For many years, scientists and policy makers alike have been aware that sprawl increases the amount of pollution entering our waterways. We've all witnessed it: parking lots, driveways and highways shining with the iridescence of oil-sheened puddles, sediment from new developments clogging streams. The crush of new housing developments along rivers, streams and lakes means millions of gallons of household cleaners and sewage enter our state's waterways unchecked.

But sprawl may pose a deeper threat to our water-all the way down to the recharging of our aquifers. A new study conducted by American Rivers, the Natural Resources Defense Council and Smart Growth America concludes that sprawl not only exacerbates pollution problems, it also alters the ability of our natural resources to cycle water and store it, aggravating drought in many parts of the country and permanently altering the delicate patterns of water movement through the Great Lakes and their associated aquifers.

Paving the Way to Water Shortages investigated what happens to water supplies when natural areas, which both filter and absorb water, are replaced with endless miles of impervious strip malls, parking lots and giant big box stores.

"Sprawl not only pollutes our water, it also reduces our supplies," the report states. "As the impervious surfaces that characterize sprawling development-roads, parking lots, driveways and roofs-replace meadows and forests, rain no longer can seep into the ground to replenish our aquifers. Instead, it is swept away by gutters and sewer systems." Undeveloped land, the report reminds us, is valuable not just for recreation and wildlife, but for the natural filtering function it performs, as wetlands, for example, absorb precipitation and runoff and slowly release it into the ground where it recharges aquifers, streams, rivers and lakes.

The report calculates the amount of rainwater we lose as it pours off developed land instead of filtering in and recharging our vital groundwater resources. Comparing the level of imperviousness in 1997 to 1982, the report found the Detroit area probably loses between 7.8 billion and 18.2 billion gallons each year to this runoff effect. Atlanta's losses topped the list at between 56.9 billion to 132.8 billion gallons in 1997-enough water to supply the average daily household needs of 1.5 million to 3.6 million people per year.

The root of the problem, the report claims, is governmentally-subsidized sprawl and its accompanying networks of new, wider roads and highways, parking lots and other impervious surfaces. The report estimates that more than one-third of Americans get their drinking water directly from groundwater, and the remaining two-thirds who depend on surface water also are affected, given that about half of a stream's volume comes from groundwater.

Adding to the problem is the fact that most of Michigan's sewage and wastewater infrastructure is aging and outdated. Cracked, crumbling pipes cause several problems, the most obvious of which is untreated sewage and wastewater leaking into groundwater reserves. But another, more complex problem, is that many of the pipes have become so porous and deteriorated by roots and age, they actually absorb fresh water as it moves down through the ground, adding it to the wastewater in the pipe and sending it off to treatment plants rather than letting it recharge water systems. Rather than focusing on fixing this existing infrastructure, however, resources are too often dedicated to building new pipes to keep up with growing communities that are outpacing their septic systems.

The NRDC report is available on the Internet at: http://www.americanrivers.org/landuse/sprawldroughtreport.htm.