How Important is High Sierra Nevada Snowpack for Recharging the Central Valley Aquifers?

During dry years, notably the recent record-breaking droughts, California's communities and farms continue to depend on groundwater supply from deep Central Valley aquifers, and the resource is depleted to unprecedented levels. Aquifer recharge is an essential component of sustainable groundwater management plans. While the importance of the high Sierra Nevada snow melt for aquifer recharge is widely recognized, details of this connection are unclear. Here, we investigate geodetic, hydrologic, and climate datasets to study seasonal variations in groundwater resources. We apply a Wavelet multi-resolution analysis of all datasets to isolate their seasonal signal component. We examine the timing and amplitude of the various datasets to gain insight into seasonal recharge mechanisms, which indicate that the Sierra Nevada Mountains play a more prominent role in the recharge of California's deep Valley aquifers than previously assumed. Process-based model experiments further support our findings. We suggest that models used for groundwater management plans include the Sierra Nevada Mountains for accurate predictions of groundwater development impacts in the Central Valley.