STUDY AREA

North Cascades National Park Service Complex (NOCA) is located in the north-central portion of Washington State (Whatcom and Skagit Counties) in the North Cascades Mountain Range. The northern border of the 204,000 ha park borders Canada (Figure 2.1). Most of the mountain range is underlain by hard crystalline bedrock, primarily gneiss and granite, although some sedimentary and volcanic outcroppings exist (Misch 1977). Regional uplifting, which initially formed the mountain range in the Cenozoic 50 million years ago, created a base template that is highly jointed, faulted, and fractured (Misch 1977). Glacial activity during the Pleistocene and the neoglacial period formed the basins of the study lakes.

Differential precipitation across a hydrologic divide separates the region into two major climatic units (Porter 1976; Jackson and Kimerling 1993). A maritime climate prevails on the west due to the influence of warm, moist air masses from the Pacific Ocean and Puget Sound.

This climate is characterized by wet, relatively warm winters, and cool summers. A semi-arid continental climate exists on the east and is characterized by colder winters and relatively hotter, dryer summers compared to the west. Throughout the park, ice and snow cap the lakes for many months each winter. Rains during the brief snow-free season are common, particularly on the west. Drainages west of the hydrologic divide empty into Puget Sound, whereas drainages to the east flow into the Columbia River basin.

Lomnicky (1996) classified NOCA lakes according to the type of vegetation surrounding the lakes (Table 2.1). Based on a vegetation cover type map developed by Agee and Pickford (1985), Lomnicky (1996) identified three main vegetation zones in NOCA: alpine, subalpine, and forest. The forest zone was further subdivided into high-forest and low-forest zones, distinguished by the presence of snow pack until spring (high forest) versus intermittent snow-free periods in winter (low forest). Each vegetation zone occurred at higher elevations on the east slope than on the west slope (Table 2.1).

Table 2.1 Elevations of all NOCA lakes (Lomnicky 1996) and dates of ice-out for study lakes in 1989 by vegetation zone east and west of the hydrologic divide.