Water Resource Planning An Uphill Battle, But a Vital One

October 14, 2008

At the CCST Council meeting on October 8, one of the world's leading experts on hydrometeorology brought the message that California urgently needs to plan its water future using every tool available.

"Over the past decades, the tools available for gathering information useful to hydrologists have greatly expanded," said UC Irvine Distinguished Professor Soroosh Sorooshian, Director of the Center for Hydrometeorology and Remote Sensing. "Nonetheless, at present the accuracy of regional-scale climate model predictions still falls short of meeting the requirements of water resources planning. Factoring in as much resiliency as possible in water resources systems design and planning is still the safest approach."

Sorooshian was one of several speakers who addressed the Council on water issues, which were the focus of the meeting. He described a range of factors that are complicating water resource management in California, including warming, population growth, the region's water balance, consumption rates, dam capacity, and aquifer overdraft.

"There are a number of warning signs California needs to pay attention to," noted Sorooshian. "The Colorado River, for example, is a major source of water for the state. However, the river flow has been fully utilized since 1962 - it is a limited resource. Moreover the salinity increases as the water moves downstream towards California, which is a major problem. Each year, desalination facilities remove hundreds of thousands of tons of salt, but levels may be varying due to climate fluctuation."

California is particularly at risk due to its large population and the substantial imbalance in the distribution of its water resources.

"Nearly 75% of California's water supply is in the Northern half of the state, but almost 65% of its demand is in the Southern half," said Sorooshian. "This imbalance is likely to grow with projected urban growth in Southern California." This water distribution system is at risk from a variety of factors, including more rapid melting of the snowpack in the Sierra Mountains due to warmer temperatures - which is a major source of the water - and vulnerabilities along the distribution lines through the Sacramento Delta, where a thousand miles of levees are at risk of disruption by rising sea levels, seismic activities, and more extreme flooding due to increases in climate variability.

Moreover, the current water distribution system also requires a substantial amount of energy for delivery of water.

"The State Water Project (SWP) is the single largest user of energy in California," said Sorooshian. "It takes approximately three thousand kilowatt hours to pump one acre-foot of water [326,000 gallons] through the system to Los Angeles. WIth an increasing demand scenario, this may not remain a sustainable option indefinitely."

More integrated use of remote sensing systems to provide better real-time data will help states like California better understand factors affecting its current water supply, and improve its ability to model projected changes in the future.

"Droughts are not a new phenomenon," said Sorooshian, "but the rise in our demand for water is. The U.S., particularly the West, has a good track record of building in resiliency to its water resource systems so far, but we will need to do an even better job to cope with the 'perfect storm' of rising population, increasingly variable precipitation, and declining resources."