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Restoration of Aquatic Ecosystems: Science, Technology, and Public Policy
gravity drains controlled by refuge managers. The water regime in the restored Kissimmee River will be constrained at the upstream and downstream ends by the need to control water levels in Lake Kissimmee and Lake Okeechobee, respectively. However, this control can be achieved by leaving gates at the lakes and relatively short lengths of the river channelized at the upper and lower ends. In between, the natural flood cycle and dynamic equilibrium will be restored (see case history, Appendix A).
Previous sections of this chapter have documented the types and extent of alteration and degradation of the nation's river-riparian ecosystems. Of the nation's total mileage of rivers and streams only 2 percent are high quality, free-flowing segments according to an analysis (Benke, 1990) of the 1982 Nationwide Rivers Inventory (NRI) (but see "Inadequate Information Base," below). According to American Rivers, a conservation organization, approximately 8 percent of the nation's river miles are of sufficient quality to be worthy of special designation and preservation, based on analysis of the NRI and compilation of lists provided by state agencies and conservation groups (Echeverria and Fosburgh, 1988). Only 58 stream segments in 39 states are in the hydrologic benchmark system set up by the U.S. Geological Survey (USGS) to represent streams little changed by man. The point is that 92 to 98 percent of the miles of rivers and streams in the United States are currently so altered that they do not fit legislative criteria for national rivers or wild and scenic rivers, or USGS criteria for a benchmark stream. Estimates of the total river miles in the United States range from 3,120,000 (NRI, as cited in Benke, 1990) to 3,200,000 (Leopold et al., 1964). Given the extent and economic value of water resource development in the United States, it is infeasible to restore 2,870,400 (92 percent of 3,120,000) to 3,136,000 miles (98 percent of 3,200,000) to a "close approximation of [the] condition prior to disturbance" (see Box 1.1).
It does seem reasonable to set a target of restoring as many miles of river-riparian ecosystems as have been affected by point source pollution and urban runoff: 400,000 miles, or 12 percent of the total 3.2 million miles (U.S. EPA, 1990). This target is also commensurate with recommendations of the President's Commission on Americans Outdoors (1986) regarding the need for outdoor recreation and aesthetic environments. The goal should be to move fluvial ecosystems as many steps as possible from the negative side of the habitat quality index toward the positive side (through rehabilitation, creation, or full restoration).