Grassy Lake Dam is a small dam operated by the U.S.

Bureau of Reclamation The Bureau of Reclamation, and formerly the United States Reclamation Service, is a federal agency under the U.S. Department of the Interior, which oversees water resource management, specifically as it applies to the oversight and opera ...

Teton County, Wyoming Teton County is a county in the U.S. state of Wyoming. As of the 2020 United States Census, the population was 23,331. Its county seat is Jackson. Its west boundary line is also the Wyoming state boundary shared with Idaho and the southern tip o ...

, immediately to the south of

Yellowstone National Park Yellowstone National Park is an American national park located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the 42nd U.S. Congress with the Yellowston ...

. The dam lies in a corridor of Bridger-Teton National Forest that runs between Yellowstone and

Grand Teton National Park Grand Teton National Park is an American national park in northwestern Wyoming. At approximately , the park includes the major peaks of the Teton Range as well as most of the northern sections of the valley known as Jackson Hole. Grand Teton Na ...

s. The dam structure and outlets are within a few hundred feet of the south boundary of Yellowstone. The zoned earthfill dam was built between 1937 and 1939 as part of the

Minidoka Project The Minidoka Project is a series of public works by the U.S. Bureau of Reclamation to control the flow of the Snake River in Wyoming and Idaho, supplying irrigation water to farmlands in Idaho. One of the oldest Bureau of Reclamation projects in t ...

, which provides water to irrigate farmland in

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...

's Snake River Plain. The dam provides only water storage, impounding . Given the small catchment area of Grassy Creek, inflow is augmented by a ditch that moves water from Cascade Creek into the reservoir.

Bechler Meadows dam proposals

The Grassy Lake Dam and the Island Park Reservoir in Idaho were the outcome of an ambitious plan to use the abundant waters of Yellowstone National Park for irrigation in Idaho, Montana and Wyoming. A variety of projects were proposed starting in 1919, the most advanced of which involved a proposed reservoir in the Bechler Meadows and Falls River regions of the southwest corner of the park, immediately to the north of the Grassy Lake site. In 1926 Idaho politicians led by Representative

Addison T. Smith Addison Taylor Smith (September 5, 1862 – July 5, 1956) was a United States House of Representatives, congressman from Idaho. Smith served as a Republican Party (United States), Republican in the United States House of Representatives, U.S. Hou ...

proposed the withdrawal of the Bechler area from the park for construction of a reservoir to collect water for use in Idaho. The backlash from conservationists, who compared the proposed reservoir to the

Hetch Hetchy Reservoir Hetch Hetchy is a valley, a reservoir, and a water system in California in the United States. The glacial Hetch Hetchy Valley lies in the northwestern part of Yosemite National Park and is drained by the Tuolumne River. For thousands of years bef ...

Yosemite National Park Yosemite National Park ( ) is an American national park in California, surrounded on the southeast by Sierra National Forest and on the northwest by Stanislaus National Forest. The park is managed by the National Park Service and covers an ar ...

, derailed the plan, along with disagreements between Wyoming, Montana and Idaho over water rights. The Grassy Lake and Island Park reservoirs were built outside the park as alternative storage sites.

References

External links

Grassy Lake Dam
{{Webarchive, url=https://web.archive.org/web/20120926032745/http://www.usbr.gov/projects/Facility.jsp?fac_Name=Grassy+Lake+Dam&groupName=Overview , date=2012-09-26 at the Bureau of Reclamation Dams in Wyoming Buildings and structures in Teton County, Wyoming Minidoka Project United States Bureau of Reclamation dams Dams completed in 1939 1939 establishments in Wyoming