River assimilative capacity analysis via fuzzy linear programming

The assimilative capacity of a river, that is the so-called allowable pollution loading in a river basin, is a problem of water quality management involving optimization subject to constraints of standards of water quality and their models. This study is an up-to-date evaluation of assimilative capacity in a river basin with consideration of the imprecision of the water environment, i.e. water quality and river flowrate. The purposes of this study, in comparison with crisp linear programming (LP), is to select and evaluate four well-known fuzzy linear programming (FLP) approaches and to apply them to the assimilative capacity of a river basin, Tou-Chen River Basin in Taiwan. The results show the models of assimilative capacity of FLP are better than those of a crisp one, which reflect the flexible characteristics of the former approaches. The emphases in this paper are on how to formulate problems of assimilative capacity of a river according to FLP models and on how to solve them according to algorithms of crisp LP. Furthermore, the results of river analysis serve as criteria for regulatory agencies to implement the control of pollution sources and to accomplish finally the sustainable use of water resources.