Instream Flow Needs Analysis - Okanagan Basin Water Board

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FINALOkanagan Basin Instream Flow Needstime series with estimates of weekly naturalized flow values does not represent enough data (orenough precision) to adapt the BCIFN approach to a weekly time scale.Q6: These BCIFN minimum risk flow thresholds are generally much higher than some of thecriteria used historically in the province (e.g., 20% MAD criteria for rearing, etc.). Why?”A: Past standard setting methods for instream flow thresholds used in B.C. have generally sufferedfrom three weaknesses: the high degree of professional judgment embedded in the method, theabsence of peer-reviewed publications and the lack of biological validation. Such historiccriteria are not necessarily wrong, but at this point cannot be adequately supported with existingdata.Q7: In the Okanagan, what processes are in place to resolve fish vs. human water trade-offs?”The flow thresholds identified in this report emphasize the needs of fish for minimum stress.Clearly, other human uses also need to be considered when allocating water. Water use conflictsoften arise where minimizing ecological risks create suboptimal water supplies for otherresources or interests. We cannot anticipate these cases, and we expect project proponents and therelevant agencies in the Okanagan to undertake studies and negotiations to assess the appropriatebalance of trade-offs. This ideally would involve multi-stakeholder evaluations of alternatives andtradeoffs amongst competing objectives, inside a formal Water Use Planning framework. WUPstudies also typically include technical evaluations of site-specific biophysical linkages andconditions.Depending on who is at the table and the terms of reference, WUPs can be formal agreements forhow water will be shared between licensees while still providing adequate flows for fish andwildlife. The goal of a WUP is to avoid litigation by achieving consensus on a plan that satisfiesthe range of water use interests at stake. Detailed guidelines for preparing Water Use Plans havebeen prepared by an inter-agency committee including BC Hydro, the Province, and Fisheries andOceans Canada. In British Columbia, the Water Act gives priority to senior licence holders underthe first-in-right, first-in-line doctrine. This means that during shortages the newest licenceholders are legally obliged to stop diverting water first. The Fisheries Act also provides legalavenues to remedy deleterious effects on fish habitat, such as when instream flow rights for fishare inadequate. The use of the Water Act, its bailiff procedure, or law suits brought by Fisheriesand Oceans Canada or First Nations is a litigious approach usually generating a suboptimaldistribution of winners and losers. In WUPs, priority rights are set off the table – that is, peoplewith senior rights do not demand that others concede to their needs. The process is intended to becollaborative and cooperative, including a variety of stakeholders in decision-making who areinterested in fair, stable solutions over the long-haul.Q8: Does your analysis take into account water temperature requirements and impacts?”A: No it does not. Neither the BCIFN guidelines or Hatfield-Bruce (2000) meta-analysis approachexplicitly consider temperature requirements or impacts in their recommended flow thresholds.Future work should seek to incorporate water temperature modeling as decreased flows,particularly in late summer, are considered a primary reason for increased stream temperaturesin many areas, with consequent negative effects on cold/cool water fish. For example, activitiesthat reduce cool groundwater flows to surface streams can significantly increase temperaturestress to fish populations and global warming is expected to further exacerbate these problems.A variety of tools are now available in B.C. for assessing risks to fish populations withintemperature sensitive streams which could be explored within future stages of analysis.ESSA Technologies Ltd. &Solander Ecological Researchxii
FINALOkanagan Basin Instream Flow NeedsOrganization of this ReportThis report lays out a framework for calculating instream flow needs (IFN) for salmonids, other aquaticbiota and general ecosystem processes at Okanagan Basin stream “nodes”.• Methods for calculating default weekly recommended minimum risk instream flow thresholds,maximum diversion rates and recommended minimum conservation flows based on theprovince’s BCIFN methodology are described in section 2.5 and results of these analyses arepresented in section 3.1.3 and in Appendix B.• Methods for calculating instream flows that optimize spawning and rearing habitat for particularsalmonid species based on a meta-analysis of PHABSIM studies are described in section 2.4 andresults of these analyses are presented in section 3.1.4 and in Appendix B.• Alternative methods for calculating instream flow needs based on the Fish/Water Managementtool (www.ok.fwmt.net) and existing/draft water use plans for two other Okanagan creeks arepresented in section 2.6. Results of these analyses for the Okanagan River mainstem, and Troutand Mission Creeks are presented in section 3.3.• An exceedance probability and hazard mapping approach for assessing the inherenthydrologic sensitivity of different tributary nodes is described in section 2.9 and results based onthis approach are presented in section 3.5 in both tabular and map-based formats.• All data (and supporting metadata) relating to these calculated weekly instream flow needs ateach node have been uploaded and can be accessed from the Okanagan Water Database(OkWaterDB) website (www.essa.com/okwaterdb).Note: Due to the large number of scenarios and variable combinations used in our analysis, most of thegraphs and maps in this report cannot be made suitable for black and white printing. Hard-copies of thisreport should therefore be printed in color.xiiiESSA Technologies Ltd. &Solander Ecological Research
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Instream Flow Needs Analysis - Okanagan Basin Water Board

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