Pumping from the Paso Robles groundwater sub-basin continued at unsustainable levels last year — with agriculture extracting more water than domestic well owners and municipal water systems combined, according to a new report.
The sub-basin, which pools underground from the area east of Highway 101 to north of Highway 58, was designated as “critically overdrafted” by the California Department of Water Resources.
Basin users pumped 75,100 acre-feet of water in 2024, up from 63,600 acre-feet in 2023 — an 18% increase, according to the latest annual report for the basin. An acre-foot of water is roughly enough to cover a football field in a foot of water.
That’s far from the estimated sustainable yield of 61,100 acre-feet per year. In fact, people pumped 25,500 acre-feet more than was returned to the basin in 2024, the report said.
This is the eighth year in a row that pumping exceeded the sustainable yield.
Agriculture consumed 70,900 acre-feet, or 94% of total water pumped in 2024, the report said.
Meanwhile, municipal public works systems consumed 1,044 acre-feet while small public works systems, golf courses and rural domestic wells combined consumed 3,134 acre-feet.
Municipal users’ water consumption decreased by 90 acre-feet, or 7.9%, in 2024, while public water systems and rural domestic users together increased their use by 258 acre-feet, or almost 9%, last year.
Agricultural users increased their pumping by 19%, or 11,300 acre-feet, in 2024, the report said.
Of agricultural pumping, vineyards extracted the most water. The 34,533 irrigated acres of vineyards above the basin pumped 58,585 acre-feet of water, the report said.
Alfalfa required the most water per ace, with 1,789 irrigated acres pumping 6,074 acre-feet, the report said.
San Luis Obispo County enjoyed more rain than usual last winter, with about 21 inches recorded at the Paso Robles Weather Station in 2024.
This was a few inches more than the long-term average of 14.5 inches, the report said.
But the county still didn’t receive as much rain as it did during the 2022 winter storms, SLO County groundwater sustainability director Blaine Reely said.
“Even though we got a lot of good rainfall, we didn’t get great rainfall.” he said. “There just wasn’t as much natural precipitation that was making its way into the soil profile, and so the farmers had to supplement with irrigation.”
The county also endured heat spells that required farmers to apply more water to their crops.
During the 2024 growing season, there were 36 days that reached at least 100 degrees, while in 2023, there were only 24 days with temperatures higher than 100 degrees, the report said.
Additionally, the number of irrigated acres in the Paso Basin increased from 2023 to 2024 — which required more water, Reely said.
Reely said he’s confident that participating agencies will bring the basin back into sustainability by 2040.
“The solution is we have to reduce pumping,” he said. “It’s achievable.”
San Luis Obispo County, the city of Paso Robles, the Shandon-San Juan Water District and the Estrella-El Pomar-Creston Water District recently formed a Joint Powers Authority, which will have the power to levy water use fees in all of the basin except areas served by the San Miguel Community Services District.
Reely hopes the fees will motivate growers to make their operations more efficient so they can reduce their water use, he said. Meanwhile, those fees will fund programs designed to balance the basin.
One such program is the Paso Robles Groundwater Basin Multibenefit Irrigated Land Repurposing Program, also known as the MILR Program.
Through the program, a staff member will support irrigators who want to pivot to farming practices that use less water. This could look like changing the property’s irrigation system so it is more efficient, changing farming practices, or converting irrigated farmland to dry land farming, open space or a project like a solar farm.
A consultant identified 566 farming units that encompass 39,000 irrigated acres who are eligible to volunteer for the program, the report said.
Right now, it’s too expensive to connect to the State Water Project or use recycled water to recharge the basin, but those projects could become viable in the future, Reely said.
If farmers don’t voluntarily reduce pumping over the next few years, the Groundwater Sustainability Agencies governing the basin may need to implement pumping restrictions — an action authorized by the Sustainable Groundwater Management Act.
“We have that hammer if we ever need it, we just are hoping — and have been working towards a strategy where — we don’t pull that hammer out of the tool kit,” Reely said.
San Luis Obispo County submitted the annual report to the California Department of Water Resources on Monday.
The new Joint Powers Authority will meet for the first time on Monday to discuss the potential water use fees.
The meeting starts at 4 p.m. in the Paso Robles City Council Chambers at 1000 Spring St.
The Tribune
805-781-7816
Stephanie Zappelli is the environment reporter for The Tribune. She grew up in San Diego, and graduated from Cal Poly with a journalism degree. When not writing, Stephanie enjoys reading and exploring the outdoors.
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