Impacts of neglecting spatial heterogeneity in the water quality assessment of large lakes: evaluation on remote sensing and 3D-model data
Impacts de l'hétérogénéité spatiale dans l'évaluation de la qualité de l'eau des grands lacs : évaluation par la télédétection et la modélisation tri-dimensionnelle
Résumé
Context : In 2000, the European Parliament set out a framework (European Water Framework Directive) for managing and protecting water bodies in Europe. Classification of water bodies into «ecological status» is a key issue for the implementation of that framework. For lakes, the assessment of this status is based on biological (e.g . fish, phytoplankton and macrophyte), physical-chemical and hydro-morphological indicators. The physical-chemical and phytoplankton indicators are based on 4 observations given by integrated samples over the growing season during one year for a 6 years management plan. The sampling occur in the euphotic zone over the deepest point of the lake. However, in large lakes, ecological parameters, used for water quality assessment (e.g . chlorophyll-a concentration and Secchi depth), exhibit strong spatial-temporal heterogeneities. Consequently, the representativeness of those data versus the whole lake might be questionable and needs to be verified (Kiefer et al., 2015). The objective is to evaluate how spatial and temporal heterogeneities in chlorophyll-a may impact the assessment of Lake Geneva ecological status; we propose to combine remote sensing data and 3D modelling