Mitigation for diversion of the Bull River, British Columbia

In September 2008 BC Hydro completed an upgrade to the Aberfeldie power project that is located on the Bull River, 35 km east of Cranbrook, British Columbia.  Before the upgrade, water spilled over the Aberfeldie dam during eight to nine months of late March to late December but spill is now limited to three to four months in late April to late July.  During the new non-spill periods in spring (March through April) and late summer through fall (August through December), all flow in the river can be diverted through the new penstock leaving only gate leakage and seepage flow as low as 0.05 to 1 m3·s-1 in a 1.2 km diversion reach between the dam and powerhouse. To protect fish and fish habitat in the diversion reach, a seasonally staged minimum water release to the diversion reach was implemented: 0.5 m3·s-1 in April and May, 2.0 m3·s-1 in June – September, 0.5 m3·s-1 in October – November, and 0.25 m3·s-1 in December – March.  A side channel was constructed near the Aberfeldie project to compensate for lost habitat and biological production in the diversion reach at the minimum flows.

Following two years of background data collection before the change in flow in the diversion reach (2005 and 2006), several studies are ongoing studies (2009 to present) to determine if the side channel is compensating for lost biological production in the Bull River.  Limnotek is examining the effectiveness of biological production in the side channel in offsetting loss of benthic invertebrate and periphyton production  in the Bull River. These studies are ongoing with expected completion in 2013.