Threats to Wildlife and the Platte River

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INTRODUCTION P. 5 The river is now so controlled that stream flows result more from human manipulation of the water than from natural processes. Diversions have lowered the water table in some areas but seepage from reservoirs and canals have raised the water table in other areas, no doubt contributing to the changes that have occurred on and along the Platte and its tributaries. In the current state of development, "natural cycles are not major influences, except for periods of flood flow (Hendricks and Dehaan 1981, p 324). More than 250 water diversion and storage projects exist on the Platte system today and have reduced the area of the river channel by 90 percent in places (Krapu et al. 1982; Currier et al. 1985). Sediments trapped behind dams no longer wash downstream to replace river - transported sediments (Lyons and Randle 1988). This contributes to channel narrowing and deepening and loss of transient sandbars which birds, such as Sandhill and Whooping cranes, Least Terns and Piping Plovers, require for sleeping and/or nesting. The migratory and breeding bird species mentioned above, which require a broad shallow river, are already abandoning reaches of the Platte (see chapter II). The damming and diversion of water over the course of more than 100 years has dramatically altered stream flows (see chapter III), resulting in habitat changes that cause biologists to seriously question whether the river can maintain its current wildlife values: Recent changes in habitat conditions along the Platte and North Platte Rivers have prompted concern for the welfare of the sandhill cranes and other migratory birds found there. With approximately 70 percent of the Platte's annual flows diverted for various consumptive uses upstream in Colorado, Wyoming, and western Nebraska, channel width in many areas has been reduced to 10 -20 percent of former size. Habitat conditions within the existing channel have also changed as a result of reduced scouring of sandbars and shifting of alluvial sediments. A broad band of mature deciduous woodland now occupies tens of thousands of acres that formerly were part of the river and numerous islands overgrown with woody vegetation exist within the channel. (USFWS 1981, pg i). Approximately 70 percent of the estimated 2.9 million acre -feet of the historic natural flow in the basin is removed in Wyoming, Colorado, and western Nebraska before reaching the mainstem Platte in central Nebraska between Lexington and Grand Island (Krapu et al. 1982). This "Big Bend" reach is the major Sandhill Crane spring staging area and Critical Habitat for the endangered Whooping Crane. Migrating birds also depend on wetlands in the Rainwater Basin, south of the Platte in central Nebraska. However, a large part of that particular wetland habitat has been converted to cropland. While these wetlands are not hydrologically linked to the Platte River, the shrinking of this habitat