be leaching from oxidized pyrite--or iron sulfide,
commonly referred to as fool's gold--within the aquifer, the source of which
was coal-bearing bedrock beneath portions of the aquifer west of the Piatt-Champaign
county line. Within the aquifer above the shale bedrock, arsenic concentrations
range from 20 to 70 parts per billion (ppb), which may exceed the new lower
limit of 20 ppb under consideration by the U.S. Environmental Protection
Agency (the current limit is 50 ppb). Fortunately, arsenic can be effectively
removed with commercially available water-treatment systems.
 As with other deep aquifers,
the greatest threat to the continued viability of the Mahomet Aquifer comes
not from contamination but overpumping; that is, removing water faster than
it is replaced. Water consumption from the aquifer now averages 84 million
gallons a day. Of that amount, approximately 38 million gallons is consumed
by the region's 800,000 residents, 24 million by industry, 15 million by
commercial enterprises, and the remaining 7 million gallons by miscellaneous
uses, such as irrigation. (These estimates are extrapolated from water consumption
data for Champaign-Urbana, the only data readily available).
The rate at which water is recharging
the aquifer has been thought to be hundreds of millions of gallons per day,
but that estimate may be overly optimistic. Recent studies of the aquifer
by scientists from the ISGS and the Illinois State Water Survey indicate
that well-water levels around Champaign and Urbana are dropping. If the
original estimates are incorrect, the surplus could vanish with the addition
of a few high-demand users |
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To
prevent future problems with water supply or contamination, the Mahomet
Aquifer Consortium, consisting of 70 representatives from water companies;
local, county, and state governments; and the public are developing a study
and management plan for the aquifer. If they obtain the necessary funding
and complete the study, they'll be able to use computer models of the aquifer
system to predict water levels in the aquifer under an array of variables
for 20 to 50 years in the future. One of the things the research will determine
is the location of recharge areas. Recent carbon-14 analyses of water by
ISGS geochemists indicate that the water below Champaign County is 5,000
to 7,000 years younger than water 50 miles to the west, which told them
that the aquifer was mostly recharging-refilling in the northern part of
Champaign County.
Not surprisingly, water conservation and protection measures are a tough
sell. Planning for the long term is not one of the state's nor the nation's
strengths, says former Senator Paul Simon, who has written extensively about
water-related issues. Warning Illinoisans against complacency, he says that
east-central Illinois is not immune from water scarcities. Even if water
usage here remains within the aquifer's recharge rate, he says, "Southwestern
states, which already face severe shortages, are likely to demand the right
to purge the water here. There is no escaping."
Planning now will provide the
state with the information it needs to combat such requests and prevent
overpumping, as well as potential contamination. Given that it takes many
thousands of years for water to flow through the Mahomet Aquifer, the development
of a management plan for the next 20 to 50 years is a mere drop in the bucket.
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