Northern Prairie Wildlife Research Center
Natural Permanent Basins
These basins consist chiefly of natural lakes and deep potholes. They total 603, cover 194,037 ac (78,526 ha), and comprise from 0.0% to 5.2% of eastern South Dakota counties (Table 8). Natural permanent basins are most dense at the northern end of the Prairie Coteau. Most permanent basins in this area are small potholes and were formed in the manner described for natural semipermanent basins in this area. Large natural, permanent basins (lakes) are scattered throughout eastern South Dakota but are concentrated in a chain of large, natural lakes that occur along the long axis of the Prairie Coteau from near its northern end to southern Minnehaha County (Fig. 40). Most of these basins occur at the eastern limit of advance of the James lobe and are probably ice-block lakes. Large blocks of ice persisted in stagnant glacial debris near the margin of glacial advance because they were remote from the active ice margins and were not subjected to the shear and compression applied elsewhere (R. Hammond, South Dakota Geological Survey, pers. comm.).
|Figure 40. Distribution of permanent basins in eastern South Dakota.|
Permanent Basins due to Dugouts or Other Excavations
Basins with permanent water regimes due to excavations total 470 and cover 4,008 ac (1,622 ha) (Table 8). Permanent basins due to excavations are distributed in approximately the same pattern as semipermanent basins due to the presence of dugouts or other excavations.
Permanent impoundments in eastern South Dakota include deep stockdams and small to large reservoirs. They total 384, cover 264,156 ac (106,902 ha), and comprise 0.0% to 7.93% of eastern South Dakota counties (Table 8). Approximately 95% of permanent impoundment acreage in eastern South Dakota is associated with the three Missouri River reservoirs. Reported acreages of Missouri River reservoirs are limited to the area within the boundaries of eastern South Dakota counties (Table 8).