SACRAMENTO December 13, 2016 – Years after invasive northern pike were eradicated from Lake Davis in Plumas County, the Department of Water Resources (DWR) announced today it is resuming normal operations at the reservoir.
This means the reservoir near Portola will be allowed to fill. DWR lowered the lake in the 1990s to prevent storms from spilling the predatory pike into downstream waterways. The California Department of Fish and Game (now Fish and Wildlife) used a chemical treatment (rotenone) to eradicate the pike in September 2007. Out of an abundance of caution to protect native fish species, DWR has kept the reservoir level well below the dam’s rim.
Spills also were avoided to protect a “strainer” at the base of the dam designed to keep northern pike from escaping downstream. Although the strainer structure has not been operating for several years, it was kept in place in case the pike reappeared. DWR now plans to dismantle the device, as it has been causing operational difficulties.
Even while operated at low levels, Lake Davis has provided drinking water to the City of Portola as well as recreation for area residents and visitors.
A possible consequence of allowing the reservoir to fill is that spillway flow during flood conditions could cause higher flows in Big Grizzly Creek below the lake.
Lake Davis is part of DWR’s Upper Feather River Project within Plumas National Forest. In addition to water supply, the 84,000 acre-foot reservoir provides recreational camping, fishing, picnicking and boating. The reservoir is created by Grizzly Valley Dam on Big Grizzly Creek, a tributary of the middle fork of the Feather River.
Non-native northern pike were first observed in Lake Davis in 1994. If they had reached downstream waters, including the Sacramento-San Joaquin Delta, the voracious predators would have threatened native trout, salmon and other species.
The Department of Fish and Wildlife initially attempted to eradicate pike from Lake Davis via rotenone treatment in 1997, but the fish were rediscovered in the reservoir in 1999. The treatment in 2007 was successful, aided by reduced lake volume as DWR lowered the water level.