The mouth of the Eel River, the third-largest river in California,
is nearly two hundred miles north of the mouth of the Russian River, yet high
up at the rivers’ headwaters, only two miles naturally separates these
two rivers. In 1908 humans breached that separation, completing a diversion
tunnel to link the two river systems. Eel River water travels through this tunnel
to turn turbines to generate electricity below, in Potter Valley. After
being used for this purpose, Eel River water is released to flow into the East
Fork of the Russian River.
The complex of facilities (including dams, reservoirs, tunnel,
and machinery) used to store water and generate electricity is currently owned
by PG&E and is known collectively as “The Potter Valley Project”
(PVP). The Potter Valley Project has been characterized in a Sonoma County Water
Agency Report as “not economic as a hydroelectric project.” Furthermore,
the dams have contributed to the collapse of the Eel River salmon populations
which once “supported runs of salmon and steelhead trout that were estimated
to exceed one-half million fish” (Dept. Fish and Game 2001, p. 57).
Details
Cape
Horn Dam built in 1908 to create a bay, the Van Arsdale Reservoir,
to move water from the Eel River down the mile long diversion tunnel to create
electricity for the city of Ukiah on the Russian River. 5 cubic feet per second
is allowed over 50' high Cape Horn Dam into the Eel River - not enough for fish
to survive. Natural late summer flows are 50 to 55 cubic feet per second. Cape
Horn Dam was built without a fish ladder and cut off hundreds of stream miles
in prime spawning grounds for the largest of the Eel River salmonids. A fish
ladder was finally built in 1922 as part of the permit to built Scott Dam. Fish
migrating here travel more than 800 hundred river miles and climb 4,500 feet.
Diversion Tunnel: This sinister tunnel sucks
the life out of the Eel River at the rate of 340 cubic feet per second, sending
it south into the Russian River. Eel River water is sold as far south as Marin
by the Sonoma County Water Agency, while fish struggle to survive in the shallow
water of the Eel River.
Scott
Dam (1922), 130' high, forms Lake Pillsbury and holds 80,560 acre-feet
of water. The area upstream of the dam contains 1,000 miles of prime spawning
and rearing habitat that is off limits to salmon. Lake Pillsbury is the incubator
for the predator pikeminnow that has supplied this invasive fish to the entire
system.
Sonoma County Progress and Problems by David
Keller, Bay Area Director, FOER - June 1, 2006
While Sonoma County still appears to be on a trajectory for water system
collapse, some exciting progress is being made on water consumption and
ending reliance on Eel River diversions through the Potter Valley Project.
How a Dam Gets
Removed: YouTube video from the removal of Milltown Dam on the Clark Fork River,
near Missoula Montana. The dam was breached on March 28th, 2008.
After
being used for this purpose, Eel River water is released to flow into the East
Fork of the Russian River. 
Cape
Horn Dam built in 1908 to create a bay, the Van Arsdale Reservoir,
to move water from the Eel River down the mile long diversion tunnel to create
electricity for the city of Ukiah on the Russian River. 5 cubic feet per second
is allowed over 50' high Cape Horn Dam into the Eel River - not enough for fish
to survive. Natural late summer flows are 50 to 55 cubic feet per second. Cape
Horn Dam was built without a fish ladder and cut off hundreds of stream miles
in prime spawning grounds for the largest of the Eel River salmonids. A fish
ladder was finally built in 1922 as part of the permit to built Scott Dam. Fish
migrating here travel more than 800 hundred river miles and climb 4,500 feet.
