8221

• UCREFRP Catalog Number: 8221
• Author: Van Steeter, M. M.
• Title: Historic and Current Processes Affecting Channel Change and Endangered fish Habitats of the Colorado River Near Grand Junction, Colorado.
• USFW Year: 1996.
• USFW - Doc Type: Doctor of Philosophy.
• Copyright Material: NO

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Chapter 1
INTRODUCTION

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Native fishes of the upper Colorado River now experience a very
different environment than the conditions under which they evolved. As
early as 1000 A.D., water from the Colorado River was removed for
irrigated agriculture (Graf, 1985). Diversions were small and had no
significant effects on the ecology or channel morphology of the river, but
in the late 1800s this began to change. The first major water development
on the upper Colorado River was the Grand Valley diversion, completed
in 1883. With a capacity of 520 cfs (15 ems), it was one of the largest in the
upper Colorado River basin (Follansbee, 1929). Larger and more
significant impacts related to construction of dams continued throughout
the 20th century. These projects have had a significant impact on the
character of the Colorado River by changing its natural flow regime,
turbidity, temperature, and aquatic community (Fradkin, 1981). In
conjunction with these impacts, the introduction of nonnative vegetation
and fish species has placed additional stress on native fish communities
(Carlson and Muth, 1989). Changes in flow regime and negative
interactions with nonnative fishes are believed to be the primary causes of
the severe decline in their populations (Tyus, 1992). There are currently
four federally-listed endangered fishes in the upper Colorado River basin:
the Colorado squaw fish (Ptychocheillts Iucius), razorback sucker