Thursday, October 15, 2009

Champaign County's current use of Mahomet Aquifer unsustainable

Champaign County's current use of Mahomet Aquifer unsustainable

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Last week’s Environmental Almanac drew attention to a report issued in June by the Regional Water Supply Planning Committee for East-Central Illinois. It also highlighted some of the inadequacies of current water-use law in the state. This week I want to call attention to the issue of water use, particularly the current overuse of water from the Mahomet Aquifer in and around Champaign-Urbana.

The report by the Regional Water Supply Planning Committee characterizes the current state of affairs by saying “East-Central Illinois is not facing an immediate water crisis,” rather than commenting on where the continuation of current trends would take us. And it asserts the committee’s belief that a plan with “no new laws or regulations and voluntary participation” can pave the way to a rosy future, one that would be described by the headline, “Sustainable Water Supplies for East-Central Illinois.”

I hope for that future, too. But I think we’re unlikely to get there unless we come to grips with the fact that we already have a problem. Here’s what it is: In Champaign County we use water from the Mahomet Aquifer faster than it can be recharged. We’re over budget. We’re running a deficit. It seems to be true we won’t drain the account completely in the next two generations, but that’s not because we’re managing it well. We’re comparatively rich in water only because we inherited such a big account in the first place.

The movement of water through aquifers is complex, and there are limits to current understanding, but I think we can reasonably draw such conclusions.

Using information from modeling done by the Illinois State Water Survey, Clark Bullard, a U of I engineering professor and board member of the conservation group, Prairie Rivers Network, constructed a water budget for Champaign County, which provides a simplified version of what’s going on below the ground.

Bullard starts out with the fact that Champaign County withdraws about 33 million gallons per day from the Mahomet Aquifer and then sets out to answer the question, “Where does it come from?”

Recent calculations derived from the Water Survey’s computer modeling suggest about half of that--16 million gallons--comes from water that would have otherwise traveled through shallow soils into local rivers and streams, keeping them healthy. Another 13 million gallons of that is water that would otherwise be available in neighboring counties: roughly 4 million from Ford, Vermilion and Iroquois counties together, and 9 million from counties to the west. That leaves a difference of 4 million gallons withdrawn from storage, which is the daily amount by which we are depleting the water “bank account” we will leave to future generations.

So in Champaign County the answer to the question “Where does our water come from?” is from our rivers, from our neighbors and from our children.

I mentioned earlier that the report by the Regional Water Supply Planning Committee doesn’t call attention to the deficit in our water budget, but I would add that a careful reader can find hints of that problem in the report. Dwain Berggren who represented the interest of the environment on the committee created a list of them, which you can find posted with this segment on the Environmental Almanac Web site.

But for now, let me leave you with this one. Between the years 1930 and 2007 the water-level elevation of an observation well on Rising Road declined about 83 feet—a little over a foot per year. The water level at that well can be safely drawn down only about another 80 feet. I bet you don’t need a calculator to figure out how long it will take for that to happen.


Following is Dwain Bergrenn's commentary on the implications of the Regional Water Supply Planning Committee's report. The report itself can be downloaded at


As a Champaign County resident and member of the committee issuing the MAC-RWSPC final report, I note that it does not express a definite opinion about the sustainability of our county’s groundwater resources. But implications of statements in the report that are quoted below lead me to a negative conclusion:

  • "... a well in Champaign finished in the Glasford Aquifer is reported ... to no longer yield water, probably due mainly to extensive pumping from nearby wells in the deeper [underlying] Mahomet Aquifer." (page 10)

  • "In 2007, water-level elevation (head) in the Petro North observation well on Rising Road, a few miles west of Champaign, was about 83 feet lower than the predevelopment (1930) water level (Figure 7 (page 17)). The current water level is about 80 feet above the top of the aquifer at that location. The historical records indicate an average drop in water level of 1.08 feet per year since 1930." [p. 74; Figure 17 shows four different estimates for the 2050 head in the well which range from about 35 to 70 feet above the top of the Mahomet Aquifer.]

  • "... withdrawals in and around Champaign County have formed a large, persistent cone of depression tens of miles across, extending into neighboring counties." (p. 10)

  • A 2006 study reporting computer-simulated pumping studies of the Illinois American well field concluded that "dewatering of shallow water-bearing zones [above the Mahomet Aquifer] will affect some local wells and ultimately reduce the capacity of the Mahomet Aquifer due to deceased vertical leakage." (p. 16)

  • "... Mahomet Aquifer groundwater flow from Champaign County to Piatt County, estimated to have been 10 mgd [million gallons daily] in predevelopment times, already has been reversed and Champaign County now "imports" an estimated 3 mgd from Piatt County. By 2050, water from even farther west will be pulled into the expanding cone of depression centered in Champaign County. Possible implications of this groundwater flow reversal for water availability in Piatt County have not been evaluated." (p. 17)

  • "Heads in some wells finished in shallow confined aquifers – the Glasford Aquifer in and around Champaign-Urbana, for example – are likely to continue to decline and more wells finished in the Glasford Aquifer are likely to go dry with increased withdrawals from the Mahomet Aquifer." (p. 42)

  • "Especially in the eastern and central parts of the Mahomet Aquifer, the groundwater it contains generally is 3,000 to 10,000 ... [radiocarbon years in age]. ... ‘Rain and snow that falls on the surface in Champaign County begins a roughly 3,000-year journey downwards to the Mahomet Aquifer, traveling at an average rate of less than an inch a year. Once it reaches the aquifer, it travels laterally in every compass direction but south. After about 7,000 years, water that journeyed westward seeps into the Illinois River along the river bottom near Havana, Illinois.’ Such were the natural predevelopment conditions, but these have been modified by groundwater development. It takes much longer to replace water taken out of storage from the more deeply buried, till-confined parts of the Mahomet Aquifer than it does to replace water withdrawn from surface waters and shallow unconfined aquifers." [my emphasis; p.65.]

So, considering these points, is our present use of the Mahomet Aquifer System reasonable and sustainable? Certainly, further studies of our water resources are urgently needed to define their dynamics and nature more clearly and exactly. But the conditions cited in the RWSPC report argue for a negative judgement when examined by the standards of a conservative definition of sustainable water resource and supply systems (see also page 56 of the report).

To be truly – in the strictest sense – sustainable, our use and management of an already compromised county water resource will require us to (1) preserve the Mahomet Aquifer System in perpetuity, (2) maintain the natural integrity of its waters and protect them from irreparable harm, (3) distribute water equitably to sustain the good health and vitality of the living communities in its surrounding ecosystem, and (4) continually monitor the natural resources it affects.

--Dwain Bergrenn