Riparian shading of streams is recognized as an important component of a healthy thermal regime, but the role of forest shading in maintaining groundwater temperatures has received much less attention. The primary objectives of this study are to determine if forest management practices influence groundwater temperature, and if so, whether these changes in turn can affect stream temperatures. 10,000 Years Institute, in partnership with the Hoh tribe and the Pacific Watershed Institute, used Forward Looking Infrared technology (FLIR), aerial photographs, wetlands inventory, soil maps and field reconnaissance to identify areas of groundwater recharge and discharge to streams in the Hoh River watershed.

Three study sites were chosen: two from managed forestlands including a recent clear-cut and a mature second growth stand as the control. An unmanaged old growth forest site was chosen as the reference site. Instrumentation was installed in 2001, establishing ground and surface water networks to continuously monitor water levels and temperatures in the stream, soil, groundwater and air of each site. Preliminary results indicate that there are significant groundwater, stream soil and air temperature differences between harvested sites and control and reference sites.