WSP00979

• File Number: 8220.101.10.A
• Description: Colorado River-Water Projects-Glen Canyon Dam/Lake Powell-Glen Canyon Adaptive Management-AMWG
• State: AZ
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 3/3/2004
• Author: USGS
• Title: AMWG Meeting Attachments-March 3-4 2004-Computation and Analysis of the Instantaneous Discharge Record for the Colorado River at Lees Ferry-Arizona May 8 1921-Sep 30 2000
• Water Supply Pro - Doc Type: Report/Study

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MAY 8, 1921-SEPTEMBER 30, 2000, CONTINUOUS RECORD OF INSTANTANEOUS DISCHARGE

PEAK DISCHARGE OFTHE 1884 FLOOD
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CLOSURE OF GLEN CANYON DAM

DAM OPERATIONS
CONSTRAINED
ON AUGUST 1, 1991

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DATE

Figure 21.IAI The continuous record of instantaneous discharge of the Colorado River at Lees Ferry, Arizona, May 8, 1921-Septelnber 30,2000,

ANALYSIS OF THE CONTINUOUS
RECORD OF INSTANTANEOUS
DISCHARGE

The tinal objectives of this study were to
determine: (1) the pre-darn natural variability in the
hydrology of the Upper Basin, (2) the effects of the
operation of Glen Canyon Darn on the discharge of the
Colorado River at Lees Ferry, and (3) the implications of
the natural variability in hydrology and the effects of darn
operations for sediment transport and storage in the reach
downstream li'om Lees Ferry in Grand Canyon National
Park. To accomplish these objectives, analyses of
flow duration, sub-daily discharge variability, and
flood frequency were conducted on the Lees Ferry
instantaneous discharge data for May 8, ]921, through
September 30,2000, the available pre-gage historical
flood data, and the 4,500-year paleoflood data of
O'Connor and others (1994).

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Flow Duration. Sub-Daily Discharge
Variability. and Sediment Transport during the
Pre-Dam Period

To evaluate the natural variability in the discharge
of the Colorado River at Lees Ferry over both long and
short time scales and the implications of this natural
discharge variability for sediment transport downstream
from Lees Ferry, flow-duration analyses and analyses of
the snb-daily variability in discharge were condneted on
the pre-darn part of the continuous record of instantaneous
discharge. These analyses indicate that, prior to the
closure of Glen Canyon Dam, the duration of 110ws varied
substantially over multi-year and decadaltime scales.
These analyses also indicate that the discharge of the pre-
dam river was fairly steady over sub-daily time scales, and
that the daily range in discharge was the most extreme
during the summer thunderstorm season,

42 Computation llnd AnalVsis of the Instantaneous-Discharge Record forthe Colorado River at Lees Ferrv, Arizona-Mav 8, 1921, through September 30,2000

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