Spatiotemporal Variation in Chemical Fluxes across the Last Undammed Watershed Draining the Sierra Nevada, California: a Paired Basin Study
Abstract
The Cosumnes River is the last remaining river draining the Sierra Nevada without a major dam impounding its course. In order to determine the baseline biogeochemical characteristics of this free flowing river we have established an array of 28 sampling sites over the 2745 sq km of the watershed. Additionally 6 sampling sites have been located on the adjacent Mokelumne River both above and below the Pardee-Camanche Reservoir system. The Cosumnes has revealed seasonal chemical fluctuations that can be explained by variations in hydrologic flow paths and storm intensity/timing. Spatial variation in water quality within this system can be explained by changes in rock type, vegetation, and land use. The Mokelumne is a more hydrologically complex system with numerous dams and powerhouses. Consequently, seasonal and spatial variations in water quality can not be explained in the same manner as they are in the Cosumnes. The contrast in chemical dynamics between the two basins has given us the opportunity to study the influence that large dams have on water chemistry at the watershed scale. Our data show that the Pardee and Camanche Reservoirs act to buffer stream temperature, reduce total dissolved salts during storm events, and significantly alter the timing of nutrient discharge to the lowlands. Major dams, similar to those found on the Mokelumne, exist on 19 of the 20 rivers that drain into the Central Valley of California. Our data suggest that this ubiquity of large impoundments has drastically altered the spatiotemporal chemical dynamics of California's waterways.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.H52D0913A
- Keywords:
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- 1800 HYDROLOGY;
- 1803 Anthropogenic effects;
- 1806 Chemistry of fresh water;
- 1857 Reservoirs (surface);
- 1871 Surface water quality