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13 324 Widespread interest in the potential effects of Glen Canyon Dam operations on river 325 resources resulted in the establishment of the Glen Canyon Environmental Studies (GCES) 326 Program by the Bureau of Reclamation (BOR) in 1982 (NRC 1987). That program operated 327 until October 1996, and accumulated extensive research information on physical, biological, 328 cultural, and socio-economic resources. There has also been significant study of canyon 329 resources by organizations and individuals not directly affiliated with the GCES Program. 330 These projects were ongoing before establishment of the GCES program, and they have 331 continued through the duration of that program. Unlike those projects, the GCES program 332 had unified themes in several resource areas. 333 The GCES Program general mission was to investigate relationships between Glen 334 Canyon Dam operations and changes in Colorado River resources throughout Glen and 335 Grand canyons. Although some effects of flow regulation were relatively obvious in 1982, 336 many other cause-and-effect relationships and ecosystem links between Glen Canyon Dam 337 operations and the downstream river environment were poorly understood. 338 The GCES Program was conducted in three phases: Phase I from 1982-1988, Phase 339 IT from 1989-1991, and Interim Flows from 1991-1996. Phase I studies involved Federal and 340 state agency related research, with some studies and summary efforts extending to 1988. The 341 program included descriptive studies of aquatic and terrestrial biology, avifauna, sediment- 342 transport processes, hydrology, and recreational use. The results of Phase I research were 343 presented as a series of single discipline technical reports and publications (DOl, 1988a; 344 1988b). These studies confirmed that dam operations affected downstream resources. 345 However, 1983 through 1986 were high inflow years and the resulting reservoir spills limited 346 scientific understanding of the effects on resources of fluctuating flows resulting from typical 347 hydropower operations, the primary focus of the original research. 348 In 1987, the National Research Council (NRC) commented that despite extensive 349 research during Phase I, the GCES single-discipline reports lacked integration (NRC 1987). 350 No conceptual ecosystem model had been developed to guide hypothesis testing, and the 351 resulting understanding of the system was therefore less complete than it could have been 352 had the studies been integrated from the start. For example, information on hydrology and -' , , , ,. ~ ;: ~" ' ~:. ~ ._,1 ~" ~-, L,i ~. it. ':< ., November S, 1998 SecoDd Draft - Do Not Cite, Pbotocopy, or DistrIbute