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

0/023 J8

Lake Powell is not yet at a point where this type of modeling is possible. This section will

describe some of the important factors affecting reservoir and release water quality, primarily

focusing on the operation of Glen Canyon Dam.

, 1,v Meteorological Conditions

-"_.~~-'-----~": ,---~-

Weather patterns playa significant role in determining inflow density, reservoir warming and

stratification, convective mixing processes, and variation in release quality, both on a daily and

seasoual basis. Warming or cooling of reservoir inflows from localized or seasonal

meteorological conditions can affect the density of these currents, the depth at which these

'currents enter the reservoir, and the amount of diffusive mixing that occurs between the inflow

and the receiving reservoir water. The surface temperature of the reservoir is affected by these

conditions and results in setting up stratification during spring warming or breaking down this

stratification through convective mixing with the onset of colder winter conditions. The amount

of claud cover over the reservoir affects how much radiant energy the reservoir receives to raise

its heat content or stimulate photosynthetic processes. Wind patterns from storm events can

impede the onset of stratification or accelerate convective mixing. Of significance to downstream

releases, wind events can cause internal seiches, or oscillations of stratification boundaries in the

reservoir that can cause temporary fluctuations in temperature or salinity levels in the tailwater

(Fig 16).
2. Inflow Hydrology

One of the most important factors driving short-term and long-term processes in the reservoir

is the inflow hydrology, characterized by the volume and quality of inflows to Lake Powell and
their seasonal variation. Approximately 57% of the inflow volume occurs from April to June due
to snow-melt runoff (Gloss et al. 1981). This runoffis characterized very low salinity snow-melt
that has warmed on its course through the canyon lands. This combination results in a large

03/06/98

DRAFT

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