BOARD00259

• Board Meeting Date: 1/12/1998
• Description: WSP Section - Colorado River Issues - San Juan Recovery Program and Section 7 Consultation for the City of Durango
• Board Meetings - Doc Type: Memo

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Lt. Colonel Dorothy F. Klasse

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. reach aquatic environments in domestic and industrial sewage effluents. in
surface runoff from land. from deposition of airborne particulates. and
particularly from spillage of petroleum and petroleum products into water
bodies (Eisler 1987). PAHs were the first compounds known to be associated
with carcinogenesis (Lee and Grant 1981). Several PAHs are among the most
potent carcinogens known to exist. producing tumors in some organisms through
single exposures to microgram quantities. Analysis of bile samples taken from
fish in the San Juan River indicate that these organisms are being exposed to
high levels of three PAH compounds. and strongly suggest that the aquatic
environment of the river is heavily impacted by PAHs.

Phvsical Habitat

The quantity and timing of flows influence how various habitats are formed and
maintained. Water depletions reduce the ability of the river to create and
maintain these habitats: degradation of water quality lessens the ability of
endangered species to survive in these habitats.

Osmundson and Kaeding (1991) reported observations on the Colorado River (15-
mile reach) during the drought years of 1988 -1990. that backwaters were
filling in with silt and sand because spring flows were not sufficient to
flush out the fine sediment. Also they reported that tamarisk colonized sand
and cobble bars. stabilizing the river banks. On the San Juan River. lack of
flooding since Navajo Dam was completed has caused establishment of exotic
riparian vegetation (tamarisk and Russian olive) that has armored the channel
banks resulting in a narrowing of the channel with reduced flood capacity
(81iesner and Lamarra 1994).

Bioloaical Fnvironment

Food supply, predation. and competition are important elements of the
biological environment. Food supply is a function of nutrient supply and
productivity. which could be limited by the presence of contaminants.
Predation and competition from nonnative fishes has been identified as a
factor in the decline of the endangered fishes. Depending upon species-
specific tolerance levels. nonnative fishes may have competitive advantages in
habitats damaged by the presence of contaminants and altered flow regimes.

EFFECTS OF THE PROPOSE!}. ACTION

To determine the effects of the Project on water quantity and alteration of
the hydrologic regime, changes in flow of the Animas River was provided by the
City of Durango in Table 2.

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