Studies find sprawl exacerbates drought, threatens farmlands.

• Author: Runyan, Curtis
• Position: Environmental Intelligence

The rapid spread of sprawling suburbs in the United States is substantially limiting the amount of water that can filter into the soil to recharge aquifers and provide underground flows to rivers and lakes, according to a new report by American Rivers, the Natural Resources Defense Council (NRDC), and Smart Growth America.

The report estimates that billions of gallons of water in U.S. metropolitan areas are washed away each year due to the rapid growth of impervious, paved-over areas resulting from car-centered development. Transportation-related surfaces--including roads, parking lots, and driveways--account for more than 60 percent of impervious areas in suburban communities. Commercial parking lots constitute a large share of the problem, according to the report: "a one-acre parking lot produces 16 times more runoff than an undeveloped meadow."

The study examined the 20 most sprawling metro areas in the country and estimated the imperviousness of new development in each region, factoring in soil types and rainfall patterns. In Atlanta, the U.S. city leading the way in sprawl, suburban growth that has occurred since 1982 causes 57 to 133 billion gallons of precipitation to run off into streams and rivers each year. The amount of water lost in Atlanta alone could supply between 1.5 and 3.6 million people with water for a year. Boston, which lost 433,000 acres to sprawl between 1982 and 1997, loses between 44 and 102 billion gallons of water each year. Other cities with the highest rates of sprawl and water loss are Washington, D.C., Houston, Texas, and Philadelphia, Pennsylvania.

More than a third of Americans depend on wells and ground water for their drinking water. With rapidly growing paved-over and built-up area, however, large amounts of water are being washed down storm drain systems rather than filtering into the soil to recharge aquifers and provide underground flows to rivers and streams. "As overdevelopment washes more rainwater away instead of replenishing the water table, drought conditions get worse," warned Deron Lovaas of NRDC.

Another study, conducted by the Washington, D.C.-based American Farmland Trust, found that the United States is losing two acres of farmland every minute, mostly due to urban sprawl. Between 1992 and 1997, cities and their suburbs paved over more than 6...