watervulnerability

Chugach National Forest Watershed Vulnerability Assessment, Alaska Region (R10)
Road density is low (0.12 km/km 2 ) with a total of 25.1 km of road in the watershed. One publication
(NOAA 1996) rates this as well within the level of a properly functioning watershed (< 1.2 km/km 2 ).
Residential development and roads along the lake have reduced lakeside vegetation. Invertebrates that
fall from terrestrial vegetation make up a large part of the diet for juvenile coho salmon and this dietary
input will be reduced. The effect on the water temperature of the lake as a whole is probably negligible,
given the large areas far from shore and stream inputs. However, cooler, shallow shoreside areas,
preferred by juvenile coho salmon for habit and rearing habitat, are reduced.
Salmon spawning area in Eyak Lake has been reduced from 63,011 m 2 (Professional Fishery Consultants
1985) to a currently unknown amount. This is a result of housing development, construction of a water
treatment plant, and sedimentation from roads in one area.
An unknown amount of salmon spawning area exists in the creeks. Culverts have reduced salmon
spawning by several hundred meters, but the overall percentage of spawning area is minimal. There are
perched culverts that do not prevent access to usable habitat, but do eliminate intergravel flows in alluvial
fans in the lake that could be used for sockeye salmon spawning.
Cutthroat trout spawning area has been reduced by 35% due to culverts, houses, and roads covering
potential spawning areas (Hodges et al. 1995).
Another possible stressor is the reduction in the number of returning salmon due to the commercial, sport,
and subsistence harvests. This harvest not only reduces the number of spawning fish, but also the
availability of salmon for predators and the amount of nutrients provided by the carcasses for organisms
throughout the food chain. A greater abundance of nutrients might help populations stressed by climate
change in the future.
There are anecdotal reports that there used to be more sockeye salmon early in the season, with the first
fish reaching the spawning areas in May. This could be an effect of the variability of run sizes. The
ADFG generally has the first commercial fishing opener on May 15. There is a need to carefully manage
the early part of run to maintain the full genetic diversity.
Water use is not seen as a stressor. The only water diversions are for backup municipal water use and for
hydroelectric power generation. However, the backup municipal water use is infrequent and the water
used for power generation is returned to the channel upstream of fish habitat, so there is minimal effect.
Trends
The population of Cordova has declined from 2500 residents in 2000 to 2240 residents in 2009. The use
of migrant non-resident labor at canneries, decreased government employment, and the lack of other
resource jobs are likely to keep the population and development from growing.
Almost all of the areas suitable for housing lots and roads in the watershed have already been utilized.
Runoff from recently constructed roads and building lots should decrease as raw areas revegetate. The
opening of 50 or more residential lots outside of the Eyak watershed will reduce development pressure.
Overall, there have been no detectable trends for the salmon populations. The commercial salmon fishery
is managed well, and minimum escapements in the watershed have been maintained. Population levels
generally follow changes of weather patterns associated with the Pacific Decadal Oscillation and the El
Nino and La Nina patterns (Chittenden et al. 2009). The sport fishery is not managed closely, but the
280 Assessing the Vulnerability of Watersheds to Climate Change