A Comparison of 1D Phabsim, River2D, and HEC-RAS Habitat Models from 85 Km of the Lower Wapiti River in Alberta, Canada

Grande Prairie Alberta is one of the fastest growing cities in North America.  Aquatera withdraws water from the Wapiti River for Grande Prairie’s consumptive use and returns treated effluent.  In order to proactively plan for additional growth by assessing hydraulic habitat impacts to bull trout, Arctic grayling, longnose sucker, walleye, burbot, mountain whitefish, and slimy sculpin, Aquatera, the Water Management Plan Steering Committee, a consortium of resource agencies, Palmer Environmental Consulting Group, and Normandeau initiated an instream flow study that consisted of 38 1D transects and a 1 kilometer 2D site encompassing a complex  island habitat including Aquatera’s intake and outfall.  Low flows can occur twice per year, late summer and winter.  The PHABSIM model included transects distributed over the 85 km study area, but could not model the winter low flow period due to ice cover.  HEC-RAS can accommodate the ice cover, but provided less definition to the velocity patterns.  The River2D model provided detailed velocity patterns and accommodated ice cover, but was limited to a single study area.  Together, these three models represent the hydraulic habitat.  This presentation compares these habitat models, and identifies similarities and dissimilarities in the results and reasons for observed differences.