ABSTRACT:

There is still limited understanding of how waters mix, where waters come from and for how long they reside in tropical catchments. In this study, we used a tracer-aided model (TAM) and a gamma convolution integral model (GM) to assess runoff generation, mixing processes, water ages and transit times (TT) in the pristine humid tropical rainforest Quebrada Grande catchment in central Costa Rica. Models are based on a four-year data record (2016 to 2019) of continuous hydrometric and stable isotope observations. Both models agreed on a young water component of fewer than 95 days in age for 75% of the study period. The streamflow water ages ranged from around two months for wetter years (2017) and up to 9.5 months for drier (2019) years with a better agreement between the GM estimated TTs and TAM water ages for younger waters. Such short TTs and water ages result from high annual rainfall volumes even during drier years with 4,300 mm of annual precipitation (2019) indicating consistent quick near-surface runoff generation with limited mixing of waters and a supra-regional groundwater flow of likely unmeasured older waters. The TAM in addition to the GM allowed simulating streamflow (KGE > 0.78), suggesting an average groundwater contribution of less than 40% to streamflow. The model parameter uncertainty was constrained in calibration using stable water isotopes (δ2H), justifying the higher TAM model parameterization. We conclude that the multi-model analysis provided consistent water age estimates of a young water dominated catchment. This study represents an outlier compared to the globally predominant old water paradox, exhibiting a tropical rainforest catchment with higher new water fractions than older water.

ABSTRACT:

Global bottled water consumption has largely increased (14.35 billion gallons in 2020) during the last decade since consumers are demanding healthier and safer forms of rehydration. Bottled water sources are normally labeled as mountainous and pristine mineral springs (fed by rainfall and snow/glacier melting processes), deep groundwater wells or industrial purified water. The advent of numerous international and national-based bottled water brands has simultaneously raised a worldwide awareness related to the water source and chemical content traceability. Here, we present the first database of stable isotope compositions and reported chemical concentrations from imported and national-based bottled waters in Costa Rica. In total, 45 bottled waters produced in Costa Rica and 31 imported/produced from USA, Europe, Asia and other countries of Central America were analyzed for δ18O, δ2H, and d-excess. Reported chemical compositions were obtained from available bottle labels. National-based bottle waters ranged from -2.47‰ to -10.65‰ in δ18O and from -10.4‰ to -78.0‰ in δ2H, while d-excess varied from +4.2‰ up to +17.0‰. International bottle waters ranged between -2.21‰ and -11.03‰ in δ18O and from -11.3‰ up to -76.0‰ in δ2H, while d-excess varied from +5.0‰ up to +19.1‰. In Costa Rica, only 19% of the brands reported chemical parameters such as Na+, K+, Ca+2, Mg+2, Fe+2/+3, F-, Cl-, NO3-, SO4-2, CO3-2, SiO2, dry residue, and pH; whereas 27% of the international products reported similar parameters. The absence of specific geographic coordinates or water source origin limited a spatial analysis to validate bottled water isotope compositions versus available isoscapes in Costa Rica. This information highlights the potential and relevance of the use of water stable isotope compositions to improve the traceability of bottled water sources and the urgent need of more robust legislation in order to provide detailed information (i.e., water source, chemical composition, purification processes) to the final consumers.

ABSTRACT:

Tropical peatlands are distributed mainly in coastal lowlands; however high elevation regions include a large prevalence of small and fragmented peatlands that are mostly understudied. Anthropogenic pressure to expand cattle farming, agriculture, and urbanization frontiers via artificial drainage of peatlands is increasing carbon losses to the atmosphere and streams. Here we present, the first characterization of dissolved carbon optical properties in ombrotrophic peat bogs of the Talamanca range of Costa Rica, across an altitudinal gradient (2,400-3,100 m asl) during the rainy season. Dissolved organic matter (DOM) sources and decomposition processes were evaluated in the light of dissolved organic and inorganic carbon (DOC and DIC), optical properties, excitation-emission matrices (EEMs), and major water chemistry. DOC concentrations ranged from 0.2 mg/L up to 47.0 mg/L, with a mean value of 12.5 ± 10.2 mg/L. DIC concentrations were below 2 mg/L and δ13CDIC values indicated a mixture between soil organic matter, CO2 in soil water, and in less degree DIC derived from bacterial CO2. Fluorescence intensity of humic-like peaks was 6-7 times greater than fresh-like peaks across all sites. Fluorescence peak ratios coupled with the biological and humification indexes point to a greater relative contribution of recalcitrant soil-derived DOM. EEMs denoted a high prevalence of humic and fulvic acids in the peat bogs, with particular high intensities in soluble microbial by-products-like and aromatic protein regions at three sites. Rainfall variability plays a remarkable role in controlling (acid and anoxic conditions) carbon storage and humification processes. Our data provides a baseline to underpin tropical carbon dynamics across high elevation peatlands.

