Glen Canyon Dam Adaptive Management Program Administrative History

ABSTRACT: This book is a response to the USGS’s call for a research design that could be used as a framework for prioritizing cultural resources in the Colorado River ecosystem below Glen Canyon Dam. Changing River includes summaries of current environmental conditions and previous research and brings together diverse archaeological opinions about Grand Canyon’s human story. It then presents a theoretical basis for using a landscape approach to organize future research efforts in the canyon. The research presented here explores the geophysical, paleoclimatic, and biological parameters that have shaped the canyon landscape and influenced choices made by humans as they attempted to adapt to this ecosystem. It then focuses on the distribution of cultural materials and patterns using several archaeological approaches, and investigates natural and cultural realms as mutually reinforcing and interacting components of an integrated ecosystem to which humans have applied meaning and value over time.

An Adaptive Environmental Assessment and Management workshop process was used to assist Grand Canyon scientists and managers in developing conceptual and simulation models for the Colorado ecosystem affected by Glen Canyon Dam. This model examines ecosystem variables and processes at multiple scales in space and time, ranging from feet and hours for benthic algal response to diurnal flow changes, to reaches and decades for sediment storage and dynamics of long-lived native fish species. Its aim is to help screen policy options ranging from changes in hourly variation in flow allowed from Glen Canyon Dam, to major structural changes for restoration of more natural temperature regimes. It appears that we can make fairly accurate predictions about some components of ecosystem response to policy change (e.g., autochthonous primary production, insect communities, riparian vegetation, rainbow trout population), but we are moderately or grossly uncertain about others (e.g., long-term sediment storage, response of native and non-native fishes to physical habitat restoration). Further, we do not believe that existing monitoring programs are adequate to detect responses of native fishes or vegetation to anything short of gross habitat changes. Some experimental manipulations (such as controlled floods for beach/habitat- building) should proceed, but most should await development of better monitoring programs and sound temporal baseline information from those programs.