Application of the 'snapshot' methodology to a basin-wide analysis of phosphorus and nitrogen at stable low flow

The `snapshot' sampling methodology was applied to the spatial analysis of phosphorus and nitrogen concentrations and fluxes in the transnational upper Sûre watershed (Belgium-Luxembourg) during stable low discharge summer periods in 1991 and 1992. The results show clear differences in nitrogen concentrations and specific loads between agricultural and forested sub-basins, whereas for phosphorus the dependence on land use is less evident. The simultaneous measurement of stream discharge and nutrient concentrations permitted a quantitative evaluation of the input from point respectively diffuse sources and loads from the tributaries as well as the retention capacity by self-purification or sedimentation of the different phosphorus and nitrogen forms in the various sections of the Sûre river. The results illustrate the utility of the `snapshot' sampling as an important tool for an integrated watershed management.[PUBLICATION ABSTRACT]