Multiattribute Methods as a Means for Solving Ecological Problems in Water Resources—Lake Pollution

Water as a natural resource refers to the groundwater and surface water (lakes, rivers, etc.) in the environment. Lake resources are considered to be a renewable resource of the freshwater which is essential for life of humans, animals, and plants. The pollution of lake resources, caused not only by humans, restricts its function in the ecosystem, including use for human need. Human negative influence and lack of protection measures for lake resources as freshwater reservoirs can be overcome and solved using multiattribute methods. As pollution problems are very complex due to the many environment variables and many solution alternatives, researchers use more than one method as a support to undertake scientific sustained decisions which are based on economic, ecological, social, technological,… goals in order to obtain the best solutions. Short literature review presented in this paper points out two most commonly used methods for this type of problems—Promethee II and AHP method. Promethee II is used for comparing the alternatives pair-wise for each criterion, finding the strength of preferring one over the other and the main objective of using AHP is to identify the preferred alternative and also determine a ranking of the alternative when all the decision criteria are considered simultaneously. Methodological framework proposed in this paper is designed in order to rank alternatives for each criterion by combining these two methods. Qualitative character of the AHP is exceeded using Promethee II in the first stage of the analysis by cutting off the alternatives with negative net outranking flow. The benefit is direct consistency increase of the AHP. Numerical example for the lake Vrutci, the most important freshwater supplier for the Užice area in western Serbia, is given in the paper. Long-term impact of human factors caused eutrophication of the lake Vrutci and led to the exclusion of the lake from the water supply system. The solution for pollution reduction of the lake Vrutci is obtained by implementing the methodological framework and combined application of the two methods and the results are discussed.