From The SF Chronicle:
The Sonoma County Water Agency was directed by the State Water Resources Control Board on Wednesday to reduce its water diversions from the Russian River by 15 percent to protect the fall spawning of salmon. That order spurred Thursday's restrictions, which will be implemented by individual water districts and other entities that get water from the agency.
While flows in the Russian River are down because of the dry winter, Sonoma's situation is complicated by reduced flows into one of its reservoirs, Lake Mendocino, because of changed federal licensing requirements for a Pacific Gas and Electric Co. hydroelectric power plant upstream.
In Santa Clara County, about half of the water supply comes from reservoirs and aquifers and the other half from the Sacramento-San Joaquin River Delta. Supplies from the delta have been cut because of restrictions at pumping stations to protect the delta smelt, a tiny fish on the brink of extinction.
It looks like next year could be pretty bad if CA doesn't have an above average rainfall...