Listen. Can you hear the river? It's the Cahaba: the longest-190 miles of free-flowing river in Alabama. Bubbling from an underground spring in the Appalachian foothills, it rushes across the rocky streambeds of the Piedmont Plateau, supplying drinking water to one million people around Birmingham. It rolls southward, coddling the famous Cahaba lilies and lapping at the toes of swimmers on the gravel bars of the Coastal Plain. Seemingly undisturbed, the Cahaba meanders on, to the Alabama River near Selma, emptying into the Mobile-Tensaw Delta and the Gulf of Mexico. Many sister Southern rivers, such as the Tennessee, the Coosa, the Chattooga, the Flint and the Chunky, encounter similar geographic diversity in their waterslides to the sea.

Even after centuries of man's use, these are no ordinary rivers. Biologically, they are among the most valuable systems in the world, according to Dr. Edward O. Wilson, Pulitzer-prize winning author and University Research Professor at Harvard University. "The variety of life in the rivers of the South is enormous," says Wilson, a native of Mobile. "For example, there are more kinds of salamanders and crayfish than in any other place on the globe. These waters are among those containing the largest numbers of turtles and freshwater fishes in the world. In Alabama alone, there are 350 species of freshwater fish. The rivers of the South and their tributaries are America's threatened aquatic treasurehouse."

According to the U.S. Environmental Protection Agency (EPA), problems in the nation's waterways date back to the late 1960s, when scientists discovered the nation's rivers and streams were polluted. Fish kills were common. Wetlands were disappearing. In 1972, the U.S. Congress passed the National Clean Water Act with the twin goals of eliminating the discharge of pollutants into the nation's waters; and restoring waters to fishable and swimmable conditions. This act, which revived many waters from coast to coast, did so by attacking point-source pollution-discharges of pollutants directly into rivers and lakes from industrial and municipal sewage treatment systems.

More than a quarter century later, the EPA says 40 percent of the nation's waterways are still too polluted for fishing or swimming. The major problem today is nonpoint-source pollution resulting from low stream flows, rivers disconnected from flood plains, sediment-choked streams and lakes, erosion and stormwater run-off (full of mud, fertilizers, oil and pesticides) that is carried into creeks, rivers and streams. To combat this kind of pollution, Southerners must place their conservation efforts on entire watersheds and the people living in them, says Brad McLane, Executive Director of Alabama Rivers Alliance.

Standing on the shore of Locust Fork, which is part of the Black Warrior River watershed north of Birmingham, McLane says the demand for water in this watershed will only continue to increase with the projected residential and commercial growth.

"Unfortunately, it's already one of the more polluted systems as a result of agricultural and urban run-off. Eventually, a supply of water that is limited in quality will soon be limited in quantity. We should be able to do something to conserve this water resource.

But how do you put an economic value on a healthy river ecosystem? How much do you assess for the wetlands and streamside forests that cleanse the water? The floodplain that's used for storage? The forest cover that protects the headwaters? These are questions we have to answer, as a community, in the 21st century."