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dimensional hydrogeologic maps of the groundwater resources of Kendall County. The ISGS is
studying the susceptibility of the shallow sand and gravel aquifers to contamination from various
land uses associated with urban growth in Kane County (Hwang, 2004) and McHenry County
(Hwang, et al., 2003). The USGS has completed a local model of the ground-water flow system
under Campton Township to assist the township in assessing their resources and for planning
development within the township. Field data collection and model simulations are complete.
Results of the study will be released by January 2006.
Availability of groundwater resources is of significance in DeKalb County as the demand for
water increases to meet the needs of its growing population. Vaiden et al. (2004) described the
shallow groundwater resources of the county and concentrated on the sand and gravel deposits
within the buried Troy Bedrock Valley.
Metro East St. Louis - The availability of groundwater resources and the sensitivity of aquifers to
contamination is of increasing importance in Madison, Monroe, and St. Clair Counties that
comprise the Metro East St. Louis area. Mapping the Quaternary deposits establishes the
lithostratigraphic framework of these sediments and provides the basis for mapping the extent,
thickness, and characteristics of the aquifers within these deposits (Grimley et al., 2004; Smith et
al., 2004).
Mahomet Aquifer - The Mahomet aquifer remains a high priority. This major aquifer extends
from the Indiana state line to the Illinois River, crossing eastern and central Illinois. Mehnert et
al. (2004) described the results of continued investigations of the Mahomet aquifer.
Groundwater flow within the aquifer and both the rates and locations of groundwater recharge
are not well understood. Studies being conducted at the ISGS are focused on using geochemical
techniques to determine the age of the groundwater in Mahomet aquifer, locate major recharge
areas, examine the evolution of groundwater geochemistry, and develop a conceptual model to
help explain the current geochemical characteristics of water in the Mahomet aquifer. The ISGS,
ISWS, USGS/Urbana and DNR/Office of Water Resources continued to serve as technical
advisors to the MAC, which has sought funding and support for studying this major source of
supply that underlies east-central Illinois. For more information, see the Consortium’s website at
www.mahometaquiferconsortium.org/.
The ISWS continues to conduct both field and modeling studies of groundwater flow and
recharge in the Mahomet aquifer. In April 2003, a 23-day aquifer test was conducted using
Decatur’s wellfield to study interactions between the aquifer and the Sangamon River in Piatt
County. Water levels have been measured in wells completed in the Mahomet aquifer in
Champaign, Ford, Iroquois, and Vermilion Counties to better understand groundwater flow
directions in the northeastern section of the aquifer. A critical component of this effort is
identification of locations where the aquifer interacts with streams and to determine if water is
flowing into or out of the aquifer. The ISWS continues to update a groundwater flow model with
all of the new information. The model is being used to confirm our conceptual understanding of
the flow system and to determine where additional data are needed. Flow budgets computed by
the model are being compared to streamflow records of major streams. Future work will focus
on the overlying Glasford aquifer and how it supplies water downward into the Mahomet
aquifer.
