Area is in the Western Lake Section of the Central Lowland Province of the Interior Plains.
Area entirely in South Dakota.
Total Land Area 2,215 square miles (5,735 square kilometers).
Madison, Canton, Parker, and Vermillion, South Dakota
It is characterized by glaciated, nearly level to hilly plains. It has many depressions and ill-defined drainageways.
The major landforms are stagnation moraines, end moraines, glacial outwash terraces, and flood plains. The area is dominated by drift-covered moraines.
The stagnation moraines generally are nearly level to gently rolling and have many depressions and ill-defined drainageways. The steeper slopes are on end moraines and on breaks adjacent to some of the larger tributaries. Small outwash areas are adjacent to the minor moraines.
Elevation ranges from 1,140 feet (350 meters) on the edge of the bottom land along the Missouri River in the southern part of the area to 1,880 feet (575 meters) in central Lake County.
The average annual precipitation in this area is 23 to 26 inches (585 to 660 millimeters).
Most of the rainfall occurs as high-intensity, convective thunderstorms during the growing season.
The average annual temperature is 43 to 49 degrees F (6 to 9 degrees C).
The freeze-free period averages about 165 days and ranges from 155 to 175 days.
|Missouri-Big Sioux||(1017)||Not Reported|
* this is the percent of area drained by each named hydrologic unit
There is only one Major Hydrologic Unit in this area.
|Public supply||surface water||2%||ground water||19.1%|
|Livestock||surface water||1.6%||ground water||2.8%|
|Irrigation||surface water||16.3%||ground water||50.6%|
|Other||surface water||2.1%||ground water||5.5%|
Total daily withdrawls average 61 million gallons per day (230 million liters).
78% Ground water sources
22% Surface water sources
Surface waters are not plentiful in this area.
The Missouri River, south of this area, has the best quality water in this region, so it is increasingly being used by rural water systems in the area.
A limited supply of ground water is in the glacial drift and alluvial aquifers near the surface in this area. These aquifers consist of unconsolidated sand and gravel. They provide fresh or saline water that is hard and is a calcium-magnesium, bicarbonate, and sulfate type. The median level of total dissolved solids, 670 parts per million (milligrams per liter), exceeds the national secondary (esthetic) standard for drinking water.
Many private wells have high levels of nitrate plus nitrite. Most of this contamination occurs because the wells are located downslope from septic tank absorption fields, feedlots, barnyards, or fertilizer storage areas.
The dominant parent materials are silty drift, glacial till, glacial outwash, and alluvium.
They generally are very deep, and range from well drained to poorly drained, and tend towards being clayey or loamy.
|Calciustolls||Ethan series||formed in till on the steeper slopes on moraines.|
|Calciustepts||Betts series||formed in till on the steeper slopes on moraines.|
|Calciaquolls||Wakonda series||formed in silty drift|
|Davison series||formed in glacial till in areas characterized by upward water movement.|
|Haplustolls||Huntimer series||formed in lacustrine sediments.|
|Wentworth and Trent series||formed in silty drift.|
|Egan and Viborg series||formed in silty drift over glacial till.|
|Dempster, Graceville, Delmont, and Enet series||formed in glaciofluvial deposits on outwash plains.|
|Argiaquolls||Chancellor series||formed in alluvium in wet drainageways.|
|Argialbolls||Tetonka series||formed in alluvium in depressions|
|Argiaquolls||Worthing series||formed in alluvium in depressions|
|Endoaquolls||Baltic series||formed in alluvium in depressions|
This area is in the western part of the tall grass prairie. Big bluestem, little bluestem, Indiangrass, porcupinegrass, and green needlegrass are the dominant species in the native plant communities. Needleandthread and prairie dropseed are important species on the steeper soils.
Cattails, prairie cordgrass, bulrush, and reed canarygrass commonly grow in wet areas.
Some of the major wildlife species in this area include whitetailed deer, red fox, coyote, white-tailed jackrabbit, pheasant, gray partridge, ducks, and geese.
|71% -||Cropland||- private|
|16% -||Grassland||- private|
|1% -||- Federal|
|1% -||Forest||- private|
|4% -||Urban development||- private|
|2% -||Water||- private|
|5% -||Other||- private|
Most of this area is in farms, and about 70 percent is cropland used for crops grown for sale or for feeding livestock. Corn, soybeans, alfalfa, and oats are the principal crops.
Corn, soybeans, alfalfa, and oats are the principal crops.
Wooded areas generally occur as narrow bands along streams and rivers or as shelterbelts around farmsteads.
The major resource concerns include wind erosion, water erosion, maintenance of the content of organic matter and productivity of the soils, wetness, and management of soil moisture.
Conservation practices generally include systems of crop residue management, especially no-till or conservation tillage systems that conserve moisture and contribute to soil quality. Other practices include terraces, vegetative wind barriers, grassed waterways, and nutrient management.