Jerry Kuny makes a phone call as flames from the LNU Lightning Complex fires approached in rural Napa County on Aug. 18, 2020. Noah Berger, Associated Press

Napa Reservoirs Spared the Worst from 2020 Wildfires

Jan 7, 2021 at 8:00am

Howard Yune

Two reservoirs feeding water to the city of Napa apparently were spared the worst of the onslaught from last year’s historic wildfires that tore through the county’s rural north, the director of the municipal water system reported this week.

Watershed lands around Lake Hennessey and Milliken Reservoir escaped high-intensity burning during the Hennessey Fire that erupted Aug. 16, according to city water manager Joy Eldredge.

Although the lightning-triggered blaze spread to about 9,800 of the 38,800 acres of watershed surrounding the two reservoirs, trees and plant life that burned should regrow within a year, thus reducing the risk of long-term erosion that could degrade water quality to more than 80,000 Napa-area customers, she told the City Council Tuesday afternoon.

The Hennessey Fire’s burn zone covered the eastern portion of Lake Hennessey’s watershed including the drainage area of Sage Creek, the smallest of three tributaries into the reservoir.

Less than 1% of the area touched by the fire burned at the highest severity, which Eldredge said raises the risk of longer recovery time for vegetation – and thus increased erosion and runoff into streams as wildlands remain bare for longer.

Severely burned terrain also increases the level of total organic carbon levels in water sources, which can harm water quality as the carbon reacts with the disinfectants used to kill microbes in drinking water.

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