Threats to Wildlife and the Platte River

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WILDLIFE p. 27 Crowding, which is due to habitat deterioration, is the main problem confronting waterfowl in south - central Nebraska. The large die -offs that occur in the Rainwater Basin area, where the birds are now so concentrated, are associated with the lack of moving water there; stagnant water provides a medium for harmful bacteria to multiply and be transmitted. River currents dilute and carry off the bacterium responsible for avian cholera, but habitat changes and resulting crowding of waterfowl have sparked concern that the potential for large -scale cholera outbreaks is increasing on the river (USFWS 1981). Small, nearby populations of summer breeding ducks, nesting in parts of the valley where standing water exists in sedge meadows, marshes, and grasslands, fluctuate annually in proportion to the amount of surface water. Drought conditions and groundwater pumping for irrigation have caused some of these areas to dry up during summer, resulting in reduced waterfowl production in central Nebraska (Currier et al. 1985, p 44). Quantitative Flow Rates Suggested for Wildlife As a result of competition for water in the Platte, analysts have attempted to quantify the amount of water "needed" for wildlife. The following table (21)) summarizes these estimates. Note that different criteria are used for each: 1) threshold for survival; 2) threshold for use of the river, or 3) optimal habitat that would be generated if these flows were met. More is understood about wildlife roosting habitats than the complex dynamics maintaining the morphology of a braided river and riparian ecological conditions. Studies for flows and fluctuations needed to sustain riparian wet meadows are still in their infancy. Footnotes to the table describe in detail the origin of each estimate. For a quick summary of flow data, Table 3B in chapter III, presents a condensed version of Table 2D.