Observing the influences of critical zone architecture on streamflow generation processes: A granitic mountain-meadow headwater system in a Mediterranean climate
Abstract
Observations from a granitic watershed within a Mediterranean climate reveal the hydrologic and critical zone functioning of a perennial stream source and its upslope contributing area within a headwater meadow system in the Sierra Nevada, California. Chemical and physical data collected from stream measurements, piezometer clusters, monitoring wells, meteorological stations, subsurface geophysics, and a time-variable partitioning analysis indicate there are two primary pathways of water input into the meadow system. One input is a shallower and younger subsurface pathway that resembles snowpack chemistry, and the other a deeper and older subsurface pathway that reflects the chemistry of the groundwater derived from the contributing hillslopes. Multi-year observations reveal that regardless of snowpack amount, during the period of peak hillslope infiltration, shallow and deep pathways in the hillslope behave similarly to initiate headwater streams. But during late summer dry periods, similarities within the meadow center are not maintained between high and low snowpack years. With less snow, perennial groundwater discharge within the meadow center is eliminated, but subsurface flow still supports the perennial headwater source at the meadow's base. At the meadow's edge, geophysically-observed rises in the bedrock cause constrictions in the overlying saprolite creating co-located initiation points for headwater streams via enhanced groundwater discharge of upslope water. Combined, these findings suggest how critical zone structure can mediate hydrologic function in an endmember system dominated by crystalline lithology and a Mediterranean climate. Findings aid in explaining why sites may either continue or alter in their function as wet meadows under a changing climate, and elucidate new considerations for water resources and other environmental services tied to these mountain-meadow systems.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP43A..07C
- Keywords:
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- 1824 Geomorphology: general;
- HYDROLOGY;
- 1825 Geomorphology: fluvial;
- HYDROLOGY;
- 1830 Groundwater/surface water interaction;
- HYDROLOGY;
- 1856 River channels;
- HYDROLOGY