Modeling Artificial Recharge in Coachella Valley, California: Historical Data, Model Approach, and Simulation Results

 

by Gerald T. O'Neill [1] , Eric M. LaBolle [2] , and Graham E. Fogg [3]

 

Abstract

 

A regional groundwater flow model of Coachella Valley, California, developed for testing the effects of various management alternatives on the groundwater resources, was used to simulate historical artificial recharge events in the upper part of the basin. Development of groundwater resources in the basin has steadily increased since the early 1900's. From 1936-73, water levels had declined nearly 100 ft in the Palm Springs area. Since 1973, significant artificial recharge has occurred from spreading basins located a few miles west of Palm Springs. The artificial recharge, combined with a few years of above average rainfall, reversed the declining trend in water levels in 1979, and by 1996, water levels in the Palm Springs area had increased over 80 ft to their early 1950's levels. The spreading basins overlie a thick gravel and sand alluvial aquifer. Infiltration through the vadose zone was not explicitly modeled, but recharge rates were sufficiently high (>1 ft/d) that effects on measured water levels were typically observed within a year. The regional flow model was calibrated to hydrologic conditions in the basin from 1936-96. The historical period was divided into fifty-one, mostly one-year, stress periods. Calibration focused primarily on estimation of the significant water budget terms, i.e., recharge and pumpage. Natural and artificial recharge rates were estimated along the Whitewater River stream channel and at the spreading basins. Parameter calibration was moderate and geologically based. The full 60 years of hydrologic record, including effects of major precipitation events and drought, pumping, agricultural drainage, and artificial recharge, was reproduced with unusual accuracy by the model. Results provide insights into the interplay between these major hydrologic phenomenon on a basin scale and highlight the impacts of the artificial recharge.

 

 

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[1] WellWare, Palo Alto, California

[2] University of California, Davis

[3] University of California, Davis