LAKE POINSETT PROFILE
One of the largest natural lakes in the state, Lake Poinsett was named after the U.S. Secretary of War, Joel Poinsett in 1838.
Lake Poinsett is of glacial origin and a meandered lake with its waters state owned and its fishery managed by
the SDGFP. The surface area covers 7,903 acres with a maximum depth of 22 ft. The water level fluctuates significantly through the years; evaporation takes off approximately 34” annually. The Ordinary High Water
Mark (OHWM) elevation is 1651.5 feet above mean
sea level (fmsl).
The lake receives most water inflows directly from the Dry Lake sub watershed to the north and from Lake Albert. The SDGFP maintain four developed public access areas on the Lake. Lake Poinsett Recreation Area located on the Southeast side in Brookings County maintains 116 full utility camping pads and cabins for public use.
LAKE POINSETT'S OUTLET
459th Avenue Outlet Control Structure (Gate)
Within the watershed, water runs through a chain-of-lakes and finally into Lake Poinsett, its
single natural outlet is three miles long to its entrance into the Big Sioux River. Lake Poinsett’s
outlet channels water under the HWY 28 bridge (northeast section of the lake) and under the
459th Avenue bridge.
After flooding in 1986, the natural outlet of Lake Poinsett was modified to include a control
structure to prevent the backflow of high waters from the Big Sioux River into the lake. The
structure was completed in 1989 and constructed to an elevation of 1,650.5 feet above mean
sea level (msl), one foot below the Lake Poinsett ordinary high-water mark of 1,651.5 msl.
These outlet gates beneficially affect the lake’s water quality, water flow, and lake level. The river holds pollutants and high nutrient levels that could harm the lake’s clean qualities enjoyed by all and reverse the collaborative environmental efforts by many organizations. The Sioux City Journal (May 7, 2012) reported that the advocacy group, Environment America, ranked the Big Sioux River as the nation's 13th dirtiest river.
The permanent outlet gate is maintained and operated by the Lake Poinsett Water Project
District, who strictly adheres to specific rules documented and regulated by the US Corps
Gates closed if the Big Sioux is higher than lake.
Gates open when the lake is higher.