Abstract
The study introduces a new atmosphere-land-aquifer coupled model and evaluates terrestrial water storage (TWS) simulations for Southern California between 2007 and 2016. It also examines the relationship between precipitation, groundwater, and soil moisture anomalies for the two primary aquifer systems in the study area, namely the Coastal Basin and the Basin and Range aquifers. Two model designs are introduced, a partially-coupled model forced by reanalysis atmospheric data, and a fully-coupled model, in which the atmospheric conditions were simulated. Both models simulate the temporal variability of TWS anomaly in the study area well (R2 ≥ 0.87, P < 0.01). In general, the partially-coupled model outperformed the fully-coupled model as the latter overestimated precipitation, which compromised soil and aquifer recharge and discharge. Simulations also showed that the drought experienced in the area between 2012 and 2016 caused a decline in TWS, evapotranspiration, and runoff of approximately 24%, 65%, and 11%, and 20%, 72% and 8% over the two aquifer systems, respectively. Results indicate that the models first introduced in this study can be a useful tool to further our understanding of terrestrial water storage variability at regional scales.
Highlights
Terrestrial water storage (TWS) is defined as the summation of water on the land surface and in the subsurface
This study introduces a new atmosphere-land-aquifer coupled model formed by the Weather Research and Forecasting (WRF), the Simplified Simple Biosphere (SSIB), and the Simple Groundwater (SIMGM)
We introduced two versions of a new atmosphere-land-aquifer modeling system and described the performance of simulated TWS anomalies in Southern California during a 10-year period marked by drought conditions
Summary
Terrestrial water storage (TWS) is defined as the summation of water on the land surface and in the subsurface It includes soil moisture and groundwater, as well as water stored in vegetation and snow. The ability to estimate TWS accurately is essential for hydrological studies and water resource assessment, in arid and semi-arid regions where access to rainfall-fed surface water storage is limited These areas are vulnerable to climate extremes, such as droughts, which often further deteriorate TWS through enhanced evaporative losses and increased groundwater extraction [1,2,3]. The region of Southern California, located along the west coast of North America between the latitudes 31◦ N and 36◦ N, is mainly characterized by a semi-arid and mild-winter Mediterranean climate This region has experienced a rapid population growth over the last 50 years [4], which has continuously increased the demand for agricultural and urban water uses in the region. Variations in TWS in the region are primarily driven by changes in soil moisture and groundwater contents
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