Terminus Dam

Terminus Dam is a dam on the Kaweah River in Tulare County, California in the United States, located near Three Rivers about from the western boundary of Sequoia National Park and east of Visalia. The dam forms Lake Kaweah for flood control and irrigation water supply. Completed by the U.S. Army Corps of Engineers (USACE) in 1962, Terminus is an earthfill dam high and long. The reservoir has a maximum capacity of of water, although it usually sits at much lower levels.

Background

Various informal proposals to dam the Kaweah River existed in the early 20th century. In April 1917, a group formed in Visalia, representing irrigation ditch companies across the region, to discuss building the dam. Around the same time, the California legislature approved plans to investigate the project's feasibility. Initial engineering surveys began in May 1917 along the Kaweah. After the California legislature passed the Water Control Act of 1927, the Kaweah Delta Water Conservation District was formed in January 1928, which was the first flood control district in the state. In the early 1940s, the United States Army Corps of Engineers took surveys for the purpose of a flood control dam along the Kaweah, as well as the nearby Tule River. Amid World War II, the Bureau of Reclamation blocked the release of the report for more than two years, due to an executive order by President Franklin Delano Roosevelt. In March 1943, Tulare County created a committee to launch their own studies on building the dam, to present their findings to the United States Congress. In June of year, the Kaweah Delta Water Conservation District also petitioned the United States Congress to build the dams. The Army Corps of Engineers took additional surveys for the dams in 1943 into 1944, proposing a high structure along the Kaweah River, which would create a reservoir of . In March 1944, the United States House Flood Control Committee approved $4.6 million toward building both the Kaweah and Tule dams, as part of legislation that became the Flood Control Act of 1944, signed into law that December.

By January 1945, the planned Terminus Dam along the Kaweah was constructed to be high, which was higher than initial estimates to account for larger and more regular flooding. The structure was named for originally being the terminus of a railroad extending from Visalia. The project was delayed at first due to the ongoing war, but by August 1945, Congress authorized funds for preliminary tests for the planned dams. In May 1946, preliminary drilling work began for the site. However, lack of funding prevented more immediate action for construction. In 1948, with plans for the dam on the Kaweah River nearly complete, an archaeological survey of the future reservoir site revealed an unusually rich selection of Native American artifacts. In 1950, two Yokuts villages were excavated, which would be underwater after the dam was finished. Many of the artifacts were removed by the U.S. National Park Service's Interagency Archaeological Salvage Program before the beginning of work on the dam. Following downstream floods in December 1955 into early 1956, the United States Congress authorized $18.6 million toward building the Terminus Dam in July 1956, partly as a response to the floods. A month later, the Army Corps of Engineers publicly released their updated plan – the new dam would be earth-filled, with a height of , a length of long, and enough storage capacity to hold more than double of the December 1955 floods. In preparation for the new dam, the California Highway Department relocated a portion of SR 198 to higher ground. In December 1958, the Army Corps approved a $9.4 million contract by a joint venture based in Monrovia, California.

History

Construction for the Terminus Dam began in January 1959, with a formal groundbreaking ceremony held on February 19. By the end of July 1959, construction work was 9% complete, consisting of tree removal, soi movement, and an outlet tunnel. During the fall of 1959, water flow along the Kaweah was low, which allowed workers to divert the river and start building the dam's base. By December 1959, construction work was 27% complete, with 151 workers and engineers building the dam, and another 138 people relocation the portion of SR 198. That month, an observation area opened to allow visitors to view the progress of the construction.

Terminus Dam is one of four dams built on the rivers of the Tulare Lake basin, located at the southern end of the San Joaquin Valley. Construction of Terminus Dam started was completed in 1962. The dam was dedicated along with the Success Dam, further south on the Tule River, on May 18, 1962.Brewer, p. 55 The reservoir filled for the first time in 1964 to its initial capacity of . Sedimentation had reduced this to by 1977.

Together with the three other major dams in the Tulare basin, Terminus Dam contributed to the desiccation of Tulare Lake, once one of the largest wetland regions in the United States.

Spillway expansion

In the 1990s the USACE began studies for a project to increase the capacity of the dam's spillway, which was considered inadequate to pass the probable maximum flood on the Kaweah River. In 2001 work began to enlarge the spillway channel and between 2003 and 2004 six fusegates were installed in the spillway channel, raising the maximum elevation of the reservoir by . The fusegates, invented and patented by François Lempérière for Hydroplus, subsidiary of GTM Entrepose, are the largest in the world, and are designed to open automatically by water pressure when Lake Kaweah reaches dangerously high levels. The design was chosen because it would provide cost savings over conventional options such as a concrete or gated spillway.

The project increased the storage capacity of Lake Kaweah by more than , to its current capacity of , and ensured the capability of Terminus Dam to pass a flood of up to . The dam is now capable of completely controlling a 70-year flood, as compared to a 46-year flood before the fusegates were installed.

Functions

As a dry dam, Terminus Dam's primary purpose is flood control; consequently, the reservoir is usually maintained at a very low level, except in late spring and early summer when it is used to store snowmelt runoff from the Sierra Nevada. The dam provides flood protection for of farmland and 300,000 people along the lower Kaweah River. Shortly after its completion, the dam and reservoir were put to the test by record floods in December 1966, during which Terminus, Success and Isabella Dams prevented a collective $81.9 million of damages. Between 1962 and 2012, Terminus Dam has prevented $373,225,000 of flood-related damages.

Water releases from Terminus Dam are made based on agricultural demand when flood control releases are not required. Snowmelt runoff stored in Lake Kaweah are released at high rates between May and late July-early August during the peak of the irrigation season. The water serves multiple local water districts such as the Tulare Irrigation District (TID) and Kaweah Delta Water Conservation District (KDWCD), as well as urban areas including Visalia and Tulare. The dam also generates hydroelectricity from a plant built in 1992 by the Kaweah River Power Authority (KRPA), which is jointly managed by TID and KDWCD. Electricity generated here is distributed by Southern California Edison. The power plant currently has a capacity of 20.09 megawatts (MW), upgraded from its original capacity of 17 MW, and generates roughly 40 million kilowatt hours (KWh) per year. The KRPA planned to expand this capacity by a further 9 MW, which would allow for the generation of an additional 9.2 million KWh, but construction has not yet started . In February 2020, the KRPA filed to transfer their operating license to Eagle Creek Renewable Energy, the US subsidiary of Ontario Power Generation.

See also

* 2025 water release from Lake Kaweah and Lake Success
*Central Valley Project
*List of dams and reservoirs in California

References

Works cited

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External links

Lake Kaweah
- U.S. Army Corps of Engineers
Daily data for Terminus Dam and Lake Kaweah
- California Department of Water Resources

{{Tulare Basin Hydrography

Terminus
Buildings and structures in Tulare County, California
United States Army Corps of Engineers dams
Dams completed in 1962
Earth-filled dams
Dams in the Tulare Basin