 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 Canadian border and I @-@ 90 in central Washington . These contain 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 870 @,@ 000 m3 ( 1 @,@ 140 @,@ 000 cu yd ) . 