ABSTRACT:

Groundwater recharge in highly-fractured volcanic aquifers remain poorly understood in the humid tropics, whereby rapid demographic growth and unregulated land use changes are resulting in extensive surface water pollution and a large dependency on groundwater extraction. This database presents a multi-tracer approach including δ18O-δ2H, 3H/3He, and noble gases within the most prominent multi-aquifer system of central Costa Rica, with the objective to assess dominant groundwater recharge processes. Wells and large springs were sampled across an elevation gradient from 868 to 2,421 m asl.

ABSTRACT:

The inter-mountainous region of central Honduras has been experiencing abrupt urban water shortages during the last decade. Land use fragmentation to increase pasture, crop, and peri-urban areas has rapidly reduced surface water quantity and quality. Here we present a 3-yr (2018-2020) water stable isotopes database within the headwaters of the Choluteca River basin (2,949 km2). We sampled rainfall (weekly N=156; daily N=270), drilled wells (N=166; up to 300 m depth), boreholes (N =70; 4-12 m depth), and springs (N=128) to assess the spatio-temporal connectivity between rainfall and groundwater recharge elevations (MREs).

ABSTRACT:

Here we report on the spatial and temporal isotope variations of 21 precipitation monitoring stations across Mexico. Our database includes 608 monthly samples collected from 2018 to 2021 over four main domains (between 5 and 2,365 m asl): the Pacific coast, the Gulf of Mexico/Caribbean Sea region, and the Central and Northern Plateaus. All linear regressions and statistical diagnostics were computed using R (R Core Team, 2022). The nationwide isotopic lapse rate (-1.75‰ in δ18O/km) (including monitoring sites influenced by tropical cyclones (TCs) (Loreto, Culiacan, and Hermosillo) explained 65% (p<0.001) of the total variance. The direct influence of TCs passages and landfalls across the Pacific coast resulted in depleted monthly compositions in low-elevation coastal sites. By removing these sites, the isotopic lapse rate increased to -2.20‰ in δ18O/km (85% of the total variance explained, p<0.001). The precipitation-weighted isotope lapse rate (including all sites) resulted in a similar slope -2.10‰ in δ18O/km (72% of the total variance explained, p<0.001). Raster interpolations were performed in ArcGIS 10.8.1 (ESRI, USA) using a 10m digital elevation model.

ABSTRACT:

Here we report on the spatial and temporal isotope variations of 21 precipitation monitoring stations across Mexico. Our database includes 608 monthly samples collected from 2018 to 2021 over four main regions (between 5 and 2,365 m asl): the Pacific coast, the Gulf of Mexico/Caribbean Sea region, and the Central and Northern Plateaus.

ABSTRACT:

This dataset describes isotopic and ionic data across a tropical and volcanic multi-aquifer system in central Costa Rica, where springs and wells across an altitudinal range (~800 to 2,400 m asl).

ABSTRACT:

This database documents the isotopic characteristics of 40 tropical cyclones (ranging from tropical depressions/storms to Category 5 hurricanes), including recent (2012-2023) and archived (1984-1995) observations. This database is part of the isotope tempestology collaborative research network (2016-present) (known as STORM; https://tropicalwaterscr.wixsite.com/hydro/storm) across the North Atlantic and Eastern Pacific Ocean basins. This initiative has been centered mainly on collecting and analyzing recent high-frequency (hourly to daily) samples of precipitation (P), surface water (SW), and groundwater (GW) during TC landfalls and passages to improve the understanding of isotope tempestology processes.