The Mahomet Aquifer is the most important

aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...

in east-central

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolita ...

. Composed of sand and gravel, it is part of the buried Mahomet Bedrock Valley. It underlies 15 counties and ranges from 50 to 200 feet (15 to 60 m) thick. It supplies over per day of

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...

for public water use, industrial supply, and

irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...

Hydrogeologic setting

The Mahomet Aquifer consists of sand and gravel deposited by glacial meltwater flowing westward along the Mahomet Bedrock Valley during the

Pre-Illinoian The Pre-Illinoian Stage is used by Quaternary geologists for the early and middle Pleistocene glacial and interglacial periods of geologic time in North America from ~2.5–0.2 Ma (million years ago). North America As the oldest stage in t ...

glacial episode. This

bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...

valley forms the western part of the Teays-Mahomet Bedrock Valley System that extends into

from

Indiana Indiana () is a U.S. state in the Midwestern United States. It is the 38th-largest by area and the 17th-most populous of the 50 States. Its capital and largest city is Indianapolis. Indiana was admitted to the United States as the 19th s ...

(Larson et al., 2003). Most of the

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of s ...

and

gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...

of the Mahomet Aquifer is from the lower half of the Banner Formation and belongs to the Mahomet Sand Member which is buried 100 to 200 feet (30 to 60 m) below the ground surface. The aquifer underlies 1.26 million acres (5,100 km²) of land in east-central Illinois and spans 15 counties (Panno and Korab, 2000). The Mahomet ranges from four to fifteen miles (24 km) wide (6 to 24 km) and 50 to 200 feet (15 to 60 m) thick, although the average thickness is 100 feet (30 m). The aquifer is confined except in Mason, Menard, and Tazewell Counties in the west near the

Illinois River The Illinois River ( mia, Inoka Siipiiwi) is a principal tributary of the Mississippi River and is approximately long. Located in the U.S. state of Illinois, it has a drainage basin of . The Illinois River begins at the confluence of the D ...

Groundwater use

The Mahomet Aquifer supplies approximately 850,000 people with water. The Illinois Bureau of the Budget projects that the population could increase to about 910,000 people by 2020. An estimated per day of

is pumped from the aquifer to supply municipal, agricultural, commercial, industrial, and rural domestic users (Larson et al., 2003). Approximately 45% of the water withdrawn is consumed by the public, 29% by industry, and 18% by commercial users (Panno and Korab, 2000). The remaining percentage is for other uses such as livestock and irrigation. As the population increases and economic growth occurs in the region, the demand for water also rises. Concern about additional groundwater withdrawal and the resulting repercussions has encouraged planning, management, and groundwater studies. The Illinois State Geological Survey and the Illinois State Water Survey have collected data that indicate declining water levels in certain parts of the Mahomet Aquifer.

Water quality

The water quality in the Mahomet Aquifer is high in dissolved minerals and iron, which is typical of all groundwater. Neither of these pose a human health risk. One

contaminant Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc. Types of contamination Wi ...

that is of concern is naturally occurring

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but ...

. The arsenic

leach Leach may refer to: * Leach (surname) * Leach, Oklahoma, an unincorporated community, United States * Leach, Tennessee, an unincorporated community, United States * Leach Highway, Western Australia * Leach orchid * Leach phenotype, a mutation in ...

es from oxidized pyrite. Concentrations can range from 20 to 70

parts per billion In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they ...

(ppb), which exceeds the new standard adopted by the

U.S. Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...

(Panno and Korab, 2000). The new standard is 10 ppb. Water-supply systems must comply with the new standard from January 23, 2006 (EPA, 2004). The arsenic can be effectively removed with commercially available water-treatment systems.

Mahomet Aquifer Consortium

The Mahomet Aquifer Consortium (MAC) was formed in 1998 with the purpose of developing a study and management plan for the aquifer. The group consists of 70 representatives from the public, water authorities, water companies, professional groups, and local, county, state, and federal governments. The goal of the MAC is to study the aquifer so that informed decisions can be made about meeting future water demand as populations increase and extreme weather events occur (MAC, 2004).

References

* Panno, S.V. and H. Korab. 2000. The Mahomet Aquifer. The Illinois Steward, v. 9, no. 1, p. 19-21. * Larson, D. R., E. Mehnert and B. L. Herzog. June 2003
The Mahomet Aquifer: A Transboundary Resource in East-Central Illinois
''Water International'', v. 28, no. 2, p. 170–180.

External links

* ttp://www.mahometaquiferconsortium.org/ Mahomet Aquifer Consortium
A Plan to Improve the Planning and Management of Water Supplies in East-Central Illinois (pdf)
{{Aquifers Aquifers in the United States Geology of Illinois Geography of Champaign County, Illinois