The Henry's Fork watershed, located mainly in eastern Idaho (with a small portion in Wyoming bordering Yellowstone National Park), is well situated for modeling studies of the combined effects of climate change and forest management practices on water quality and quantity. The Henry's Fork basin drains an area of 8444 km². Major tributaries are Henry's Lake Outlet, Buffalo River, Warm River, Fall River, and Teton River. Snowmelt, springs and seeps provide surface water flows for hundreds of miles in rivers and creeks across the watershed.

Vegetation ranges from aspen groves to riparian cottonwoods to closed canopy forests of Douglas-fir, lodgepole pine, Englemann spruce and subalpine fir with large expanses of sagebrush-steppe grasslands and wet and dry mountain meadows (map Figure). Outbreaks of mountain pine bark beetle destroyed many of the lodgepole pine stands in the surrounding Targhee National Forest during the 1960's and early 1970's. National Forest managers attempted several methods to halt the advance of the pine bark beetle, but few of them were successful.

The first major storage reservoir to be constructed in the Henry's Fork basin was a dam on Henry's Lake in 1923. The dam raised the level of Henry's Lake about 5 meters and provided 111 million m³ of water storage. Grassy Lake Dam on Fall River and the much larger Island Park Dam on the Henry's Fork were completed in 1939. Below these impoundments, water temperatures can exceed Idaho Department of Environmental Quality standards (average daily temperature 19° C and maximum daily temperature 22° C) at sites on the Henry's Fork in Harriman State Park, in Sheridan Creek, Icehouse Creek, Henry's Lake Outlet, the Buffalo River, and Waterfall Creek. On some of these streams, high water temperatures occur where riparian vegetation is lacking, resulting in little shading and high width-to-depth ratios.