Keyhole Reservoir Water Level
Keyhole Reservoir is at 4,083.65 ft today (Oct 31), 15.65 ft below its 4,099.3 ft full pool, down 0.05 ft this week.
Wyoming · Belle Fourche River
Get a text when Keyhole Reservoir crosses a level you pick →
Sponsor Keyhole Reservoir
Put your marina, real-estate, or local business in front of everyone checking this lake's level. One exclusive sponsor per lake.
Renews automatically each month or year until you cancel. Cancel anytime online. Terms · Manage or cancel · Questions?
Water level history
About Keyhole Reservoir
Keyhole Reservoir is a reservoir on the Belle Fourche River in Wyoming, operated by U.S. Bureau of Reclamation. Its full summer pool sits at 4099.3 ft above sea level. Live water levels come from the U.S. Army Corps of Engineers (CWMS) and update hourly.
Understanding Keyhole Reservoir's water level
Keyhole is a Wyoming reservoir that mostly works for South Dakota farms. The Bureau of Reclamation closed the earthfill dam on the Belle Fourche River in February 1952, about 17 miles northeast of Moorcroft, as part of the Pick-Sloan Missouri Basin Program. Under the 1944 Belle Fourche River Compact, unappropriated river flow is split 90 percent to South Dakota and 10 percent to Wyoming, and Wyoming was allowed to buy 10 percent of Keyhole's storage. The Crook County Irrigation District bought 18,080 acre-feet of that share. The rest of the conservation pool backs up the Belle Fourche Project around Newell, South Dakota, about 146 miles downstream, where 57,068 acres are irrigated. Water released from Keyhole runs down the river to the Belle Fourche Diversion Dam, then through the Inlet Canal into Belle Fourche Reservoir before it reaches fields. Releases are made when the two irrigation districts ask for them, which is why the lake can fall several feet in a dry summer.
Full pool, 4,099.3 feet, is the crest of an ungated concrete spillway at the right abutment. Between 4,051.0 and 4,099.3 lies the conservation pool, about 188,700 acre-feet in Reclamation's 2003 survey, which also found the reservoir had lost 6.2 percent of its original capacity below the crest to sediment since 1952. Everything above the crest is flood space that no one can open a gate to empty: water simply pours over the spillway until the lake drops back. Flood control storage runs to 4,111.5 feet and surcharge to 4,128.7, against a dam crest of 4,134. The outlet tunnel can pass only about 1,480 cubic feet per second, and the safe channel capacity downstream is 3,000. Filling took a long time. The lake did not reach the spillway crest until May 1978, 26 years after the dam closed, and Reclamation's daily record shows water going over the spillway in only five years: 1978, 2012, 2015, 2019 and 2020.
In 2026 the lake has been at its lowest in nearly two decades. It sat near 4,089 feet in May, then dropped 3.9 feet between May 1 and August 18, when Reclamation engineer Ronald Bengs told the Moorcroft Leader the reservoir was 46 percent full at 4,085.09. He cited low precipitation and snowpack, and downstream irrigation demand that had not been needed in past years. By mid October the level was about 4,083.8 feet, holding roughly 81,900 acre-feet, the lowest since May 2008. Low water hits the ramps first. Keyhole State Park runs five boat ramps, and in May 2025, with the lake at 4,090.3, the superintendent kept the Wind Creek ramp closed because it needs at least 4,091 feet. For anglers, Wyoming Game and Fish samples have shown fast walleye growth, with many fish reaching 12 inches by age two, fed partly by gizzard shad the department restocked in 2015 after the long ice cover of the 2012-13 winter wiped them out.
Keyhole Reservoir — frequently asked
What is Keyhole Reservoir's full pool elevation?
4,099.3 feet, the crest of the ungated spillway and the top of the conservation pool. Below it, Reclamation's 2003 survey measured about 188,700 acre-feet of storage. Water above that level goes into flood control space that reaches 4,111.5 feet, and it can only leave through the outlet tunnel or by spilling over the crest, so Reclamation cannot hold the lake at a set level during a wet spring.
Why is Keyhole Reservoir so low?
A dry year combined with heavy irrigation calls. Reclamation said the lake dropped 3.9 feet between May 1 and August 18, 2026, citing low precipitation and snowpack and downstream irrigation demand that had not been needed in past years. Most of the conservation pool serves the Belle Fourche Project in South Dakota, so releases continue on request even as the lake falls. By mid October 2026 it was near 4,083.8 feet.
What is the record high at Keyhole Reservoir?
4,101.98 feet on 28 March 2019, about 2.7 feet over the spillway crest, according to Reclamation's daily record. Snowmelt inflow ran around 1,300 cubic feet per second while the lake was still frozen over. Wind Creek and Pat's Point campgrounds lost sites to flooding, and Keyhole releases helped push minor flooding down the Belle Fourche River to the South Dakota line. The previous high was 4,100.38 feet in May 1978. The gauge panel on this page covers only the last few years, so its high is far below these figures.
What is the lowest Keyhole Reservoir has ever been?
The period of record low is 4,046.35 feet in March 1955, but that was three years after the dam closed, long before the lake first filled. Once the reservoir was established, the low point came on 1 November 1992 at 4,060.32 feet, at the end of a dry stretch that began in the early 1980s. The October 2026 level of about 4,083.8 feet is the lowest since 2008.
Which boat ramps at Keyhole close when the water is low?
Keyhole State Park has five boat ramps. The Wind Creek ramp needs a lake elevation of at least 4,091 feet, according to the park superintendent, and it stayed closed in May 2025 when the lake was at 4,090.3 while Colter Bay and Pat's Point were open. With the lake several feet lower in 2026, check with the park at 307-756-3596 before towing a boat.
Who gets the water stored in Keyhole Reservoir?
Mostly South Dakota. The 1944 Belle Fourche River Compact gives South Dakota 90 percent of unappropriated river flow, and that state's share of Keyhole storage supports about 57,000 irrigated acres around Belle Fourche and Newell. Wyoming holds 10 percent of the storage: 18,080 acre-feet bought by the Crook County Irrigation District and 500 acre-feet by Shattuck Hills. Releases are made when these districts request them.
What fish live in Keyhole Reservoir?
Walleye are the main draw, and Wyoming Game and Fish has stocked them, including 300,000 young fish planned for 2018. Wyoming State Parks also lists crappie, perch, smallmouth bass, northern pike, drum and catfish. The state record freshwater drum, 22.58 pounds and 29 years old, came from Keyhole in July 2018. Asian clams were found in the lake in 2017, so boats must be inspected and drained.
Other lakes near Keyhole Reservoir
See current levels for all 5 Wyoming lakes and reservoirs →
Add this gauge to your website
Run a marina, boat rental, guide service, or real-estate site on Keyhole Reservoir? Put this free live-level widget on your page — just copy and paste the code: