 There are an estimated 9 @,@ 600 miles ( 15 @,@ 400 km ) of perennial and intermittent streams and 15 @,@ 400 acres ( 62 km2 ) of lakes and reservoirs in the forest . The Forest Service provides access to and recreation opportunities at the seven reservoirs it borders , although it does not own or manage them . There are numerous natural lakes in the forest , most of which are <unk> created by alpine glaciers during the Pleistocene . The largest , Warm Lake , is 26 miles ( 42 km ) east of Cascade in Valley County ; many of the smaller lakes are in the Trinity and West mountains . Annual water yield on the forest is estimated at 4 @.@ 1 million acre @-@ feet ( 5 @.@ 1 × 109 m3 ) . The southern portion of the forest is drained by the Boise River , the central and western portions by the Payette River , northeastern portion by the Salmon River , and far western portions of the Emmett Ranger District by the <unk> River . All four rivers are tributaries of the Snake River , which itself is a tributary of the Columbia River in the Pacific basin . 
