Endangered and Threatened Species of the Platte River

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and engineering community. The committee reviewed that information, as well as oral and written testimony critical of the research conducted by DOI agencies, and it concluded that the methods used during the calculations in the early 1990s were the most widely accepted at that time. Revisions were made as improved knowledge became available. Although the Instream Flow Incremental Method (IFIM) and Physical Habitat Simulation System (PHABSIM) were the best available science when DOI agencies reached their recommendations regarding instream flows, there are newer developments and approaches, and they should be internalized in DOI's decision processes for determining instream flows. The new approaches, centered on the river as an ecosystem rather than focused on individual species, are embodied in the concepts of the normative flow regime. Continued credibility of DOI instream flow recommendations will depend on including the new approach. The instream flow recommendations rely on empirical and model -based approaches. Surveyed cross sections along the river provided DOI investigators with specific information on the morphology of the river and vegetation associated with the river's landforms. The portions of the cross sections likely to be inundated by flows of various depths were directly observed. Model calculations to simulate the dynamic interaction of water, geomorphology, and vegetation that formed habitat for species were handled with the prevailing standard software PHABSIM, which has seen wide use in other cases and has been accepted by the scientific community. The software was used by DOI researchers in a specific standard method, IFIM, which permits observations of the results as flow depths are incrementally increased. The continuing DOI model developments, including the emerging SEDVEG model, are needed because of the braided, complex nature of the Platte River —a configuration that is unlike other streams to which existing models are often applied. The committee did not assess the • newer models, because they have not yet been completed or tested, but it recommends that they be explored for their ability to improve decision - making. The committee also recognizes that there has been no substantial testing of the predictions resulting from DOI's previous modeling work, and it recommends that calibration of the models be improved. Monitoring of the effects of recommended flows should be built into a continuing program of adaptive management to help to determine whether the recommendations are valid and to indicate further adjustments to the recommendations based on observations. • 8. Are the characteristics described in the USFWS habitat suitability guidelines for the central Platte River supported by the existing science and are they [the habitat characteristics] essential to the survival of the listed avian species? To the recovery of those species? Are there other Platte River habitats that provide the same values that are essential to the survival of the listed avian species and their recovery? The committee concluded that the habitat characteristics described in USFWS's habitat suitability guidelines for the central Platte River were supported by the science of the time of the original habitat description during the 1970s and 1980s. New ecological knowledge has since been developed. The new knowledge, largely from information gathered over the last 20 years, has not been systematically applied to the processes of designating or revising critical habitat, and the committee recommends that it be done. The committee also concluded that suitable habitat characteristics along the central Platte River are essential to the survival and recovery of the piping plover and the interior least tern. No alternative habitat exists in the central Platte that provides the same values essential to the E