Report: Groundwater was at or near record levels in 2011
After a series of drought-stricken years, 2011’s wet weather and decreased water demand by agricultural, municipal and industrial users left San Benito County with groundwater levels at or near historic highs, according to the recently-released Annual Groundwater Report.
Issued by the San Benito County Water District, the more than 100-page report details water demand and usage in the area, during a year in which the 12.96 inches of rainfall was close to the long-term average of 13 inches.
Despite the near-normal rainfall total, the report credits the effects of water conservation prompted by the recent multi-year drought as contributing to the stable groundwater levels and total water use.
Local water users, such as farmers and municipal and industrial customers, utilize a combination of private wells and U.S. Bureau of Reclamation water pumped to the county through pipes connecting the San Luis Reservoir to the California Aqueduct. The latter source of water is of a higher quality than local well water, though often more expensive to use.
“Last year was an average year for rainfall, but above average for runoff and the amount of water we were able to capture,” said Jeff Cattaneo, director of the San Benito County Water District.
He noted that despite scant rainfall in the county so far this winter, Hernandez Reservoir near Paicines is still at 60 percent capacity, which is “fairly high considering we haven’t gotten any rain.”
That surplus is owed in part to last year’s frequent, spread-out rainfall. Much of last year’s rainfall resulted from “small precipitation events,” the report says, noting that 62 days in 2011 had measurable rainfall – up from the average of 50 days. Also, 40 percent of the total rainfall occurred within the first three months of the water year, which is substantially more than the average 28 percent. January and April were relatively dry.
“This distribution likely facilitated deep percolation and stream percolation,” the report noted, indicating that rainwater had time to filter into natural underground aquifers from which groundwater is pumped by well users.
Last year’s decrease in water demand also in part to the use of high-efficiency irrigation techniques instituted in response to the recent drought and a shift to more low-water-use crops as farmers were uncertain how much water they would get from state supplies through the Central Valley Project.
It was a “very good year” for CVP deliveries last year, Cattaneo noted, as agricultural users received 80 percent of their contracted amount and municipal and industrial users received their full allotment.
“We had a lot of water to work with last year,” he said. “This year that’s coming up, rainfall hasn’t materialized this year so far, but we’re looking at having more than enough water to release to keep groundwater levels at or near their historic highs.”
The groundwater report stated that local water demand over the past four years has been the lowest on record.
“While this indicates the adverse impacts of an uncertain CVP supply and economic downturn, it also reflects the success of water conservation efforts,” the report said.
No substantial change is foreseen for water demand in 2012, which the report says is expected to be another average precipitation year. Continuing La Nina conditions in the Pacific Ocean could bring increased rainfall to Northern California during the remaining winter months, “but there is tremendous uncertainty” and there also remains the possibility of a drier-than-normal spring.
The report says that current groundwater storage in San Benito County is “sufficient to accommodate several successive dry years with negative water budgets” and groundwater capacity in wet years is expected to continue to balance moderate increases in well pumping in dry years without causing an overdraft.
“We have plenty of water to work with for up to four years without having any significant depletion of our groundwater supply,” Cattaneo said. “Long term, we’re looking at being able to manage the basin fairly well so that even in dry years when groundwater levels start to drop, we anticipate being able to recover quickly after that when the rains return.”
Uncertainty over CVP deliveries will remain an annual question while state and federal agencies and agricultural interests quibble over water usage rules designed to protect salmon and delta smelt. Those issues could take “two to three years to work themselves out,” Cattaneo said.
The county water district also detailed its involvement in projects and programs that address the supply and quality of water as well as wastewater management.
In 2011, the district joined with the Sunnyslope County Water District and the City of Hollister on a Hollister Urban Area Water Management Plan designed to support long-term water supply planning for the region, including expanded capacity for the Lessalt Treatment Plant that will improve the quality of CVP water sent to the county.
The Sunnyslope district also began work on improvements to the Ridgemark wastewater facilities that should be done by Fall 2013.
Recycled water will continue to be a focus of local water agencies in 2012 and beyond, as the report notes that recycled water used for agricultural irrigation will eventually be of higher quality than groundwater now being pumped for farming. The City of Hollister uses recycled water as a supplemental water source – mainly for park irrigation – and hopes to eventually increase the local water supply by 3,000 to 4,000 acre-feet per year. One acre-foot of water – the amount of water covering one acre to a depth of 1 foot – equals 326,000 gallons.
Water conservation efforts in the county during the past year included a water softener rebate program, which over the past four years has issued 426 rebates, including 61 in 2011. The county water district and the Water Resources Association also continued to offer a series of classes on irrigation efficiency and salinity management.
“We’re fortunate here that over the years we’ve been managing the groundwater basin proactively over the last 40 years to bring in Hernandez and Paicines reservoirs and CVP water,” Cattaneo said. “We’re in better shape here than they are in the Central Valley. We have a significant amount of water in storage and we can recover after dry years.”
To read the Annual Groundwater Report for Water Year 2011, go to www.sbcwd.com and click on the “Publications” link.