Mahomet Aquifer
The Mahomet Aquifer is the most important aquifer in east-central Illinois. Composed of sand and gravel, it is part of the buried Mahomet Bedrock Valley. It underlies 15 counties and ranges from thick. It supplies over per day of groundwater for public water use, industrial supply, and irrigation.
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 glacial episode. This bedrock valley forms the western part of the Teays-Mahomet Bedrock Valley System that extends into Illinois from Indiana. 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 below the ground surface.The aquifer underlies of land in east-central Illinois and spans 15 counties. The Mahomet ranges from and thick, although the average thickness is. The aquifer is confined except in Mason, Menard, and Tazewell Counties in the west near the Illinois River.
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 groundwater is pumped from the aquifer to supply municipal, agricultural, commercial, industrial, and rural domestic users. Approximately 45% of the water withdrawn is consumed by the public, 29% by industry, and 18% by commercial users. 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.