Bighorn Lake Water Level
Bighorn Lake is at 3,626.40 ft today (Oct 31), 13.60 ft below its 3,640 ft full pool, down 0.09 ft this week.
Montana & Wyoming · Bighorn River
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Water level history
About Bighorn Lake
Bighorn Lake is a reservoir on the Bighorn River in Montana & Wyoming, operated by U.S. Bureau of Reclamation. It runs through Bighorn Canyon, where the walls rise more than 1,000 feet. Its full summer pool sits at 3640 ft above sea level. Live water levels come from the U.S. Army Corps of Engineers (CWMS) and update hourly.
Understanding Bighorn Lake's water level
Bighorn Lake is the reservoir behind Yellowtail Dam, a 525 foot concrete thin arch dam on the Bighorn River near Fort Smith, Montana, about 43 miles southwest of Hardin. Reclamation built it between 1963 and 1966 as part of the Pick-Sloan Missouri Basin Program, and the dam is named for Robert Yellowtail, a former Crow tribal chairman. At maximum elevation the lake backs up roughly 72 miles through Bighorn Canyon, crossing from Montana into Wyoming, and most of the canyon is surrounded by the Crow Reservation. Tribal lands inside the Bighorn Canyon National Recreation Area, which Congress established in 1966, are closed to the public. At Devil Canyon Overlook the fault blocks rise about 1,000 feet above the water. The dam's crest sits at 3,660 feet, and the reservoir holds about 1.38 million acre-feet at that height. Its authorized jobs include irrigation, flood control, hydropower, sediment retention, fish and wildlife, recreation, and water allocations to the Crow and Northern Cheyenne tribes.
The level moves on a yearly cycle that Reclamation's Montana Area Office sets around spring snowmelt, much of which arrives through releases from Boysen and Buffalo Bill reservoirs upstream in Wyoming. The 3,640 foot figure is the top of the joint use pool, which is the number this site treats as full. Through winter the lake is drawn down to make room for runoff, with current criteria aiming for roughly 3,617 to 3,621 feet by the end of March, then it refills through spring with a target of 3,640 by the end of July. Above 3,640 is an exclusive flood control pool reaching 3,657 feet, and when the lake is in that zone the Army Corps of Engineers in Omaha directs releases, aiming to hold the river near 20,000 cubic feet per second at St. Xavier and 25,000 at the town of Bighorn. The 3,657 to 3,660 band is surcharge. Releases are also bound by downstream needs, including a preferred instream flow of about 2,500 cfs for the trout river below the dam.
For people on the water, the number to watch is the Horseshoe Bend ramp near Lovell at the shallow Wyoming end. The Park Service lists 3,620 feet as its working minimum for small flat bottom boats and 3,625 for larger surf and ski boats. Ok-A-Beh near the dam and Barry's Landing in the middle of the canyon both work down to 3,580. Sediment is building up at the south end, and in August 2021, with the lake near 3,623, the park warned boaters about sandbars and damaged props south of the south narrows toward the causeway. Since 2000 the lake has swung between flood levels above 3,640 and a low of 3,572.70 feet. The gauge on this page covers only about the last six years, so its recent high of 3,647.78 (2023) and recent low of 3,613.08 (2024) are not all time records.
Bighorn Lake — frequently asked
What is Bighorn Lake's full pool level?
3,640 feet, the top of the joint use pool at Yellowtail Dam. Reclamation targets that elevation at the end of July most years. Above it sits an exclusive flood control pool up to 3,657 feet, which the Army Corps of Engineers manages when the lake rises into it, and then a surcharge band to the dam crest at 3,660. A reading above 3,640 means the lake is holding floodwater.
Why does Bighorn Lake drop every winter?
Reclamation draws it down to leave space for spring snowmelt. Recent operating criteria aim for about 3,617 to 3,621 feet at the end of March, with the low point of the year usually falling between April and July before runoff peaks. The lake then refills toward 3,640 by the end of July. In dry years the refill falls short, and the south end near Horseshoe Bend feels it first.
What lake level do I need to launch at Horseshoe Bend?
The Park Service lists 3,620 feet for small flat bottom boats and 3,625 for larger surf and ski boats. Below that the Horseshoe Bend facilities are pulled and boaters move to the Montana ramps. Ok-A-Beh near Fort Smith and Barry's Landing both work down to 3,580 feet. The south end is silting in, and the park has reported boats grounding on sandbars there in low water years.
How high did Bighorn Lake get in 2011?
It peaked at 3,655.03 feet on May 20, 2011, about two feet below the top of the exclusive flood pool. That year set a record for April through July inflow at 2,572,304 acre-feet, 223 percent of average and about 301,000 acre-feet more than the previous record set in 1967. Releases from Yellowtail reached 15,460 cubic feet per second during the 2011 water year.
What is the lowest Bighorn Lake has been?
The Park Service lists a historic low of 3,572.70 feet within the period since 2000, a stretch that included the 2000 to 2007 drought Reclamation compares to the 1930s dry period used to plan the project. That is below the 3,580 feet the Montana ramps at Ok-A-Beh and Barry's Landing now need. The gauge on this page covers only about the last six years, with a recent low of 3,613.08 feet in 2024.
Who controls the water level at Bighorn Lake?
The Bureau of Reclamation's Montana Area Office owns and operates Yellowtail Dam and sets releases for most of the year. When the lake rises into the exclusive flood control pool between 3,640 and 3,657 feet, operations shift to the Army Corps of Engineers in Omaha, which manages releases against flood targets on the Bighorn River at St. Xavier and the town of Bighorn and farther down the Yellowstone.
How good is the trout fishing below Yellowtail Dam?
Strong. Montana Fish, Wildlife and Parks found about 2,446 trout per mile of 7 inches or longer in 2025 in its upper survey section above Mallard's Landing, split roughly evenly between rainbows and browns, and about 2,187 per mile in the lower section below Three Mile. Public access covers the first 13 miles below Afterbay Dam, and bait is allowed only in the first 200 yards below the Afterbay.
Other lakes near Bighorn Lake
- Canyon Ferry LakeMT
- Tiber Reservoir (Lake Elwell)MT
- Fort Peck LakeMT
- Lake AshtabulaND
- Boysen ReservoirWY
- Flaming Gorge ReservoirUT/WY
See current levels for all 4 Montana lakes and reservoirs →
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