A state agency's opinion on what salmon need to survive has water users warning of an economic disaster.
The State Water Resources Control Board has suggested greatly increased flows through the Sacramento-San Joaquin Delta.
That could mean a reduction of more than 40 percent in the amount of water that farms and cities take from the Tuolumne, Stanislaus and Merced rivers, one attorney involved in the issue said last week.
Water users say this would force an overreliance on wells and could even take farmland out of production.
"It's a huge hit to our water supply," said Jeff Barton, assistant general manager for civil engineering and water resources at the Turlock Irrigation District. "It would be devastating."
The suggested flows were in a report that lawmakers ordered last year as part of a package of bills aimed at fixing California's water system. The findings are not binding, but they could influence future decisions, board spokesman David Clegern said.
Environmentalists hailed the report as a key step toward restoring the delta, where Central Valley rivers meet before heading out to San Francisco Bay and the Pacific Ocean.
"This is something that really shouldn't be startling to anybody," said Zeke Grader, executive director of the Pacific Coast Federation of Fishermen's Associations. "There is solid science saying that to maintain this estuary, which is the most important on the west coast of two continents, it needs fresh water."
The members of his San Francisco-based group include commercial fishermen who have been out of work because of the recent plunge in salmon numbers.
Mike Jackson, an attorney for the California Sportfishing Protection Alliance in Stockton, also praised the report.
"These numbers make it clear -- as we have always believed -- that the delta needs substantially more water than it has been receiving over the last 30 years if it's going to survive," he said in a news release.
Flows cut in 19th century
The report is the latest of many dealing with the delta, where about 700 miles of channels wind amid about 60 levee-lined islands.
The flows were reduced by upriver diversions starting in the 19th century. This was compounded by the massive delta pumps that send water south.
A series of laws and court rulings has restored some delta flows, but environmentalists want more.
Most of the extra water would come from the Sacramento River and its tributaries. Some would be from the San Joaquin River and its feeders, including the Stanislaus, Tuolumne and Merced.
The latter rivers irrigate several hundred thousand acres of farmland in and near Stanislaus County. They also help supply domestic water to the region and to San Francisco and nearby cities.
Tim O'Laughlin, general counsel for the Modesto Irrigation District, explained the state board's suggested flows last week:
Under natural conditions, without dams or other diversions, about 6.13 million acre-feet of water would flow into the delta from the San Joaquin River and nearby streams in an average year. (An acre-foot covers an acre of land a foot deep.)
• Today, that flow averages about 3.03 million acre-feet because of the diversions.
• The main part of the state board's proposal would add 1.24 million acre-feet to this flow, 41 percent of what now goes to farms and cities.
The main releases would happen February through June, when the rivers under natural conditions would be running strong with storm runoff and snowmelt. This would help young salmon migrate toward the ocean, the report said.
This time of year also brings the start of irrigation season, when water managers like to see reservoirs rising. The releases would mean that Don Pedro Reservoir would never fill again, as it did this summer, O'Laughlin said.
The report suggests a smaller increase in October flows to help attract salmon returning from the sea to spawn.
Farmers could replace some of the river supplies by pumping groundwater, but it is expensive and uncertain, irrigation district officials say.
The river water that could be lost is enough to irrigate 125,000 to 200,000 acres of San Joaquin Valley farmland, O'Laughlin said. To put that in perspective, the MID and the TID together supply about 200,000 acres from the Tuolumne.
Water users could face even greater cutbacks in dry years so the fisheries get enough, he said.
O'Laughlin is working on the issue on behalf of several irrigation districts that lie east of the San Joaquin River.
Officials fear that they could face what happened in recent years in parts of the west valley, where drought combined with delta fish protections to reduce farming.
"When they lost water, they lost production, and then they lost jobs," MID General Manager Allen Short said. "It will replicate here if large amounts of land go out of production."
The economic damage would ripple to food processors and other employers, he said.
Water managers say factors other than stream levels are harming salmon and other native fish. They point to predation by non-native striped bass, pollution from sewage treatment plants and other sources, and poor conditions in the Pacific, where salmon spend most of their lives.
"It is a combination of a lot of things," Barton said. "There is no science out there that says that if we drain all of our reservoirs, the fish will return."
Grader said predators and pollution are factors but river flows matter most. He urges water agencies to increase efforts at conservation and reuse.
Steve Knell, general manager of the Oakdale Irrigation District, said the delta proposal would mean much less storage in New Melones Reservoir on the Stanislaus. That would hurt Tuol-umne County's visitor-based economy, he said.
Water officials note that under natural conditions, the rivers sometimes would run dry in summer. The reservoirs provide releases to keep them going, including the cold water that salmon and trout need.
The delta proposal, Knell said, "would kill the very thing they are trying to protect."
Storage means hydropower
Water officials say that keeping ample reservoir storage in summer means plenty of cheap hydropower during peak demand.
The report acknowledges the economic concerns and the possibility of nonflow factors affecting fish. But Clegern, the spokesman at the state board, said legislators told the authors to focus only on flows at this point.
The MID and its allies are gathering data on how a reduction in water supplies could affect employment, food prices and other indicators.
Short said the districts face several million dollars in legal costs in the coming years to counter advocates for increased flows.
"As far as I'm concerned," MID Director Paul Warda said, "I'm not going to give them one damned drop."
Bee staff writer John Holland can be reached at email@example.com or 578-2385.