PUBLICATIONS
April 2002 Issue
The Geographical Review
April 2002, Vol. 92 (2), pp. 192-212
Snowshed Contributions to the Noorsack River Watershed. North Cascades Range, Washington
Andrew Bach
Keywords: environmental change, glaciers, hydrology, North Cascades
Range, Washington State, water resources.
ABSTRACT:
Meltwater contributes to watershed
hydrology by increasing summer discharge, delaying the peak spring
runoff, and decreasing variability in runoff compared with
unglacierized basins. High-elevation snowshed meltwater, including
glacier-derived input, provides an estimated 26.9 percent of summer
streamflow (ranging annually from 16 to 40 percent) in the Nooksack
River Basin above the town of Deming, Washington, in the North Cascades
Range. The Nooksack is a major spawning river for salmon and once was
important for commercial, recreational, and tribal fishing, and in
the past its flow met the demands of both human and aquatic
ecosystems. But the river is already legally overallocated, and
demand is rising in response to the rapidly growing human population.
Variability in snowshed contributions to the watershed is
considerable but has increased from an average 25.2 percent in the
1940s to an average 30.8 percent in the 1990s. Overall stream
discharge shows no significant increase, suggesting that the glaciers
are melting, and/or precipitation levels (or other hydrologic
factors) are decreasing at about the same rate. If glaciers continue
to recede, they may disappear permanently from the Cascades. If that
occurs, their summer contribution to surface-water supplies will
cease, and water-management policies will need drastic revision.
Keywords: environmental change, glaciers, hydrology, North Cascades
Range, Washington State, water resources.
ABSTRACT:
Meltwater contributes to watershed hydrology by increasing summer discharge, delaying the peak spring runoff, and decreasing variability in runoff compared with unglacierized basins. High-elevation snowshed meltwater, including glacier-derived input, provides an estimated 26.9 percent of summer streamflow (ranging annually from 16 to 40 percent) in the Nooksack River Basin above the town of Deming, Washington, in the North Cascades Range. The Nooksack is a major spawning river for salmon and once was important for commercial, recreational, and tribal fishing, and in the past its flow met the demands of both human and aquatic ecosystems. But the river is already legally overallocated, and demand is rising in response to the rapidly growing human population. Variability in snowshed contributions to the watershed is considerable but has increased from an average 25.2 percent in the 1940s to an average 30.8 percent in the 1990s. Overall stream discharge shows no significant increase, suggesting that the glaciers are melting, and/or precipitation levels (or other hydrologic factors) are decreasing at about the same rate. If glaciers continue to recede, they may disappear permanently from the Cascades. If that occurs, their summer contribution to surface-water supplies will cease, and water-management policies will need drastic revision.