There are two hydroelectric dams on the Eel – 130-foot (40 m) Scott Dam, which forms Lake Pillsbury, and 50-foot (15 m) Cape Horn Dam, which forms Van Arsdale Reservoir just north of Potter Valley.
At Cape Horn Dam, the majority of the water is diverted through a tunnel and hydroelectric plant, and then to the headwaters of the Russian River in Potter Valley and is known as the Potter Valley Project.
Originally conceived in the late 1800s and built between 1906 and 1922, the project provides about 159,000 acre feet (0.196 km³) of additional waters for the Russian River system, for about 500,000 people in Mendocino and Sonoma Counties.

The Potter Valley Project has been argued by environmental groups to have significant impacts on the salmonid (Chinook and coho salmon and steelhead) populations of the basin.
Although dam operators are required to maintain certain flows below the diversion during the dry season, these flows can be cut during exceptionally dry years, preventing salmonids from reaching certain spawning streams in the Eel River basin.
Project water is disproportionately important to salmonids in the Eel River system as a whole because the water released from the bottom of Scott Dam is the only cold water available in the basin during the dry season.
During July, August and September, temperatures in the lower Eel River occasionally hit 85 °F (29 °C) or higher, creating fatal conditions for these fish.

In 1983, the Federal Energy Regulatory Commission relicensed the project under the condition that more water be provided to the Eel River during the dry season and less be diverted to the Russian River basin.
Dam releases are now timed to mimic natural flows in the Eel River system.
Occasional large "blocks" of water are also released from Scott Dam to help juvenile salmonids migrate to the sea before temperatures in the lower river become unsuitable for their passage.
These conditions were revised in 2004, when stricter minimum release standards were established.
In combination with drought in the early 21st century, average diversions through the project have decreased by about 69,000 acre feet (0.085 km³) for the period 2004 through 2010.
In December 2013, due to record low levels of water in the Eel River and the associated dammed lakes, levels of fish and lampreys in the rivers were at lowest recorded levels, and Pacific Gas and Electric Company sought to have FERC change their operating license to permit even lower releases of water to Eel until the drought eases.
Under current agreements, the dams must release at least 100 cubic feet per second (2.8 m³/s) beginning every year on December 1 to aid salmon migration.

The federal United Western Investigation study in 1951 proposed multiple large dams on the wild North Coast rivers of California, including the Eel River.
These dams would have been far bigger than those of the Potter Valley Project, and would create some of the largest reservoirs in California.
 The Army Corps of Engineers and Bureau of Reclamation both sought to build dams in the Eel River system, which starting in the 1960s was targeted as a potential new source for the California State Water Project.
Major dams proposed in the watershed included ones at English Ridge, Bell Springs and Sequoia (Alderpoint) on the main stem, and the infamous Dos Rios on the Middle Fork.
Dos Rios Dam would have flooded 110,000 acres (45,000 ha) of Mendocino County, creating a reservoir of 7.5 million acre feet (9.3 km³) – the largest in California, at nearly twice the size of Shasta Lake.

Water would have been diverted from English Ridge north to Dos Rios and through a 40-mile (64 km) tunnel to the offstream Glenn-Colusa reservoir in the Sacramento Valley, from which the water would travel by canal to the Sacramento River.
An alternate proposal would have sent the water south from Dos Rios, through English Ridge and then a tunnel to Clear Lake, from which the water would flow down Cache Creek to the Sacramento River.
From the beginning, these dams were heavily contested by local residents as well as by environm
There are two hydroelectric dams on the Eel – 130-foot (40 m) Scott Dam, which forms Lake Pillsbury, and 50-foot (15 m) Cape Horn Dam, which forms Van Arsdale Reservoir just north of Potter Valley. At Cape Horn Dam, the majority of the water is diverted through a tunnel and hydroelectric plant, and then to the headwaters of the Russian River in Potter Valley and is known as the Potter Valley Project. Originally conceived in the late 1800s and built between 1906 and 1922, the project provides about 159,000 acre feet (0.196 km³) of additional waters for the Russian River system, for about 500,000 people in Mendocino and Sonoma Counties.
The Potter Valley Project has been argued by environmental groups to have significant impacts on the salmonid (Chinook and coho salmon and steelhead) populations of the basin. Although dam operators are required to maintain certain flows below the diversion during the dry season, these flows can be cut during exceptionally dry years, preventing salmonids from reaching certain spawning streams in the Eel River basin. Project water is disproportionately important to salmonids in the Eel River system as a whole because the water released from the bottom of Scott Dam is the only cold water available in the basin during the dry season. During July, August and September, temperatures in the lower Eel River occasionally hit 85 °F (29 °C) or higher, creating fatal conditions for these fish.
In 1983, the Federal Energy Regulatory Commission relicensed the project under the condition that more water be provided to the Eel River during the dry season and less be diverted to the Russian River basin. Dam releases are now timed to mimic natural flows in the Eel River system. Occasional large "blocks" of water are also released from Scott Dam to help juvenile salmonids migrate to the sea before temperatures in the lower river become unsuitable for their passage. These conditions were revised in 2004, when stricter minimum release standards were established. In combination with drought in the early 21st century, average diversions through the project have decreased by about 69,000 acre feet (0.085 km³) for the period 2004 through 2010. In December 2013, due to record low levels of water in the Eel River and the associated dammed lakes, levels of fish and lampreys in the rivers were at lowest recorded levels, and Pacific Gas and Electric Company sought to have FERC change their operating license to permit even lower releases of water to Eel until the drought eases. Under current agreements, the dams must release at least 100 cubic feet per second (2.8 m³/s) beginning every year on December 1 to aid salmon migration.
The federal United Western Investigation study in 1951 proposed multiple large dams on the wild North Coast rivers of California, including the Eel River. These dams would have been far bigger than those of the Potter Valley Project, and would create some of the largest reservoirs in California.  The Army Corps of Engineers and Bureau of Reclamation both sought to build dams in the Eel River system, which starting in the 1960s was targeted as a potential new source for the California State Water Project. Major dams proposed in the watershed included ones at English Ridge, Bell Springs and Sequoia (Alderpoint) on the main stem, and the infamous Dos Rios on the Middle Fork. Dos Rios Dam would have flooded 110,000 acres (45,000 ha) of Mendocino County, creating a reservoir of 7.5 million acre feet (9.3 km³) – the largest in California, at nearly twice the size of Shasta Lake.
Water would have been diverted from English Ridge north to Dos Rios and through a 40-mile (64 km) tunnel to the offstream Glenn-Colusa reservoir in the Sacramento Valley, from which the water would travel by canal to the Sacramento River. An alternate proposal would have sent the water south from Dos Rios, through English Ridge and then a tunnel to Clear Lake, from which the water would flow down Cache Creek to the Sacramento River. From the beginning, these dams were heavily contested by local residents as well as by environm
Eel River (California)