Napa’s water supplies require stronger safeguards amid the threats from vineyard development, drought and invasive species, the city’s water manager is predicting.

In a report to the City Council Tuesday night, Joy Eldredge detailed the encroachment of wine grape cultivation that – combined with the pollution risk from wildfires and scant protection from boats and swimming – she said present the greatest risk to the watersheds surrounding Napa’s two local water sources.

Lake Hennessey, which holds 31,000 acre-feet of water, and the 1,390-acre-foot Milliken Reservoir supply some 84,000 people. Their surrounding watersheds cover a combined 40,200 acres in rural Napa County, but barely 5,000 acres are city-owned – leaving its integrity largely in the hands of private landowners, particularly around Lake Hennessey’s year-round water supply, the report says.

Lake Hennessey is located in the hills northeast of Yountville, along Highway 128, while Milliken Reservoir is off of Atlas Peak Road above Silverado Resort.

Increasing vine planting in the watershed carries the risk of more sediment, fertilizers and pesticides coming closer to the reservoirs, Eldredge reported to the council. Although she credited farmers with reducing pesticide use and sediment runoff over the years, she called development a continuing challenge to water protection.

In particular, she said the growing volume of watershed vineyard applications is raising the risk of sedimentation reaching unhealthy levels, even if individual projects stay within county and city standards.

“I’ve had three or four projects go across my desk in the last two months, over 100 acres,” she told council members. “That concept of death by a thousand cuts starts to add up.”

Eldredge pointed to increasing algae levels – often a by-product of fertilizer runoff – in Napa’s reservoirs as one possible marker of the effects of grape cultivation. Anti-algae treatments increased from five in 2007 to 10 in 2013 and up to 22 this year, she said.

Meanwhile, four years of drought have left vegetation around the reservoirs dangerously dry, raising the risk of a fire that would create water pollution levels impossible to treat to state standards, she said.

In the short term, Eldredge recommended strictly enforcing the swimming ban and motorboat restrictions at Lake Hennessey, more carefully managing recreational use and continuing to clear excess drought-parched tinder in watershed zones.

But a lasting safeguard of water quality, she added, demands shifting more responsibility onto would-be builders – requiring water monitoring upstream and downstream of a development, and imposing watershed protections and even improved water treatment on projects near a reservoir. Keeping recreational users away from water sources also will require fines rather than warnings to be effective, she said.

Eldredge’s message received sometimes vociferous support from audience members, many of whom used the occasion to attack the proposed Walt Ranch watershed vineyard complex as a major threat to water supplies. The project would include some 300 acres of grapevines, and 500 acres of disturbed land in all, in the hills between the city and Lake Berryessa along Highway 121.

“If Milliken cannot be protected, then what water source can be protected?” said Jim Wilson of Napa. Walt Ranch, he continued, “is a huge mistake – but it’s not too late to save (Milliken). In the end, it’s a lot easier to protect water quality than to restore water quality; it costs less and it’s forever.”

“The county and city are connected through their water sources,” said Mike Hackett of Angwin. “If there is an idea that puts the impetus on the county to restrict runoff and sediment, this is a great time for it, because you have the public on your side.”

Residents’ grievances over the Walt Ranch plan – whose location is well north of city limits – show the need for the city and Napa County to work together on stronger watershed protections, said Councilman Scott Sedgley.

“I’d like to immediately start working with the county to strengthen their code and discuss appropriate zoning for watersheds,” he said. “It’s time; we need to move ahead on this, and we need to move quickly.”

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City of Napa/Town of Yountville Reporter

Howard Yune covers the city of Napa and the town of Yountville. He has been a reporter and photographer for the Register since 2011, and previously wrote for the Marysville Appeal-Democrat, Anaheim Bulletin and Coos Bay (Oregon) World.

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