The agency is taking a slightly different approach to mustering up 100,000 acre feet of water. It is asking farmers to either not irrigate with water from the Reclamation project, or to switch to irrigating with groundwater at the government's request, which could come any time during the growing season.

What percentage of the water will be banked from either approach isn't generally known until applications are turned in.

Reclamation spent about $7.6 million last year to buy the same amount of water, which was used to bolster spring flows on the lower Klamath River above what the agency's plan called for. This year, the program is open to nearly all surface-water users above Keno Dam, not just those part of the 200,000-acre federal project on the central California-Oregon border.

The program is part of 2002 demands by the National Marine Fisheries Service to increase river flows. Last March, the U.S. General Accounting Office waded into the water bank project, saying Reclamation was meeting its obligations, but needed to provide for greater transparency.

The GAO said that the water bank seems to have increased the amount of water available for salmon down river. But how the program might affect river diversions and groundwater use was questioned.

State and federal water agencies believe that drought-stricken aquifers aren't refilling as quickly as hoped following groundwater pumping, which in 2004 Reclamation relied heavily on to create the water bank, the GAO report read.

The bureau bought 50,000 acre feet from farmers in 2003, 75,000 acre feet in 2004 and 100,000 acre feet last year.

In October, Judge Dorothy W. Nelson of the 9th Circuit Court of Appeals ruled that Reclamation's 10-year plan meant to protect threatened coho salmon could wipe the fish out by 2010. The court sent the case back to district court to draft injunctive relief.