The assets considered to be components of the Potter Valley Project (PVP), include the Scott Dam, Cape Horn Dam, the powerhouse and a system of tunnels and pipes through a mountain diverting 70,000-acre-feet of water annually south via the Russian River’s East Fork leading to Lake Mendocino. PG&E bought the PVP in 1930.

Formed in 1996, MCIWPC is a joint powers authority that includes the County of Mendocino, City of Ukiah, Redwood Valley County Water District, Potter Valley Irrigation District (PVID) and the Mendocino County Russian River Flood Control and Water Conservation Improvement District. Collectively, these groups are working together to assume ownership and control of this essential regional resource.


The history of water-related issues in and around Potter Valley goes back more than a century beginning with the building of Mendocino County’s Cape Horn Dam, the diversion tunnel and powerhouse in 1908 on the Eel River, followed by the Scott Dam in 1922 forming Lake Pillsbury.

In 1906, the Potter Valley Irrigation District (PVID) was formed dedicated to supporting local agriculture. Now there is concern over the future of the Cape Horn Dam, Scott Dam, the powerhouse and river diversion that supplies water to farms and towns in southern Mendocino, Sonoma and Marin Counties.

In Mendocino County, the Eel River flows west from Lake Pillsbury and the Scott Dam to a hydroelectric powerhouse. After passing through the powerhouse, water enters a diversion tunnel at the Van Arsdale Reservoir and continues south via the East Branch of the Russian River in the Potter Valley area to Lake Mendocino and the Coyote Valley Dam built in 1959.

From Lake Mendocino, Russian River water flows into Sonoma County passing the confluence of Dry Creek and on to the Pacific Ocean. Water not entering this diversion tunnel continues to supply the Eel River on its journey west to the coast.

Immediate Challenges

The challenge this summer for MCIWPC is meeting the Federal Energy Regulatory Commission’s (FERC) deadline of July 1, 2019 by preparing a Notice of Intent and Pre-Application Document, while beginning a feasibility study to draft a re-licensing proposal for the Potter Valley Project (PVP). At the same time, MCIWPC is continuing to build a broad regional coalition among entities dependent upon this inter-river project.

“For us, public outreach and support is essential, as well as obtaining short term and long-term funding,” according to Dr. Pauli. “Our objective is to maintain the PVP diversion at a rate, and timing, that continues to provide the water supply that currently supports our quality of life and the economy of the Russian River watershed. We also want to continue to collaboratively manager our shared water resource to enhance the riverine ecology of both the Eel River and the Russian River.”

Water Value to PVID

Potter Valley has 272 landowners in the PVID who grow pears (195 acres), grapes (2,136 acres); have pastures for cattle (2,354 acres) and produce other crops (on 87 acres). The value of tree and vine crops alone is estimated at between $30 and $35 million.

The PG&E Potter Valley powerhouse has the capacity to generate 9.2 megawatts (MW). Three smaller privately-owned powerhouses downstream have the capacity to generate 1,180 kilowatts (kW). If one assumes that a typical home uses three to 3.5kW, these powerhouses can generate enough power to supply energy for 2,885 to 3,366 homes.

This lake had an original capacity of 122,400-acre feet (AF), but this has fallen to about 116,000 AF due to sediment infill over the years. The water supply comes from a small watershed above Lake Mendocino (105 sq. miles) as well as from the PVP. A fish hatchery is located at the lake and the City of Ukiah has a hydro-electric power plant producing 3.5 MWs of power.

Water releases are controlled by the Army Corps of Engineers (ACOE) and the Sonoma County Water Agency (SCWA). ACOE and MCIWPC are currently studying the feasibility of increasing the storage capacity of Lake Mendocino – by raising the Coyote Valley Dam 36 feet — to make more water available and to avoid droughts, such as occurred at the end of October 2014 that left this lake dry.

The $300 million cost of raising the dam is virtually the same as the cost of dredging sediment accumulated over the years (some 5,000 AF). However, raising the dam’s height would double lake capacity and increase yield by 20,000 AF.

Mendocino County communities are dependent on Eel River water stored in this lake. For examples, Redwood Valley’s agriculture community, including domestic users, uses 1,500 AF; Calpella and Millview use 1,600 AF; the City of Ukiah, Ukiah Valley and Talmage use 2,200 AF; Hopland uses 200 AF and the Russian River Flood Control – State Water Resources Control Board (SWRCB) has a right to 8,000 AF.

Collectively, Lake Mendocino provides drinking water for more than 31,000 people that live in these towns, as well as water for fire protection, all commercial/industrial uses and for agricultural economy all along the Russian River corridor.

According to research findings developed by Dr. Robert Eyler, with Economic Forensics and Analytics, Inc., in 2015, “It’s important to recognize that Lake Mendocino is considered the main source of water for agriculture use in the study area” (within the Russian River Flood Control and Water Conservation Improvement District and Redwood Valley County Water District). He said, “Groundwater is not a direct substitute for water coming directly from the lake.”

He said farmers that use water from Lake Mendocino “to generate or support over $743 million of business revenue of the county’s economy of just over $3.5 billion, over 5,000 jobs out of 32,000 county workers and support approximately $16.1 million in local tax revenue annually.”

In Sonoma County, the Russian River is the main source of water for 8,600 people in the City of Cloverdale (100%); the City of Geyserville’s 2,100 residents (100%) and the City of Healdsburg’s 11,500 residents (77%). The agricultural economy of Sonoma County borders corridors adjacent to both sides of the Russian River. Upstream of the Dry Creek confluence, some 14,916 acres of vineyards and orchards would be potentially impacted if Russian River flows were reduced.

