The CALFED Bay–Delta Ecosystem Restoration Program: Complexity and Compromise *

The great Central Valley of California, ringed by mountains, has only one outlet: the San Francisco Bay/Sacramento-San Joaquin Delta estuary (Bay–Delta). The two largest rivers flowing to the Bay–Delta are the Sacramento and the San Joaquin. Smaller streams include the Mokelumne and Cosumnes Rivers. Together these rivers and smaller tributaries in the system drain an area of 158,000 km². Runoff is highly variable and ranges from less than 10 km³ to over 60 km³ annually, and has averaged 29.6 km³ per year (Monroe and Kelly, 1992). The estuary itself is a maze of braided channels, sloughs, and diked islands covering just less than 300,000 ha in five California counties (California Department of Water Resources, 1993). It is the largest estuary on the west coast of North America.