Suggested research on the effect of climate change on California water resources

Abstract

Quite significant changes in climate are being predicted for the latter part of this century due to global warming. The changes would be the result of increases in greenhouse gases from human activities, such as carbon dioxide, methane, and other trace gases. These potential changes are expected to affect many of our water resources systems. Some of the more important changes would be temperature increases which would raise temperate zone snow levels and change the pattern of runoff from mountain watersheds, thereby affecting reservoir operation. Other consequences would be sea level rise which could adversely affect the Sacramento San Joaquin River Delta, source of major water exports for the State; possibly larger floods and more extreme precipitation events; and changes in the water requirements of crops. By and large, reservoirs and water delivery systems and operating rules have been developed from historical hydrology on the assumption that the past is a good guide to the future. With global warming, that assumption may not be valid. This paper will briefly look at the major factors affecting water resources systems and go on to suggest eleven priority items of research. The emphasis will be on items important in California and other western states. In view of these forecasts of a significant change in future climate, with the author's knowledge of the existing water resources system in California, an analysis of potential effects and a list of higher priority research items has been developed. In summary, the list is as follows, and will be explained in more detail subsequently in the paper: --Monitoring of hydrologically important variables --Test operation of the Central Valley Project and State Water Project system with modified runoff --Modeling of future precipitation --Update depth-duration-frequency rainfall data --Evaluate Golden Gate Tide Gage datum --Catalog sea level trends along the coast, in San Francisco Bay and the Delta --Check for recent changes in evapotranspiration --Estimate future changes in evapotranspiration and crop water use. --Evaluate effect on major multipurpose flood control reservoirs --Water temperature modeling in major reservoir/river systems --Effect of climate change on regions adjoining California, such as the Colorado River and the Pacific Northwest.