California Basin Model

California Basin Model

This is a six day simulation of the California Basin using the coupled HydroGeoSphere and Weather Research and Forecasting models. 

Originally shared by Jason Davison

Integrated Hydrosystem Modeling of the California Basin

The Western United States is facing one of the worst droughts on record. Climate change projections predict warmer temperatures, higher evapotranspiration rates, and no foreseeable increase in precipitation. California, in particular, has supplemented their decreased surface water supplies by mining deep groundwater. However, this supply of groundwater is limited, especially with reduced recharge. These combined factors place California’s water-demanding society at dire risk. 

In an effort to quantify California’s risks, we present a fully integrated water cycle model that captures the dynamics of the subsurface, land surface, and atmospheric domains over the entire California basin. Our water cycle model combines HydroGeoSphere (HGS), a 3-D control-volume finite element model that accommodates variably-saturated subsurface and surface water flow with evapotranspiration processes to the Weather Research and Forecasting (WRF) model, a 3-D finite difference nonhydrostatic mesoscale atmospheric simulator. The two-way coupling within our model, referred to as HGS-WRF, tightly integrates the water cycling processes by passing precipitation and potential evapotranspiration data from WRF to HGS, while exchanging actual evapotranspiration and soil saturation data from HGS to WRF. Furthermore, HGS-WRF implements a flexible coupling method that allows each model to use a unique mesh while maintaining mass conservation within and between domains. Our simulation replicated field measured evapotranspiration fluxes and showed a strong correlation between the soil saturation (depth to groundwater table) and latent heat fluxes. Altogether, the HGS-WRF California basin model is currently the most complete water resource simulation framework as it combines groundwater, surface water, the unsaturated zone, and the atmosphere into one coupled system.

The simulation below illustrates the coupled model running for a six day time period. The first plot, Log Depth, is the surface water elevations over the entire basin in log base 10 units (so a value of -2 is actually 1 cm). The next plot illustrates Precipitation shown as meters per second. The third plot Evapotranspiration is the amount of water coming out of the surface and subsurface as evaporation and from plants (transpiration). The last plot is the change in soil moisture from the initial condition, these values are negative values because the soil is drying with time. 

I am presenting this research at the American Geophysical Union Tuesday, 15 December 2015 in San Francisco. Hope to see you there!

http://www.youtube.com/watch?v=IOZ_UMo6hg4//cdn.embedly.com/widgets/platform.js