The Alsea Watershed Study Revisited provides a unique opportunity to compare water resource responses to current forest practices with the impacts of unrestricted logging in the 1960s. By looking at watershed data collected over a 50-year record and using a control watershed that has not had significant human impacts since before the 20th century, the study will consider how management impacts compare with natural disturbance and variability.
The Original Study
The earlier Alsea study lasted fourteen years in Oregon’s Coast Range. It was the first paired watershed study that analyzed the effects of clearcuts without stream buffers on water quality and quantity, aquatic habitat and fish populations. In the original study, three watersheds were compared—one was left untouched (Flynn Creek), another was completely clearcut (Needle Branch Creek), and a third was patchcut with buffers left along the fish-bearing stream reaches (Deer Creek). After clearcutting and slash burning, the Needle Branch drainage experienced some of the most dramatic effects to water quality ever observed from logging—for example, the stream’s maximum daily temperature increased to 85ºF, which was 30ºF higher than pre-harvest. The original Alsea study evaluated the effects of conventional logging practices at the time of the study, including clearcuts to the edge of streams and large old trees being dragged across the ground, disturbing the soil.
Logging practices of the day resulted in long-term depression of cutthroat trout population in Needle branch, while the patchcut/buffered watershed did not experience same impacts. The original Alsea study also documented naturally high variations in most fish parameters which were used to refine study designs. The comparison from this study between the temperatures in a completely clearcut stream and one that was buffered were very noticeable in that the buffered creek was cooler.
Investigations and research continued on including dissolved Oxygen, bedload dynamics, and long term fish population response patterns.
The regenerated forest of the Needle Branch watershed is once again ready for commercial harvest. Flynn Creek remains an undisturbed Research Natural Area. Conducting a new harvest in this revisited paired watershed study offers a unique scientific opportunity to compare the effects of contemporary forest practices to those used in the past. In the new study, the trees are smaller and harvested through state-of-the-art skyline logging, using aerial cables that elevate the logs as they are removed.
During the Alsea Study Revisited, the calibration period occurred between 2006 and 2009. The first harvest of Needle Branch occurred in the summer of 2009. The first post-harvest monitoring period is 2010-2013. The second and final harvest of Needle Branch will occur in the summer of 2014. The second post-harvest monitoring period will be 2015-2017.
Two main locations at Needle Branch measure discharge and sediment, while a network measures temperature and nutrients among other physical responses. The biological responses are monitored in fish habitat, invertebrate comparisons, and the movement and growth of fish.
One of the Cooperators for this study, The National Council for Air and Stream Improvement, Inc. (NCASI), also has a mention of this study on their site here.