WSPC12525 ‎(2)‎

• File Number: 8220.101.10
• Description: Colorado River Water Projects - Glen Canyon Dam-Lake Powell - Adaptive Management
• State: CO
• Basin: Colorado Mainstem
• Date: 6/2/1998
• Author: DOI-GCMRC
• Title: Assessment of Impacts of Glen Canyon Dam Operations on Water Quality Resources in Lake Powell and the Colorado River in Grand Canyon - Grand Canyon Monitoring and Research Center - Draft - 06-02-98
• Water Supply Pro - Doc Type: Report/Study

002371
Abstract

The effects of the construction and operation of Glen Canyon Dam have been studied,

documented, and manipulated in the downstream environment in Grand Canyon. Glen Canyon

Environmental Studies led 13 years of study that focused on addressing and mitigating the adverse

impacts of the Dam on that ecosystem. While data has been collected from Lake Powell throughout

its filling history, there has been no concerted effort to evaluate the impacts of dam operations on

the physical, biological, and chemical processes of the reservoir and downstream releases. Using

data from the 33-year history of water quality monitoring on Lake Powell, primarily from Bureau

of Reclamation efforts, we will begin to demonstrate the effect of dam operations and other factors

on the water quality and hydrodynamics of Lake Powell. Of special importance are the historical

record reflecting the flood years of 1980 to 1986, modified operations of Glen Canyon Dam which

began in 1991, the results from the Experimental Beach/Habitat Building Flood of the spring of

1996, and most recently, the high sustained releases starting in February 1997. No special data

collection was designed to answer the question, but rather, the stock of existing data was analyzed

to provide the answers and to fuel the questions that formed the assessment. The results show that,

combined with other influences, dam operations have an undeniable effect upon the stratification

and mixing of the reservoir, and those effects are consequently passed downstream through the

dam. Not all aspects of dam operations could be answered or analyzed under the scope of the nine

months allowed for the assessment. The experimental flood demonstrated the effects of using

alternate structures for the release of water, in this case, the hollow jet tubes that are positioned 100

feet below the penstock withdrawal ports. The historic record of the 1980's indicated that the

combination of high and repeated spring floods and high and sustained discharge from penstocks as

well as spillways and hollow jet tubes caused substantial mixing of the reservoir. The recent

06/02/98

DRAFT

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