The Methow River Watershed is located in north central Washington State. A tributary of the Columbia River, the Methow is bordered on the west by the Cascade mountains, on the north by Canada, on the east by Buckhorn Mountains and the Okanogan River drainage, and on the south by the Columbia River and the Sawtooth Ridge. The Methow River extends approximately 80 miles from the headwaters near the crest of the Cascade Range to the confluence of the river with the Columbia River at Pateros, Washington. The river drains a 1,805 square mile area. Topography within the basin is varied, and ranges from mountainous sub-alpine and alpine terrain along the Cascade Crest to the gently sloping, wide valley found along the middle reaches of the Methow River. Elevation above mean sea level ranges from 9,000 feet in the headwaters of the Basin to 775 feet at the confluence of the Methow and Columbia Rivers at Pateros. The basin is a closed hydraulic system, with all water originating as precipitation, and no water leaving the Basin other than via evaporation and streamflow.
The Methow Watershed is one of the coldest watersheds in the west being of the same latitude as that of Duluth, Minnesota and Bangor, Maine. Because the Cascade Mountains remove much of the marine influence out of the weather systems that pass west to east across them, arctic air plays a role in the climate.