The North and Middle Fork of the Flathead River bound the park on the west and the south respectively. Glacier National Park is home to 1,557 miles of streams that are fed by alpine glaciers and snowpack. McDonald Creek is the longest stream inside of the park boundary, over 25 miles (40.2 km). Countless other intermittent streams exist during melt-off, some raging torrents at times, but many dry up as quickly as they started.