Towards a physico-chemical assessment consistent with the biology of continental aquatic environments

Abstract

The WFD considers some physico-chemical parameters (ex. nutrients, water temperature, oxygen balance, salinity, pH, transparency) as quality elements supporting the biological elements and contributing to the classification of the ecological status of surface waters. The WFD requires Member States to produce 1) physico-chemical indicators that should reflect "the functioning of the characteristic ecosystem" and 2) threshold values corresponding to different levels of degradation of these ecosystems. In France, the ecosystems diversity, the lack of knowledge of real physico-chemical conditions and their interactions with multiple anthropogenic pressures has led to the proposal of innovative statistical methods to establish some physico-chemical quality thresholds. We recommend completing the existing monitoring networks, which are sometimes insufficient, and rethinking the assessment strategy, to take into account the connectivity between the different water bodies and the effects of climate change in order to obtain an integrated vision of the physico-chemistry and to guarantee a coherent ecological functioning of the whole watershed including its coastal area.