GROUNDWATER-SURFACE WATER INTERACTIONS IN MONTANE MEADOWS OF THE SIERRA NEVADA, CALIFORNIA

Meadows often lie in low gradient, groundwater fed terrain of the Sierra Nevada. These settings result in near saturated conditions for much of the year, shallow groundwater tables, and groundwater discharge to surface flow. Our hypothesis is that groundwater fluctuations integrate watershed processes rather than meadow specific processes. We utilize a series water column data from monitoring wells and piezometers in two meadows, soil moisture and snow depth data from nodes in the associated catchment, located within the Southern Sierra Critical Zone Observatory, from water years 2008-2012. Water samples from wells and associated streams were analyzed for major ions and stable water isotopes. Results from the monitoring wells and piezometers show groundwater tables and pressure heads that are highest during snowmelt and decrease over the summer growing season. Groundwater elevations exhibit diurnal fluctuations influenced by snowmelt and evapotranspiration (ET) processes in the spring, transitioning to an ET dominated signal during the summer growing season. These fluctuations are of greatest magnitude near the meadow-forest boundary and least near the center of the meadow. The piezometer data shows seasonal variation in the direction and magnitude of groundwater flux. Analysis of the geochemical data show that major ion concentrations vary little temporally; spatial variation is observed from the edge of the meadow to the center. Consistent groundwater discharge, with little variation in the geochemical profile of the groundwater, suggests a shallow groundwater source that is not being fully utilized by the adjacent forest landscape. These montane meadow systems provide a window for investigating groundwater surface water interactions in the catchments of the Southern Sierra Critical Zone Observatory.