WSP08799

• File Number: 8220.200.05.P
• Description: Hoover Dam/Lake Mead/Boulder Canyon Project
• Basin: Colorado Mainstem
• Date: 9/1/1990
• Author: USDOI/BOR
• Title: Colorado River Basin: Probable Maximum Floods Hoover and Glen Canyon Dams
• Water Supply Pro - Doc Type: Report/Study

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TABLE OF CONTENTS

c-. Summary S-l

1.0 Introduction 1
1.1 Authority and Background 1
1.2 Study Scope and Participants 2
1.3 Basin Description 3
1.4 Historic Floods in the Colorado River Basin 7
1.5 Previous Studies 8

2.0 Meteorological Analysis 17
2.1 Introduction 17
2.2 Data Collection 17
2.3 Design Rainstorm Scenario 18
2.4 Magnitude of Uldrs 19
2.5 Spatial and Temporal Distributions of U1drs 21
2.6 Storm Sequences 21
2.7 Seasonal Variation 26

3.0 Hydrologic analysis 29
3.1 Basin Field trips 29
3.2 Subbasin Delineation 30
3.3 Basin Parameters 30
3.4 Loss Rates 36
3.5 Lag Coefficients - "C" Factors 39
3.6 Travel Times 39
3.7 Dimensionless Graphs 40

4.0 Antecedent Flood Analysis 47
4 . 1 General . . . . . . 47
4.2 Methodology for Developing the Antecedent Floods 47
4.3 Antecedent Floods for Hoover and Glen Canyon 48
4.4 Monthly Inflows to Major Upper Basin Reservoirs 56

5.0 Depletion Analysis 61
5.1 Background 61
5.2 1985-Level Depletions Above Glen Canyon 61
5.3 Depleted Monthly Antecedent Flood Flow for
Glen Canyon ........... 62
5.4 Daily Depletions for Glen Canyon Dam 63
5.5 1985-Level Depletions for Reservoirs Upstream
from Glen Canyon . . . . . . . . . . . . . . 66
5.6 Depleted Monthly Antecedent Flood Inflows for
Reservoirs Above Glen Canyon 67

6.0

Basin
6.1
6.2
6.3
6.4
6.5

Modeling .........
"Fhar" - Computer Program
Reservoir Operating Criteria
Reservoir Routing of 100-Year Snowmelt Flood
Glen Canyon and Hoover Probable Maximum Floods
Peak Discharge Envelope Curve

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97

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103

8.0 Acknowledgements

9.0 References

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