8188 - Laserfiche WebLink

Home Browse Search

Final Report 1-3 September 2000 Dam operations and the flow contributions from tributaries. Of particular importance is the Yampa River, the largest tributary ofthe Green River. This report focuses on Colorado pikeminnow, razorback sucker, and humpback chub and the physical processes that affect their habitats because information was available to recommend specific flow and temperature regimes to benefit extant populations of each species. Similar information was not available for bonytail, but the flow and temperature recommendations that are made for the other endangered fishes would presumably benefit any bonytails that may remain in the system and would not limit their future recovery potential. The report summarizes the scientific information currently available on the effects of Flaming Gorge Dam on the endangered fishes. This information will be used to develop a new biological opinion on operation of the dam and may also serve as a basis for evaluating potential impacts and mitigation measures for other ongoing or future projects that could affect flow, temperature, and sediment regimes in the Green River. Information is presented on river hydrology, geomorphology, and the biology of the endangered fishes (including distribution and abundance, flow-habitat requirements, reproduction, recruitment, diet, population dynamics, and interspecific interactions) in the Green River system. Other important resources and concerns could be directly or indirectly affected by implementation of the flow and temperature recommendations for the endangered fishes. These include other threatened or endangered species (e.g., bald eagle Haliaeetus leucocephalus and Ute ladies'-tresses Spiranthes diluvialis), other native and nonnative fishes, riparian wildlife, flooding of private and public properties, nuisance weeds and pests (e.g., mosquitos), power generation, water supply, and recreation. However, assessment of the overall effects of implementing the recommendations is deferred to other regulatory or public-involvement processes. Reclamation intends to prepare an environmental impact statement (EIS) on implementation of the flow and temperature recommendations included in this report. This EIS would examine impacts of the proposed action (implementation of the recommendations) on other resources. 1.2 CHANGES IN RIVER ECOSYSTEMS OF THE COLORADO RIVER BASIN The riverine ecosystem of the Colorado River basin (Figure 1.1) has been greatly altered over the past 100 years by human activities. Throughout the basin, major changes in the physical and biological characteristics of rivers have resulted from the cumulative effects of (1) construction and operation of dams for water supply and hydroelectric generation, (2) channelization and diking of main-stem areas and tributary streams, (3) water withdrawals for irrigation and municipal use, (4) introduction and proliferation of nonnative fishes, and (5) pollution. The construction and operation of dams have had profound effects on riverine ecology in the basin. Large areas of riverine habitat upstream of the dams have been eliminated by inundation and replaced by lentic habitat. Through time, aquatic communities have developed in reservoirs;