Refinement of biomonitoring of urban water courses by combining descriptive and ecohydrological approaches

Two approaches are proposed for developing adapted metrics, proposing realistic and sustainable ecologic objectives, and suggesting a management strategy for stream rehabilitation. The first approach implemented a harmonization system of French standardized biotic indices. The second one was based on the development of functional traits (FTrs), which were defined by oligochaete assemblages inhabiting coarse surface sediments and the hyporheic system. The harmonization system allowed to define a weighted general ecological quality. The FTrs characterized an ecological potential (EP) resulting from interactions between physical factors (dynamics of hydrologic exchanges between surface water and groundwater) and chemical factors. An example of using both approaches at the same urbanized site is presented and serves for planning of rehabilitation activities. The benefits, drawbacks and progress of both approaches are discussed.