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"How should we manage our water supply? - Episode #3 of 4 in a public radio series by Bill Hammack

(Return to Water Supply Series)

Bill I'm with an Illinois State Geological Survey Team standing on the edge of a road just south of Champaign's Willard Airport. I'm watching a key, but difficult step in taking care of our water supply: Knowing what's underground. We can only "see" the aquifer indirectly. In this case the team slowly lowers a special microphone into a borehole . . . taps a metal plate on the surface . . . and then measures how quickly the sound travels. They can interpret this time to reveal the make up of the Mahomet Aquifer so we can then carefully plan how to use it.

Winstanley "Its not infinite.....you can't just withdraw infinities amount of water, otherwise you would suck the whole system dry ....

Bill But Derek Winstanley of the Water Survey assures us that the aquifer is not drying up under our feet.

Winstanley "It's renewable from that fact that the water in the aquifer is slowly replaced by water from new precipitation as it infiltrates through the ground in the process of recharge."

Bill About ten percent of rainfall makes a 3,000 year journey through the ground to the aquifer 200 or so feet below. The nests nests in between the sand and gravel of the aquifer. This rain refills it by one-half inch a year, but because it covers so large an area this is a vast amount of water. Winstantley told me that the "... key challenge is not just how much is down there" but instead this.

Winstanley "... [H]ow much can you safely withdraw - and what you mean by safely. As I said before every time you withdraw water from the aquifer there are some impacts. Its really a matter of public policy decision on how much impact the people, the public are willing to accept."

Bill Will we accept, for example, the seven proposed corn to ethanol plants, which would all draw heavily on the Mahomet Aquifer? A single gallon of ethanol takes three gallons of water, that's about 300 million gallons a year or about 1 million a day. Al Wehrmann of the Water Survey evaluated for me the plants' possible impacts.

Wehremann "Frankly I think the liberal sprinkling of six or seven ethanol plants across the aquifer is not a problem. The aquifer can handle that. The concern is what are the local impacts, because of interference effects of a large withdrawer on, say, other existing uses, say, within a mile or two of those wells."

Bill One million gallons a day for ethanol pales when compared to the twenty-four million gallons a day used by Champaign and Urbana alone. Yet, if not carefully managed we can end up with more expensive water. A severe drought might make us alter the aquifer by pumping too much, thus requiring costly movement of wells and pipelines. In planning for the future we also need to know one more thing: How much rain will replenish the Mahomet Aquifer. We must consider how climate changes affect Illinois weather. Derek Winstanley explained to me that the state, so far, is no warmer now than it was in the 1920s.

Winstanley "Whereas globally on the average over the whole globe there has been, of course, significant warming, but on a regional basis we haven't seen that. When we look at the climate models their ability to predict and simulate regional climate over Illinois, for example, are much more limited then their ability to predict global average conditions. So we have to look at the complexities of regional climate. [And] don't get caught up in this simple argument of talking about 'global warming' as if global average conditions also applied to Illinois -- they don't."

Bill This means we need to develop Illinois-specific models to predict the effect of global climate change locally. This last item raises the specter of what it means to be a global user of water, which includes all of us. Tomorrow I look at how we use water ... including how much we import from China. For AM-580 news I'm Bill Hammack.