City Sprawl Worsens Water Shortages

By Cat Lazaroff

WASHINGTON, DC, August 28, 2002 (ENS) - Sprawling development slows the replenishment of underground aquifers, making it harder for communities to cope with drought, warns a report released today by three environmental groups. The first of its kind study details the impacts of paving over the landscape, sending billions of gallons of water into streams and rivers as polluted runoff, rather than into the soil to replenish groundwater.

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Sprawling development is replacing farmland and forests, reducing the rate of aquifer replenishment. (Two photos courtesy USDA Natural Resources Conservation Service)
Sprawl is making the nation's drought even more painful by impairing the landscape's ability to recharge aquifers and surface waters, argues the new report, "Paving our Way to Water Shortages: How Sprawl Aggravates Drought." The report released by American Rivers, the Natural Resources Defense Council, and Smart Growth America, estimates the extent of this phenomenon in 18 rapidly growing cities across the country.

"Sprawl development is literally sending billions of gallons of badly needed water down the drain each year ... the storm drain," said Betsy Otto, senior director for watershed programs at American Rivers. "Sprawl hasn't caused this year's drought, but sprawl is making water supply problems worse in many cities."

The report gives the first estimates of groundwater losses due to sprawl development in the 1980s and 1990s. The authors defined sprawl as automobile dependent, low density urban and suburban development characterized by widening roads, parking lots, roofs and expanses of turf grass.

Since the increase in impervious surfaces can be most directly traced to land consumption, the authors chose to look at the most land consuming metropolitan areas, using data from the U.S. Department of Agriculture's Natural Resources Inventory for the years 1982 to 1997. The report uses estimates of impervious surfaces, approximate rates of groundwater infiltration for each metropolitan area, and average annual precipitation for those areas.

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Housing developments, like this one in Las Vegas, Nevada, include streets, parking lots and roofs - all of which send water streaming into storm drains.
In Atlanta, Georgia, the nation's most rapidly sprawling metropolitan area, the report estimates that development over the past two decades sends an additional 57 billion to 133 billion gallons of polluted runoff pouring into streams and rivers each year - enough water to supply the average daily household needs of 1.5 million to 3.6 million people per year.

This water would have otherwise filtered through the soil to recharge aquifers and provide steady underground flows to rivers, streams and lakes. Overall, the effect is to reduce the average flow of rivers and streams, and the availability of groundwater for human uses.

"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," the report explains.

This stormwater often carries high levels of toxic chemicals, sewage, fertilizer and sediment. The sudden influxes of storm runoff accelerate erosion in streambeds, increasing pollution and the frequency of flash floods.

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About 40 percent of the American public gets its water directly from underground aquifers. (Photo courtesy U.S. Environmental Protection Agency)
The impacts of sprawl on the public's water use vary from city to city. On average, 40 percent of Americans get their water directly from underground sources across the country. Groundwater also supplies, on average, 50 percent of the water in the rivers and lakes that serve everyone else.

"As over development washes more rainwater away instead of replenishing the water table, drought impacts get worse," said Deron Lovaas, deputy director of the smart growth program at the Natural Resources Defense Council. "Sprawl is hanging us out to dry. Smart growth is a way to ease our water crisis."

Sprawling land development - characterized by strip malls and highway-dependent residential, commercial, and office developments - is gobbling up the American countryside at an alarming rate. Government figures suggest that 365 acres of forest, farmland and other open space succumb to sprawl per hour. In most communities, the amount of developed land is growing much faster than the population.

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On average, 50 percent of the water in rivers and lakes comes from underground aquifers. (Photo courtesy USDA Natural Resources Conservation Service)
The report's authors found that 11 of the top 20 fastest growing metropolitan areas are located in the south, such as Atlanta, Orlando, Florida, and Greensboro, North Carolina. The northeast, west and midwest each had three of the top 20 fast growing cities.

In several cases, such as Pittsburgh, Pennsylvania, cities gobbled up increasing amounts of land even as their populations shrank, showing that many urban centers are not using land efficiently.

The authors of the report urge communities to adopt smart growth policies to reign in sprawl and protect water supplies and watersheds into the future. For example, strengthening regional cooperation on planning and concentrating development in already urbanized areas can protect water supplies by slowing the development of open space and containing the spread of impervious surfaces.

The authors conclude that the link between sprawl and drought needs to be examined more closely. The report's results suggest that policies to promote smart growth and low impact development techniques are needed to ensure adequate water supplies and to protect aquatic resources into the future.

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Rain and melting snow run across the surfaces of streets and parking lots, slipping into storm drains instead of soaking into the ground. (Photo courtesy South Florida Water Management District)
"By investing wisely in places we live, we can both protect our environment and improve our quality of life," said John Bailey, associate director of Smart Growth America.

The report's authors emphasize that they are not recommending an end to urban growth. Rather, they are promoting smarter land use, protecting open space and offering a variety of housing and transportation options.

"By directing growth to communities where people already live and work, we can limit the number of new paved and other impervious surfaces that cover the landscape, make existing communities more attractive, and discourage new infrastructure that alters natural hydrologic functions and increases taxpayer burdens," the authors conclude.

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By redeveloping properties in already urbanized areas, like this community in Michigan, communities can slow the rate of new development at the city's edge. (Photo courtesy Michigan Department of Environmental Quality)
Besides helping to protect water quality and water supplies, smart growth planning will also help communities improve their air quality by reducing traffic congestion, the report notes. Encouraging compact development that mixes retail, commercial and residential development will cut down on commuter and leisure traffic hours, the authors wrote.

The report also calls on city planners to include natural stormwater control systems incorporating wetlands and other low impact mechanisms for retaining and filtering polluted runoff.

The full report is available at: http://www.americanrivers.org/docs/PavingOurWay1.pdf