Northern Puget Sound Watersheds

This characterization includes the Nooksack River, Drayton Harbor, Samish River, and San Juan Island watersheds because they are geographically close, connected through human activities, and drain to the marine waters of northern Puget Sound. The Nooksack River side of the watershed has contrasting features, including geomorphologic, geological, climatic, vegetative, and soil characteristics. It is, therefore, no surprise that the hydrology differs between the Nooksack watershed and the other lowland streams. Melting snow and rain drive the hydrologic system of the Nooksack watershed and determine the timing of peak flows.

Watershed Boundaries Delineated from Digital Elevation Models (pdf) [Courtesy of U.S. Geological Survey]

Influence of Glaciers on Hydrology

13 alpine glaciers drain from Mt. Baker (from north to south): the Sholes, Mazama, Hadley, Rainbow, Roosevelt, Park, Coleman, Thunder, Boulder, Tatum, Deming, Squak, and Easton Glaciers. Of these, the Coleman Glacier is the most conspicuous and well known, as it is visible from many parts of Bellingham and is the destination of a popular hiking route.

Mount Baker is drained on the north by streams flowing into the North Fork of the Nooksack River and on the west by the Middle Fork of the Nooksack River.1

Hydrologic differences between the glacial and lowland systems include seasonal runoff, water quality, and volume. The volume of flow from the mainstem of the Nooksack River can be many times as much as that from lowland rivers and streams. The spring and fall rain-on-snow events bring a huge amount of freshwater into Bellingham Bay. The runoff from these glaciers has important implications for the Bellingham Bay's oceanography because it delivers so much water and sediment to the Bay.1

Glacial recession is an important factor that can change the region's hydrology over a long period of time. Glaciers sequester vast amounts of water, and as they melt, the fresh water drains into the Bay, altering salinity and possibly the circulation patterns. Receding glaciers may indicate warming trends that have long-term impacts on hydrology. Glaciers can also cause flooding when rain-on snow events coincide with high tides that force the Nooksack over lowland containment dikes. The Nooksack River is one of the few free-flowing rivers in Washington State and has no flood control dams.

Glaciers1

Glaciers, moving rivers of perennial ice, characterize the mountain range and the streams and rivers that emerge below them. Many cascading waterfalls in the North Cascades never run dry. They flow continually because of the enduring contribution of water by glaciers. The 318 glaciers within the North Cascades National Park Service Complex occupy about 60 percent of the total glacier-covered area in the contiguous United States.

Today's alpine glaciers have formed on high peaks where more snow falls in the winter than melts each summer. As the snow accumulates and compacts, it eventually begins to flow downhill under its own weight. This movement, usually no more than a few feet per year, sculpts the mountains. The North Cascades are characteristically carved into rugged knife-edged ridges called aretes, steep solitary peaks called horns, and deep depressions known as cirques. A glimpse into the Picket Range and up onto T-bone Ridge shows all these elements from Newhalem.

During the last ice age, glaciers filled most valleys and covered most of the area with an ice sheet up to a mile thick. Those continental glaciers bulldozed through the mountains, leaving U-shaped valleys.

Globally, glaciers store 75% of the world's freshwater. In the North Cascades glaciers contribute 21 billion cubic feet of water every year to streamflow. That is about one-fourth of the total volume of water draining from the North Cascades. Yet the almost 700 alpine glaciers in the northern Cascade Range are a fraction of the size of their ice age counterparts. Glacial concentrations surround all major peaks. Mt. Baker's slopes support 13 glaciers.

Glaciers are sensitive to changes in temperature and snowfall. Their constant changes are important climatic indicators. They influence vegetation patterns, move and carve rock, add minerals to the ecosystem, and serve as reservoirs for domestic and hydroelectric water supplies.

Glaciers have tremendous effects on the hydrology of streams. The most important effects are related to changes in the supply of runoff from melting and the seasonal storage of water within glaciers. In drought years glacial meltwater is the only thing flowing in some streams. Salmon exist in some streams of the North Cascades because of glacial meltwater. Streams that begin as glaciers have water that is typically cloudy and cold. The weight of glaciers grinds the underlying rock into fine "flour." When sunlight hits the surface of the lake, it is refracted at a different angle because of the fine rock flourlike particles. As a result, we perceive only the green band of the light spectrum when we view a glacial lake. This contrasts with the blue water of a non-glacier lake.

Two places to view glaciers closely are at the end of the Cascade River road and near Schrieber's Meadow on the south flank of Mt. Baker. These glaciers are carving the mountain into an arete.

Reference Cited

1. National Park Service. Glaciers in the North Cascades. <http://www.nps.gov/noca/glaciers.htm>

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