There are three reservoirs within Ross Lake NRA, all behind dams built to provide hydroelectric power. A small hydroelectric project on Newhalem Creek provides further power via a stream diversion. Lake Chelan, which developed within a deep, glacial trough, is the third deepest natural lake in the United States. It was dammed in the 1920's to regulate its elevation for hydroelectric power. All four reservoirs provide recreational opportunities and transportation routes as well as power.
Dams also influence stream processes downstream and the migration of fish throughout the watershed.
Reservoirs affect microclimate, cause erosion of terrestrial habitat, and limit the ranges of terrestrial species. The abundance of water and the wide variation in landforms, soil types, elevation, slope, and aspect create many types of habitat that support a diversity of flora and fauna. About 260 non-native plant species are also found, including diffuse knapweed, spotted knapweed, rush skeletonweed, St. Johnswort, Scotch broom, Japanese knotweed, foxglove, and common mullein. Non-native stocks of rainbow trout, cutthroat trout, brook trout, golden trout, and kokanee salmon are also found within North Cascades NPS Complex. Visitors from around the world enjoy the many resources of the North Cascades NPS Complex.