By some measures, the drought in California is the worst in modern record. But a new study suggests that by using more efficient farmland irrigation measures, encouraging homeowners to install water-efficient appliances, capturing storm water, and reusing treated wastewater for landscaping and groundwater recharge, California could see significant decreases in its water demand. Photo by Tim McCabe, USDA Natural Resources Conservation Service
A new report examines the potential impacts of improving water-use efficiency in urban areas and agricultural regions, as well as increases in water recycling and storm water capture.
July 1, 2014—California is in the grips of a severe drought that is the accumulated effect of 10 dry years out of the last 13. As state leaders search for options to bolster water supplies to its large urban centers and rich agricultural regions, a new report contends that there is as much as 13.7 million acre-feet of water available by increasing water-use efficiency, water reuse, and storm water capture.
The report, “The Untapped Potential of California’s Water Supply: Efficiency, Reuse, and Stormwater,” was prepared by the Pacific Institute in Oakland, California, in conjunction with the Natural Resources Defense Council, headquartered in New York City.
“The institute has worked for many, many years—over a quarter-century now—on California water issues and sustainable water [issues] in general,” says Peter Gleick, Ph.D., the president of the Pacific Institute. “We thought it was a good time to really think about solutions to these problems. What are some of the most effective things that we could do to tackle the untapped water potential in the western U.S.?”
By some measures, the drought in California is the worst in modern record. According to data from the National Oceanic and Atmospheric Agency’s National Climatic Data Center, in the 36-month period between July 2011 and May 2014, an average of 45.92 in. of precipitation fell in the state, 21.39 in. below the 20th-century average. Additionally, California’s Palmer Drought Severity Index (PDSI) for the 12-month period between June 2013 and May 2014 shows that this is the driest 12-month period on record.
The authors of the report began by assessing the growing gap between supply and demand for water in California, which is difficult to quantify because of the great degree of natural variability in the climate in California, as well as the undocumented use of water in many areas. The report points to groundwater overdraft and stressed conditions in the San Joaquin River Delta as evidence of this gap. Groundwater levels in California’s important Central Valley area, for instance, have declined by more than 50 million acre-feet since 1962. And though there have been rebounds during wet periods, this never fully makes up for the sharp declines during droughts.
Gleick says that the variability between wet and dry years has caused state leaders to default to larger storage projects to address water issues during past droughts. Water issues are further complicated in the state because precipitation falls largely in the north and the mountains, yet demand is heaviest in the central valley and the southern coast. That has created a highly politicized environment.
“Water is a political issue when there is tension over how much is available and who gets to use it. Scarcity makes for competition,” Gleick says.
For the report, researchers conducted a series of assessments into the potential of four interventions to improve the water picture in the state. The researchers examined the effects of the expansion of agricultural efficiency improvements, urban efficiency improvements, increased reuse of treated wastewater, and increased capture of urban stormwater runoff.
“The total magnitude of the potential was unexpectedly large,” Gleick says. “One surprise was despite efforts in all of these areas in the last few decades, there is still enormous untapped potential. We have made progress in every one of these areas, but not nearly as much as we could in the future.”
The report notes that significant water use savings are possible in California’s important agriculture regions—which account for approximately 80 percent of all water used in the state.
The research examined the effects of such large-scale irrigation improvements as changing from flooded trenches to sprinklers or more precise drip systems combine with soil-monitoring systems that would deliver irrigation only when necessary. Also examined was a technique known as regulated deficit irrigation in which growers only irrigate certain types of crops during key growing periods.
“We have these old, antique irrigation canal systems that are not very flexible,” Gleick says. “Greater flexibility in delivery could lead to greater water savings.”
Researchers found a potential savings of 5.2 million acre-feet per year in urban areas via the widespread use of efficient fixtures and appliances, the mitigation of leaks, and a wider adoption of such voluntary programs as those recently pursued in Los Angeles and Las Vegas, which encourage homeowners to remove grass in favor of more natural, drought-tolerant landscaping.
The report notes that the reuse of treated wastewater for landscaping, industrial applications, groundwater recharge, and ecosystem flows can also have a large impact on water issues in the state. “There is enormous potential for water reuse and we are beginning to pursue it,” says Gleick, who notes that one barrier to be overcome is the fact that large, centralized wastewater treatment plants are often located far from the potential customers of recycled water.
Gleick says the Pacific Institute hopes to hold a series of workshops around the state later this year.
“[Politics] is a long-standing part of the California water world. That’s the reality of a big state,” Gleick says. “If we are really going to solve our problems we are going to have to find ways of overcoming those differences.”