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1~~trf.~~\~x:~ILn+-q u~ 1~75 UNITED STATES GOVERNMENT memorandum " TO Memorandum Head, Remote Sensing Section Denver, Colorado DATE: May 12, 19S9 FROM Michael J. Pucherelli, Environmental Biologist Richard C. Clark, Applications Specialist - Advanced Sciences, Inc. SU~ECT: Comprehensive Report (19S6-198S) on the Effects of Green River Flows on Backwater Habitat Availability as Determined by Remote Sensing Techniques (Remote Sensing) Applied Sciences Referral Memorandum No. AP-S9-4-5 Principal Investigator: Michael J. Pucherelli INTRODUCTION Fish populations in the Colorado River system historically have been dominated by endemic species adapted specifically for this river system. The recent decline in abundance and range of some endemic species has been sufficient to classify them as endangered by the U.S. Fish and Wildlife Service (FWS) (Archer et ale 19S4). In response to this situation, the Colorado River Fishes Project (1979-19S1) and the Colorado River Fishery Monitoring Program (19S2-present) were initiated to expand the information base of endemic species and determine their flow requirements. Studies have centered on the Green River because it currently has the most viable population of Colorado squawfish. This remote sensing study focused on backwater habitat in the Green River as a key element for the survival of the Colorado squawfish. BACKGROUND Following the construction of Flaming Gorge Dam in 1962 the abundance of endemic fish species in the Green River decreased. These species included the endangered Colorado squawfish (Ptychocheilus lucius) and humpback chub (Gila cypha), and the rare but unlisted razorback sucker (Xyrauchen texanus). The long-term impact of the operation of Flaming Gorge Dam is unknown. However, the dam has altered the natural state of the Green River by reducing flood events and their severity, increasing late fall and winter fluctuations to accommodate peaking operations and in general altering natural flows throughout the year (Tyus et al. 19S7, Andrews 19S6, Graf 19S0). Since 1979 the U.S. Bureau of Reclamation (Reclamation) and FWS have been in consultation on the effects of various Reclamation projects including the operation of Flaming Gorge Dam and its effects on endangered fish populations in the upper Colorado River system. Early studies were conducted to establish life history and flow criteria information for