Author(s): Shigeya Maeda; Toshihiko Kawachi
Linked Author(s):
Keywords: River basin management; Optimization; Fuzzy sets; Nitrogen; Wastewater
Abstract: A fuzzy linear programming model is presented to allocate total nitrogen (T-N) load to distributed nonpoint sources (NPSs) and point sources (PSs) in a watershed of a river. As management goals, maximizations of (i) total allowable NPS loads, (ii) total allowable PS loads, and (iii) total yield of rice are considered. The watershed is divided into grid cells to control loads to the outlet of the watershed delivered from NPSs such as paddy fields, upland crop fields and city. A prime constraint is an effluent limitation standard for total controllable T-N load transported to the outlet, where watershed-wide self-purification is expressed as distance-related first-order kinetics. A geographic information system and a digital elevation model are used for preparation of input data and for calculation of the flow length from each cell of NPS to the outlet of the watershed. Fuzzy sets theory is adopted to describe vagueness of some constraints and achievement levels of conflicting goals considered. An application of the fuzzy optimization model, developed as an improvement over our last non-fuzzy model, to a real existing river basin demonstrates that the model embodies our last model and this study enhances the model’s ability as a decision support tool for providing more acceptable management alternatives for T-N load allocation.
Year: 2007