region M Area 108 A larger picture

Illinois and Iowa Deep Loess and Drift, Eastern Part

Most of this area is on the glaciated Bloomington Ridged Plain in the Till Plains Section of the Central Lowland Province of the Interior Plains.
The northern tip is in the Eastern Lake Section of the same province and division.

Area includes portions of the following states:
97% in Illinois
3% in Indiana

Total Land Area 11,145 square miles (28,875 square kilometers).

Towns/cities include:
Decatur, Champaign, Urbana, Bloomington, and De Kalb, Illinois

The numerous State parks in the MLRA include Moraine Hills in the northern part of the area and Moraine View in the southern part.


This area is underlain by Pennsylvanian shale, siltstone, and limestone in the southern part and Ordovician and Silurian limestone in the extreme northern part.

The area is a relatively young, moderately dissected, rolling plain with stream terraces adjacent to the broad flood plains along the major streams and rivers. Glacial moraines are numerous in the area and tend to form elongated ridges tending from northwest to southeast.

Glacial drift covers all of the MLRA, except for some areas along the major streams where the underlying bedrock is exposed. The glacial drift is Wisconsin in age and consists of distinct till units as well as sorted, stratified outwash. The entire area has been covered by a moderately thin or thick layer of loess. In a few areas the loess directly overlies the bedrock.

Slopes are generally less than 5 percent but are significantly steeper on the moraines and along the major streams.

Topography -

Elevation ranges from 660 feet (200 meters) in the southern part of the area to about 985 feet (300 meters) in the northern part.
The maximum local relief is about 160 feet (50 meters) along the major streams.
It typically is only 3 to 10 feet (1 to 3 meters) on the broad, flat uplands.


The average annual precipitation in this area is 35 to 43 inches (890 to 1,090 millimeters).
Most of the rainfall occurs as high-intensity, convective thunderstorms during the growing season.
The average annual temperature is 47 to 54 degrees F (8 to 12 degrees C).
The freeze-free period averages about 195 days and ranges from 175 to 210 days.

Major Hydrologic Unit Areas

Name Code Extent*
Lower Illinois (0713) 46%
Wabash (0512 ) 26%
Upper Illinois (0712) 13%
Upper Mississippi-Kaskaskia-Meramec (0714) 10%
Rock (0709) 5%

* this is the percent of area drained by each named hydrologic unit

The Illinois, Rock, and Wabash Rivers drain this MLRA.


Estimated withdrawls in this MLRA:
Public supply surface water 50% ground water 15.9%
Livestock surface water 0.1% ground water 6.8%
Irrigation surface water 0% ground water 3.9%
Other surface water 19.3% ground water 3.9%

Total daily withdrawls average 260 million gallons per day (985 million liters).
31% Ground water sources
69% Surface water sources

The surface water is of fair or good quality and is suitable for most uses. Sediment, nutrients, and pesticides from agricultural activities and wastewater discharges from cities can contaminate the surface water in the area.

The principal sources of ground water in the area are glacial drift, the Sand-and-Gravel aquifer, alluvial aquifers along the major streams, and Paleozoic bedrock.

Glacial drift aquifers typically has high levels of iron. The iron is not dangerous to public health, but it causes esthetic problems of iron stains and scale. Alluvial deposits are similar in quality to the surface water and is suitable for most uses.

The shallow Sand-and-Gravel aquifer is extensive throughout Illinois. It typically consists of glacial outwash deposits within the drift. The water in this aquifer is very hard and may have very high levels of iron. The median level of total dissolved solids is very near the national secondary drinking water standard of 500 parts per million (milligrams per liter).

Paleozoic bedrock aquifers are not utilized very much in this area. The Pennsylvanian-Mississippian aquifer underlies the lower three-fourths of the area. Well yields from this aquifer are generally low, so the aquifer is not used extensively. The water is extremely variable in quality. It is generally more heavily mineralized than the water in the surficial aquifers, and it has high levels of iron.

The Shallow Dolomite aquifer occurs only in the extreme northern part of this area. The water in this aquifer is similar in quality to the water in the Pennsylvanian- Mississippian aquifer and is not used unless no other aquifer is available.

The Cambrian-Ordovician aquifer underlies the northern quarter of this MLRA. This aquifer is used extensively in the northern third of Illinois. Its water is of good quality and is suitable for almost all uses.

Wells can penetrate the St. Peter Sandstone in the upper part of this unit or the deeper Ironton-Galesville layer. The median level of total dissolved solids is typically less than the national secondary drinking water standard of 500 parts per million (milligrams per liter), and iron levels are much lower than those in the water from the other bedrock aquifers.


  • Mesic soil temperature regime.
  • Aquic or udic soil moisture regime.
  • Mixed mineralogy.
  • Dominant Soils:

  • Mollisols
  • Alfisols
  • The soils generally are moderately deep to very deep, range from poorly drained to moderately well drained, and silty or clayey.

    Great Group Series Location
    Endoaquolls Drummer series formed in loess over loamy till on uplands.
    Argiudolls Saybrook and Catlin series formed in loess over loamy till on uplands.
    Hapludalfs Birkbeck and Mayville series commonly occur along the major stream valleys.
    Strawn series on the steep or very steep valley bluffs.
    Argiudolls Plano and Warsaw series are on gently sloping to sloping stream terraces along the major streams and on broad outwash plains.
    Hapludalfs St. Charles and Fox series are on gently sloping to sloping stream terraces along the major streams and on broad outwash plains.
    Cumulic Endoaquolls Sawmill series formed in alluvium on nearly level, broad flood plains and in the smaller upland drainageways.
    Cumulic Hapludolls Lawson and Huntsville series formed in alluvium on nearly level, broad flood plains and in the smaller upland drainageways.

    Fauna and Flora

    This area originally supported prairie vegetation with hardwood forests on scattered upland sites. The areas of tall prairie grasses are characterized by big bluestem, Indiangrass, prairie dropseed, and switchgrass.

    White oak, shingle oak, black oak, hickory, white ash, basswood, sugar maple, and walnut grow on the better drained soils.

    Silver maple, black willow, cottonwood, and sycamore grow on flood plains.

    The wildlife species in this area include whitetailed deer, coyote, turkey, red fox, beaver, raccoon, skunk, muskrat, opossum, cottontail rabbit, fox squirrel, Canada goose, red-tailed hawk, great horned owl, blue heron, wood duck, mallard duck, redheaded woodpecker, and ring-necked pheasant.

    Land Use

    80% - Cropland - private
    3% - Grassland - private
    1% - - Federal
    5% - Forest - private
    8% - Urban development - private
    1% - Water - private
    2% - Other - private

    Nearly all of this area is in farmed for cash and grain crops and livestock. Winter wheat is also grown in this area.

    The forested areas in this MLRA are mainly along the major streams.

    The major resource concerns include wind erosion, water erosion, and maintenance of the content of organic matter and productivity of the soils.

    Conservation practices generally include systems of crop residue management (especially no-till systems), cover crops, windbreaks, vegetative wind barriers, and nutrient management.

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