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I I I I I I I I I I I I I I I I I I I SECTION VII: MODIFIED OPERATIONS In this chapter we describe five ways in which the operations of Glen Canyon Dam could be modified to protect or enhance environmental and recreational resources. Each of these. modified water release scenarios addresses one key environmental or recreational resource. All five scenarios eliminate flood' releases and reduce or eliminate fluctuating releases, the adverse consequences of which were de- tailed in the previous chapter. These scenarios only approximate ideal release patterns for downstream resources. They illustrate the types of changes that could be ,made to protect or enhance resources, but do not represent the full range of possible options and should not be considered as fully developed or recommended operational plans. The critical resources targeted for each scenario are: (1) Humpback chub (2) Common native fish (3 ) Trout (4) Beaches, terrestrial vegetation, and wildlife (5) Fishing and white-water recreation We combined resources that respond similarly to flows or that can be protected or enhanc~d within the same pattern of annual releases. Two additional modifica- tions to current operations are addressed here: mimicking pre-dam releases to simulate "natural" .flows and increasing the peak powerplant capacity from 31,500 cfs to 33,100 cfs. Each scenario is represented here (see Figures VII-1 to VII-6) as an annual release pattern showing monthly releases.. Except where noted, the release levels shown are steady releases. In recognition of the variability of the annual runoff, each scenario has been developed in two versions: a "high-water year" version that pro- vides roughly 16 maf of release, and a "low-water year" version which provides roughly 8 maf of release. Scenarios for each resource were developed around the sensitive periods in lifestage or use patterns shown in Table VI-1. The rationale for these release patterns is presented in the impacts analysis below and de- tailed in Appendices A-C. For each scenario, we describe the benefit that results for the targeted resource and also impacts to the other critical resources ,when the scenario is compared to currrent 61