Mahomet Aquifer
Encyclopedia
The Mahomet Aquifer is the most important aquifer
in east-central Illinois
. The sand and gravel aquifer
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 100000000 gallons (378,541.2 m³) per day of groundwater
for public water use, industrial supply, and irrigation
.
valley forms the western part of the Teays-Mahomet Bedrock Valley System that extends into Illinois
from Indiana
(Larson et al., 2003). Most of the sand
and gravel
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
.
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 Approximately 45% of the water withdrawn is consumed by the public, 29% by industry, and 18% by commercial users (Panno and Korab, 2000).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 http://www.isgs.uiuc.edu/ and the Illinois State Water Survey http://www.sws.uiuc.edu/ have collected data that indicate declining water levels in certain parts of the Mahomet Aquifer.
. Neither of these pose a human health risk. One contaminant that is of concern is the naturally occurring arsenic
. The arsenic leach
es from oxidized-pyrite
. Concentrations can range from 20 to 70 parts per billion (ppb
) which exceeds the new standard adopted by the U.S. Environmental Protection Agency http://www.epa.gov/ (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). Fortunately, arsenic can be effectively removed with commercially available water-treatment systems.
demand as populations increase and extreme weather
events occur (MAC, 2004).
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
in east-central Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
. The sand and gravel aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
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 100000000 gallons (378,541.2 m³) per day of groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
for public water use, industrial supply, and irrigation
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...
.
Hydrogeologic setting
The Mahomet Aquifer consists of sand and gravel deposited by glacial meltwater flowing westward along the Mahomet Bedrock Valley during the pre-Illinois glacial episode. This bedrockBedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
valley forms the western part of the Teays-Mahomet Bedrock Valley System that extends into Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
from Indiana
Indiana
Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...
(Larson et al., 2003). Most of the sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
and gravel
Gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...
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
Illinois River
The Illinois River is a principal tributary of the Mississippi River, approximately long, in the State of Illinois. The river drains a large section of central Illinois, with a drainage basin of . This river was important among Native Americans and early French traders as the principal water route...
.
Groundwater use
The Mahomet Aquifer supplies approximately 850,000 people with water. The Illinois Bureau of the Budget http://www.state.il.us/budget/ projects that the population could increase to about 910,000 people by 2020. An estimated 100000000 gallons (378,541.2 m³) per day of groundwaterGroundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
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 http://www.isgs.uiuc.edu/ and the Illinois State Water Survey http://www.sws.uiuc.edu/ 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 the water quality of all groundwaterGroundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
. Neither of these pose a human health risk. One contaminant that is of concern is the naturally occurring arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
. The arsenic leach
Leach
Leach may refer to:Placenames* Leach, Oklahoma in the United StatesSurnames* Al Leach* Archie Leach, real name of actor Cary Grant* Ben Leach, player in Liverpool-based pop group The Farm* Bernard Leach , British potter* Bobby Leach...
es from oxidized-pyrite
Pyrite
The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
. Concentrations can range from 20 to 70 parts per billion (ppb
PPB
PPB can stand for:* Party political broadcast, a type of political programming in the United Kingdom* parts-per-billion, a unit of concentration* Portland Police Bureau, a police agency for the city of Portland...
) which exceeds the new standard adopted by the U.S. Environmental Protection Agency http://www.epa.gov/ (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). Fortunately, arsenic can be effectively removed with commercially available water-treatment systems.
Mahomet Aquifer Consortium
The Mahomet Aquifer Consortium (MAC) http://www.mahometaquiferconsortium.org/ 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 waterWater
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
demand as populations increase and extreme weather
Weather
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...
events occur (MAC, 2004).