Linking Central Valley Deep Aquifer Recharge and High Sierra Nevada Snowpack

Abstract

California’s arid Central Valley relies on groundwater pumped from deep aquifers and surface water transported from the Sierra Nevada to produce a quarter of the United States’ food demand. The natural recharge to deep aquifers is thought to be regulated by the adjacent high Sierra Nevada mountains, but the underlying mechanisms remain elusive. We investigate large sets of geodetic remote sensing, hydrologic, and climate data and employ process-based models at annual time scales to investigate possible recharge mechanism. Peak annual groundwater storage in the Central Valley lags several months behind that of groundwater levels, which suggests a longer transmission time for water flow than pressure propagation. We further find that peak groundwater levels lag the Sierra Nevada snowmelt by about one month, consistent with an ideal fluid pressure diffusion time in the Sierra’s fractured crystalline body. This suggests that Sierra Nevada snowpack changes likely impact freshwater availability in the Central Valley aquifers. Our datasets, analysis and process-based models link the current precipitation and meltwater in the high mountain Sierra to deep Central Valley aquifers through the mountain block recharge process. We call for new hydroclimate models to account for the role of the Sierra in California’s water cycle and for revision of the current management and drought resiliency plans.

Drought Characterization with GPS: Insights into Groundwater and Reservoir Storage in California

“…In addition, intensities of meteorologic and hydrologic drought are rarely equivalent with variation in hydrologic drought lagging meteorologic drought due to runoff, evapotranspiration, and the time scales of drainage basin dynamics and aquifer recharge (Barker et al, 2016;Entekhabi et al, 1992;Lin et al, 2023;Werth et al, 2023). In other words, the unique behaviors and geographic contexts of each watershed affect TWS and hydrological drought, but do not impact meteorological assessments of drought.…”

“…north versus south here) may be representative of variations in groundwater aquifer characteristics including material properties and anthropogenic effects. Thus, time scales of 1-to 3-months in northern California (primarily driven by northern Central Valley wells) are likely to reflect a combination of agricultural pumping and recharge driven by precipitation and snowpack in the Sierra Nevada mountains (Werth et al, 2023). Moreover, the longer 12-month time scale in southern California (driven by Coastal Basin aquifer wells) are likely to reflect a greater dependence on natural aquifer recharge dynamics rather than agricultural effects.…”