RHYHABSIM as a Stream Management Tool: Case Study in the River Kornerup

Abstract: Th is study applied the habitat-hydraulic model RHYHABSIM (River Hydraulic HABi-tat SIMulation) on three small streams within the River Kornerup catchment in eastern Denmark. Th e relationship between the fl ow and habitat area for spawning and juvenile brown trout was modelled to determine fl ows needed to produce enough habitat area to sustain naturally recruit-ing populations of brown trout. A comparison of the model results with actual fl ow data for the streams for the years 1999-2002 found that the stream fl ow in two of the streams provided enough available habitat for the survival of juvenile brown trout every year, however the stream fl ows in the third stream failed to provide adequate habitat area for a three week period in 2001. All three streams provided adequate habitat for spawning in all four years. Th is case study illustrated that the habitat-hydraulic model RHYHABSIM, which was relatively easy and non-labour intensive to apply, could quickly provide useful information for use by water managers in Danish streams. However, it must be stressed that these types of habitat models do not include all factors that aff ect ecosystem functioning and therefore carrying capacities of streams for indicator species such as fi sh, but they should be viewed as useful management tools for giving information on how the hydro-morphological regime in a river or stream is aff ecting a chosen indicator species