County may redraw water basin boundary


In an effort to sidestep the need to form a new governmental agency and management plan, Marin County has filed an application with California’s Department of Water Resources to reconfigure the boundary of the water basin below Tomales and Dillon Beach. 

The move, which supervisors authorized last month, will save the county “a lot of time and a lot of money,” Rebecca Ng, deputy director of Environmental Health Services, said. 

The department oversees compliance with the Sustainable Groundwater Management Act, a 2014 law designed to prevent the overuse of water in California’s groundwater basins. The act requires local agencies with high- or medium-priority basins to prevent overdrafting and to achieve balanced pumping and recharging. 

Under the law, jurisdictions with water basins rated high or medium priority by California’s Department of Water Resources must create a local groundwater sustainability agency. These agencies are tasked with developing a plan to make the basins sustainable by 2020. 

In Marin, Environmental Health Services is responsible for administering compliance with the law, in part because Marin’s five basins are classified as low or very-low priority—meaning the county does not have to form a special agency to track them. (The Community Development Agency funds the groundwater monitoring program.)

But that threatened to change this past May, when the state water department released a proposal to reprioritize the Wilson Grove Formation Highlands Basin—one-quarter of which lies beneath Tomales and part of Dillon Beach, with the rest in Sonoma County—from low to medium priority. If the lines are not re-drawn, Marin would have to form a joint agency with Sonoma County and the cities of Petaluma and Sebastopol. 

In fact, those cities are also considering sectioning off their portions of the basin, in hopes that dividing it will allow each of its parts to revert to low-priority status, preventing the need for a new agency or plan. 

The Sonoma County Water Agency estimates that each additional agency costs it over $2 million in workshops, outreach, reports and additional duties.

Marin officials felt strongly that some of the reasons given for the planned re-prioritization of Wilson Grove—the amount of groundwater used, the quantity of irrigated acreage and overall population—had little to do with its own usage, but instead stemmed from Sonoma County’s agricultural and population use. 

Environmental Health Services proposed a modification that would bring the Marin portion of Wilson Grove into the contiguous Sand Point Area Basin—a low-priority basin—located below Dillon Beach and Lawson’s Landing. 

In fact, “under the ground there’s no line between the two—it’s all just a continual flow of groundwater,” explained Drew McIntyre, general manager of the North Marin Water District. “Expanding the Sand Point Basin to bring it north to the county line just allows management of that basin to be within one county agency. That makes sense from a management standpoint.”

Ms. Ng explained that most of northwestern Marin is unirrigated ranchland. 

“There’s not a lot of population, not a lot of irrigated land—we don’t have grapevines or orchards or anything out there,” she said. “There is the Estero Mutual water system, but it’s less than 200 houses. There are individual wells, but the amount of water they take out of the basin is pretty minor.”

According to her, re-drawing the boundaries will also allow Marin to develop sustainable groundwater practices based on land and water usage specific to the county. And “any state monitoring requirements that would have to take place, the county could do it, and that simplifies the process rather than getting multi-counties to address the response,” she added. 

During the Board of Supervisors vote to submit the application to the state water department, Supervisor Kate Sears raised concerns about Marin’s water potentially being overseen by an agency from another county, since the basins all flow into each other. Even with the re-drawing, she wondered if heavy use from Sonoma County would impact Sand Point, and what kind of local oversight there would be. “We’d want to know if a high-population area is using our groundwater,” she said. 

Brian Crawford, director of the Community Development Agency, replied that the existing California Statewide Groundwater Elevation Monitoring Program “gives us an opportunity to continue to monitor our groundwater operations. And if we see a problem, we can revisit it in conjunction with Sonoma, Petaluma and Sebastopol to re-evaluate our approach.” 

If the county saw evidence of an imbalance between pumping and recharging, he said, it could still form an agency and plan outside of an order by the state for the reconfigured Sand Point basin.

The state water department reviews basin classifications every few years, so it is possible that Sand Point could be reclassified if, say, the population grows or agricultural needs shift. But for now, the county anticipates the basin will stay low priority.