bayou Creek, a
second-order perennial stream, 340 m southwest of the river. Flow of Little
Bayou Creek was partly sustained by discharge of process water from PGDP,
which obtained at least 498 L/s of water from the river via two pipelines.

With graduate students and other collaborators, I have conducted three
USDOE-funded studies of groundwater discharge to Little Bayou Creek
(1996-98, 1999-2003, and 2011-12). We observed focused discharge via seeps
and springs along the upper ~ 300 m of the channelized reach, where the
channel appears to have intersected preferential pathways within the
confining unit. Diffuse discharge was evident downstream where the channel
is incised into the semi-confined Regional Gravel Aquifer. During 19 days
in fall 2011, we deployed a FO cable with a CTEMPs Oryx DTS unit along the
head of the channelized reach, running the cable ~ 500 m along one bank and
then looping the cable back down the opposite bank. The DTS results
corroborated manual temperature probing and visual observations of seeps
and springs.

I am seeking to revisit these previous studies to examine changes in
groundwater discharge along the channelized reach of Little Bayou Creek
during the past 11 years. PGDP stopped uranium enrichment in 2013; the
Olmsted Lock & Dam was completed in 2018, raising Ohio River pool elevation
by 3.7 m; and TVA installed a sheet pile wall along ~ 850 m of the creek. I
envision running the DTS sequentially along three segments of ~ 1000 m for
periods of ~ 1 week each during June-July 2024, when temperature contrasts
between groundwater and stream water are likely to be pronounced. I
purchased a 1000-m FO cable from CTEMPs for our previous DTS study. We
intend to follow this new deployment with a year-long monitoring study of
groundwater discharge along the channelized reach of Little Bayou Creek.
This would involve quarterly stream gaging, tracer (dilution) tests,
sampling of stream water and seeps for solutes and stable isotopes of water
(for end-member mixing calculations), and real-time monitoring of discharge
rates at selected seeps.

ABSTRACT:

see attached

ABSTRACT:

The interplay of surface evolution, shallow magmatism, a large hydrothermal system,
and hazards at Puyehue-Cordon Caulle Volcanic Complex, Chile

see attached

ABSTRACT:

Experiment description: Life on Earth can often be found at the boundary
between two physical layers, as energy exchange often occurs at these
boundaries. One of the least studied interface is the ice-water boundary.
On Earth, the dynamic freezing environment of the ice-water interface leads
to an exchange of gases, ions, and other compounds that modulate the
habitability of both lake and marine environments. We proposed a study to
investigate the ice-water interface in a methane-enriched lake on the North
Slope of Alaska (Sukok lake). We plan to map and study the sources,
abundance, and transformation of methane up from lake sediments, into the
water column, into the ice, and ultimately its release to the atmosphere.
We plan to use a DTS system to measure the freeze-down of the lake with the
onset of Arctic winter. This will allow direct calibration of data
collected by the under-ice rover so that we can model the timing and
process of freeze down at high resolution. We’ll use a 1km cable wrapped
around a non-compressible composite pipe to deploy in the shallow, 2m lake.
The data collected at 1-2 mm-level resolution will be used to follow the
freezing front of the lake, in addition to recording ice vs. underlying
water temperatures throughout the winter. In addition the timing of spring
melt processes will also be recorded. This data will be combined with the
buoyant rover-collected data to derive freezing rate. The larger project is
studying the incorporation of solutes and microorganisms into the freezing
front, and the ice as a habitat.