San Diego Pursues Drought-Proof Water Supply
Tuesday, February 13, 2018
Credit: San Diego County Water Authority
The desert-like grounds around the San Diego County Water Authority offices are dressed in a water-wise xeriscape of cacti and aloe. The sky is a monotone blue and — even though it’s January — the temperature is in the 80s.
Dennis Cushman, assistant general manager for the Water Authority, doesn’t look very comfortable in this setting in his dark wool suit. But when asked about the county’s water supply, he said he is actually feeling pretty good, because San Diego has plenty of water for 2018.
“We’d like to see more precipitation. But we’re prepared. And we spent billions of dollars and several decades preparing for years like this, and stretches of years like this,” Cushman said.
Cushman’s confidence about the water supply says a lot following last year’s record dry June-to-December in San Diego. So far this rainy season only 1.7 inches have fallen at Lindbergh Field. Average rainfall this time of year is three times that much.
But thanks to Water Authority investments and steep price hikes for ratepayers, Cushman says San Diego has a diversified set of water sources and an impressive network of infrastructure that, last year, won an Achievement Award from the American Society of Civil Engineers.
“It‘s a series of reservoirs — new and expanded reservoirs — interconnecting pipelines and pump stations that allow us to store enough water for emergencies. About 90-thousand acre-feet of water," Cushman said. "That’s in case we get our supplies cut off from the north.”
An acre-foot of water is enough to serve two four-person households for a year in San Diego.
When Cushman speaks ominously of being cut off “from the north,” he’s mining a narrative that describes the days when San Diego was dependent on water from the Metropolitan Water District of Southern California (MWD). In the early 1990’s, nearly all of San Diego’s water supply came from the Los Angeles-based MWD, a wholesale agency that gets its water from the Colorado River and the Sacramento Bay Delta.
In 1991, California was in a devastating multi-year drought, and and the MDW cut water supplies to San Diego by 30 percent. Luckily the gods intervened and a “miracle March” that year brought California a deluge of rain that put the San Diego region back on a safe footing. Since then San Diego County has been storing more water and getting it from a lot of places than just the MWD.
"The supply from Metropolitan used to be about 95 percent of our supply. Now it's down to about 40 percent of our supply," said Cushman.
Where else is water coming from? Figures from the County Water Authority show that last year approximately 40 percent came from the Metropolitan Water District. Another 38 percent came from a water transfer deal San Diego struck with the Imperial Irrigation District. The new ocean water desalination plant in Carlsbad provided nearly ten percent of the county’s water supply, and recycled water for irrigation accounted for 5 percent.
One step beyond water recycling is sanitizing wastewater for drinking and it’s the next frontier of local water production. The County Water Authority expects potable reuse to provide 16 percent of local water by 2035.
Cleaning the water we’ve been throwing away
A water engineer stands near a series of ponds and a small water purification plant in western Santee. His name is Al Lau, with the Padre Dam Water District, and the plant is a demonstration project which he says is the beginning of a process that will lead to millions of gallons a day of purified wastewater.
Today the pipe that carries treated wastewater from East County to be dumped in the Pacific Ocean is just a couple miles away.
“We see all the wastewater flow past us, 14 million gallons a day, all the way to the Pacific Ocean. We see that as a wasted resource. We see the opportunity to capture that and turn that into a resilient water supply for our community,” Lau said.
At a cost of $460 million, Padre Dam wants to phase in a system that will eventually treat East County wastewater and make it clean enough to drink.
“We’re going to take all of that 14 million gallons of wastewater, generate a purified water supply and pump it into Lake Jennings,” he said. “That water, once it’s in Lake Jennings, will blend with other imported water supplies, where it will be treated again…and that water will be provided to the entire community of East County.”
The City of San Diego Public Works Department is building an even bigger system of purifying wastewater. Spokesman Brent Eidson said they plan to eventually divert 100 million gallons a day from the Point Loma treatment plant and turn it into potable water. A San Diego City Council vote on the environmental review documents for the new facilities comes up in April. The cost of building phase one of the project is $1.3 billion.
The diversification of San Diego’s water supply has come at a cost. Since the early 1990s, the cost of an acre-foot of water has tripled even as per capita demand for water has dropped substantially.
Water authorities justify the rising cost of water in a variety of ways. They cite growing populations and the cost of infrastructure maintenance. They predict that, over time, the cost of imported water will pull even with local water supplies. But for now, desalinated water - to cite one example - is twice the cost of imported water from the MWD. Even so, Dennis Cushman says there’s a reason for that.
“It’s way more reliable. So it’s not an apples-to-apples comparison. It’s the most reliable supply in our portfolio contrasted with the least reliable water supply, from the Bay Delta, that we get from Metropolitan,” Cushman said.
The future of California water
The water supply for California can never be free from the cycle of rain and drought, not to mention the faster snowmelt and evaporation that comes with global warming. Marty Ralph is a meteorologist and director of the Center for Western Weather and Water Extremes at UC San Diego. He says California’s rainfall future may not be any more wet or dry - just more unpredictable.
“I do think the likely scenario for the future is a continuation of the very dynamic climate we’ve had here in California, which goes from very wet to very dry from year to year,” Ralph said. “The climate projections are saying that’s going to increase. The extremes are going to become greater. The papers I’m familiar with, the work we’re doing, all point in that direction.”
He said that means we need to predict weather patterns more precisely and make more effective use of our system of dams and reservoirs.
“We’re in the 21st century now. We need every drop of water to do more work for us than it used to,” he said, quoting a colleague. “So we need the systems, the knowledge, the science, the policies all to support that greater use and conservation of the water.”
That’s especially true in San Diego, which gets less rainfall than all of California’s ten largest cities, except for Bakerfield. Cushman said the last year San Diego's native water supply was sufficient to support our population was in 1946.
Following a record dry June-to-December, San Diego water officials still say the region has plenty of water.
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