“In California, desalination should be an alternative to proposed $20 billion water tunnels”
There is a connection between the proposed $20 billion Sacramento Delta Water Tunnels, the proposed mining/pumping of water from the Mojave Desert, Central Valley farmers lacking the water resources to maximize food production, and the Sacramento River and fishing stocks suffering from inadequate water flows. That connection is the State Water Project (SWP), which pumps water to Southern California and reduces the river water needed for fisheries, farmers, and the Sacramento River, itself.
The reality is — Southern California needs water and if we don’t produce it here, then we’re going to take it anywhere we can find it, regardless of environmental damage and economic considerations. But we believe the SWP should not be considered the primary source of outside water for Southern California as it is today, and a better alternative is seawater desalination (DESAL). But DESAL suffers from two misconceptions due to inappropriate comparisons: 1) DESAL is too costly, and 2) pumping its brine back to the ocean may create environmental damage. Let’s examine these.
1)DESAL is costly primarily because of the electricity needed to pressurize seawater to about 1,000 pounds per square inch (psi). Yes, this electrical cost is significant, but it should be compared to the cost of pumping water in the SWP, not local groundwater pumping, as it often is. The electricity required for DESAL is about the same as the electricity needed by the SWP to pump water from Northern California down its 400-mile aqueduct and over the Tehachapi Mountains to the south. The elevation change of the Tehachapi Mountains alone is about 2,000 feet, which requires 900 pounds per square inch (psi) of pressure, about the same pressure needed for DESAL. Yes, the SWP makes power through its hydroelectric plants, but overall, its energy requirements are on par with DESAL. For example, State Water requires about 3,400 kWh/acre-feet to deliver water to West Basin Municipal Water District located in Los Angeles[i] and West Basin has projected that a seawater desalination plant located in the South Bay of Los Angeles would consume approximately 3,600 kWh/acre-ft[ii].
2) Seawater is about 35,000 parts per million (ppm) salt or sodium chloride, and the brine that is pumped into the ocean is about double that concentration (70,000 ppm). Double concentration salt is only present in a plume in front of the pipe carrying brine out to the ocean. The plume doesn’t adversely affect fish and other swimming animals, and instead, Australian DESAL plants have recently shown increased sea-life around brine outlets. If one wants to compare a double concentrate DESAL plume with something logical, it should be compared to the plume created by dumping treated sewage into the ocean. The concentration of salt in sewage is approximately 1,000 ppm and so is 1/35 the salt concentration in ocean water. If fish stay in a plume of sewage, they will most certainly die due to the extreme difference in salt concentration. But fish do not stay in the plume, and so are not adversely affected. However, there is often environmental damage associated with sewage plumes due to the reduction of oxygen levels around the plume and this damage is far greater than any environmental concern from DESAL brine disposal in the ocean.
The Carlsbad DESAL plant opened in 2015 and cost $1 billion. It produces 50 million gallons of water daily or 56,000 acre-feet of water yearly. Using these numbers, if the $20 billion proposed for the Sacramento Water Tunnels was spent for DESAL in Southern California, it would pay for over 1 million acre-feet of water yearly (and more, if the environmental review process was reduced from the 10 years it took for the Carlsbad review). One million additional acre-feet of water yearly for California agriculture and fisheries is a little less than half of the water that travels through the SWP yearly and would allow the reduction of that same amount of Sacramento Delta River that must now be sent to Southern California.
The bottom line is, seawater desalination is not seriously considered as a significant source of water for Southern California because of perceived costs and environmental concerns. But when its cost and environmental concerns are compared to the State Water Project and dumping sewage into the ocean respectively, DESAL compares very favorably here in Southern California. It could reduce the need to pump half of the 2.4 million acre-feet of water yearly from Northern California into Southern California as is done today. In addition, multiple desal plants in Southern California would make California’s overall water system more earthquake-resilient by increasing the number of local sources of water in Southern California. We firmly believe that more reliable water sources for Southern California would bring our state into the 21st century in a much more significant way than the speed of a bullet train.
[i] Water Sources Powering Southern California, by Robert C. Wilkinson Ph.D., January 2004.
[ii] Optimizing Seawater Reverse Osmosis for Affordable Desalination – CA Proposition 50 DWR Final Report, by John P. MacHarg.
Ted Kuepper is the retired managing director of the Navy’s Seawater Desalination Test Facility, located in Port Hueneme, CA 1983-2005; John P. MacHarg is owner of Ocean Pacific Technologies, Ventura, CA; OPT is a developer of advanced, ceramic-enhanced, high pressure pumps.