ABSTRACT:

This file includes the data published in: Johnston, A.J., Runkel, R.L., Navarre-Sitchler, A. and Singha, K. (2017). Exploration of diffuse and discrete sources of acid mine drainage to a headwater mountain stream in Colorado, USA. Mine Water and the Environment, doi:10.1007/s10230-017-0452-6, 16 p.

We investigated the impact of acid mine drainage (AMD) contamination from the Minnesota Mine, an inactive gold and silver mine, on Lion Creek, a headwater mountain stream near Empire, Colorado. The objective was to map the sources of AMD contamination, including discrete sources visible at the surface and diffuse inputs that were not readily apparent. This was achieved using geochemical sampling, in-stream and in-seep fluid electrical conductivity (EC) logging, and electrical resistivity imaging (ERI) of the subsurface. The low pH of the AMD-impacted water correlated to high fluid EC values that served as a target for the ERI. From ERI, we identified two likely sources of diffuse contamination entering the stream: (1) the subsurface extent of two seepage faces visible on the surface, and (2) rainfall runoff washing salts deposited on the streambank and in a tailings pile on the east bank of Lion Creek. Additionally, rainfall leaching through the tailings pile is a potential diffuse source of contamination if the subsurface beneath the tailings pile is hydraulically connected with the stream. In-stream fluid EC was lowest when stream discharge was highest in early summer and then increased throughout the summer as stream discharge decreased, indicating that the concentration of dissolved solids in the stream is largely controlled by mixing of groundwater and snowmelt. Total dissolved solids (TDS) load is greatest in early summer and displays a large diel signal. Identification of diffuse sources and variability in TDS load through time should allow for more targeted remediation options.

ABSTRACT:

This file includes the data published in: Malenda, H.F., Sutfin, N.A., Stauffer, S., Guryan. G., Rowland, J.C., Williams, K.H., and Singha, K. (2019). From Grain to Floodplain: Evaluating heterogeneity of floodplain hydrostatigraphy using sedimentology, geophysics, and remote sensing. Earth Surface and Planetary Landforms, doi:10.1002/esp.4613.

Floodplain stratigraphy, a major structural element of alluvial aquifers, is a fundamental component of floodplain heterogeneity, hydraulic conductivity, and connectivity. Watershed-scale hydrological models often simplify floodplains by modeling them as largely homogeneous, which inherently overlooks natural floodplain heterogeneity and anisotropy and their effects on hydrologic processes such as groundwater flow and transport and hyporheic exchange. This study, conducted in the East River Basin, Colorado, USA, combines point-, meander-, and floodplain-scale data to explore the importance of detailed field studies and physical representation of alluvial aquifers. We combine sediment core descriptions, hydraulic conductivity estimates from slug tests, ground-penetrating radar (GPR), historical maps of former channels, LiDAR-based elevation and Normalized Difference Vegetation Index data to infer 3-D fluvial stratigraphy. We compare and contrast stratigraphy of two meanders with disparate geometries to explore floodplain heterogeneity and connectivity controls on flow and transport. We identify buried point bars, former channels, and overbank deposits using GPR, corroborated by point sediment descriptions collected during piezometer installment and remotely sensed products. We map heterogeneous structural features that should control resultant flow and transport; orientation and connectivity of these features would control residence times important in hydrologic models.

ABSTRACT:

Data from Wieting, C., Ebel, B., and Singha, K. (2017). Quantifying the effects of wildfire on changes in soil properties by surface burning of soils from the Boulder Creek Critical Zone Observatory. Journal of Hydrology-Regional Studies, http://dx.doi.org/10.1016/j.ejrh.2017.07.006, 43-57.

Infiltration processes are not well understood in fire-affected soils because soil hydraulic properties and soil-water content are altered by the heat. This study uses intact soil cores, which should maintain preferential flow paths, that were collected in the field to explore the impacts of fire on soil properties and infiltration processes during rainfall. Three soil scenarios are presented here: unburned control soils, and low- and high-severity burned soils. Fire severity was simulated in the laboratory using a heating gun, and established based on temperature and duration of heating. Soil properties pre- and post-burn were measured using laboratory techniques including: Mini Disk Infiltrometer tests, Water Drop Penetration Time (WDPT) Tests, and measurements of dry bulk density and total organic carbon (TOC). Soil moisture and temperature were recorded at approximately 2.5 cm and 7.5 cm in soil cores as was the cumulative volume of water exiting the core during rainfall simulations. Mini Disk infiltration experiments suggest a decrease in both cumulative infiltration and infiltration rates from unburned to low-severity burned soils. High-severity burned soils saw an increase in cumulative infiltration. We interpret these changes as a result of the burning off of organic materials, enabling water to infiltrate more instead of being stored in the organics. The field saturated hydraulic conductivity did not vary from unburned to low-severity burned soils, but increased in high-severity burned soils due to the lack of organics that help inhibit water movement. During rainfall simulations, soil-water storage decreased from when soils were burned, likely because of the inability to store water within organic materials since they were burned. Vulnerability to raindrop impact also increased with fire severity. Together, these results indicate that fire-induced changes from low-severity wildfires were not as drastic as high-severity wildfires, and that high-severity burned soils can infiltrate more water, but not necessarily store it. Quantifying soil properties affected by wildfire, which can be gained through controlled laboratory simulations like this study, will aid in predicting post-wildfire behavior on the watershed scale.

ABSTRACT:

This file includes the data published in: Mares, R., Barnard, H.R., Mao, D., Revil, A. and Singha, K. (2016). Examining diel patterns of soil and xylem moisture using electrical resistivity imaging. Journal of Hydrology, https://doi.org/10.1016/j.jhydrol.2016.03.003, 12 p.

The feedbacks among forest transpiration, soil moisture, and subsurface flowpaths are poorly understood. We investigate how soil moisture is affected by daily transpiration using time-lapse electrical resistivity imaging (ERI) on a highly instrumented ponderosa pine and the surrounding soil throughout the growing season. By comparing sap flow measurements to the ERI data, we find that periods of high sap flow within the diel cycle are aligned with decreases in ground electrical conductivity and soil moisture due to drying of the soil during moisture uptake. As sap flow decreases during the night, the ground conductivity increases as the soil moisture is replenished. The mean and variance of the ground conductivity decreases into the summer dry season, indicating drier soil and smaller diel fluctuations in soil moisture as the summer progresses. Sap flow did not significantly decrease through the summer suggesting use of a water source deeper than 60 cm to maintain transpiration during times of shallow soil moisture depletion. ERI captured spatiotemporal variability of soil moisture on daily and seasonal timescales. ERI data on the tree showed a diel cycle of conductivity, interpreted as changes in water content due to transpiration, but changes in sap flow throughout the season could not be interpreted from ERI inversions alone due to daily temperature changes.