May - June 2010
Vol. 73 No. 3


The potential for water conservation

Water consumption in California, both per capita and per ton of crops, has actually come down in the past 30 years. Farmers have been switching from water-intensive field crops to orchard and specialty crops requiring less water. Estimated per-household water use has dropped 36% between 1975 and 2009, according to a National Housing Foundation study, even as the state's population increased.

There is still room for great improvements in water efficiency. The Pacific Institute concluded in 2003 that "one third of California's current urban water use - more than 2.3 million acre-feet - can be saved with existing technology. At least 85% of this (more than 2 million acre-feet) can be saved at costs below what it would cost to tap into new sources of supply and without the many social, environmental, and economic consequences that any major water project will bring." Residential indoor and outdoor water use and the combined commercial, industrial, and institutional sectors could each be brought down by as much as 39%. A detailed 2006 CalFed analysis determined the urban potential for conservation at 1.2 - 2.1 million acre-feet per year.

Several recent policy changes may speed urban water conservation. SBx 7 7 requires utilities statewide to reduce urban water use 20% by 2020 (see article, page 10). A revamped Model Landscape Ordinance limits water consumption of new landscaping (see article, page 12). The California Green Building Code going into effect in 2011 requires water-conserving features for new construction.

While graywater- and rainwater-harvesting systems (see article, pages 12 - 13), will provide some reductions in potable-water use, more-efficient fixtures and appliances will have the quickest and most far-reaching effects. Toilet flushing is an easy area for significant improvements. Since 1994, federal law has required new toilets to use no more than 1.6 gallons per flush. But there is still wide potential for installing ultra-low flush and dual-flush toilets in existing buildings. Hot-water recirculation systems, and more-efficient clothes washers also reduce residential water use significantly. Aggressive in-home and utility-wide leak detection and elimination can bring large savings.

Smart irrigation technology and water-wise landscape design offer great conservation potential in landscape irrigation. In the longer term, lifestyle and behavioral changes will play an important role.

Most utilities continue to offer rebates for efficient fixtures, appliances, and irrigation sytems. Some offer incentives for graywater reuse and turf replacement. These programs have not reached their hoped-for potential. Some officials believe the savings potential to be "maxed out", but we urge them to think further about ways to encourage wider participation.

According to the Pacific Institute, agriculture could realize significantly larger conservation gains than urban use, "between 4.5 million acre-feet in a wet year and 6.0 million acre-feet in a dry year", by implementing currently available irrigation management and technology. Useful strategies include drip and micro-spray irrigation, mulching, stemming leaks, more precise irrigation scheduling, and crop shifting.

The Pacific Institute has expressed water savings as "dam equivalents". At an assumed 174,000 acre feet of water per dam, their potential urban and agricultural water savings taken together could yield as much water as 37 - 45 new dams. What's more, they conclude, "water savings achieved through conservation and efficiency improvements are just as effective as new, centralized water storage and are often far less expensive."