Aquifer Relief: Purisima

Soquel Creek Water District heard some hard news in September, 2009. Their consultant, Hydrometrics, reported that water levels in the Purisima Aquifer are still dangerously low, despite four years of conservation that reduced pumping from the Aquifer to 3000 acre feet per year. Hydrometrics advised the District that “revised sustainable yield goals would seem to be approximately 2500 acre-ft. per year”. That’s a reduction of 17% from the average pumping in 2004-2008 of 3000 acre-ft per year.

Can that reduction be achieved without desalination? We think so. In 2009, water customers reduced their use by 14% during the months of peak water use. That savings was achieved partly through voluntary restrictions on landscape watering. The more ambitious water reduction goal of 17% for the entire year could be achieved through cutbacks in landscape water alone. Or residents could decide to conserve in other ways, such as shorter showers, as did residents of Queensland, Australia. See “Australian Water Crisis Offers Clues for California”

The Queensland experience offers an important lesson in how to achieve changes in water use behavior. Rather than impose detailed restrictions on water use, it works better to give people a target for their daily consumption that will result in a sustainable water supply. People will then decide on their own how to achieve it. Some people would rather flush the toilet less often than let their petunias go dry.

The situation in the southern part of the Soquel Creek Water District, from Rio del Mar to La Selva Beach, is another story. No amount of desalinated water will be able to save the Aromas Aquifer, underlying the Pajaro Valley, from salt water intrusion. See Aquifer Relief: Pajaro Valley for a discussion of what needs to be done.

As of July, 2010, the District Board of Directors has asked the staff to come up with “Plan B”, a scenario for achieving sustainable use of the aquifers that does not include building a desalination plant. We are advocating that part of Plan B include purchase of Santa Cruz water during wet months when Santa Cruz streams can support Soquel water use without adverse impact on fish reproduction. During these wet periods, Soquel Creek District could reduce their pumping, allowing the aquifer to recharge. See Regional Water Swap for more information.

1 Hydrometrics letter to Soquel Creek Water District, “Modeled Outflow to Achieve Protective Water Levels”, Sept. 2009

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