Reports of people swimming and spearfishing in the turbulent waters of the Oahe Dam have sparked local concern. Swimmers beware, say officials: The turbulent waters on the downriver side of the Oahe Dam are closed to swimmers for safety reasons.

Two agencies — the Army Corps of Engineers (ACOE) and the South Dakota Game, Fish and Parks Department (GFP) — want to warn people that swimming below the dam is dangerous.

Why?

If a swimmer were to get caught in the currents around the dam they could be in serious trouble, worst case sucked through the dam by strong currents like the fish that have littered the shorelines of the lake in recent days.

ACOE determines the daily average release flow from Oahe Dam at so many cubic feet per second (cfs). Even in drought years, this can be tens of thousands of cfs. During extra wet years, as with this year’s devastating storms and flooding, the daily release is far greater, with 52,000 cubic feet per second or greater being somewhat common this summer.

Access

Access to the Missouri River in general, and to Lake Oahe specifically, is to a large degree public.

GFP uses its printed guides and its website (https://gfp.sd.gov/) to help the public in identifying public lands, including shorelines. It shows land that is managed or owned by multiple public and private agencies, not just those managed or owned by the GF&P.

The land surrounding Lake Oahe, and to a diminishing degree the water below the dam, is under ACOE management. Except for immediately around the dam and just below the dam, this area is usually a fairly thin strip of land directly adjacent to the water.

GFP District Supervisor Josh Carr calls it the ‘top of the bathtub’ explanation:

In general, from the edge of the water to the high water mark is under the management of ACOE. In general, from the high water mark beyond — this land known as “take land,” land offered to GFP and other entities by ACOE in 2007 — is under GFP management.

Swim rules

Whether swimmers get to the water from shore or from a boat, they are for the most part not restricted by GFP rules. Restrictions below Oahe Dam are for safety reasons.

People doing more than just recreational swimming are under certain GFP regulations, again based on safety. Divers and anyone using an underwater air supply, including a snorkel, must display a diver-down flag. This applies if the people are in an area where sailboats or motorboats may also be. The red flag, measuring at least 12 by 15 inches, must have a white diagonal stripe running from corner to corner. Divers must stay within 75 feet of the flag, and boaters must stay at least 75 feet away.

To not unduly restrict water enjoyment of others, underwater diving is not allowed where the flag’s perimeters would stop boats from using their public access ramps or their reasonable navigation.

If the underwater swimmers are also spearfishing, then further safety measures apply. Underwater spearfishing may not be practiced within 100 yards of a designated swimming area, of a water skiing area, boat docks, power intake tubes or spillways.

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