Session Name: Environmental Assessments or Contributed Papers

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Session Name: Environmental Assessments or Contributed Papers
Presentation Title: A comparison of desktop hydrologic methods for determining environmental
flows
Presenter Name: Todd Hatfield
All Authors, affiliations, phone number, email:
T. Hatfield1 and A. J. Paul2
1
Ecofish Research Ltd., 1220-1175 Douglas Street, Victoria, BC V8S 1C7
phone: 250-480-0050 (ext 11); ([email protected])
2
Fish and Wildlife, Environment and Sustainable Resource Development, 213 – 1 Street W.,
Cochrane, AB T4C 1A5 ([email protected])
Abstract: Determining environmental flows can be a daunting task because fluvial systems are
physically and biologically complex, and there can be difficult trade-offs between instream and
out-of-stream water uses. Desktop methods are primarily office-based exercises that often use
more readily available hydrologic information to assess a proposed diversion of stream flows.
Two-tiered water allocation decision processes, in which desktop methods represent the first tier
or filter, and detailed methods the second tier, are common in many jurisdictions. A primary
objective of desktop and detailed methods is to protect environmental resources, but the
required information, time, and cost may be substantially different. This paper reviews six wellknown desktop hydrologic methods. Seventeen performance measures (PMs), for ecosystem
health (hydrology, habitat, geomorphology, connectivity, and water quality) and out-of-stream
water use, are used to compare and contrast the predicted outcome of the desktop methods to
three mid-size rivers with different hydrologic regimes. Results of the PM calculations
demonstrate that absolute and relative performance of the six desktop methods is not consistent
across the three streams. As a group, the methods clearly underscored the trade-off between
water use and ecosystem health; however, the methods had widely divergent performance for
water use PMs and variable performance on the different ecosystem health PMs. All desktop
methods performed well on the fish habitat PMs, but performance on the other ecosystem
health PMs was variable and not consistent among methods. The results emphasize the need
for clearly articulated objectives as an integral component of any desktop method and the
benefit of transparent trade-off considerations during any water allocation decision.
Student Presenter?: No
Presentation Type: Oral presentation only
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