Donnelly Reservoir

Donnelly Reservoir
Name	Donnelly Reservoir
Location	El Dorado County, California, United States
Type	reservoir
Inflow	Diversion from South Fork American River, consumptive water rights, local streams
Outflow	North Fork American River tributaries, managed releases
Basin countries	United States
Area	224 acres
Max-depth	140 ft
Volume	10,000 acre·ft
Created	1968
Coordinates	38°50′N 120°34′W

Donnelly Reservoir is a man-made impoundment in El Dorado County, California formed by the Donnells Dam complex on tributaries of the North Fork American River watershed. The reservoir functions as part of regional water supply and hydropower networks, supporting recreational activities near Auburn, California and Placerville, California. It sits within the Sierra Nevada foothills and interacts with state and federal water projects, regional districts, and federal agencies.

Geography and Location

The reservoir is situated in the western Sierra Nevada near the Tahoe National Forest boundary and lies within the political boundaries of El Dorado County, California and close to the Placer County, California line. It occupies a canyon formed by tributaries feeding the North Fork American River, downstream of mountainous terrain that includes the Emigrant Gap corridor and near route connections to Interstate 80. Surrounding land uses include parcels administered by the United States Forest Service, private holdings linked to El Dorado Irrigation District operations, and areas influenced by historical mining claims from the California Gold Rush era.

History and Construction

Planning for the reservoir dates to mid-20th-century water development schemes coordinated among the U.S. Bureau of Reclamation, Pacific Gas and Electric Company, and regional water districts such as the El Dorado Irrigation District and the South Tahoe Public Utility District. Construction of the dam and impoundment occurred in the 1960s, influenced by post-war infrastructure initiatives that also produced projects like the Oroville Dam and expansions of the Central Valley Project. Engineering involved rock-fill and concrete structures designed to withstand Sierra Nevada seismicity, with oversight from state agencies including the California Department of Water Resources. The site's history also intersects with local communities such as Pollock Pines, California and historic routes used during the California Gold Rush.

Hydrology and Water Management

Hydrologic inputs include seasonal snowmelt from the Sierra Nevada crest and rainfall from Pacific storm systems traveling along the Pacific Ocean coast. The reservoir participates in regulated releases that coordinate with downstream facilities on the American River system, serving roles in municipal supply for districts like the El Dorado Irrigation District and recreational flow maintenance for reaches managed by the California Department of Fish and Wildlife. Water quality monitoring aligns with standards influenced by the Safe Drinking Water Act and state water boards such as the California State Water Resources Control Board. Hydropower turbines and bypass works were designed in consultation with utility entities including Pacific Gas and Electric Company and regional transmission planners connected to California Independent System Operator operations.

Ecology and Wildlife

The reservoir and riparian corridors support habitats for species recorded in the Sierra Nevada ecosystem, including fish populations managed by the California Department of Fish and Wildlife such as introduced trout strains and native minnows. Terrestrial species in adjacent forests include populations of black bear, mule deer, and avifauna like bald eagle sightings associated with reservoir fisheries. Vegetation communities reflect mixed-conifer stands similar to those in the Tahoe National Forest with understory plants found in habitats studied by researchers at institutions like University of California, Berkeley and University of California, Davis. Conservation concerns involve invasive species management, sedimentation linked to historic hydrologic disturbance, and wildfire risk discussed in publications from the U.S. Forest Service and California Department of Forestry and Fire Protection.

Recreation and Public Use

Public access supports boating, angling, and shoreline camping under permits administered by county and federal agencies including El Dorado County, California parks officials and the United States Forest Service. Recreational fishing targets trout and warmwater species, and regional guides reference access routes from communities such as Pollock Pines, California and Placerville, California. Nearby trail systems connect to recreational corridors used by hikers and mountain bikers traveling toward Desolation Wilderness and other Sierra preserves; visitor services intersect with commercial outfitters licensed by local counties and overseen by state entities like the California Department of Parks and Recreation.

Infrastructure and Access

Access roads link the reservoir to primary highways including U.S. Route 50 and feeder roads serving El Dorado County, California communities; maintenance and emergency response coordination involve county sheriffs and the California Highway Patrol. Infrastructure adjacent to the reservoir includes dam safety instrumentation monitored under protocols developed by the California Division of Safety of Dams and federal guidelines from the Federal Energy Regulatory Commission where applicable. Utilities and transmission lines serving hydropower components coordinate with regional providers such as Pacific Gas and Electric Company and grid operators like the California Independent System Operator.

Category:Lakes of El Dorado County, California