Donlay Ranch Hot Spring
Donlay Ranch Hot Spring flows at 131 degrees Fahrenheit just 115 feet from Southfork Road in the Boise National Forest, combining serious geothermal heat with convenient roadside access in the South Fork Payette River drainage near Idaho City. The water's pH of 9.2 makes it among the more alkaline springs in this already alkaline corridor.
At 3,200 feet elevation, the spring occupies a transitional zone between the dry, open foothills and the denser forest of the higher canyon. Ponderosa pine stands nearby, and the South Fork Payette River runs through the valley below. The mineral outflow traces pale lines across dark rock. Annual snowfall of nearly nine feet keeps the area white through winter and into spring, and steam rises from the source in any month when air temperatures drop below the water temperature, which is most of the year given the 82-degree differential.
The highly alkaline pH of 9.2 with low calcium at 2.0 mg/L and sodium at 75 mg/L is characteristic of water that has circulated through the silica-rich granitic rocks of the Idaho Batholith. Donlay Ranch's name recalls the homesteading era when settlers along the South Fork Payette claimed land near thermal features, sometimes using the hot water for agricultural purposes. USGS records confirm a source temperature of 54.5 degrees Celsius.
At 131 degrees Fahrenheit, the source water requires significant cooling before any contact. Look for downstream mixing zones where cold creek water brings temperatures into a tolerable range. Hot Springs Campground is about 3.5 miles away along the Banks-Lowman Highway and takes reservations. Southfork Road is accessible but unpaved in sections. The spring is on Forest Service land with open access and no fees.
Is Donlay Ranch Hot Spring worth visiting?
Best for
- Hot spring soaking
- Easy day trips
- Overnight camping trips
The water at Donlay Ranch Hot Spring is alkaline (pH 9.2).
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Overview Hot Springs Campground is located just east of Garden Valley, Idaho along the Banks-Lowman Highway at an elevation of 3169 feet. Visitors enjoy rafting, kayaking, fishing on the South Fork Payette River, and soaking in the hot springs at the river's edge. Recreation The South Fork Payette River is across the road from the campground, offering fishing, whitewater rafting, and kayaking. A natural hot springs soaking pool is located on the river directly across the road and down a...