ASSESSMENT OF HYDRO-MORPHOLOGIC QUALITY OF RIVERINE BIOTAS: A CASE STUDY WITHIN AN ALPINE CATCHMENT

Abstract

The Water Framework Directive WFD (Directive 2000/60/EC) requires that all European rivers reach a good ecological status by 2015. Implementation of the WFD in Italy is however lagging. Further, climate change may affect restoration, hampering return to the previous ecosystem status, so strategies to manage freshwater ecosystems under climate change are utmost needed. Alpine rivers hosting salmonids are particularly fragile. Habitat evaluation for fish and macro-benthos is a key factor for stream ecology assessment. Here, we present a hydrologically based methodology to evaluate spatial and temporal distribution of river habitat in Alpine rivers, which we apply within the Alpine part of the Serio river (BG). Experimental suitability curves developed using data from field surveys were used to assess weighted usable area WUA for brown trout (Salmo Trutta) in different stages (adult, young, spawning), and four macro-invertebrates families (Leuctridae, Heptageniidae, Limnephilidae, Limoniidae). Discharge-WUA curves were obtained using IFIM-PHABSIM, and seasonal WUA assessment was carried out at different river sections along the river. A hydrological model tuned for the Serio river was then used to mimic daily flow regime, and related values of WUA. The results of the study provide a seasonal evaluation of river habitat, given by frequency of exceedance of standard values of WUA. The results display how seasonal regimes feature different level of river quality for different target species. The proposed method can be used to evaluate the quality of rivers in space and time as per different weather and hydrological patterns, and can be useful to integrate the present methods for river quality analysis for implementation of WFD, and to evaluate the potential effects of future climate change upon the quality of river biomes.