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 ecological survey of the riparian zone of the Colorado River from Lees Ferry to the Grand Wash Cliffs, Arizona, was initiated between 1 June 1974 and 30 June 1976. The purposes of this study were:

First, to describe vegetational changes as a result of the controlled water release from Glen Canyon Dam, second, preparation of a vegetation map from river level up to the 500 foot contour level, third, to describe population densities, home ranges, and demography of important vertebrates, fourth, to inventory insects of the riparian zone, fifth, to describe the distribution and impact caused by feral burros, and sixth, to describe the interrelationships of humans with the biota.

The major findings include the following: (1)The construction of Glen Canyon Dam has permitted the development of a new riparian community. This community is characterized by salt cedar, arrowweed, coyote willow, desert broom, and seep willow. (2) Botanical investigations in the riparian and adjacent habitats discerned the presence of 807 species of vascular plants representing 92 families. Also, two species, previously undescribed, Flaveria mcdougallii and Euphorbia rossii, are presented. (3) An accessment of important vertebrates and insects revealed: a) rodent communities on beaches tend to be less productive and less stable than those rodent communities of the terrace areas, b) Peromyscus eremicus appears to be the most successful small mammal in the riparian zone, c) rodent survivorship is very low and suggests a nearly annual population turnover, d) 178 species of birds utilize the riparian zone, of these 41 breed there, e) the most common bird species is the Lucy's Warbler, f) over 12,000 insect specimens in 20 orders and 247 families were collected and prepared, g) insect production on the exotic salt cedar fluctuate dramatically in comparison to insect production on dominant native plants. (4) Feral ass distribution was found to be greater than previously believed. It has been determined that the expanding feral ass populations are systematically destroying riparian and desert habitats within the study area and their immediate removal is suggested. (5) Human impact seems to be a function of visitor activities and the specific biotic sensitivity of the use area rather than a function of the total number of users. (6) In 1974, 395 different campsites were reported between Lees Ferry and Pierce's Ferry. In 1975, 350 different campsites were used. (7) Establishment and maintenance of an inner canyon trail system, the removal of all future human fecal waste material and education of river users may be the means to minimize habitat destruction rather than just setting a user-day limit.