Originally the area now known as Lake Yankton was part of the main channel of the Missouri River. During the construction of Gavins Point Dam, the U.S. Army Corps of Engineers redirected the main channel of the Missouri south to its current location, just south of the Training Dike. The state line between Nebraska and South Dakota is located the mid-point of the original historical main channel. Therefore the lake is located in both Cedar County, Nebraska and Yankton County, South Dakota, even though it is widely incorrectly assumed that the lake is located entirely in South Dakota. Most of the northern and eastern portions of the lake and shoreline are in South Dakota, and most of the southern and western portions of the lake and shoreline are in Nebraska. After dam construction completion a dike, called the Training Dike, was constructed by the Corps to "train" the river to its current location and flow, thus creating a land barrier separating Lake Yankton from the Missouri River. The lake was then impounded in order to control the lake level for fish and wildlife enhancement, along with recreational opportunities. The outlet from the lake known locally as "The Bubble" is a popular fishing spot, where the lake flows into the Missouri River. The lake is a public water managed by the U.S. Army Corps of Engineers, and fisheries are managed jointly between the Nebraska Game and Parks Commission and the South Dakota Department of Game, Fish, and Parks.
Recreation and wildlife
Lake Yankton is a very popular public recreational and fishing lake with good populations of Largemouth Bass, Bluegill, Walleye, Black Crappie and Channel Catfish. There are two boat ramps for boat access to the lake, along with two kayak/canoe launches. There are also two fishing piers and two fishing jetties with handicapped fishing accesses.
No gasoline-motors restriction
The U.S. Army Corps of Engineers placed an "electric-motors only" restriction on the lake in the 1980s due to its size and for environmental considerations. Therefore the use of gasoline-powered boat motors on the water is prohibited. This regulation is enforced by USACE Park Rangers, Conservation Officers and other law enforcement that may issue fine to violators. This has led to the lake being very popular for swimming, kayaking, canoeing, paddleboarding and bird watching.
During the 2011 Missouri River Floods the Missouri River water rose high enough that the river had backed into Lake Yankton, as a result the lake was infiltrated with Asian Carp, an aquaticinvasive species not native to South Dakota/Nebraska that are well-established in the Missouri River below Gavins Point Dam. The lake fisheries and water quality began to decline. Therefore in 2014 a cooperative effort between the U.S. Army Corps of Engineers, the Nebraska Game and Parks Commission and the South Dakota Department of Game, Fish, and Parks completed a controlled fish kill to rid the lake of the invasive carp. Restocking efforts by the Nebraska Game and Parks Commission began following the fish kill. The kill was hailed as a success by agencies involved and the fisheries and water quality have increased to exceptionally good levels.