Instream Flow Needs Analysis - Okanagan Basin Water Board

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ESSA Technologies Ltd.1765 West 8th Avenue, Suite 300Vancouver, BC V6J 5C6Phone: 604.733.2996Fax: 604.733-4657email: mporter@essa.comwebsite: www.essa.comNov. 3, 2009Okanagan Basin Water Board1450 KLO RoadKelowna BC V1W 3Z4c/o Brian GuySummit Environmental Consultants Ltd.#200 – 2800 29 th StreetVernon, BC V1T 9P9Dear Mr. Guy,Re:Letter of Transmittal—Instream Flow Needs Analysis (draft) forthe Okanagan Water Supply & Demand Project. Reference OBWB 08-007ESSA Technologies Ltd. and Solander Ecological Research are extremely pleased to enclose three boundhard-copies, one unbound copy, and one electronic copy on CD of our final report entitled “InstreamFlow Needs Analysis for the Okanagan Water Supply & Demand Project.” This final report includesadditional sections, supporting text and figure revisions requested on Oct. 13, 2009 by the IFN Committeeafter review of our earlier draft report. The major report revisions that have been completed based onCommittee comments are:‣ Inclusion of a discussion of the value of a natural flow regime for maintaining a range of aquaticecosystem processes.‣ Inclusion of a 25th percentile of weekly naturalized flows as an arbitrary lower flow referencelevel to assist readers making comparisons relative to naturalized and BCIFN/meta-analysisflows, with commentary on the significance of these for the range of production that biota mayachieve. This 25 th percentile flow is provided in the report figures.‣ Exemplary figures used to illustrate the report’s main points have been revised as suggested bythe IFN Committee (e.g., focus only on rainbow trout and kokanee). Text for figure legends hasbeen adjusted to be more specific to the IFN methods we employed. Multiple speciesinterpretations are retained in the appendices.‣ Inclusion of a consolidated section in the discussion that deals with the management implicationsof landscape-scale pressures on aquatic habitats in the context of meta-population dynamics(dispersal, recolonization and seasonal to decadal scale refuges, importance of groundwaterrefuges within streams, regional strongholds among streams etc.)
Our analysis and this report represent a significant undertaking: provision of alternative default and sitespecific instream flow guidelines for 36 sub-basin tributary streams in the Okanagan Basin that supportfish populations. As described in our report, these guidelines rely on two major methodologies forsystems where detailed site specific and species specific biophysical data are unavailable. We believe wehave exceeded the RFP requirements with respect to providing alternative risk cases (prediction intervals)and we are also excited to provide a first-order hydrologic risk assessment of seasonal vulnerability basedon the exceedance probability concept emphasized during the Water Supply/Demand (WSD) User NeedsAssessment phase. This first pass risk assessment based on naturalized flows does not make anyecological vs. socio-economic value trade-offs; that would require a participatory stakeholder processbeyond the scope of this study. Nevertheless, it defines a method of integrating the complex timelocation-risk preference- species- and life-stage dimensions that must be taken into account whendefining instream flow needs.Possible future steps the Steering and Instream Flow Needs Committees may wish to consider include:1. Re-running the exceedance probability risk analysis in this report vs. net water availability timeseries following completion of water balance modelling scenarios. This is required to enable aproper ecological vulnerability for setting fish protection priorities;2. Enhancing the prototype desktop reporting tools used by our team (and demonstrated to the IFNcommittee in April 2009), and releasing it on a pilot basis to select water license managers;3. Based on the results of #2 (or instead of-), simplify and web-enable one or more of these reportsinside the WSD Web-Reporting Tool to allow wider dissemination and use throughout theOkanagan basin fish/water management community;4. Support a research project that explicitly considers water temperature requirements and impactson recommended flow thresholds. Decreased flows due to water extraction activities combinedwith climate warming, particularly in late summer, is now widely considered a primary reason forincreased stream temperatures in many areas, with consequent negative effects on cold/cool waterfish; and5. Preparing short summaries of these results for different stakeholders. In the interim, ourExecutive Summary and Frequently Asked Questions (FAQ) section will provide valuablesummaries of the extensive analysis results provided in our report.We hope that this report will provide an important reference for Okanagan instream flow needsnegotiations in the coming years. On behalf of our team (Todd Hatfield, Clint Alexander, DavidMarmorek, Russell Smith, David Carr and Katy Bryan) thank-you for the opportunity to contribute to thisvery important project in the Okanagan Basin.Yours Sincerely,Marc PorterSystems EcologistESSA Technologies Ltd.
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