7780

• UCREFRP Catalog Number: 7780
• Author: Brooks, J. E., et al.
• Title: San Juan River Seven Year Research Program Summary Report 1992.
• USFW Year: 1992.
• USFW - Doc Type: \
• Copyright Material: NO

INTRODIICTION - Development of western river systems for consumptive
use has resulted in profound changes to stream .channel
characteristics and resident fish communities. The San Juan River
Basin has been impacted by water development for much of this
century. Average flow of the river has been depleted by
approximately 27 percent and the magnitude and pattern of the
natural hydrograph altered as a result of the construction and
operation of Navajo Dam and other water projects.
The native ichthyofauna of the San Juan River Basin and the
underlying ecology that supports that fauna has been altered.
Native species such as the Colorado squawfish (Ptychocheilus
lucius) and razorback sucker (Xyrauchen texanus) have become rare
and have been listed as endangered under the Endangered Species Act
(ESA). Other native fish species, such as the flannelmouth sucker
(Catostomus latininnis) and bluehead sucker (C. discobolos), while
not listed under the ESA, have undergone reductions in range and
abundance and their long term survival prospects are unknown.
Further development of the San Juan Basin was proposed by the U.S.
Bureau of Reclamation (Reclamation) and the Bureau of Indian
Affairs (BIA). The Reclamation authorized Animas-LaPlata Project
is proposed to divert surface flows from the Animas River and
potentially impact downstream habitats and fish communities in the
San Juan River. The Navajo Indian Irrigation Project (NIIP), with
8 existing blocks of irrigated agricultural land and an additional
three blocks proposed, will, with full development, include
additional diversion of water at Navajo Reservoir. Thus, available
water for reservoir-controlled releases downstream to the San Juan
River will be reduced.
During 1990 and 1991 several actions occurred involving the ESA and
projects in the San Juan River Basin. These actions included the
issuance of jeopardy Biological Opinions for Animas-La Plata and
NIIP (Blocks 1-8) projects by the U.S. Fish and Wildlife Service
(Service) . Reasonable and prudent alternatives were formulated for
the Biological Opinions which resulted in modifications to the
project designs and also included provision for a research program
to assess the effects of flows on endangered species in the San
Juan River. In addition, in a memorandum dated July 30, 1991, to
the Service, Reclamation requested that consultation on the
operation of Navajo Dam be initiated. The memorandum stated that;
"pursuant to Section 7(a)(2) of the Endangered Species Act (ESA)
and 50 CFR 402.14(d), Reclamation has the responsibility to obtain
and provide the information needed for a biological opinion and
that it has authority under Section 7(a)(1) of the ESA to take this
action. Accordingly Reclamation is herein committing to operate
Navajo Dam so as to mimic a natural hydrograph during the research
program for the ultimate benefit of the endangered species." The
memorandum further stated that; "Information obtained from the
research is needed for consultation on Navajo Dam operations and
other Federal actions in the Basin requiring consultation." The
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