A plan to connect two reservoirs moves along but questions arise around funding.

As dry times become a greater concern, taking full advantage of wet times becomes a greater priority. This is the idea behind a long – conceived $150 million tunnel project that would connect two of the county’s most important reservoirs, allowing the more common superfluous flows in one to fill the other. However, as the design moves toward a public unveiling, support for the massive project is uncertain.

Lake Nacimiento and Lake San Antonio, the two South County reservoirs that feed the Salinas River and are crucial to the sustained health of the county’s agriculture industry, sit at 14 percent and 7 percent filled, respectively – the lowest levels since 2017. Gov. Gavin Newsom in July lumped Monterey County into his extreme drought designation now impacting 56 of 58 California counties. The diminished lake levels forced the county’s water resources agency to end reservoir releases for agricultural irrigation in July.

This is the reality of dry times in the Golden State. However, during wet winters, Lake Nacimiento can refill quickly because of its highly reactive watershed, says Brent Buche, general manager of the Monterey County Water Resources Agency. Buche says the lake can rise by 20 feet in a single rain event, sometimes causing the reservoir to overflow and spill out. With climate change creating more extreme weather conditions, both dry and wet, the county and agricultural stakeholders are looking at ways to capture and store every ounce of water possible.

Lake San Antonio, though less than four miles away, is less reactive to rainfall. The interlake tunnel project would connect the two reservoirs with a 10-foot diameter pipe and allow water that might otherwise be lost to overflow from Lake Nacimiento to be transferred to Lake San Antonio and stored, balancing the production of the two reservoirs and potentially capturing an additional 34,000 acre feet of water per year. Buche says with both reservoirs full, the system could operate without rainfall for three growing seasons.

Design of the tunnel and analysis of its environmental impacts is being paid for by a $10 million grant from the California Department of Water Resources, which former State Senator Bill Monning says required “moving heaven and earth” to obtain. A challenge in the tunnel design, Monning says, is the addition of a screen to filter out the striped bass that populate Lake Nacimiento. The bass, which the California Department of Fish and Wildlife added to the lake in the 1970s to boost recreation, are considered predatory and invasive and by law have to be kept out of Lake San Antonio and the Salinas River.

An interlake tunnel was first proposed in the 1970s but Buche says it was cost prohibitive. Cost may still shelve the project. An engineering report to determine the project’s benefits will begin later this year, which will help impacted landowners in the Prop 218 process decide whether to vote in favor of a tax increase to finance the project. “Over the decades, the value of water has increased and people are willing to pay more to get more,” Buche says. “But when you’re talking about $150 million, everyone who is paying for it needs to understand the benefits.”

Projects that secure more water are increasingly important for the agriculture industry as overpumping and seawater intrusion compromise more wells in the Salinas Valley groundwater basin. However, whether the expensive interlake tunnel is the right project is up for debate, said John Farrow, an attorney for land-use watchdog LandWatch.

Farrow told Monterey County’s Board of Supervisors in late August that the interlake tunnel project needed to be coordinated with the Salinas Valley Groundwater Sustainability Agency, the public agency tasked with solving the groundwater crisis in the Salinas Valley.

“We recommend, before [the county] spends any more, it begins a… coordination process with the [SVGSA] to figure out whether this is the most optimal project, whether this would warrant pursuit versus some of the other projects that are being considered,” Farrow said.