Field estimates of groundwater circulation depths in two mountainous watersheds in the western U.S. and the effect of deep circulation on solute concentrations in streamflow
| Autor: | Marty D. Frisbee, Douglas G. Tolley, John L. Wilson |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Hydrology
geography Hydrogeology Watershed geography.geographical_feature_category 010504 meteorology & atmospheric sciences Groundwater flow Bedrock 0208 environmental biotechnology 02 engineering and technology 01 natural sciences 020801 environmental engineering Tectonics Streamflow Groundwater discharge Geomorphology Groundwater Geology 0105 earth and related environmental sciences Water Science and Technology |
| Zdroj: | Water Resources Research. 53:2693-2715 |
| ISSN: | 0043-1397 |
| Popis: | Estimates of groundwater circulation depths based on field data are lacking. These data are critical to inform and refine hydrogeologic models of mountainous watersheds, and to quantify depth and time dependencies of weathering processes in watersheds. Here we test two competing hypotheses on the role of geology and geologic setting in deep groundwater circulation and the role of deep groundwater in the geochemical evolution of streams and springs. We test these hypotheses in two mountainous watersheds that have distinctly different geologic settings (one crystalline, metamorphic bedrock and the other volcanic bedrock). Estimated circulation depths for springs in both watersheds range from 0.6 to 1.6 km and may be as great as 2.5 km. These estimated groundwater circulation depths are much deeper than commonly modeled depths suggesting that we may be forcing groundwater flow paths too shallow in models. In addition, the spatial relationships of groundwater circulation depths are different between the two watersheds. Groundwater circulation depths in the crystalline bedrock watershed increase with decreasing elevation indicative of topography-driven groundwater flow. This relationship is not present in the volcanic bedrock watershed suggesting that both the source of fracturing (tectonic versus volcanic) and increased primary porosity in the volcanic bedrock play a role in deep groundwater circulation. The results from the crystalline bedrock watershed also indicate that relatively deep groundwater circulation can occur at local scales in headwater drainages less than 9.0 km2 and at larger fractions than commonly perceived. Deep groundwater is a primary control on streamflow processes and solute concentrations in both watersheds. |
| Databáze: | OpenAIRE |
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