Review of Twin Lakes Enhancement Proposal (2008-111-00)

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At the Council’s request, the ISRP reviewed the Colville Confederated Tribes’ Twin Lakes Enhancement Proposal (#2008-111-00), a Columbia River Fish Accords project. The review included a response loop and evaluation of a revised proposal. The purpose the project is to improve summer habitat for native inland redband trout in Twin Lakes, Washington by enhancing dissolved oxygen levels in bottom waters.

The ISRP commended the Colville Confederated Tribes for fostering past studies and providing scientific information to develop management approaches for Twin Lakes. However, the ISRP found that the revised proposal does not meet scientific review criteria because the oxygenation only temporarily treats the symptom (anoxic hypolimnion) but does not consider alternative treatments that have the potential to solve or provide longer-term treatment of the phosphorous eutrophication problem.

The ISRP suggests that a future proposal having the same water quality goal might be warranted if:

  • consideration of alum treatment (possibly combined with even less expensive calcium) were included;
  • measurement of trout survival were included; and
  • significant progress in community efforts to reduce external nutrient loading could be shown by (1) presenting the calculations for quantitative estimates of external phosphorus loading before and after the program of reducing cultural inflow was undertaken (thus estimating progress until now) and (2) incorporating procedures into the project that would quantitatively measure and monitor external loading before and during in-lake treatment