A multi-criteria analysis for siting surface-flow constructed wetlands in tile-drained agricultural catchments: The case of Lithuania

This paper reports on the research techniques of application of Multi-Criteria Analysis (MCA) for the placement of surface flow constructed wetland (CW) in the tile-drained land. It points out that such applications are quite rare for managing diffused pollution from agricultural catchments and conventional MCA techniques have to account for advances of Geographical Information Systems. The objective of this paper was to present the methodology of MCA procedure and to test its effectiveness for the selection of sites. A case study is presented of the application of MCA based on the ELECTRE method that resulted in solving two tasks: 1) identification of the most pollution affected agricultural catchment out of three candidates, as characterised by 14 relevant criteria, and 2) placement of a pilot CW in the best site out of six in an intensively drained agricultural area as characterised by 19 criteria. For both cases, the criteria were clustered into three groups. To select the most appropriate site for siting a CW, soil-related, technically-related and pollution-related groups were identified. Based on a variety of numerical indices, the sites were ranked. A sensitivity analysis of the results when individual or group values of the weights are changed confirmed the robustness of the model. It should be stressed that conventional MCA is a powerful tool for selecting CW sites at a local level. The research techniques described here may be a good reference for developing other wetland placement systems.