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The data contained in these tables detail the areal extent of exposed sand, in square meters, along the Colorado River between Glen Canyon Dam, Arizona, and Bright Angel Creek, Arizona, within Glen Canyon National Recreation Area and Grand Canyon National Park. Sand exposure areas are provided as a function of Colorado River discharge, as measured at Lees Ferry, Arizona, in increments of 1000 cubic feet per second. Exposed sand extents are subdivided into mapped and unmapped sand areas; at Colorado River discharge; at flows below 8,000 cubic feet per second, the total extent of exposed sand can be estimated as the sum of field-mapped sand and that sand which was unmapped, but estimated to be present across the study...
Regional transport of water and dissolved constituents through heavily regulated river systems is influenced by the presence of reservoirs. Analysis of seasonal patterns in solute fluxes for salinity and nutrients indicates that in-reservoir processes within large storage reservoirs in the Rio Grande and Colorado basins (southwestern USA) are superimposed over the underlying watershed processes that predominate in relatively unregulated stream reaches. Connectivity of the aquatic system with the landscape is apparently disrupted by processes within the reservoir systems; these processes result in large changes in characteristics for solute transport that persist downstream in the absence of significant inputs. Additionally,...
Impoundment and diversion of watercourses for power production and water supply can have profound effects on the mayfly fauna. To explain such effects a species-specific approach is adopted on account of differing habitat requirements and life histories in the order and even within genera. Environmental conditions such as discharge and flow patterns, temperature, food availability, and predation may be changed. This leads to changes in the density and species composition of the mayfly community, especially when there is a hypolimnion drain from reservoirs. Temperature changes below such reservoirs may remove obligatory life cycle thresholds. Prolonged periods of low discharge lead to the dominance of genera, such...
Fisheries managers have often suggested that survival of trout during the winter is a major factor affecting population densities in many stream ecosystems in the Rocky Mountains. In Wyoming, trout population reductions from fall to spring in excess of 90% have been documented in some reservoir tailwaters. Though biologists have surmised that these reductions were the result of either mortality or emigration from some river sections, the specific mechanisms have not been defined and the factors leading to the trout loss are unknown. This is a review of four studies that were conducted or funded between 1991 and 1998 by the Wyoming Game and Fish Department to understand the extent of overwinter losses, identify some...
    map background search result map search result map Discharge records and sand extents along the Colorado River between Glen Canyon Dam and Phantom Ranch, Arizona Discharge records and sand extents along the Colorado River between Glen Canyon Dam and Phantom Ranch, Arizona