IGCP 565 Project Workshop

IGCP 565 Workshop 1: Science of geodetic monitoring of the hydrological cycle

Abstract:

California Drought Scenario Modeling and Uncertainties
Norman Miller
Lawrence Berkeley National Laboratory and University of California, Berkeley

A fundamental requirement for drought water management is knowledge of the total groundwater resources and the rate in which it is depleted. Application of remote sensed Gravity Recovery and Climate Experimet (GRACE) represents an important new approach toward quantifying these values. The primary uncertainties are spatial scale required for an accurate GRACE analysis and an insufficient number and frequency of well observations for ground-truth. In this study, an initial quantification of long-term droughts - an analogue for climate change related snowpack reduction – has been performed to illustrate the potential for subsurface storage to limit the adverse impacts of drought and snowpack reduction on water supply in the California. This includes estimates of the impacts of changes in groundwater levels, surface supply, and crop water demands. Analysis of California Central Valley impacts of sustained droughts are based on a series of specified reductions in net surface flows corresponding to historical 30% (below average), 50% (dry), and 70% (critically dry) effective reduction, for periods ranging from 10 to 60 years, and applied to the California Department of Water Resource’s California Central Valley Groundwater-Surface Water Simulation Model (C2VSIM). The impacts of the droughts are modeled for four different regions in the Central Valley, including the Sacramento Basin, Eastside, the San Joaquin Basin, and the Tulare Basin. Initial results show that drought scenario impacts are concentrated in the San Joaquin and Tulare Basins The Sacramento Basin and Eastside regions experience comparatively small changes in surface diversions during droughts.