With this year’s storms helping to refill the Sacramento region’s lakes and reservoirs, local water district officials and state regulators are diverting and percolating stormwater from Cache Creek into the Yolo County canal system to recharge groundwater supplies used by local farmers, city residents and UC Davis.
Groundwater normally supplements surface water to meet residential, agricultural and industrial needs. When rainfall is scarce and surface water dries up, groundwater can make up the difference. But soaring usage over the past few drought years have caused groundwater supplies to drop to levels not seen since the 1970s.
Anticipating winter storms brought on by El Niño conditions, officials at the Yolo County Flood Control and Water Conservation District recharged groundwater levels by diverting 11,000 acre-feet at the Capay Diversion Dam.
“We have 160 miles of unlined canal that normally is dry in the winter,” said Max Stevenson, the district’s assistant general manager. “We took extra creek water from Cache Creek and put it into the ground so we could have it for pumping out later.”
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The agency diverted water mostly between March 15 and April 15. During that period, which some now call the March Miracle, the storms unleashed higher water flow and allowed the agency to flood the canals to provide immediate surface water for irrigation. It also recharged groundwater levels as water seeped through the canal, saving up for drier seasons.
Average groundwater levels in Yolo County decreased annually between 2011 to 2013. In 2014, the levels dropped more dramatically, from 40 feet to nearly 70 feet, before recovering slightly in 2015. Groundwater levels are measured by depth to water, and so larger depths indicate less groundwater.
Yolo County groundwater levels have normally fluctuated between 30 and 50 feet, dating back to the 1980s.
The district received the necessary state approval to divert the water when an executive order issued by Gov. Jerry Brown last November prioritized application reviews seeking to capture stormwater to recharge local groundwater supplies. The State Water Resources Control Board issued the temporary permit for Cache Creek diversion just days after receiving the application.
One other application for water diversion to recharge groundwater was approved in 2016. The application by the Scott Valley Irrigation District near the Oregon border allowed the diversion of 5,400 acre-feet of stormwater from the Scott River through unlined canals to percolate into dormant agricultural fields.
Water managers, elected officials, farmers and other residents gathered at the Winters Canal on Wednesday to celebrate the groundwater recharging in Yolo County.
“I survive 100 percent on the water that goes down this canal or comes out of the groundwater in this area,” said Bruce Rominger, a Yolo County farmer and district board member. “Being able to do this when we have excess flows in the wintertime is really crucial for the future of our (water) district, and it’s really a great model that we need to spread.”
Robert Kuo: 916-321-1161