FRESNO, Calif. - Gov. Arnold Schwarzenegger announced new measures Tuesday to protect the Sacramento-San Joaquin Delta, but farmers and environmentalists said they didn't go far enough to ensure they would have enough water to irrigate crops and protect a threatened fish species.

The interim plans - all of which build on existing programs - include boosting efforts to keep invasive plant and animal species from expanding in the freshwater estuary and installing screens to keep the delta smelt and other fish from being pumped onto the region's farm fields.

They also call for expanding the habitat of the threatened smelt and the plankton the three-inch-long fish consume. State and federal courts ruled this spring that water pumping operations in the delta were killing the smelt, forcing brief shutdowns that cut the flow of water to cities and farms.

"The pump shut-off along with the dry winter contributed so much to the water crisis that we have right now in our state," Schwarzenegger said while standing on one of the estuary's low-lying islands. "If we want to have a permanent solution to this problem, we have to think big."

The governor issued an executive order last year launching a comprehensive review of the delta and its problems, saying the state could no longer base its water-delivery system around the estuary because its mosaic of waterways could be crippled by floods and earthquakes.

Freshwater from Northern California's rivers is sent through the delta to about 750,000 acres of farmland and 25 million people in Southern California and the San Francisco Bay area.

In January, Schwarzenegger proposed asking voters to approve a $5.9 billion comprehensive water plan that includes spending $4.5 billion on two reservoirs, $1 billion to restore the delta and $450 million for water conservation efforts.

Two-thirds of the cost would be paid for by taxpayers and one-third by water users, including irrigation districts, municipalities and local taxpayers, said Department of Water Resources Deputy Director Jerry Johns.

On Monday, Schwarzenegger said the measure may appear on the Feb. 5 presidential primary ballot and that some of the money originally intended for the delta projects he outlined earlier this year would be used to explore building a canal that would divert water around the estuary.

The steps he proposed Tuesday are meant to improve the estuary's health in the meantime, he said.

They include ramping up scientific research on the smelt, stockpiling rock and sheet pilings in towns ringing the delta to safeguard against a levee collapse, and growing rice on the delta's islands as an experimental method for preventing them from sinking.

The immediate actions do not require additional funding, Johns said.

"This state has wrestled with delta issues for decades, and now is the time to get on with a long-term fix," said Lester Snow, director of the state Department of Water Resources.

The delta's crucial role in the state's water delivery system means any solution would have to address multiple - and sometimes opposing - interests.

Environmental groups said the measures announced Tuesday could help expand scientific understanding of the smelt, but might not be enough to save the species, which is considered a harbinger of the delta's health.

"Much more needs to be done," said Ann Hayden, a water analyst for Environmental Defense. "The future of the delta is at a crossroads and the smelt … are currently hanging in the balance."

Irrigation districts and urban water agencies that deliver much of the state's water said a comprehensive plan was needed - now.

"Water deliveries for some of our most productive farmlands are being drastically cut in a vain effort to protect the fisheries," said Randy Fiorini, president of Association of California Water Agencies. "(The delta) doesn't work for fish, it doesn't work for people."