By HEATHER COOLEY and JULIET CHRISTIAN-SMITH

For the Capital Press

California's cities and agricultural communities depend upon a reliable water supply. As California's population and economy grow, there is growing concern about the ability to meet future water demand amid pressure on our complex water systems.

There is no "silver bullet" solution to our water problems, as all rational observers acknowledge. Instead, we need a diverse portfolio of solutions. But the need to do many things does not mean we must, or can afford to, do everything. We must do the most effective things first.

A new Pacific Institute report, "California's Next Million Acre-Feet: Saving Water, Energy and Money," details how California can save 1 million acre-feet of water at a fraction of the cost of other new water supply options. About 30 percent, or 300,000 acre-feet, of these water savings come from urban water users, by replacing old, inefficient devices in our homes and businesses with high-efficiency models, as well as replacing some lawn area with low-water-use plants. The water savings represent a 3 percent reduction in total urban water use, based on the Department of Water Resources' 2005 estimate of urban applied water.

The remaining 700,000 acre-feet of water savings would come from a 2 percent reduction in agricultural water use, based on the Department of Water Resources' 2005 estimate of agricultural applied water. These savings come from measures some farmers are already using: weather-based irrigation scheduling, regulated deficit irrigation on appropriate crops, and switching from flood irrigation to sprinkler or drip irrigation systems.

But more can be done.

The agricultural efficiency improvements identified in the "California's Next Million Acre-Feet" report require an up-front investment of $575 million. Annual operation and maintenance costs associated with these measures would cost $47 million per year. All in all, the cost of conserved water for the agricultural measures would be $185 per acre-foot over the lifetime of the measure, significantly cheaper than most sources of new water supply. These costs could be shared by a combination of state and federal agencies, irrigation districts, energy utilities and individual farmers.

There are already several successful examples of programs at the federal and state levels to help finance these kinds of improvements, e.g., the Farm Bill's Agricultural Water Enhancement Program and state bond funding. These programs could be expanded.

Many different approaches will be required to fully address California's water supply issues, but in both the short and the long run, many are coming to the conclusion that it makes sense to invest in the most cost-effective things first. Water conservation and efficiency must be a central component of a portfolio of solutions for California's water problems. Water conservation and efficiency are the cheapest, fastest and least destructive sources of water.

In an era of increasing uncertainty, investing in cost-effective water conservation measures makes sense, particularly for farmers who are on the front lines of water shortages.

Heather Cooley is the water program co-director and Juliet Christian-Smith is a senior research associate at the Pacific Institute, a nonpartisan research institute in Oakland, Calif., that works to advance environmental protection, economic development and social equity.