Instream Flow Needs Analysis - Okanagan Basin Water Board

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FINALOkanagan Basin Instream Flow Needsneeds were also evaluated even though they are not currently present in Okanagan tributary streams.These may be useful in the evaluation and design of future restoration initiatives. The IFN scenario resultsfor Okanagan nodes are presented in a variety of formats – as weekly IFN values for nodes uploaded tothe OKWaterDB, as graphical representations of weekly IFN recommendations (minimal and optimalflows) at individual nodes, as tables of exceedance probability matrices (linked to “traffic light” plots insome cases) across all tributary nodes, and as hazard maps of inherent hydrologic risk for a subset of IFNscenarios.It is very important to recognize that consideration of socio-economic water demands and the appropriateecological trade-offs were outside the scope of this study. Anthropogenic water needs are typically readilyavailable from regulatory authorities (e.g., water license information) and at the forefront of legalagreements (e.g., flood protection, recreational flow needs). Where we were able to acquire water useagreement information related directly to fish flow needs, as in the case of Okanagan River, Trout Creekand Mission Creek, we compared these instream flow targets to the default guidelines generated by ourBCIFN and meta-analysis methods.Here is a synopsis of key findings:o Naturalized flows at individual nodes varied in their ability to achieve optimal fish flows fordifferent salmonid species during critical life-stage periods. In general, however, naturalizedflows were sufficient in most years to achieve mean optimal flows for rainbow trout and steelheadspawning but often failed to provide optimal flows for kokanee and sockeye spawning intributaries in which they occur, or for (hypothetical) spawning of Chinook and coho in selectedkey tributaries. Achievement of optimal rearing flows for rainbow trout, steelhead and cohovaried throughout their year-long residence in the streams but optimal flows were generallyachieved within the shorter time period of Chinook rearing.ooTributary nodes in the northeast section of the Basin displayed a better inherent ability to achieveIFN flows defined for different species and during different time periods of the year, whereas theopposite seemed to be the case for tributary nodes in the northwest section of the Basin (i.e.,poorer ability to meet IFNs).These results reflect the fact that the Okanagan is a naturally dry region, and even in the absenceof human water use (as illustrated by naturalized flows), flows are frequently sub-optimal for fishproduction when considering the flow levels these species prefer throughout their range.We compared exceedance probabilities for select regulated flows and naturalized flows (this comparisonwas not possible for most nodes as we did not have the net water availability time series that are to begenerated by the water balance modelling project). This comparison indicated that at some nodesrecommended BCIFN minimum risk flows were achieved more frequently in the late summer dry periodwith regulated flows than with naturalized flows. This was presumably due to increased storage in somewatersheds during the freshet with subsequent release of this stored water later in the summer. However,regulated flows generally met BCIFN minimum risk flow thresholds less often than naturalized flowsduring other critical time periods (e.g., mid-winter). Increased water storage (where possible) linked toecological releases targeting critical fish needs represents a valid management avenue for betterachievement of instream flows needs – especially in the context of projected future climate change.Developing such strategies (e.g., ecological water reserves) requires an acceptance that instream valueshave a right comparable to anthropocentric rights (though the relative weights of these rights will varycase by case, and with human values). Historically water has often been allocated among priority rightsholders first with instream needs being allocated as an afterthought or only if “excess” water exists.Hopefully this value-system will evolve with future implementation of the Okanagan Sustainable WaterStrategy, which emphasizes attaining a better balance between human and ecosystem needs.ESSA Technologies Ltd. &Solander Ecological Researchii
FINALOkanagan Basin Instream Flow NeedsTable of ContentsList of Tables................................................................................................................................................................vList of Figures ............................................................................................................................................................viiList of Figures ............................................................................................................................................................viiFrequently Asked Questions (FAQs) .........................................................................................................................xOrganization of this Report .....................................................................................................................................xiiiGlossary.....................................................................................................................................................................xiv1 Introduction ..........................................................................................................................................................11.1 Background..............................................................................................................................................11.1.1 Methods considered................................................................................................................11.2 Project scope and objectives ....................................................................................................................21.2.1 Project oversight.....................................................................................................................51.3 Interpretation and appropriate use of guidelines......................................................................................72 Methods .................................................................................................................................................................92.1 Principles .................................................................................................................................................92.2 Natural flow regime ...............................................................................................................................102.3 Hierarchy of methods.............................................................................................................................112.3.1 Fundamental input: naturalized streamflows........................................................................132.3.2 Method categories ................................................................................................................132.4 Method 1: Meta-analysis of western North American PHABSIM studies ............................................142.4.1 Fish presence/absence ..........................................................................................................162.4.2 Fish species periodicity (critical periods for meta-analysis) ................................................182.4.3 Validation of meta-analysis approach for Canadian Okanagan streams ..............................202.4.4 MAD correction factor .........................................................................................................242.5 Method 2: British Columbia Instream Flow Guidelines for Fish (BCIFN) ...........................................252.5.1 Exploratory analysis of altering data frequency and duration ..............................................272.6 Method 3: Flow guidelines from site specific studies............................................................................292.6.1 Okanagan River mainstem – Fish/Water Management Tools guidelines.............................292.6.2 Trout Creek and Mission Creek – surrogate stream approach..............................................342.7 Lower reference flows ...........................................................................................................................362.8 Additional sensitive species and ecological functions ...........................................................................382.9 Treatment of uncertainty and risk ..........................................................................................................413 Results .................................................................................................................................................................443.1 Understanding instream flow guideline plots: a walk-through ..............................................................453.1.1 Natural variation and measurement error in naturalized flows.............................................453.1.2 Lower reference flows..........................................................................................................463.1.3 BCIFN minimum risk flows.................................................................................................483.1.4 Meta-analysis optimal fish flows..........................................................................................523.2 Instream flow recommendations by subbasin node ...............................................................................573.3 Site specific studies................................................................................................................................58Okanagan River mainstem: juvenile sockeye salmon flow envelopes ...............................................603.4 Additional sensitive species and ecological functions ...........................................................................613.4.1 Mexican Mosquito Fern (Azolla mexicana) .........................................................................633.4.2 Tiger Salamander (Ambystoma tigrinum).............................................................................633.4.3 Great Basin Spadefoot (Spea intermontana)........................................................................643.4.4 Vivid Dancer (Argia vivida).................................................................................................65iiiESSA Technologies Ltd. &Solander Ecological Research
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Instream Flow Needs Analysis - Okanagan Basin Water Board

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