Based on an assessment of vine and tree crop values for Sonoma County’s Alexander Valley, there were 13,868 acres of wine grapes with a crop value in 2018 of approximately $180,158,900 (compiled by the Sonoma County Agriculture Commissioner, not including a multiplier valuation). Many of these vineyards border the Russian River – including water for irrigation being diverted from underflow. Also produced are a few acres of olives, tomatoes and other specialty crops. The SCWA estimates that agriculture in this valley uses about 11,000 AF of water annually from the Russian River.

Water conservation efforts, including PVID’s annexation moratorium since 2000, have included water wasting resolutions and bylaws. All cities dependent upon Lake Mendocino Water have water conservation ordinance and/or moratoria in place.

Redwood Valley had a domestic annexation moratorium in 1989, and an Ag moratorium since 2007. The City of Ukiah has a water conservation coordinator and active program. The City of Cloverdale has a summer water conservation program with limits on residential landscape water use, etc. Healdsburg has Water Conservation Ordinance 1077, and Resolution 58-2013.

At the same time, agricultural irrigation of vineyards is very conservative, using on average only 0.54 to 1.1-AF of water per acre each year. This is less than an average housing development, when it comes to per acre us. (Note: Rates of unregulated illegal diversions in the Eel and Russian River watersheds are unknown.)

Lake County Concerns

Lake County derives economic benefits from Lake Pillsbury recreation and from homeowners at the lake that contribute to the county’s economy through property taxes. In addition, Lake Pillsbury has been sourced extensively during recent and historical fires as a water supply for U.S. Forest Service and CalFire wildfire suppression.

Marin County Concerns

Northern Marin is dependent on Lake Mendocino’s water as a percentage of its domestic water supply. Some 80% of the water purchased by the North Marin Water District comes from the Sonoma County Water Agency via the Russian River.

Summer and fall recreation in Lake Pillsbury, the Upper Main Eel River, Lake Mendocino and the Russian River from Coyote Valley Dam to Jenner is supported by water stores in Lake Pillsbury from winter rains and snowmelt.

Environmental Concerns

Water releases below Scott Dam and the Van Arsdale Reservoir on the Eel River are based on FERC license requirements developed by fishery agencies to protect habitat for migrating, spawning and rearing of salmon and steelhead.

Water flows on the East Branch of the Russian River in Potter Valley, below the PVP, have fishery protection requirements imposed by CDFW (California Department of Fish and Wildlife). Some of the water stored in Lake Mendocino is dedicated to fishery migration flows (water releases) required at specific times of the year in the Russian River below Lake Mendocino.

Diversion Impacts to Eel River Ecology

The building of Scott Dam, forming Lake Pillsbury in 1922, blocked 8% of the upper Eel River watershed to migrating salmonids. On average, since the flow changes based on the NMFS (National Marine Fisheries Service) RPA in 2007, 21% of the unimpaired flows in the Upper Eel River above Cape Horn Dam are diverted annually through the Potter Valley Project. Water diverted from the Eel to the Russian River averages 1.8% of the annual flows of the entire Eel River watershed.

Some 2,500 AF of “Block Water” stored in Lake Pillsbury can be released annually as directed by the fisheries agencies to assist with upstream and downstream fish migration in the Eel River watershed. For example, stored water was released to protect stranded fish in the lower Eel River during the drought years of 2013-2016.

Potter Valley Project Relicensing

The pending relicensing of the Potter Valley Project is a major issue today, since fixed deadlines are set in FERC’s relicensing schedule. In 2017 PG&E filed a Notice of Intent and the Pre-Application Document along with study plans (AQ1-TERR 2). These study plans were accepted by FERC. The studies were underway and scheduled to be completed by the end of 2019. The report of study results was to have been filed with FERC. PGE was supposed to file the final application for the license by April 2020, since the current license expires on April 14, 2022.

However, on May 10, 2018, PG&E announced its intention to auction the PVP in a letter sent to the Eel Russian River Commission. PG&E stated that small hydro facilities, especially like PVP which is remotely located, are no longer economically viable for them to operate because of lower generation needs.

Consequently, MCIWPC signed a Non-Disclosure Agreement and prepared an IP which was due February 1, 2019. On January 25, 2019, PG&E withdraws its NOI to relicense and both the auction process and relicensing studies ended. Four days later on January 29, 2019 PG&E filed its notice for bankruptcy.

As of March 1, 2019, FERC started its 120-day timeline for a new NOI and PAD (Pre-Application Document). In May 2019, a planning agreement was signed by MCIWPC, CalTrout and Sonoma Water to prepare the process NOI and begin a feasibility study for relicensing the Potter Valley Project.

In 2017 Congressman Huffman convened an ad hoc committee of stakeholders with the goal to discuss water supply and ecological concerns and develop a Two Basin Solution for PVP.

This committee had two major goals: Improve fish passage and habitat in the Eel River Basin sufficient to support recovery of naturally reproducing, self-sustaining salmon and steelhead populations, including fish passage past Scott Dam; while also minimizing or avoiding adverse impacts to water supply reliability, fisheries, and water quality in the Russian River Basin.

Water Supply and Fish Passage Subcommittees were formed along with a commitment to develop a hydrological model, along with a study of alternative fish passage options for Scott Dam and costs analyses while also providing updates on progress.

For more information, go to the Mendocino County Inland Water and Power Commission Website:; the Potter Valley Irrigation District website:; as well as the Mendocino County Farm Bureau website: To learn more about Congressman Jared Huffman’s ad hoc committee, go to the website: