A review of assessment approaches for lake hydro-morphology before and after the European Water Framework Directive (WFD)

Europe, as well as the other continents, is characterized by the presence of both natural lakes and reservoirs. The first scientific approach on lakes dealt with the biological and chemical aspects, in order to face the eutrophication problem; at the same time, physical aspects, such as mixing and stratification dynamics, started to be considered. It was only several years later that chemical, physical, biological and hydro-morphological aspects were considered all together, when researchers focused on the whole ecosystem. In fact, methods are aimed at evaluating the hydro-morphological quality through the use of indexes and related to biological quality have been defined only after WFD 2000/60. Before, only some Member States have developed studies and assessment methods based on single morphological or hydrological features. In this study, we will describe the change in the focus of research studies on lakes, considering in particular the development of methods for the evaluation of the hydro-morphological features in the European countries. In addition, we want to contribute to introduce different approaches on the same topic highlighting the strengths, the weaknesses and the shortcomings of each one. A summary of the main hydro-morphological features, typology of survey and feasibility on lakes is also presented. The new knowledge on hydro-morphology aspects and pressure on ecosystem will be useful to develop new studies and research to improve ecosystem and environmental quality.