SIOUX FALLS, S.D. (KELO) — The Hot Springs area recently got a dump of snow, which locals said was needed.

How can all that snow impact the Angostura Reservoir?

“Right now, we still have 11 feet to fill to reach what we call top of conservation,” Ginger Wessels, a civil engineer for the U.S. Bureau of Reclamation (Reclamation), said after the recent storm.

The Angostura Reservoir and dam (Angostura Unit) is in the Pick-Sloan Missouri Basin Program in the Great Plains region in southwestern South Dakota on the Cheyenne River. The river starts in Wyoming and flows into South Dakota near Edgemont.

Wessels speculated much of the April snow would be absorbed into the ground rather than flowing into the reservoir.

“It will help,” but “We are coming off two dry years,” Wessels said of dry and drought conditions that have persisted in western South Dakota.

A Reclamation website said the reservoir was 64.5% full. The site said a reservoir is considered full when “pool elevation is at top of active conservation pool. Percentage is based on total reservoir volume below that level.”

The reservoir has had other years of reduced lake levels.

In August of 2021, news media reported that Belle Fourche, Angostura and Shade Hill reservoirs were ranging from just above 50% to 60% full.

A report from South Dakota State University Extension said the reservoir was 77.5% as of May 5, 2022.

An August 2022 GPF Angostura Resort prospectus said historically, water elevations on the lake have fluctuated with wet and dry weather cycles. During a dry or drought cycle, lower water levels result in limited lake access.

The Angostura did have some tough times around 2007 and 2008 when water levels dropped and some boat ramps were removed by the GFP.

The irrigation to 50 junior water right holders along the Cheyenne River and tributaries upstream of Angostura Reservoir was stopped for a time in 2008.

The reservoir has about 4,407 water surface acres, 4,546 land acres and 42 miles of shoreline. The maximum depth is 75 feet.

The South Dakota Game Fish and Parks Department (GFP) manages the recreational use of the reservoir and the Angostura Recreation Area.

Angostura Dam. Bureau of Reclamation photos

The reservoir is a popular spot for local recreational users and for tourists. According to the GFP December report, the Angostura Recreation Area had 20,878 campers through November. The area had 179,929 visitors through November.

“It is absolutely an asset,” Hot Springs Area Chamber of Commerce Executive Director Olivia Mears said. “It is a water lover’s paradise.”

Angostura is about 10 miles southeast of Hot Springs.

The Hot Springs area is on the southern edge of the Black Hills.

A 1996 report from the BLM talked about the growing attraction of the reservoir.

“The reservoir is growing in prominence as a recreation spot for Black Hills residents and
for visitors as far away as Minnesota and Colorado. Angostura is the largest warm-water
recreation lake within a hundred-mile radius,” said the Historic Reclamation Projects
Bureau of Reclamation 1996 report by Robert Autobee

“We’re lucky we can claim (Angostura) as part of our tourism area,” Mears said.

While Angostura is a recreational attraction, it’s primary function is a water supply for irrigation.

The construction of the dam started in 1946 and was completed in 1949.

A 1950 photo of the Angostura Dam from the U.S. Department of the Interior. South Dakota State Historical Society photo.

The first flow of irrigation started in 1953 and in 1956 for the entire reservoir unit, according to Reclamation.

There are water allotments for irrigation assigned to the reservoir, Wessels said.

“(Users) have contracted for it and paid for it,” Wessels said of irrigation

The reservoir supplies water to 12,218 acres of irrigable land. Alfalfa and corn are the main crops, along with wheat, barley, oats, pasture and forage.

Irrigation will start on May 1, Wessels said.

Reclamation does try to maintain a balance in the reservoir between recreational use and irrigation use, but irrigation is the priority, she said.

“With water use, we are trying to fill those contracts,” Wessels said.

Water flows from the reservoir through a main canal, Wessels said. A series of lateral ditches are connected to the main canal. “Some of those ditches have been piped, if it’s affordable,” she said.

There are 39 miles of laterals and 34 miles of open and closed drains.

The reservoir is “vital for irrigation,” Mears said. Although tourism is important to the economy, “Agriculture is vital to Fall River County.”

Wessels said the reservoir is at its fullest in May. “That will always be our highest level in the reservoir,” she said. As spring and summer continue, the water levels will drop.

Recreational users will see lower water levels in August and September, she said.