Global Warming Imperils State Water Supply, House Panel Told

The global warming trend could cripple California’s water supply by the end of the century if “radical adjustments,” such as expanding reservoirs, are not made, engineers and scientists told a House hearing Tuesday.

“This looks like a potential disaster,” said Rep. George Miller (D-Calif.), who chaired the hearing, after listening to testimony that temperature increases could reduce the water available for the summer irrigation season.

“The thesis is that you’re going to have reduced snow pack due to the warming,” John A. Dracup, professor of civil engineering at UCLA, said in an interview after testifying before the House interior subcommittee on water and power resources. That means there will be more runoff during the winter and less during the summer. To protect the winter runoff from evaporation and winter flooding, he said, California must build larger surface reservoirs, make better use of existing water resource supplies and expand underground reservoirs.

“Our whole system is designed for the current pattern” of spring runoff that fills water reservoirs for irrigation and other summer uses, he said.

Underground water reservoirs already supply Southern California with 45% of its municipal, industrial and agricultural water supply, testified Dean Peterson, professor of agriculture and irrigation engineering at Utah State University. He stressed the need for greater reliance on underground reservoirs in the West. They could be used to store surplus surface water that accumulates during the winter months for subsequent use in the summer, he said.

But these changes in water system policy will be difficult to implement, Dracup added. Planning, design and construction of large-scale water resource systems could take 20 years, he said. “Therefore, it is imperative and urgent that we begin now by giving federal, state and local water development agencies economic incentives for including in their current planning procedures” to take into account the impact of global warming.

In addition to irrigation--which accounts for 85% of all water used in California--other water uses would be affected by a warming trend and the resulting reduction in the summer water supply, Dracup said at the hearing. He predicted that navigation and water-based recreation would decrease, that there would be less water to operate air-conditioning systems and that runoff pattern changes would produce weaker summer stream flow for fish and wildlife.

Global warming occurs when the reflection of solar heat from the earth’s surface is trapped by chemicals in the atmosphere. Its possible effects, said Stephen H. Schneider of the National Center for Atmospheric Research, include an increase in extreme heat waves and summer fires in hot, dry regions, a rise in sea levels by as much as three feet in the next century, and drier mid-summer conditions for some mid-latitude areas, which could threaten water supplies and future agriculture.