Drought Resilience JAWRA Article

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION Vol�#S, No: '' AMERICAN WATER RESOURCES ASSOCIATION August 2009 DROUGHT RESILIENCE OF THE CALIFORNIA CENTRAL VALLEY SURFACE- GROUND - WATER - CONVEYANCE SYSTEM' Norman L. Miller, Larry L. Dale, Charles F. Brush, Sebastian D. Vicuna, Tariq N. Kadir, Emin C. Dogrul, and Francis L Chung ABSTRACT: A series of drought simulations were performed for the California Central Valley using computer applications developed by the California Department of Water Resources and historical datasets representing a range of droughts from mild to severe for time periods lasting up to 60 years. Land use, agricultural cropping patterns, and water demand were held fixed at the 2003 level and water supply was decreased by amounts rang- ing between 25 and 50 %, representing light to severe drought types. Impacts were examined for four hydrologic subbasins, the Sacramento Basin, the San Joaquin Basin, the Tulare Basin, and the Eastside Drainage. Results suggest the greatest impacts are in the San Joaquin and Tulare Basins, regions that are heavily irrigated and are presently overdrafted in most years. Regional surface water diversions decrease by as much as 70 %. Stream -to- aquifer flows and aquifer storage declines were proportional to drought severity. Most significant was the decline in ground water head for the severe drought cases, where results suggest that under these scenarios the water table is unlikely to recover within the 30 -year model - simulated future. However, the overall response to such droughts is not as severe as anticipated and the Sacramento Basin may act as ground -water insurance to sustain California during extended dry periods. (KEY TERMS: drought simulation; surface - ground -water response; pumping.) Miller, Norman L., Larry L. Dale, Charles F. Brush, Sebastian D. Vicuna, Tariq N. Kadir, Emin C. Dogrul, and Francis I. Chung, 2009. Drought Resilience of the California Central Valley Surface - Ground - Water- Conveyance System. Journal of the American Water Resources Association (JAWRA) 45(4):857 -866. DOI: 10.1111/j.1752- 1688.2009.00329.x INTRODUCTION The western United States (U.S.) has experienced periods of long drought conditions since the last glacial epoch 11,000 years ago. The period between 900 and 1400 A.D. was a time when severe long - duration droughts occurred in the western U.S. (Cook et al., 2004). This medieval mega- drought period was followed by a less severe drought period that was 'Paper No. JAWRA -08- 0063 -P of the Journal of the American Water Resources Association (JAWRA). Received April 9, 2008; accepted January 15, 2009. © 2009 American Water Resources Association. Discussions are open until six months from print publication. 2 Respectively, Staff Scientist and Adjunct Professor (Miller), Climate Science Department, Berkeley National Laboratory and Geography Department, University of California, Berkeley, California 90 -1116, One Cyclotron Road, Berkeley, California 94720; Staff Scientist (Dale), Energy Analysis Department, Berkeley National Laboratory, Berkeley, California 90 -4000, One Cyclotron Road, Berkeley, California; Water Resources Engineer, Senior Engineer, Water Resources Engineer, Principal Engineer, (Brush, Kadir, Dogrul, Chung), Modeling Support Branch, Bay -Delta Office, Department of Water Resources, 1416 9th Street, P.O. Box 942836, Sacramento, California 94236; and Graduate Student (Vicuna), Civil and Environmental Engineering Department, University of California, Berkeley, Davis Hall, Berkeley, California 94720 (E- Mail/Miller: nlmiller @lbl.gov). JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 857 JAWRA