Modelling reference conditions for river restoration in southern Quebec

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Restoration of impacted aquatic ecosystems must be achieved according to specific objectives based on the knowledge of the ecosystem's natural biological conditions. However, these restoration goals are generally not well defined, especially regarding the desired level of ecological integrity. Undisturbed sites are poorly surveyed in water quality surveillance networks, resulting in poor knowledge of reference situations and natural typology. A better understanding of the natural reference conditions would aid in the identification of target communities for stream and river restoration. The reference conditions of an aquatic ecosystem should correspond to its pristine or minimally disturbed condition established before the intensification of human activity. However, due to the diversity of natural conditions characterizing distinct environments, "one-size-fits-all" restoration goals can not be applied to all types of ecosystems. It is, therefore, imperative to classify stream reaches on the basis of watershed (basin area, geology, surficial deposits, etc) and habitat characteristics (stream width, water velocity, substrate, etc.) when establishing restoration goals specific to each type of environment. The primary long-term goal of the proposed research program is to classify and model the reference biological conditions of southern Quebec streams. The aquatic communities selected for the purposes of this program are benthic diatoms, benthic macroinvertebrates and fishes. These communities correspond to key trophic levels. The results from this research program will help to improve the bioassessment tools in use in Canada by quantifying the distance between the actual communities and the reference communities. Similar reference-condition approaches have been used in Europe for the implementation of the European Water Framework Directive (WFD) and in the USA for the implementation of the Clean Water Act. Biocriteria have not yet been established in the province of Quebec. There is an urgent need to establish these reference conditions in order to fulfill the need of watershed authorities and the incoming legislations.