Under the current operating license for the Pelton-Round Butte Project, Portland General Electric (PGE) and The Confederated Tribes of the Warm Springs Reservation (CTWSR) were required to conduct a macroinvertebrate survey following the initial operation of the Selective Water Withdrawal. Selective Water Withdrawal (or SWW) is the process by which surface water is now mixed with bottom water from the reservoir to facilitate juvenile fish migration across Lake Billy Chinook. The study requirement was intended to allow a comparison of lower river conditions, pre and post SWW.
R2 Resource Consultants, a contractor to PGE/CTWSR, conducted a baseline biological study in 1999-2001. The study focused on aquatic macroinvertebrates (primarily aquatic insects) and algae growth in different locations as far downstream as Sandy Beach, a few miles downstream of Maupin, OR.
R2 Resource Consultants were hired again in 2013 to conduct a repeat of that study to determine if any changes have taken place below the dams as a consequence of the change to SWW from bottom draw. In both studies, the biological sampling was conducted in the months of October and April.
PGE was kind enough to furnish us with a copy of the interim analysis of the current study. The final report should become available in late fall of 2015. The interim analysis and report is just that, a mid-way report of the findings half way through the study. The interim report is 125 pages long and contains data from well-conducted sampling protocols.
The DRA science team has reviewed the interim report and provided comments on the report to PGE. You will find our comments under the “reports” tab on our website. Our comments describe our thinking on the data collected so far, and their meaning. It’s compelling reading for anyone concerned about the lower river.
DRA will not publish the actual interim report on our website as we don’t have permission to do so, and as an interim report, probably shouldn’t be on our website. DRA’s comments do summarize much of the data and we do comment on their meaning. As our comments are our own, we are not reluctant to post our comments.
We will continue to monitor the results of the study as it continues. The quality of the work being done is excellent. This study is one of the key components of understanding what is happening in the lower Deschutes River.