Northern Prairie Wildlife Research Center
System and Classes
Wetlands in the palustrine system cover 1,780,859 ac (720,704 ha) of eastern South Dakota (Table 2). The palustrine system has no subsystems. Palustrine wetlands in the emergent class occupy 1,380,270 ac (558,629 ha) or 77.5% of total palustrine wetland area. Palustrine wetlands in the aquatic bed class comprise 59,895 ac (24,3289 ha) or 3.4% of the total area. Palustrine wetlands in mixed emergent and aquatic bed classes, that is, EM/AB and AB/EM, collectively comprise 282,430 ac (114,298 ha) or 15.8% of total palustrine wetland area. Palustrine wetlands in other classes each comprise less than 1.5% of the total area of palustrine wetlands (Fig. 11) (Table 3).
|Figure 11. Percent of total acres of eastern South Dakota palustrine wetlands by Cowardin et al. (1979) class.||Figure 12. Percent of total acres of eastern South Dakota palustrine wetlands by water regime.|
Palustrine wetlands with seasonal water regimes, which comprise 774,881 ac (313,590 ha) or 43.5% of the total palustrine wetland area, are more abundant than palustrine wetlands with other water regimes. Palustrine wetlands with temporary water regimes cover 584,489 ac (236,685 ha) or 32.8% of the total palustrine wetland area; wetlands with semipermanent water regimes cover 415,387 ac (168,105 ha) or 23.3%; wetlands with intermittently exposed water regimes cover 4,369 ac (1,768 ha) or 0.2%; wetlands with saturated water regimes cover 1,213 ac (491 ha) or 0.1%; and palustrine wetlands with permanent water regimes -- a few deep potholes, dugouts and small impoundments -- cover 731 ac (296 ha) or a trace percentage of the total area of palustrine wetlands in eastern South Dakota (Fig. 12).
Palustrine wetlands are either natural or are created by excavation or impoundment. Natural palustrine wetlands comprise 1,648,482 ac (667,131 ha) or 92.5% of total palustrine wetland area in eastern South Dakota. Of this area of natural wetlands, 195,346 ac (79,056 ha) or 11.9% are partially drained by surface ditches. Of the total area of temporary palustrine wetlands, 17.9% (104,444 ac or 42,268 ha) is partially drained. About 8.2% (63,464 ac or 25,683 ha) of seasonal wetlands and 5.8% (24,209 ac or 9,797 ha) of semipermanent wetlands are partially drained.
Created palustrine wetlands cover 132,377 ac (53,572 ha) or 7.5% of the total area of palustrine wetlands. Of this area, excavated wetlands comprise 78,032 ac (31,579 ha), or 4.4% of the total and 58.9% of the area of created wetlands. Stock dam impoundments cover 54,345 ac (21,993 ha) or 3.1% of total palustrine wetland area and 41.1% of the area of created wetlands (Fig. 13). Beaver-created impoundments delineated by the NWI cover only 14 ac (6 ha) or a trace of the total area of created palustrine wetlands.
|Figure 13. Percent of total acres of eastern South Dakota palustrine wetlands by special modifier.|
Of all eastern South Dakota excavated wetlands delineated by the NWI, 56,827 are dugouts or similar features, for example, wetlands classified as PABFx, PUBFx, PABGx, PUBGx, or PUBHx. Dugouts are concentrated where livestock production was or remains a major land use and are commonly located in natural basins or in natural stream courses (McPhillips et al. 1983). Dugouts in eastern South Dakota occurred in 22,530 existing natural basins with 1 to 13 dugouts per basin. Of the total number of dugouts, 9,010 (15.9%) are located in natural temporary basins, 19,506 (34.3%) are in natural seasonal basins, 6,021 (10.6%) are in natural semipermanent basins, and 549 (1.0%) are in natural permanent basins. The median size of existing temporary basins containing dugouts (n=3,290) is 2.1 ac (0.9 ha); the median size of existing seasonal basins containing dugouts (n=14,439) is 4.6 ac (1.9 ha); the median size of semipermanent basins containing dugouts (n=4,333) is 4.1 ac (1.7 ha); and the median size of permanent basins containing dugouts (n=468) is 3.1 ac (1.3 ha). Of the total 56,827 dugouts, 21,741 dugouts (38.3%) are isolated from existing natural wetlands, have completely drained the basin they are excavated in, or are located in linear stream channels.
Many excavated drainage ditches, which were visible on aerial photography, and many road ditches were not delineated as wetlands by the NWI because they did not display wetland characteristics at the time of photography. Nonetheless, approximately 8,849 mi (14,159 km) of linear excavated palustrine wetlands (road ditches and drainage ditches) were delineated in eastern South Dakota. Of the total length, 7,911 mi (12,658 km) have a seasonal water regime, 586 mi (938 km) have a temporary water regime, and 347 mi (556 km) have a semipermanent water regime. Wetlands in road ditches in eastern South Dakota generally have seasonal water regimes.