Level IV EcoRegions of Northeast South Dakota
46c - Glacial Lake Basins
Located in the norhtwest corner of Marshal County and the extreme northwest corner of Day County. This area was once occupied by proglacial Lake Dakota. The landscape is characterized by flat topograhy, low wetland density, and level deep soils that are intensively cultivated. Corn and soybeans are the prevalent crops. No major lakes or waterways are located in this ecoregion.
46d - Glacial Lakes Deltas
Located in the extreme northwest corner of Marshall County. This area was formed by a river entering proglacial Lake Dakota. Sand and fine gravels formed a delta at the rivers inlet. As Lake Dakota drained these gravels and sands were exposed and wind erosion formed areas of dunes. Today, this area is locally known as the Britton-Hecla Sandhills. This area has a thin vegetative cover and is prone to wind erosion and drought. The area is utilized mainly for grazing. Remnant native tallgrass prairie in the sandhills area provide habitat for a diverse population of native grasses and forbs, grassland birds, and invertebrates. Several of these remnant prairies have been protected by U.S. Fish and Wildlife Service grassland easements.
46e - Tewaukon Dead Ice Moraine
Located in northcentral and northeast Roberts County. This ecoregion is a lower level extension of the Prairie Coteau (46k) ecoregion located just below the Prairie Coteau Escarpment (46l). The area is characterized by a high density of semipermanent wetlands that provide important habitat for migrating and nesting waterfowl. These wetlands also provide the only known habitat for the Wood frog (Lithobates sylvaticus) in the state. Unfortunately, these wetlands are prone to drainage activities to provide more tillable cropland. Drier upland areas are used mainly for cultivated crops and to a lesser extent grazing. Lake Traverse borders the eastern edge of this ecoregion.
46i - Drift Plains
Located in western Day County and southcentral Marshall County at the foot of the Prairie Coteau. Area is characterized by productive glacial tills with a level or occasional “washboard” topography. Due to these features the area is heavily cultivated. At one time the area had a high density of temporary and seasonal wetlands; however in these two counties most wetlands have been drained or are being farmed. Some areas are prone to sodium-affected subsoils that hamper crop production. The native grassland of the Drift Plains ecoregion are a transition between the shortgrass and tallgrass prairie. Today, a few remnant prairies exist utilized mainly for grazing or as fall hay prairies. The Amsden Dam reservoir is located in this area on the Mud Creek drainage.
46k - Prairie Coteau
The largest ecoregion in the project area covers most of Day County, the east half of Marshall County, and the southwest corner of Roberts County. Our most important ecoregion due to the fact the majority of lakes included in this project are located on the Prairie Coteau. This area was formed by stagnant glacial ice that was covered by a layer of outwash and windborne sediment. As this glacier melted, lakes and wetlands formed in surface depressions left by melting ice, or behind glacial moraines that blocked meltwater drainages. Although major stream networks are lacking on the Prairie Coteau of Day and Marshall Counties, most lakes are located in chains connected with surface overflows of short duration and lengths that end in closed basins like Bitter Lake. The exception to this is Blue Dog Lake which is fed by Owens Creek, a lengthy coldwater spring-fed stream with several small unnamed tributaries located north and south of Ortley, South Dakota. The area is characterized by rolling rocky terrain utilized for grazing. Cultivation occurs in the flatter outwash plains and on gentler slopes void of rocks. Wooded riparian areas surround most lakes and larger permanent wetlands and provide important wildlife habitat. Bur oak, green ash, and box elders dominate the drier riparian sites, while several species of willows and red-osier dogwood dominate the lower slopes. Because of the large number and types of wetlands and lakes found on the Prairie Coteau, this area provide critical nesting habitat for several species of birds that include grebes, pelicans, herons and egrets, waterfowl, shorebirds, gulls and terns. In the future this area may be heavily developed for wind energy.
46l - Prairie Coteau Escarpment
Located along the eastern edge of the Prairie Coteau in eastern Marshall County and western Roberts County. The Prairie Coteau Escarpment rises approximately 300 to 600 feet above the Minnesota River valley in Roberts County to the top of the Prairie Coteau. Several large coulees or gulches are located along the escarpment. These include Sica Hollow, Muson’s Gulch, Long Hollow, Big Springs Coulee, and Big Coulee. Spring fed perennial coldwater streams are found in most of these locations forming the headwaters of the Little Minnesota River that eventually reaches Big Stone Lake, and the North Fork of the Whetstone River that flows into the Minnesota River. The remnant eastern deciduous forests of maple, basswood, green ash, and bur oak found in these coulees provide habitat for several species of wildlife rarely found elsewhere in eastern South Dakota. Many of these coulees are grazed, altering or destroying the woody vegetative understory. Between the coulees are native tallgrass prairies, the steepest utilized for grazing. Flatter areas along the escarpment are used as cropland. Some areas of the Prairie Coteau Escarpment may be developed for wind energy in the near future.
46m - Big Sioux Basin
Beginning in the extreme southwest corner of Roberts County, the Big Sioux River Basin is a trough that drains the majority of the eastern half of the Prairie Coteau. In our area, this ecoregion is characterized by relatively flat topography and fewer wetlands than the surrounding landscapes. The majority of land in this portion of Roberts County is drained by Owens Creek, the major tributary of Blue Dog Lake. Cropland is the major land use in this ecoregion. Steeper slopes are utilized for grazing, and in recent years have been intensively mined for gravel. The headwaters of the Big Sioux River occur between Summit and Ortley, South Dakota just south of Highway 12 in Roberts County.
46o - Minnesota River Prairie
The Minnesota River Prairie ecoregion begins in the northwest corner of Robert County continuing to the south along the Prairie Coteau Escarpment. This area is characterized by a level to gently rolling topography and moderate wetland density. The major land use today is cropland. There are no large lakes in this ecoregion of Roberts County; however the area borders Big Stone Lake to the east. The area is drained by the Little Minnesota and Whetstone River systems. These small river systems support a diverse population of freshwater clams and small fish.