region M Area 107 A larger picture

Iowa and Minnesota Loess Hills

Central Lowland Province of the Interior Plains
The western half of the area is in the Dissected Till Plains Section of the province.
The eastern half is in the Western Lake Section

Area includes portions of the following states:
89% in Iowa
11% in Minnesota

Total Land Area 4,470 square miles (11,590 square kilometers).

Towns/cities include:
Le Mars, Sioux Center, Cherokee, and Spencer, Iowa,
Adrian and Lismore, Minnesota,

There are only a few State parks are throughout the area.


The western half of this MLRA is underlain by pre-Illinoian glacial till, which was deposited more than 500,000 years ago and has since undergone extensive erosion and dissection. The eastern half is underlain by the much younger Wisconsin-age till layer that was deposited between 20,000 and 30,000 years ago. Both till surfaces are covered by about 4 to 20 feet (1 to 6 meters) of loess on the hillslopes and by Holocene alluvium in the drainageways. The Quaternary deposits range from 150 to 450 feet (45 to 135 meters) in thickness and are underlain by Cretaceous bedrock consisting of sandstone and shale.

This area is mostly an undulating to rolling glaciated plain with some nearly level, broad ridgetops and some steep slopes bordering the major stream valleys. Nearly level, broad valley floors are along a few large rivers. The natural drainage network is well established and commonly is described as dendritic, resulting in few lakes and ponds.

Topography -

Elevation ranges from 1,115 feet (340 meters) in the lowest valleys to 1,700 feet (520 meters) on the highest ridges.
Local relief is mainly 10 to 100 feet (3 to 30 meters).

Valley floors can be 80 to 200 feet (25 to 60 meters) below the adjacent uplands. Also, some upland flats and valley floors have local relief of only 3 to 6 feet (1 to 2 meters).


The average annual precipitation in this area is 26 to 31 inches (660 to 790 millimeters).
Most of the rainfall occurs as high-intensity, convective thunderstorms during the growing season.
The average annual temperature is 44 to 48 degrees F (7 to 9 degrees C).
The freeze-free period averages about 165 days and ranges from 155 to 175 days.

Major Hydrologic Unit Areas

Name Code Extent*
Missouri-Little Sioux (1023 ) 74%
Missouri-Big Sioux (1017) 25%
Des Moines (0710) 1%

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

The Rock river is a tributary of the Big Sioux River and the Little Sioux and Floyd rivers are tributaries of the Missouri River.


Estimated withdrawls in this MLRA:
Public supply surface water 8.2% ground water 31.2%
Livestock surface water 3.6% ground water 57%
Irrigation surface water 0% ground water 0.2%
Other surface water 0% ground water 0%

Total daily withdrawls average 12 million gallons per day (45 million liters).
88% Ground water sources
12% Surface water sources

Precipitation is the principal source of moisture for crops. Sediment, nutrients, and pesticides from agricultural activities impair the major streams and rivers in this area.

The glacial till is a poor source of ground water; yields to wells are small or negligible. The water commonly is highly mineralized.

The buried channel aquafirs are sources of moderate or moderately large supplies of generally good-quality water. The mineral content of the water may be high if this aquifer is hydraulically connected to bedrock aquifers beneath it.

Alluvial deposits are extensive along the Rock River in the part of this area in Minnesota. This aquifer can be a source of large supplies of generally good-quality water. It has water with a median level of 350 parts per million (milligrams per liter) total dissolved solids.

The water in the shallow aquifers in Iowa have a median level of total dissolved solids of about 500 parts per million (milligrams per liter). The ground water in this MLRA is very hard and is used for domestic purposes, livestock, and public supply.

The Cretaceous-age Dakota Sandstone Formation is at a shallow or moderate depth in this area. In areas where more shallow aquifers do not occur, a number of communities in northwestern Iowa obtain their public supplies from this aquifer. Locally, the base of the Dakota Formation contains beds of gravel from which moderately large yields of water can be obtained. The water in the aquifer in Iowa has a median level of total dissolved solids of 824 parts per million (milligrams per liter) and is very hard.

Other bedrock formations in Iowa are very deep, and wells in these formations generally are not economical. Precambrian Sioux Quartzite is near the surface in the part of this area in Minnesota, and it contains good-quality water where it is not in contact with the Cretaceous sediments. Well yields vary dramatically, depending on how many interconnected joints and fractures are penetrated by the well.


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

  • Mollisols
  • Great Group Series Location
    Hapludolls Annieville, Everly, Galva, McCreath, Primghar, and Sac series formed in loess or loess over till on uplands.
    Endoaquolls Gillett Grove, Letri, and Marcus series formed in loess or loess over till on uplands.
    Hapludolls Moneta series formed in till on steeply sloping valley slopes.
    Endoaquolls Havelock series formed in alluvium on flood plains.

    Fauna and Flora

    Prairies in this area support tall grasses on moist soils and xeric short grasses on uplands. Grama, muhly, lovegrass, and wheatgrass commonly grow beside the more familiar little bluestem, big bluestem, Indiangrass, and wildrye.

    The prairie forbs in the area include fragrant false indigo, showy milkweed, woolly milkweed, western prairie fringed orchid, dotted blazing star, Maximilian sunflower, ground plum, and wild prairie onion.

    Wooded areas have become more extensive in this area, making up 1 percent of the current landscape as compared to 0.2 percent in the mid-1800s. Wooded areas on uplands commonly support bur oak, red oak, and hackberry. Those on bottom land support slippery elm, cottonwood, willow, and plum.

    Some of the major wildlife species in this area include Great Plains toad, bobcat, prairie rattlesnake, prairie skink, smooth green snake, pygmy shrew, and northern grasshopper mouse on the prairies and blue grosbeak, pine siskin, redbelly snake, and Woodhouse’s toad in the wooded areas.

    Land Use

    84% - Cropland - private
    7% - Grassland - private
    1% - Forest - private
    4% - Urban development - private
    1% - Water - private
    3% - Other - private

    Nearly all of this area is in farmed. Cash crops, such as corn, soybeans, other feed, grains, and hay. Much of this area is drained by tile. Extensive drainage ditches provide outlets for the tile drains.

    The small acreage of woodland in the area is mainly on wet bottom land and on steep slopes bordering stream valleys.

    The major resource concerns include water erosion, depletion of organic matter in the soils, and poor water quality.

    Conservation practices generally include systems of crop residue management (especially no-till, striptill, and mulch-till systems), cover crops, subsurface drainage systems, nutrient and pest management, grassed waterways, terraces, manure management, pasture and hayland planting, and grade-stabilization structures.

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