Information contributed by Jason Shykowski and Matt Hardigree from a report dated November 25, 1994
and from a report by Diane Gentry dated November 15, 1995.
Dam Design and Construction
Current Uses and Operations
Folsom Data Links
CDEC Station-Current Sensor Data
USGS Hydrologic Data Report
Other Related links
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Folsom Dam and Lake during drought
Folsom Dam and Lake
Folsom Dam General Information
Folsom Dam and Reservoir is located downstream of the confluence of the north and south forks of the American River, near the City of Folsom. Folsom Dam is located approximately 20 miles northeast of Sacramento. The coordinates of the dam are 38° 42.5' North Latitude and 121° 9.4' West Longitude.
From Sacramento, take highway 50 east to Folsom Blvd. exit. From the off ramp, turn left onto Folsom Blvd. Continue on Folsom Blvd. until reaching Leidersdorff St. and turn left. At the traffic signal of Liedersdorff St. and Riley St.; turn left onto Riley St. and cross over the Rainbow Bridge. Next, turn right onto Folsom-Auburn Rd and proceed for about 1.5 mile, then turn right onto Folsom Dam Rd. The dam is the second gate to the right. If this gate is closed, use the first gate on the right after making the right turn onto Folsom Dam Rd.
The dam was constructed by the US Army Corps of Engineers, but is currently owned and operated by the US Government Department of the Interior, Bureau of Reclamation.
Bill Sanford, CE, (916)989-7217.
Alas, USBR no longer gives tours.
Folsom Dam Design and Construction:
Folsom Power plant is located at the base of the Folsom Dam. The water is delivered to the power plant via the three penstocks. Each penstock has a flow of 2300 cfs between the reservoir and through turbines. The water has a vertical drop of approximately 300 ft. The generators were built in 1956 and have a combined capacity of 198 Megawatts. On average, the power plant produces about 10% of the power used in Sacramento each year. (Baptista).
Folsom Dam Current Uses and Operations:
Reservoir Storage/Flood Control
Recent operating challenges
Concerns for future operations
As settlers began to move west, away from the crowded cities in the eastern portion of the United States, the Central Valley became a stopping point on the trails to Los Angeles, to San Francisco, and to the Northwest. Due to frequent flooding, the soil was very fertile and some people began settling and farming the land in the Central Valley (Devereux, 1).
The largest boom in development and growth in this area occurred after gold was discovered in 1849 at Sutter’s Mill, just east of the Sacramento foothills. The era of gold mining reached its peak in the mid to late 1800’s, finally ending in the late 1800’s, when the Sawyers Decision outlawed hydraulic mining. By this time, dredge trailings produced by the hydraulic mining industry had already clogged the valley's river system, further exacerbating the frequent flooding of this inland sea (Devereux, 1).
Farmers, merchants, and residents of the fertile valley began to evaluate their situation and contemplate ways to keep the river from overflowing their banks and flooding their homes and farms. A piecemeal flood control system consisting of levees, embankments, and channels was constructed, with each farmer or landowner working independently to protect their land from the inundation of the flooding rivers. As one would expect, this unorganized system provided little protection against the larger flood events which occurred in the late 1800’s (Devereux, 1).
In the aftermath of these failures, some people began to realize that if they worked together instead of independently, they could develop a more comprehensive and effective plan for the flood control of the river. However, no coordinated effort occurred until the State of California (by means of the Reclamation Board) and the federal government (by means of the Corps of Engineers) became involved. From the efforts of these two agencies, Congress authorized the Sacramento River Flood Control Project in 1917. This project envisioned a system of levees along the river channel, with large overflow channels connected to the rivers via a series of weirs and bypass channels to safely move any excess of the river's capacity to the Delta.
Folsom Lake impounds the runoff from 1,875 square miles of mountainous terrain. The lake is a source of flood control, water supply, electric power, and recreation. The new Folsom Dam is a product of the Central Valley Project (CVP). Final completion of the dam was in 1956. Although, by the end of 1955 the dam was able to store its first full capacity reservoir and produce electricity. The Folsom Dam was constructed to prevent flood damage. In 1986, the lake reached an all time high inflow of 813,165 cfs and with an outflow of 130,000 cfs only minor flooding resulted.
