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Mahomet Aquifer

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Mahomet Aquifer
NameMahomet Aquifer
TypeAquifer
LocationIllinois, United States
Area km23300
Coordinates40°10′N 88°50′W
Depth m5–100
Primary lithologySand and gravel
DischargeTributaries of the Illinois River, wells

Mahomet Aquifer The Mahomet Aquifer underlies portions of east-central Illinois and supplies groundwater to municipalities, industries, and agriculture in the Champaign–Urbana metropolitan area, Vermilion County, Illinois, and surrounding counties. Fed by surficial recharge across parts of the Wabash River watershed and discharging into tributaries of the Illinois River, the aquifer is a critical component of regional water resources and intersects with regional planning, public utilities, and environmental regulation administered by agencies such as the Illinois Environmental Protection Agency and the United States Geological Survey. Study of the aquifer involves hydrogeologists, geologists, and engineers from institutions including the University of Illinois Urbana–Champaign, the Illinois State Geological Survey, and federal research programs.

Geography and Hydrogeology

The aquifer occupies a subsurface extent beneath counties including Champaign County, Illinois, Vermilion County, Illinois, Piatt County, Illinois, Douglas County, Illinois, and McLean County, Illinois, bounded by glacial and bedrock features linked to the Wisconsin glaciation and the Illinoian Stage. Hydrogeologic characterization relies on mapped transmissivity, storativity, and hydraulic conductivity determined from regional well logs, pumping tests, and groundwater level networks maintained by the United States Geological Survey and the Illinois State Water Survey. Aquifer geometry includes unconfined to semi-confined sand and gravel bodies overlain by loess and till associated with glacial drift described in statewide mapping projects coordinated with the United States Geological Survey National Cooperative Geologic Mapping Program.

Geologic Formation and Stratigraphy

The aquifer is hosted in Pleistocene fluvial and glaciofluvial deposits deposited during successive advances and retreats of continental ice sheets affecting the Midcontinent Rift System environs and the broader North American glaciation. Stratigraphic frameworks reference units correlated with the Peoria Loess, local terrace deposits tied to the Illinois River record, and buried valley fills described by the Illinois Geological Survey. Borehole stratigraphy shows interbedded coarse-grained sands, gravels, and finer silt lenses that define high-permeability channels and lower-permeability layers that influence vertical flow and connectivity, which have been mapped in cooperative studies with the United States Geological Survey and university research programs.

Water Quality and Chemistry

Water from the aquifer typically exhibits chemistry characteristic of mineral dissolution from quartzose sand, carbonate cement, and clay minerals; major-ion compositions often indicate dominance by calcium, magnesium, bicarbonate, and sulfate species similar to analyses reported by the Illinois Environmental Protection Agency and the United States Geological Survey. Trace constituents monitored include nitrate, chloride, iron, manganese, and volatile organic compounds identified in surveys conducted by the Environmental Protection Agency (United States), with isotopic and age-dating studies employing tritium and carbon-14 techniques from laboratories at the University of Illinois Urbana–Champaign. Water quality varies spatially with redox conditions influenced by organic-rich sediments adjacent to agricultural areas associated with producers represented by the Illinois Farm Bureau.

Recharge, Discharge, and Flow Dynamics

Recharge to the aquifer occurs through infiltration of precipitation across recharge zones, losing streams, and artificial recharge from irrigation return and managed aquifer recharge projects evaluated by the Illinois State Water Survey and municipal utilities such as the City of Champaign Public Works Department. Discharge occurs via pumped wells, baseflow to tributaries like the Embarras River and the Kaskaskia River headwaters, and evapotranspiration in shallow phreatic zones; hydraulic gradients are influenced by glacial geomorphology and regional pumping centers including the Champaign–Urbana Mass Transit District service areas where urban demand is concentrated. Groundwater flow models developed with assistance from the United States Geological Survey and academic partners simulate transient responses to withdrawals, climate variability, and land-use change.

Usage and Water Supply Management

Major water users include municipal systems in Champaign, Illinois, Urbana, Illinois, and several university facilities at University of Illinois Urbana–Champaign, as well as agro-industrial users and rural water districts coordinated with the Illinois Environmental Protection Agency and regional planning commissions such as the East Central Illinois Planning Commission. Management strategies encompass wellhead protection, demand forecasting, and regional water supply planning documented in utility master plans and state water resource plans administered by the Illinois Department of Natural Resources. Intergovernmental cooperation involves counties, municipalities, and university stakeholders negotiating allocation, source switching, and infrastructure investments guided by technical studies from the Illinois State Geological Survey.

Environmental Concerns and Contamination

Concerns center on nitrate loading from fertilizer and manure applied in agricultural catchments represented by stakeholders such as the Illinois Farm Bureau, point-source discharges from industrial operators, and legacy contamination including chlorinated solvents and petroleum hydrocarbons tracked by the Environmental Protection Agency (United States) and the Illinois Environmental Protection Agency. Vulnerability mapping identifies areas of thin vadose zones and high permeability where contaminant migration risk is elevated; legal and regulatory frameworks such as state groundwater protection rules and local ordinances guide remediation, monitoring, and enforcement with involvement from county health departments and advocacy groups.

Research, Monitoring, and Conservation Efforts

Ongoing research programs engage the University of Illinois Urbana–Champaign, the Illinois State Geological Survey, and the United States Geological Survey in monitoring networks, isotope hydrogeology, numerical modeling, and managed recharge experiments. Conservation and stewardship initiatives include wellhead protection plans, best management practices promoted by the Illinois Farm Bureau and extension services at the University of Illinois Urbana–Champaign, and multi-stakeholder water supply consortia exploring regional resiliency and redundancy. Long-term monitoring efforts integrate groundwater level data, water-quality sampling, and land-use change analyses to inform adaptive management under changing climate conditions considered in state and federal planning documents.

Category:Aquifers of the United States Category:Hydrogeology Category:Geology of Illinois