UKIAH >> The Ukiah Valley’s residents and farmers have a consistently renewing source of water thanks to a vast underground aquifer believed to hold more water than Lake Mendocino, scientists told the Ukiah City Council Wednesday.
“There is no overdraft, or mining of the aquifer,” said Sam Sandoval Solis of UC Davis, who was hired by the city to evaluate the valley’s water supply along with Maritza Flores Marquez. “We have some periods of drought, but the supply is balanced, because half of the time there is more water in than out, and the other half of the time there is more water out than in.”
Solis and Marquez were hired in May of 2016 to complete a Groundwater Characterization Study as part of the city’s efforts to comply with the state’s Sustainable Groundwater management Act.
Since the city is designated as having a “medium priority basin,” it must have a Groundwater Sustainability Plan in place by Jan. 31, 2020, and city staff described the characterization study as the beginning of the process of “quantifying our groundwater resources.”
To characterize the basin’s water supply, Marquez said the study monitored the water flowing into and out of the Russian River in the valley, but only between Redwood Valley and Hopland because the data was dependent on water gauges.
“There is no storm gauge north of Redwood Valley, but even without that, we have a pretty good idea of what’s going on in the aquifer,” said Marquez, explaining that the study determined that there was no depletion of the aquifer storage, which is estimated to be about 120,000 acre-feet. (As of March 1, Lake Mendocino had 82,161 acre-feet).
To determine the demand on the aquifer, the study determined how much water was needed for municipal and agricultural purposes versus the recharge from rain, the Wastewater Treatment Plant and river tributaries.
Marquez said the valley had about 8,700 acres of agriculture, which Marquez said required about 10,000 acre-feet of water a year. And most of that is supplied by surface water supplies such as the lake and rain, not affecting groundwater supply.
But even when it does tap groundwater, Marquez said the amount of “recharging of the groundwater supply is much greater than the agricultural demand.
“Overall, the groundwater basin looks stable, and the gains are a lot larger than the losses,” she said.
“This sounds like we’re in good shape,” said Steve Scalmanini. “Are we bucking the trend throughout the state?”
Solis said that yes, the Ukiah Valley had more water resources than the Central Valley and the Central Coast, but it should look at this reality as an opportunity to be “proactive, than reactive,” and to make sure its water supply is properly managed.
Resident Phil Baldwin took issue with the report, questioning its validity given that the scientists were working for the city.
“To me, the supply doesn’t look stable,” said Baldwin, pointing out that since no one can know how much water really is in the aquifer, “I question why the number 120,000 acre-feet is even being presented.”
White said that number was reached and supported by looking at the amount of water flowing in versus the amount flowing out, and that the size of the aquifer would be measured conclusively within “the next couple of years by the (United States Geological Survey).”