During the flood season, Folsom Dam and Reservoir is operated in according to criteria that has been promulgated by the Secretary of the Army (Devereux, 8). There are two criteria. The first is a design release of 115,000 cfs from the reservoir during a flood event. The second is 400,000 acre-feet of storage is dedicated to flood control. In the early 1950’s when these criteria were developed, this dam was expected to provide the Sacramento area with a 250 year level flood protection. Due to more and better data, the Corps of Engineers now determine that the dam will only provide for a 63 year level protection (Carlson, 2).
Flood control capacity could be increased if releases of greater than 115,000 cfs were allowed, but the levees on the American River are not capable of handling the greater flow for any extended time period.
Folsom Dam moderates winter and spring flows to the American River and releases water to the American River during the summer and fall. The four main water users are the city of Roseville, the North Fork Ditch (SJSWD), the city of Folsom and Folsom Prison, and the pumping plant. The water supply system is meant to provide for a maximum of 65 cfs for the Natomas Pipeline and 250 cfs for the North Fork Pipeline.
The largest percentage of water demand for Folsom is agriculture (CA Water Plan, 130). Crops grown include alfalfa, sugar beets, beans, rice, cotton, almonds, apricots, asparagus, grapes, melon, oranges, peaches, pears, plums, tomatoes, and walnuts. Rice accounts for 23% of the total acreage used for farming, which is also a very water intensive crop.
Urban water uses include residential, industrial, commercial, and government uses. Residential water use accounts for more than half of all urban water use. Landscaping accounts for about 75% of all residential water use (CA Water Plan, 130).
The Sacramento River Flood Control Project is complemented by the Central Valley Project (CVP), a system of dams and reservoirs. The CVP is a system by which water is stored and distributed throughout the Central Valley. The CVP also generates hydroelectric power for the Central Valley. The primary components of the CVP are a series of multi-purpose dams and reservoirs in the foothills which collects winter rains and spring runoff for use in the summer and the fall. These reservoirs are also connected to the existing flood control system. They are used during the flood control season to provide storage space for the runoff that is generated by large flood events, in addition they provide water supply, recreation, and power (Devereux, 2). The CVP stores and transports surplus water from the American, Sacramento, San Joaquin, Stanislaus, and Trinity River Basins in northern and central California, and that water is used primarily for irrigation in the Central Valley (Folsom Brochure). From the perspective of residents in the Sacramento area, the most prominent feature of the CVP is the Folsom Dam and Reservoir.
A portion of the supply in Folsom Lake must be set aside for environmental use, the second largest percentage of Folsom’s water demand. (CA Water Plan, 130). The CVP Improvement Act (CVPIA) of 1992 reallocated 1,000,000 acre-feet of supplies from its reservoirs for fish and wildlife (CA Water Plan, 2), thus increasing the amount of water from Folsom to be used for environmental purposes. Environmental issues include (Folsom Dam & Reservoir, V-18)
The main goal of the operational plans is the upkeep of the facilities in conjunction with environmental concerns and regulations. These concerns are mainly the survival of the winter-run Chinook Salmon. The winter-run Salmon have declined from a mean of 86,000 fish during the period of 1967-69 to 2,400 fish during the period of 1982-87 and to 500 fish in 1989-90. The Salmon are now protected under Federal and State Endangered Species Acts. Temperature is an important environmental variable affecting fish growth. Thus, in 1993 a Temperature Control Device (TDC) was proposed to be located on the face of the dam at the penstock intake. This TDC would improve the temperature of the water by releasing water from different levels of the dam, then into the power house to generate electricity.
Concerns for future
Silting within the dam may present future concerns. The build up of Calcium Carbonate must be attenuated in the pipes every 2-3 years to prevent clogging. Dynamic compaction of soils beneath the Folsom's auxillary earth dam was necessary to correct for dilation.
There possibly exists a low estimate of the 100-year flood from 1949. Currently, the dam can manage a flood severity near that of a 63-year flood. By adding more flood storage capacity to the reservoir, the water supply and the power plant production would decrease.
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