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OVERVIEW 27 Despite the investment of more than $260 billion (1990 costs) from 1970 to 1984 in the construction and operation of public and private wastewater treatment facilities, the chemistry of our streams seems to have improved only slightly (U.S. EPA, 1984; Smith et al., 1987). Based on an analysis of 380 sampling stations distributed throughout the country, the concentrations of chloride, sulfate, nitrate, magne- sium, sodium, and potassium (Smith et al., 1987) have increased. Suspended solids and pH have also increased at most stations, as have the concentrations of heavy metals, including arsenic, cadmium, iron, and manganese. Although most stations reported that dissolved oxygen increased, a beneficial change, the ratio was only about 3 to 2. Decreases were reported in the concentrations of calcium and phos- phorus. Based on analyses undertaken by state personnel, the U.S. Environmental Protection Agency has concluded that progress has been made but that much remains to be done (U.S. EPA, 1990). How- ever, only 758,000 miles of stream were surveyed, 23 percent of the total streams in the United States. The apparent lack of concern for the physical structure of our nation's streams perhaps stems from the fact that no one seems to have a very clear idea of how many stream miles there are in the country, let alone their physical, chemical, and biological state of repair. Al- though basic documentation is lacking, one estimate is that there are more than 3.25 million miles of U.S. stream channels (Leopold et al., 1964) and, based on EPA's estimate, 758,000 of these miles are af- fected by effluents from municipal and industrial treatment plants. An additional 155,000 miles are constructed agricultural drains (Wooten and Jones, 1955). Incorporated into our major river systems are close to 12,000 miles of inland waterways. Fox these waterways, navigational channels axe maintained at depths of 8 to 16 ft. Along our streams, levees and flood walls traverse an estimated 25,000 miles (Johnston Associates, 1989) and enclose more than 30,000 square miles of floodplain. The floodplain estimate is extrapolated from the ratio of length of levees to enclosed area for the Upper Mississippi River. Channelization, for navigation or drainage, and levees have drasti- cally reduced the flow area of streams. At the same time, increased runoff from the draining of uplands and wetlands has been forced into the drainage system. The hydrological effects of this loss of storage are enormous. The environmental stress and altered characteristics and functions of our aquatic ecosystems caused by dispersive and extractive uses and stream modifications are reflected in the status of our fisheries, as reported by the U.S. Fish and Wildlife Service (Judy et al., 1984). Of 666,000 miles of perennial U.S. streams surveyed, more than 40