In 1992 Congress passed the Grand Canyon Protection Act (GCPA), which mandated development of an environmental impact statement to evaluate the effects of Glen Canyon Dam on downstream resources. The Act also mandated an “adaptive management” approach to resource monitoring and decision making to ensure that Glen Canyon Dam is operated “…in such a manner as to protect, mitigate adverse impacts to, and improve the values for which Grand Canyon National Park and Glen Canyon National Recreation Area were established…”

The US Department of Interior (DOI) published its Final Environmental Impact Statement on the Operation of Glen Canyon Dam in March 1995. In October 1996 it published its Record of Decision and in January 1997 Interior Secretary Bruce Babbitt signed a Notice of Establishment of the Glen Canyon Adaptive Management Work Group as a formal federal advisory committee. The GCDAMP has evolved over time into a complex, collaborative body of scientists and stakeholders and federal agency representatives, but its fundamental purpose remains to fulfill the mandates of the Grand Canyon Protection Act through research, monitoring, and advice to the Secretary of Interior.

Primarily the Grand Canyon Protection Act (Public Law 102-575, Sec. 1801-1809). But operations of Glen Canyon Dam and management of the Colorado River are also influenced of a larger body of law collectively referred to as The Law of the River. In fact, the Grand Canyon Protection Act states in Sec 1802: “The Secretary shall implement this section in a manner fully consistent with and subject to the Colorado River Compact, the Upper Colorado River Basin Compact, the Water Treaty of 1944 with Mexico, the decree of the Supreme Court in Arizona v. California, and the provisions of the Colorado River Storage Project Act of 1956 and the Colorado River Basin Project Act of 1968 that govern allocation, appropriation, development, and exportation of the waters of the Colorado River basin.” This complicated and occasionally conflicting body of law makes it difficult at times to determine exactly how to implement the resource protection mandates of the GCPA without violating other aspects of Colorado River water law.

The Glen Canyon Dam Final EIS analyzed baseline impacts of dam operations on downstream environmental and cultural resources from 1963 to 1990, and compared those baseline impacts to possible alternative operations of Glen Canyon Dam, including three alternatives that would provide steady flows from the dam and six alternatives that would provide various levels of fluctuating flows. The EIS team and the cooperating agencies identified a preferred alternative called: the Modified Low Fluctuating Flow Alternative. This EIS served as the culmination of the Glen Canyon Environmental Studies launched in the early 1980s to document the effects of Glen Canyon Dam on downstream resources, fulfilling one of the mandates of the Grand Canyon Protection Act of 1992.

The 1996 RoD formally adopted the preferred alternative from the 1995 EIS stipulating the Modified Low Fluctuating Flow Alternative for operating Glen Canyon Dam. It also initiated the Glen Canyon Dam Adaptive Management Program (GCDAMP) by establishing the Adaptive Management Work Group (AMWG) under the Federal Advisory Committee Act (FACA). AMWG’s stipulated purpose was to develop “a long-term monitoring, research, and experimental program” to evaluate the continuing effects of dam operations and to propose additional modifications when warranted.

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