A Fuzzified Multicriteria Outranking Method for Water Framework Directive Implementation in a Heavily Modified Urban Lake (Pamvotis, Greece)

Freshwater ecosystems deliver various ecosystem services providing essential goods and services, on which humans depend. These include vital provision of water for domestic, agricultural and industrial use. Lake Pamvotis, a heavily modified urban lake is providing multiple services but at the same time is under multiple pressures. Setting as target the achievement of the Water Framework Directive (WFD) “Good Ecological Status or Potential” goal and acknowledging the revised River Basin Management Plan’s Program of Measures, a set of six alternatives is suggested. For the preferable alternatives’ selection, six criteria were adopted whose relations are given through a Driving Forces – Pressure - State-Impact - Responses (DPSIR) conceptual model. Qualitative judgments based on expert opinion are selected to describe the scores of the criteria which are finally evaluated as fuzzy numbers. A hybrid method which incorporates the outranking relation and the right of veto of the ELECTRE III method, and finally the net flow of the PROMETHEE method is developed. The proposed method is based on fuzzy sets and logic in order, firstly to interpret both the monocriterion comparison and the aggregation among the criteria and secondly to enable the evaluation of the criteria with fuzzy scores. The results prioritized the increase of the water quality for the improvement of water related ecosystem services among the other alternatives in all tests. The proposed method is suitable for environmental problems where the evaluation of the scores is not crisp and furthermore, commensurate alternatives are demanded.