Environmental Problems

Industrial, agricultural, and municipal wastes that enter rivers may cause disease in fish and other animals—including humans who drink contaminated water or eat animals that have absorbed toxic wastes into their tissues. The removal of trees and other plants from river basins increases the amount of soil that is carried by runoff into rivers. As accumulating soil reduces the depth of the rivers, shipping may be hampered and flooding may increase. Hydroelectric dams sometimes have adverse effects on wildlife; for an example,

In the United States, a number of federal and state laws help to reduce these environmental problems. Federal laws include the Wild and Scenic Rivers Act of 1968, which regulates such activities as damming and logging on and near certain rivers, and the Clean Water Act of 1972, which regulates the discharge of wastes into rivers and other bodies of water.