The Cascade Range of western North America extends from southern British Columbia in Canada to northern California. Excepting Alaska, about half of the glacial area in the U.S. is contained within the over 700 glaciers of the North Cascades, a portion of those located between the Canada–US border and I-90 in central Washington. These contain as much water as is found in all the lakes and reservoirs in the rest of the state, and provide much of the stream and river flow in the dry summer months, approximating some .