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Northern Illinois and Indiana Heavy Till Plain

The northern half of this area is in the Eastern Lake Section of the Central Lowland Province of the Interior Plains.
The southern half is in the Till Plains Section of the same province and division.

Area includes portions of the following states:
79% in Illinois
11% in Wisconsin
10% in Indiana

Total Land Area 7,535 square miles (19,525 square kilometers).

Towns/cities include:
The entire northern part of this MLRA is an urban-suburban complex including Milwaukee, Wisconsin, all of the western and southern suburbs of Chicago, Illinois, and Merrillville, Indiana. Pontiac and Kankakee, Illinois, are in the southern part of this area.

Geology

Fractured dolomite and limestone bedrock of Silurian age lies beneath the glacial drift.

The surface of this area is covered by glacial drift. Till, outwash, lacustrine deposits, loess or other silty material, and organic deposits are common.

The area is a nearly level to gently sloping glaciated plain. It has relatively low relief on the glacial lake plains and more rolling topography along the major stream valleys and on glacial moraines. The numerous glacial moraines in the area tend to form elongated ridges tending from northwest to southeast.

Topography -

Elevation is about 650 feet (200 meters). Local relief is typically 10 to 25 feet (3 to 8 meters).

Streams have cut shallow valleys on much of the plain.

Climate

The average annual precipitation in this area is 31 to 40 inches (785 to 1,015 millimeters).
Most of the rainfall occurs as high-intensity, convective thunderstorms during the summer.
The average annual temperature is 45 to 52 degrees F (7 to 11 degrees C).
The freeze-free period averages about 185 days and ranges from 165 to 205 days. It is longest in a narrow belt along Lake Michigan.

Major Hydrologic Unit Areas

Name Code Extent*
Upper Illinois (0712 ) 69%
Lower Illinois (0713) 13%
Southwestern Lake Michigan (0404) 10%
Wabash (1030) 5%
Upper Mississippi-Iowa-Skunk-Wapsipinicon (0512) 8%

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

Five major tributaries to the Illinois River are in this area. They are the Des Plaines, Fox, Vermilion, Iroquois, and Kankakee Rivers.

Water

Estimated withdrawls in this MLRA:
Public supply surface water 3.4% ground water 2.1%
Livestock surface water 0% ground water 0.2%
Irrigation surface water 0% ground water 0%
Other surface water 92.5% ground water 1.7%

Total daily withdrawls average 11,815 million gallons per day (44,720 million liters).
4% Ground water sources
96% Surface water sources

Ground water is the primary source of the municipal water supply, except in the Chicago, Gary, and Milwaukee areas, where water is taken directly from Lake Michigan.

The surface water generally is suitable for almost all uses. The water in the Des Plaines River, however, is contaminated by municipal and industrial wastewater discharges from the heavily urbanized area around Chicago.

Abundant ground water in shallow glacial outwash deposits (unconsolidated sand and gravel) meets the domestic and municipal needs in much of the area. Isolated lenses of sand and gravel buried in the glacial till also provide some ground water throughout the area.

Average values of total dissolved solids are between 350 and 450 parts per million (milligrams per liter). The water in these aquifers is very hard, and the iron concentrations commonly exceed the national standard for drinking water of 1,000 parts per billion (micrograms per liter).

Some of the deeper wells in the fractured limestone and dolomite bedrock beneath the glacial drift have water that is very similar in quality to the water in the glacial deposits.

Soils

  • Mesic soil temperature regime.
  • Udic or aquic soil moisture regime.
  • Mixed or illitic mineralogy.
  • The soils are generally moderately deep to very deep, poorly drained to moderately well drained, and silty, to clayey.

    Dominant Soils:

  • Alfisols
  • Histosols
  • Inceptisols
  • Mollisols
  • Great Group Series Location
    Endoaquolls Ashkum, Bryce, and Drummer series are on broad flats and in shallow depressions.
    Milford series commonly are on broad glacial lake plains.
    Argiudolls Graymont and Varna series formed in loess and loamy till on gently sloping to sloping uplands.
    Clarence, Elliott, and Swygert series formed in areas of the more clayey till.
    Martinton series commonly are on broad glacial lake plains.
    Proctor and Warsaw series formed in loamy outwash plains or broad stream terraces underlain by sand and gravel.
    Hapludalfs Kidami and Ozaukee series commonly occur on gently sloping to moderately sloping uplands along the major stream valleys and glacial moraines.
    Eutrudepts Chatsworth series generally are in moderately well drained in the steeper areas.
    Haplosaprists Houghton and Lena series are common in wet, closed depressions.
    Hapludalfs Camden and Fox series are on outwash plains or broad stream terraces underlain by sand and gravel.
    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

    When this area was settled, about 60 percent of the total acreage supported prairie vegetation. The present potential for natural vegetation on the prairies in the area is unknown. Cattails, bulrushes, and common reed grow on organic soils in marshes. A few bogs support tamarack, pitcherplant, sundew, cranberry, leatherleaf, winterberry, and dwarf birch.

    Some of the major wildlife species include white-tailed deer, coyote, beaver, raccoon, and Canada goose.

    Land Use

    65% - Cropland - private
    4% - Grassland - private
    5% - Forest - private
    22% - Urban development - private
    2% - Water - private
    2% - Other - private

    Farmed areas are used mainly for cash-grain crops. Corn and other feed grain crops dominate the area. Hay and pasture crops are grown in support of the local livestock industry.

    The forestland in the area is mainly on wet flood plains, on steeply sloping valley sides, and on ridges formed by moraines.

    The major resource concerns include water erosion, excessive soil wetness, flooding, sedimentation, surface water quality, storm-water management, and protection and restoration of wetland habitat.

    Conservation practices generally include systems of crop residue management (such as mulch-till, no-till, and strip-till systems), cover crops, conservation cropping systems, crop rotations, and maintenance of tile drainage systems, which improve soil aeration and increase the rooting depth. Grassed waterways, grade-stabilization structures, and filter strips help to control concentrated runoff and protect water quality. Nutrient management and pest management also are important conservation practices in the area.

    Urban storm-water management helps to control flooding and improves water quality in this heavily urbanized area.


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