Water Stewardship Information Sources

Citation Linnansaari, T, Monk, WA, Baird, DJ, Curry, RA. 2013. Review of approaches and methods to assess Environmental Flows across Canada and Internationally. Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, Research Document 2012/039.
Organization DFO
URL http://www.dfo-mpo.gc.ca/library/348885.pdf
Abstract/Description or Keywords Freshwater resources are under increasing threat from anthropogenic activities, both in terms
of consumptive and non-consumptive use. The increasing societal demands for water have led
to substantial flow alterations in rivers in Canada. Flow alteration can be directly linked to
impacts on the physical and chemical attributes and processes of rivers and subsequent
ecological changes. In addition to increasing demand of water, the ecological, social and
cultural values of rivers are increasingly being recognized. With so many competing needs for
water, there is an urgent need to develop sustainable environmental flow management
guidelines to manage the risk associated with alterations to the flow regime in Canadian rivers.
A national environmental flow framework would also support the habitat protection provisions of
the Fisheries Act (S.35).
This document is intended to serve as an input for a scientific review process at a national level
and to provide background information on i) conflicting terminology used in the environmental
flows literature, ii) environmental flow assessment methodological approaches and iii) current
status of environmental flow guidelines used in different jurisdictions in Canada. The
information contained in this document was critically discussed by an assembled group of
experts who will provide further scientific advice on environmental flow regimes for the
Canadian context in a separate document.
The terminology used in environmental flow assessment literature is variable; "instream flow
needs" and "environmental flows" seem to be the most widely used and inclusive terminology.
The endorsement of these terms for wider use in Canadian context needs to be further verified
by an assembled group of experts.
The techniques used in environmental flow regime assessment were classified into four general
categories (hydrological, hydraulic rating, habitat simulation and holistic methodologies and
frameworks) and the benefits and weaknesses are reviewed. The four methodological
categories differ drastically in the scope and implementation costs and therefore, are suited for
different level of assessment of environmental flow regimes. Most assessment methods are not
based on tested relationships between the extent of flow regime alteration and ecological
response. A recent trend seems to suggest that there is an increasing recognition that any
environmental flow method used alone will not be sufficient for determining environmental flows
in all situations; the holistic methods and frameworks (wherein a combination of other methods
are used) are increasingly common especially in large scale projects.
The examination of the current methodologies used in different jurisdictions in Canada revealed
that many provinces do not have an established guideline to be used for determining
environmental flow regimes. Some provinces have established guidelines to be used in
uncontroversial situations (i.e. cases that are believed to lead to no harmful alteration,
disruption or disturbance to fish habitat, "HADD"). None of the jurisdictions appeared to have an
established environmental flow framework that is used in larger-scale projects (i.e. "potential or
incurring HADD") but evaluation is carried out on a case-by-case basis. Various options for establishing a national environmental flow regime framework are available
but at least two suggestions are to be examined more closely by an assembled group of
experts. The first option is related to incorporating a framework similar to the process
characterized by the Ecological Limits of Hydrologic Alteration (ELOHA; Poff et al. 2010) to at
least some degree in Canada. The second option is to establish a two-tiered framework
wherein the more general Level 1 ("no HADD") assessment would be based on some
combination of hydrologically-based guidelines to protect the natural variability in river flow
regimes with some cut-off values to terminate water withdrawal during the lower flows. The
more specific Level 2 ("potential HADD") assessment would be based on a holistic approach for
which a detailed protocol would need to be drafted to ensure the ecological integrity,
comparability and transparency across Canada. Regardless of the type of framework to be
established, it is fundamental that the established environmental flow standards are preceded
and followed by a controlled monitoring program and the possibility to refine the environmental
flow regime standards by adaptive management in an iterative process.
The need to establish a system to categorize Canadian rivers (or their segments) into
ecological management classes needs to be further discussed by an assembled group of
experts. The potential benefit of such classification would be the possibility to design different
environmental flow standards based on the ecological or societal "value" of various river
sections. Finally, a time-frame must be determined to ensure that a national environmental flow
framework will be established in an expedited manner.
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