San Francisco Estuary and Watershed Science

The goal of this paper is to analyze storage projects constructed and planned in California since 1980, in contrast with storage constructed before that date. As a result of California’s highly variable climate, storage is an essential tool for agricultural and urban water users. Today, the state regulates approximately 1,250 reservoirs, with a combined storage of 42 million acre-feet. Federal agencies regulate approximately 200 additional reservoirs. The vast majority of this surface storage was constructed before 1978, when New Melones Dam, the last large on-stream water supply reservoir in California, was completed. The role of storage in meeting future needs remains a high-profile issue in the California water debate. For example, funding for new storage was the largest item in Proposition 1, the most recent water bond voters approved. This analysis included a review of existing literature, such as the California Department of Water Resources Division of Dam Safety database, California Water Commission documents about new storage proposals, water agency documents, and interviews with water agency staff and others. Water managers face dramatically different conditions today, in comparison to conditions before 1980. These conditions have led to new approaches to water storage that represent a dramatic departure from past storage projects. During the past 37 years, a wide range of new water storage strategies have been planned and implemented. These facilities have created a combined new storage capacity greater than that of Lake Shasta, California’s largest reservoir. These new storage strategies suggest the need to revisit the fundamental definition of water storage. With limited potential for new storage drawing from the state’s rivers, California must choose storage projects wisely. By learning from successful strategies in recent decades, decision-makers can make better storage investment decisions to help reverse declines in ecosystem health and improve water supply reliability.