YANKTON, S.D. â€” A project under way to drain and then refill Beaver Lake, also known as State Lake, in the central part of Yankton County is the first of its kind in South Dakota and could become a template for future management of small reservoir fisheries in the state.
Officials with the Game, Fish and Parks Department (GF&P) hope the process will result in improved water quality and better fish stock at the lake.
The work being done at Beaver Lake is multifaceted and has been discussed among the GF&P, the South Dakota Department of Transportation (SDDOT) and Yankton County for years.
The process started with the need to replace the county bridge along 302nd Street and the dam spillway owned by the GF&P. Federal funds will supply 80 percent of the funds for the bridge and spillway replacement. The county will provide the remaining 20 percent for the bridge, while the GF&P is on the line for the spillway.
The SDDOT is administering the contract for the $1.9 million project, according to the SDDOTâ€™s Yankton-area engineer, Ron Peterson.
Grangaard Construction of Watertown is the primary contractor for the undertaking.
In addition to the replacement of the bridge and spillway, the lake will be drained using a siphon tube. Also, a low-level water outlet control structure will be installed so the lake can be drained in the future if necessary, rock fishing piers will be built along the south shoreline and some road work will be done on the approaches to the bridge.
Work got under way last month.
The road is expected to be closed through spring 2013 and the lake wonâ€™t be refilled until spring 2014.
â€śTheyâ€™re telling us the road will be closed in the vicinity of State Lake all winter,â€ť Peterson said. â€śTheyâ€™ll get the bridge deck ready to pour by the end of November but wonâ€™t be able to pour it until the spring.â€ť
The GF&P began its preparations for the project several years ago.
â€śFor the last three years, weâ€™ve visited the lake a couple times a year to take any game fish,â€ť said Todd St. Sauver, the regional fisheries manager for the GF&P. â€śItâ€™s never had a great game fish population. Itâ€™s had a few bass, walleye, crappie and bluegill. The greatest percentage of fish in there are rough fish like bullheads, suckers and carp.â€ť
The draining of the lake is expected to take less than two weeks. It will result in the rough fish perishing.
In 2014, the lake will be restocked with game fish that St. Sauver hopes will keep the rough fish population at bay.
Since the dam at Beaver Lake was built in the 1930s, sedimentation has occurred at a rapid pace.
The body of water is fed by the large Beaver Creek watershed to the northwest of the lake, St. Sauver explained. Water from the lake eventually drains into the James River.
He said the watershed contributes to approximately two inches of sedimentation on the lake bottom each year.
â€śSince we had to drain the lake down anyway to replace the spillway, I thought it would be nice to attempt to improve the lake,â€ť St. Sauver said. â€śThatâ€™s where the thought of totally draining the lake and leaving it dry for a while came about.
â€śThis has been done in other parts of the country, and there have been some favorable results,â€ť he added. â€śEssentially, when you dry out the lake bottom, those sediments dry out, settle, compact and there is some oxidation that goes on to tie up the nutrients. When the lake refills, that stuff stays sealed up on the bottom. It should result in improved water quality and, hopefully, increased depth (of possibly two to six feet).
â€śIn addition, while the lake is dried out, there will be a lot of vegetation that grows up along the edges of it. When the lake refills, that provides instant fish habitat. When we restock fish, they are going to have an abundance of cover and food. That will help restore the fishery in a hurry,â€ť St. Sauver said.
No money is available to do dredging of the lake, he explained.
Although the method has worked elsewhere, St. Sauver said Mother Nature provides no guarantees.
â€śItâ€™s kind of an experiment,â€ť he said. â€śWeâ€™re doing it based on reported experiences in other states. The science seems sound, but Iâ€™ve also been around long enough to know that science in one part of the country doesnâ€™t necessarily transfer over to our part of the country.â€ť
The watershed is big enough that one large rain could fill the lake overnight and take some time to drain down again, St. Sauver said.
â€śIf too many of those events happen during the period weâ€™re trying to have it dry, it could impact the results of increasing the depth of the lake,â€ť he stated. â€śItâ€™s just one of the many variables that may affect the overall result of this project.â€ť
For the most part, St. Sauver said local residents have been supportive of the effort.
â€śThere have been concerns about the odors that might be created when the fish die,â€ť he stated. â€śSome are concerned about losing the fish. There are some impacts for upstream landowners as far as a water supply for their cattle. We hope that everyone can endure this process. Hopefully, the end result is a better lake for the people in the area to enjoy.â€ť
If so, the project may be repeated in other parts of the state, according to St. Sauver.
â€śIf we see some positive results out of this, it could become a tool to manage our small reservoir fisheries,â€ť he said.