WSP01587

• File Number: 8220.101.17
• Description: Glen Canyon Dam/Lake Powell
• State: AZ
• Basin: Colorado Mainstem
• Date: 7/1/1998
• Author: Valdez/et al.
• Title: The Aquatic Ecosystem of the Colorado River in Grand Canyon - Grand Canyon Data Integration Project - Synthesis Report
• Water Supply Pro - Doc Type: Report/Study

Table a/Contents

TABLE OF CONTENTS

PREFACE .................................................................... vii

EXECUTIVE SUMMARY ........................................................ ix

CHAPTER I INTRODUCTION: EVOLUTION OF TIlE EXPERIMENTAL SlEADY FLOW. I

Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .'. ., I
Glen Canyon Environmental Studies (GCES Phases I and D) . . . . . . . . . . . . . . . . ., 6
Glen Canyon Dam Environmental Impact Statement. . . . . . . . . . . . . . . . . . . . . . . ., 8
The Fish and Wildlife Service's Biological Opinions ....................... II
Reasonable and Prudent Alternative, 1994 Biological Opinion. . . . . . . . . . . . . . .. 12

Adaptive Mmagement .................................................... 15
Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16

CHAPTER 2 TIlE CHANGING PHYSICAL ENVIRONMENT

Pre-DamlPost-Dam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19
Pre-Dam Conditions...................................................... 19
Evolution of the Colorado River Basin ................................... 19
NaturalDamsandClimaticCbange ..................................... 19

Discharge. . . . . . . . . . . . .. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20
Sediment. . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 22
Temperature .................................................... '. .. 24
Ri'Y' 24
parIlIII egetation .................................................
Post-Dam/Prasent Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 28
Discharge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 28
Sediment.......................................................... 31
Temperature ........................;.............................. 32
Riparian Vegetation ................................................. 34

CHAPTER 3 FOOD BASE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 35
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., 35
Pre-Dam Food Base ...................................................... 35
Post-Dam Food Base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 38
Primary Producers ................................................... 40
Zooplankton ....................................................... 41
Macroinvertebrates .................................................. 41
Effects of Dam Operations ............................................ 44

CHAPTER 4 mSTORY AND STATUS OF FISH ASSEMBLAGES ..................... 47
Introducti'on . .. ................................. 47
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