Assessing recent and near-future changes in Southern California’s groundwater storage from the perspective of regional modeling

Authors: Fernando De Sales*, San Diego State University, David Rother, San Diego State University
Topics: Climatology and Meteorology, Water Resources and Hydrology, Physical Geography
Keywords: Water resources, groundwater, climate change
Session Type: Paper
Day: 4/10/2018
Start / End Time: 12:40 PM / 2:20 PM
Room: Mid-City, Sheraton, 8th Floor
Presentation File: No File Uploaded

Current climate change assessments project an increase in temperature throughout the western U.S. over the next century, while precipitation is projected to decrease in the Southwest. These assessments are based mainly on coarse spatial resolution general circulation model simulations, which do not include groundwater (soil and aquifer) storage projections. However, water availability is a regionally variable resource and climate change impacts on groundwater distribution will probably differ regionally across the southwestern U.S.

We have implemented a coupled atmosphere-biosphere-aquifer regional modelling system (WRF/SSiB2/SIMGM) to generate present-day (2005-2017) and near-future (2018-2030) high-resolution groundwater projections for Southern California and adjacent areas. These projections are obtained by dynamic downscaling data from the present-day climate data, and the IPCC CMIP5 near-future climate projections. Near-future climate simulations include three IPCC representative concentration pathway (RCP) scenarios.

The coupled model can reasonably simulate the recent changes in Southern California’s groundwater as indicated by a comparison against terrestrial water storage obtained from the NASA Gravity Recovery and Climate Experiment (GRACE) dataset. In particular, the 2011-2016 California drought is simulated well with total groundwater storage declining, especially over the eastern portions of Southern California, which includes several high-populated urban centers.

In addition to the groundwater estimates, the WRF/SSiB2/SIMGM dynamic downscaling also provides high-resolution regional precipitation and surface temperature near-future projections. We believe these high-resolution regional projections can provide additional information to policy makers in the development of strategies to alleviate potential water resource deficiencies in Southern California in the near future.

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