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CHAPTER 11I- AFFECTED ENVIRONMENT AND ENWRONMENTALCONSEQUENCES This chapter describes the resources of the Colorado River through Glen and Grand Canyons and the impacts of the proposed action on these resources. The conditions that currently exist are the baseline for analysis of effects. The affected resources are broadly categorized into water and water quality, aquatic resources, endangered and special status species, cultural resources, recreation, hydropower, and air quality. More detailed information on the affected resources can be found in the final Operation of Glen Canyon Dam Final Environmental Impact Statement (USDI 1995) and the Aquatic Ecosystem of the Colorado River in Grand Canyon, Grand Canyon Data Integration Project Synthesis Report (Valdez and Carothers 1998). For the purposes of the analysis presented here, it was assumed that the temperature controls may be used whenever warm water is available (typically May through September). Warmer release temperatures would be provided to improve conditions for the warmwater native fishes. COLORADO RIVER ECOSYSTEM RESOURCE LINKAGES Resources downstream from Glen Canyon Dam are inter-related or linked, and many are associated with, or dependent on, water temperature, In such a linked system, changes in a single process can affect many resources. For example, the proposed temperature modification may directly or indirectly affect water quality, aquatic organisms, and fish. Threatened and endangered species can be affected through their linkages to other resources (non-native predators/competitors) and the effects of temperature on those resources. These changes may be adverse or positive. These linkages playa preeminent role in the development of the proposed alternative and the resource analyses presented in this document. The goal in preparing the proposed alternative was to achieve needed positive effects for endangered species while avoiding adverse impacts. Glen Canyon Dam has altered many characteristics of the Colorado River. Historically, the river and its larger tributaries were characterized by heavy sediment loads, variable water temperatures, large seasonal flow fluctuations, extreme turbulence, and a wide range of salinities. The dam has dramatically altered the temperature of the river. Before the dam, river water temperature varied on a seasonal basis from a monthly average high of about 260C (780F) to lows near freezing. Now, water released from the dam averages about 80C (46 OF) and varies little year round. The dam releases are clear and cold. The cold releases from the dam now support aquatic communities that did not exist before Glen Canyon Dam. The ecosystem now contains a mixture of native and non-native plant and animal communities that began developing (prior to the dam) with the introduction of non-native fish and vegetation (Carothers and Brown 1991). Dam construction and operation further modified this mixture and created the current system that is supported by post-dam conditions. This region of the Colorado River is forever changed.