Boysen Reservoir Water Level
Boysen Reservoir is at 4,712.47 ft today (Oct 31), 12.53 ft below its 4,725 ft full pool, up 0.61 ft this week.
Wyoming · Wind River
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Water level history
About Boysen Reservoir
Boysen Reservoir is a reservoir on the Wind River in Wyoming, operated by U.S. Bureau of Reclamation. Its full summer pool sits at 4725 ft above sea level. Live water levels come from the U.S. Army Corps of Engineers (CWMS) and update hourly.
Understanding Boysen Reservoir's water level
Boysen Dam sits at the mouth of Wind River Canyon, about 17 miles south of Thermopolis, where the Wind River leaves the Shoshoni basin and cuts north through the Owl Creek Mountains. Reclamation's Wyoming Area Office in Mills runs it as part of the Pick-Sloan Missouri Basin Program, and the figure that matters most on this page is 4,725 feet. That is the top of the joint use pool, the level at which the reservoir holds 802,000 acre-feet of controlled storage. The band from 4,717 to 4,725 feet, about 144,000 acre-feet, is the joint use pool itself. Above 4,725 sits roughly 150,600 acre-feet of exclusive flood control space reaching 4,732.2 feet, which is why the lake can climb past full in a big runoff year without anything going wrong at the dam. At the other end, 4,685 feet is the top of inactive storage. A normal year runs low through winter, when releases through the two turbines fall to a few hundred cubic feet per second, then climbs with Wind River snowmelt from May into July.
The name comes from Asmus Boysen, a local businessman who put a small concrete hydropower dam across the river in 1908 on land leased from the Shoshone and Arapaho tribes. It generated about 710 kilowatts, had silted in by 1925, and was removed in 1948 while the federal dam went up just upstream; part of it can still be seen in Boysen State Park. Congress authorized the new dam in 1944. Excavation started in 1947, the reservoir began filling in October 1951, power came on line in August 1952, and the project was declared complete on January 1, 1953, at a cost of more than $18 million. Building it meant moving 13.5 miles of Chicago, Burlington and Quincy track into a new route with a tunnel about a mile and a quarter long, and the plant's 15 foot penstock now runs through the bore of the old railroad tunnel. Below the dam the river runs through the canyon to the Wedding of the Waters, where the Wind River ends in name and continues as the Bighorn.
Water year 2026 has been a short one. Reclamation's reports show Boysen inflow at 44 percent of normal in May, 34 percent in June and 37 percent in July, the months that usually refill the lake, and the reservoir stood at 4,710.65 feet with 501,743 acre-feet at the end of August, about fourteen feet under the joint use line. The September most probable forecast has it slipping to roughly 4,708.6 feet in October before winter releases of about 400 cubic feet per second let it creep back up, with a peak near 4,724.5 feet next July if runoff is average. Wet years look very different. In late June 2017 the lake reached about 4,729 feet, four feet into flood space, and Reclamation was passing 9,000 cubic feet per second through the canyon. In June 2023 high water closed parts of the Tough Creek and Tamarask campgrounds in the state park, though the boat ramps and marina stayed open. The water stored here irrigates more than 60,000 acres along the Bighorn River below the dam.
Boysen Reservoir — frequently asked
What is Boysen Reservoir's full pool elevation?
4,725 feet, the top of the joint use pool, where the reservoir holds 802,000 acre-feet of controlled storage. Reclamation lists the top of active conservation lower, at 4,717 feet, and keeps about 150,600 acre-feet of exclusive flood control space above 4,725 up to 4,732.2 feet. Readings above 4,725 mean runoff is being held in that flood space, not that the dam is in trouble.
Why is Boysen Reservoir so low in 2026?
The spring runoff mostly failed to show up. Inflow from the Wind River ran at 44 percent of normal in May, 34 percent in June and 37 percent in July, so the lake never got its usual summer refill while irrigation releases continued downstream. At the end of August it sat at 4,710.65 feet, and Reclamation's September forecast expected it to dip to about 4,708.6 feet in October.
When will Boysen Reservoir refill?
Not before next summer. Reclamation's September 2026 most probable plan holds winter releases near 400 cubic feet per second from November through March, letting the lake rise only a few feet by February. Refill depends on Wind River snowmelt; under average runoff the forecast reaches about 4,724.5 feet in July 2027, while the reasonable minimum case shows the lake falling to around 4,701 feet by the end of August 2027.
How high has Boysen Reservoir gotten?
In wet years the lake goes well into its flood pool. In late June 2017 it stood near 4,729 feet, about four feet above normal full, with 9,000 cubic feet per second released through Wind River Canyon. In June 2023 high water flooded parts of the Tough Creek and Tamarask campgrounds at Boysen State Park. The exclusive flood control space tops out at 4,732.2 feet, and the dam crest is at 4,758 feet.
How is the walleye fishing at Boysen?
Strong right now, according to Wyoming Game and Fish. Its 2026 outlook calls the walleye population in the 14 to 20 inch range phenomenal and reports a significant number of fish over 25 inches. Sauger have been rebuilding after an early 2000s crash the department tied to extended drought, and 2019 netting found most yellow perch were keeper size at 9 to 12 inches. Shore anglers catch 17 to 20 inch rainbows in spring.
Where does the Wind River become the Bighorn River?
Below Boysen Dam and Wind River Canyon, at a spot called the Wedding of the Waters, marked by a roadside sign. The water keeps flowing north toward Thermopolis but changes its name there, ending the Wind River after about 185 miles and starting the Bighorn, the largest tributary of the Yellowstone. The Thermopolis Chamber of Commerce asked for a marker at the site in 1934.
Who was Boysen Reservoir named for?
Asmus Boysen, a local businessman who built a small concrete hydropower dam on the Wind River in 1908, on land leased from the Shoshone and Arapaho tribes. It produced about 710 kilowatts but had filled with silt by 1925 and was removed in 1948 during construction of the present Reclamation dam just upstream. Remnants of the old dam are still visible in Boysen State Park, which Wyoming established in 1956.
Other lakes near Boysen Reservoir
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