[White-water] Bull Run River cfs

[Gordon Taylor]

Greetings:

The flow in the Bull Run River below PGE's Bull Run Powerhouse (i.e., the section of the river that we boat) equals the flow on "Bull Run River at Bull Run, OR" USGS gauge plus inflow from the powerhouse.

It has always been difficult to determine the flow in the Bull Run River downstream of the powerhouse, as PGE has not ever made the flow from the powerhouse available on the internet, and before removal of Marmot Dam the flow from the powerhouse could range up to nearly one-thousand cfs.

Marmot Dam on the Sandy River has now been removed.  Marmot Dam was used to divert water for generation at PGE's Bull Run Powerhouse.  Sandy River water diverted by Marmot Dam was sent to the Little Sandy River.  Then the combined diverted Sandy River flow and the flow in the Little Sandy were in turn diverted and sent to Roslyn Lake, the forebay for the Bull Run Powerhouse.  With removal of Marmot Dam, PGE continues to generate at the Bull Run Powerhouse using water diverted from the Little Sandy River, so therefore the powerhouse continues to release water into the Bull Run River. 

With a more limited supply of water for generation, I am told by a hydrologist at the NW River Forecast Center that PGE is now generating at the Bull Run Powerhouse only during peak electric-power-demand hours (which usually means daytime on weekdays) and storing water in Roslyn Lake at other times.  To estimate releases from the powerhouse, he suggests reviewing flows in the Little Sandy River over the previous 24 hours using the "Little Sandy River Near Bull Run, OR" USGS gauge, which is upstream of the diversion dam on the Little Sandy, and estimating powerhouse release flows as half of the previous day's flow on the Little Sandy.

In summary, when the powerhouse is not generating, the "Bull Run River at Bull Run, OR" gauge should provide an accurate measure of flow in the Bull Run below the powerhouse.  Since weekend days typically have no peak electric-power-demand hours, this gauge should be reasonably accurate for weekend boating.  When the powerhouse is generating, it generally will not be able to augment the flow in the river as substantially as previously, since without diversions from the Sandy River, the powerhouse has a much more limited water supply than previously.  Thus, even when the powerhouse is generating, the flow in the Bull Run River below the powerhouse is unlikely to be substantially greater than the flow measured by the "Bull Run at Bull Run, OR" gauge.

Gordon
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://maillist.peak.org/pipermail/white-water/attachments/20071031/6c174ab1/attachment-0001.htm