WSPC12524 ‎(2)‎

• File Number: 8220.101.10
• Description: Colorado River Water Projects - Glen Canyon Dam-Lake Powell - Adaptive Management
• State: CO
• Basin: Colorado Mainstem
• Date: 3/6/1998
• 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 - 03-06-98
• Water Supply Pro - Doc Type: Report/Study

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002312

Lake Powell to the 1094 m (3,590 ft) elevation to avoid impinging on Rainbow Bridge National

Monument. During this period there was maximal powerplant production at Glen Canyon Dam.

For a third time, after initial filling of Lake Powell was achieved in 1980, releases again exceeded

. '- _.10.2 km~ (8.23 mat). For the period of 1983 to 1987 annual releases_werewel1.abovethis level-

corresponding with wet conditions in the Upper Colorado River Basin. From 1995 to 1997,

annual releases again exceeded the minimum requirements. Each of these periods was followed

by a reduction in the salinity of the hypolimnion.

c.c: Monthly Release Volumes
Monthly release volumes are determined as part of the development of the Annual Operating

Plan and are based on anticipated power demands, forecasted inflows, and other factors such as

storage equalization between Lake Powell and Lake Mead. Typically, high releases occur in the

month of January and again in August, in response to increased power demands during these

months. Of significance is that high release volumes do not always concur with peaks in reservoir

inflow. An important effect of this timing is that high releases in January occur during the

upwelling of saline hypolimnetic water normally seen shortly after the first of the year. This

upwelling and its subsidence appear to be a function of the winter density currents impinging on

this body of water. The significance of the high January release volume is that more saline water

is removed from the reservoir during this upwelling than if releases were lower. Therefore, the

timing of these high releases facilitates the replacement of the hypolimnion near the dam.

d. Daily Release Volumes
Under existing operating criteria dictated by the recent Glen Canyon Dam ElS and Record of

Decision releases cannot exceed 25,000 cfs except under emergency conditions or when required

for flood control. Furthermore, during high release months, daily fluctuations cannot exceed 8000

03/06/98

DRAFF

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