Where To Find 1 Million Acre-feet of Water for California

This story first appeared on SFGate.com.

Californians have improved their efficiency of water use over the past 25 years. The state's economy and population have grown. But total water use has not grown, and per person, each Californian uses far less today. This improvement in efficiency has saved the state's collective rear end. So far.

But plenty of water problems still remain, despite the welcome rains of the past week. Current water use is still too wasteful, as I've discussed many times in this column. Here are just two examples: Even today, after California's conservation efforts, over 60% of all toilet flushes are done by toilets whose flows are well above national standards, suggesting that many old inefficient fixtures remain in homes. More than 75% of all crops in California are still grown with inefficient flood or sprinkler irrigation systems.

The Pacific Institute has completed a series of independent reports on urban and agricultural water efficiency that provide a comprehensive statewide analysis. (See "Waste Not, Want Not: The Potential for Urban Water Conservation in California" and "Sustaining California Agriculture in an Uncertain Future.") Our findings have been adopted by the California Department of Water Resources in the California Water Plan. These studies show that existing, cost-effective technologies and policies can readily reduce current state demand for water by 6 to 8 million acre-feet per year, or around 20%. Governor Schwarzenegger's recent call for a 20% reduction in water use by 2020 is thus based on sound science and economics, even if the policies to achieve such savings are not yet in place. The recent water bill takes weak steps toward an urban savings of 20%, and it lets the agricultural sector completely off the hook.

Water Number: One million acre-feet of water per year. In a few weeks, the Pacific Institute will release a new assessment of how to save one million acre-feet of water, split 60/40 among agricultural and urban users, quickly and cost effectively. Here is an advanced look at some of our findings:

-- 400,000 acre-feet of water per year can be quickly conserved by urban users by replacing only some of the many remaining inefficient toilets, showerheads, commercial spray-rinse nozzles, and washing machines. These savings would require an investment of under $2 billion. And over the life of these fixtures the energy, water, and wastewater savings will far exceed that initial investment. Just for comparison, the proposed Temperance Flat Dam will cost an estimated $3.3 billion dollars and produce well under 200,000 acre-feet of water annually. [Some analysts think it will produce less than 100,000 acre-feet/year and cost far more than $3.3 billion.]

-- Another 600,000 acre-feet per year of water can be saved by applying smart irrigation scheduling to 30% of the state's vegetable and 20% of the orchard acreage, practicing regulated deficit irrigation on 20% of current almond and pistachio acreage in the Sacramento Valley, and converting 20% of Central Valley vegetables and 10% of orchards and vineyards to drip and sprinklers. These changes would save water at a cost of around $100 per acre-foot.

These savings are just the tip of the iceberg: far more water could be saved at far less cost than any proposed new supply option.

California's total water use in 2020 could be 20% below current levels while still satisfying a growing population, maintaining a healthy agricultural sector, and supporting a vibrant economy. Some of the water saved could be rededicated to agricultural production elsewhere in the state; support new urban and industrial activities and jobs; and restore California's stressed rivers, groundwater aquifers, and wetlands -- including the Sacramento-San Joaquin Delta, where fisheries and farmers are under pressure.