SAN FRANCISCO - CALIFORNIANS' thirst for water has pushed salmon and other fish to the brink of extinction, a federal agency ruled on Thursday as it directed officials to cut water supplies to cities and farms to save several species.

California's rivers used to brim with trout, salmon, sturgeon and more, but the federal, state and local governments built a monumental system of dams and pipelines in the most populous that turned a desert into productive farmland and left some rivers dry.

The state faces a water crisis and a third year of drought. Add climate change and a growing population to the mix, and the fate of some salmon runs looks untenable without change, the National Marine Fisheries Service said in a report ordered as part of a long-running court battle over the salmon.

It called for a 5 per cent to 7 per cent cut in water diversions for cities and agriculture from key state and federal water suppliers. Water conservation, recycling and groundwater use could offset the cuts, the report said, but water agencies described a tougher situation.

That reflects a larger argument about whether the state can conserve its way out of crisis or should build more dams and canals to capture the last trickles that bypass the system.

The fisheries agency plan is to keep more water behind big dams during the year to ensure a supply of cold water in which salmon spawn, restrict some pumping, and find ways for fish to get to historical spawning grounds upriver from dams.

That could range from fish ladders to catching fish and trucking them up and around a dam.

The National Resources Defence Council, an environmental advocacy group, said the ruling was a step in the right direction, that water cutbacks were manageable, and that the state would have to make them with or without the fish.

The State Water Contractors association criticized the approach. -- REUTERS