Nicasio Reservoir

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Nicasio Reservoir
Nicasio Reservoir in Marin County California.jpg
Nicasio Reservoir seen from Nicasio Valley Road
LocationMarin County, California
Coordinates38°04′36″N 122°45′16″W / 38.07667°N 122.75444°W / 38.07667; -122.75444Coordinates: 38°04′36″N 122°45′16″W / 38.07667°N 122.75444°W / 38.07667; -122.75444
Primary inflowsNicasio Creek
Primary outflowsNicasio Creek
Basin countriesUnited States
Surface area845 acres (3.42 km2)[1]
Water volume22,400 acre⋅ft (27,600,000 m3)[1]
Surface elevation144 ft (44 m)[2]
SettlementsNicasio, California
Nicasio Reservoir aerial, 2012

Nicasio Reservoir is a shallow, artificial reservoir in the Nicasio Valley region of Marin County, California, United States. It covers 845 acres (3.42 km2) and sits in a 35.9 square miles (93 km2) drainage basin. It was created by the construction of Seeger Dam on the Nicasio Creek in 1961. Seeger Dam is a 115-foot (35 m) tall, 400-foot (120 m) long earthen dam owned by the Marin Municipal Water District.[1]


The construction in the dam aroused much controversy among longtime residents of the area.[citation needed] The Water District forced the displacement of many farms, including the McIsaac family farm and the Tomasini Ranch, on which the majority of the reservoir sits.[3] The controversy stems from the fact the water from the reservoir is rarely used by the Water District, that the broad and shallow nature of the reservoir leads to quick evaporation, and that the dam has blocked valuable spawning areas for endangered coho salmon[4] and threatened steelhead trout.[5] Construction of Seeger Dam wiped out the salmon population in Nicasio Creek. The District briefly attempted to trap salmon below the dam and transport them by truck further up Nicasio Creek and Halleck Creek. However, the effort proved unsuccessful.[3]


A river otter (Lontra canadensis) was collected by the Museum of Vertebrate Zoology at the southwest corner of Nicasio Reservoir in January, 2008.[6]

Recreational uses[edit]

The reservoir is used for recreational purposes; mainly fishing and hiking. Largemouth bass, carp and catfish are caught in the lake. There are problems with illegal poaching.[citation needed]

The California Office of Environmental Health Hazard Assessment (OEHHA) has developed a safe eating advisory for fish caught in Nicasio Reservoir based on levels of mercury or PCBs found in the fish species.[7]

See also[edit]


  1. ^ a b c "Dams Within the Jurisdiction of the State of California" (PDF). Retrieved 2008-01-17.
  2. ^ a b U.S. Geological Survey Geographic Names Information System: Nicasio Reservoir
  3. ^ a b Resneck, Jacob (October 28, 2004). "Nicasio History Revealed by Low Reservoir". Point Reyes Light.
  4. ^ "North-Central California Coast Recovery Program 5-Year Review: Summary and Evaluation of California Coastal Chinook Salmon ESU, Central California Coast Coho Salmon ESU" (PDF). National Oceanic and Atmospheric Administration. 2011. Retrieved 2013-12-03.
  5. ^ "North-Central California Coast Recovery Domain 5-Year Review: Summary and Evaluation of Central California Coastal Steelhead DPS Northern California Steelhead DPS" (PDF). National Oceanic and Atmospheric Administration. 2011. Retrieved 2013-12-03.
  6. ^ "Lontra canadensis brevipilosus". Museum of Vertebrate Zoology. 2008-01-29. Retrieved 2011-05-23.
  7. ^ Admin, OEHHA (2014-12-30). "Nicasio Reservoir". OEHHA. Retrieved 2018-06-13.