USING CALIFORNIA’S DROUGHT TO QUANTIFY CONTRIBUTIONS TO GROUNDWATER STORAGE IN HIGH ELEVATION MEADOWS, YOSEMITE NATIONAL PARK

Scientific studies in high elevation meadows have focused on fluxes from snowmelt, streams, and hillslopes to support mountain meadows. Under normal hydrologic conditions these sources of water are the major contributors to groundwater storage in high elevations meadows. However, predicted of future climate scenarios suggest a reduction in snowpack and a shift to drier conditions. As a result of drier conditions, groundwater discharges from deep fractured bedrock sources, which are unaccounted for in current studies, are expected to be a larger percentage of the overall water balance. Using California’s multi year drought we are able to start to quantify groundwater contributions to Tuolumne meadows in Yosemite National Park from these deep bedrock sources. Through the use of a suite of naturally occurring geochemical tracers, we are able to identify the locations of discharge from fractured bedrock sources and develop mixing models to quantify the volume-fractured bedrock sources contribute to meadows. In normal water years these signals are masked by much larger geochemical signals produced from spring snowmelt. As a result of the reduced snowpack, contributions from deep fractured bedrock flowpaths represent a higher fidelity signal, which was only detectable due to the current California drought. These results will provide new field observations to support future hydrologic modeling investigations of the impact of both multi year drought and climatic shifts in snowpack on groundwater availability in high elevation meadows.