watervulnerability

Chugach National Forest Watershed Vulnerability Assessment, Alaska Region (R10)
ASSESSMENT AREA DATA
Assessment Areas
• Eyak Lake watershed – coastal rainforest ecotype
• Resurrection Creek watershed – drier boreal forest ecotype
Of the 85 fifth level HUCs and 275 sixth level HUCs on the Forest, only a handful have significant
development, infrastructure, or active land management. The two watersheds used for this assessment
have the widest variety of development and aquatic resource values for their respective ecotypes and can
serve as representative watersheds for many coastal Alaska areas. The Eyak Lake watershed contains part
of Cordova, a small city of 2,440 people. The town of Hope (182 residents) is adjacent to the lower part
of the Resurrection Creek watershed.
Eyak Lake Resurrection Creek
Area (acres) 27,748 103,215
HUC Level Two 6 th levels 5 th level w/ three 6 th
National Forest Land 25,554 (92.1%) 100,839 (97.3%)
Mean Annual Air Temperature
July
January
5.3 °C
12.5
- 4.1
Water Temperature Summer surface Eyak
Lake 5.5 - 14.5 °C
Power Creek mean 6.1°C
annual 3.0 - 8.4 °C
Mean Discharge (cfs)
387 (ungauged)
10-yr Flood
8,700
274 Assessing the Vulnerability of Watersheds to Climate Change
2.6 °C
14.1
- 7.2
Resurrection Creek
Mean 8.4 °C
Range 5.5 -12.0 °C
275
2,400
Mean Precipitation (inches) 130.25 22.15
Lake/Pond Area (acres) 2,400 (8.6%) 80.5 (0.07%)
Road Density - mile/mile 2 (total) 0.36 (25.1) 0.14 (35.1)
Residential/Commercial Area (acres) 205.3 (0.7%) 53.1 (0.05%)
Area Unvegetated Rock (acres) (%) 5,405 (19.7%) 11,391 (11.0%)
Area Icefields/Glacier (acres) (%) 3,256 (11.7%) 245 (0.2%)
Area > 70% Slope (acres) (%) 6,332 (23.1%) 7,660 (7.4%)
Avalanche Area (58-173% slope) (acres) (%) 12,001 (43.7%) 20,952 (20.3%)
Area > 500 ft Elevation (acres) (%) 20.553 (74.0%) 100,324 (97.2%)
Fire, Including Prescribed Burns (acres) (%) 0 9,400 (9.1%)
Mining Disturbance (acres) (%) 0 2,560 (2.5%)
Trails (miles) 13.1 16.8
Recreation Sites (cabins, camps, day use) 5 14
Table 1. Current conditions for the Eyak Lake and Resurrection Creek watersheds.
Assessment Area Climate Change Predictions
The general predictions for both the Eyak Lake watershed and the Resurrection Creek watershed call for
increased temperatures. Annual mean temperatures are predicted to increase 1.7 to 1.9 °C for the two
watersheds under both the A1B and B1 scenarios (Table 2). However, winter temperatures are predicted
to increase much more than summer temperatures. Monthly data for the entire watersheds were not
readily available, but the January temperatures for the towns of Cordova and Hope are predicted to rise
3.4 to 3.7 °C, and the July temperatures 1.5 to 1.8 °C.