Multiobjective Optimization of Discharged Pollutant Loads from Non-point Sources in Watershed

• Published in: Transactions of The Japanese Society of Irrigation, Drainage and Reclamation Engineering Vol. 2002; no. 221; pp. 597 - 602
• Main Authors: MAEDA, Shigeya, KUMAR, Alok, KAWACHI, Toshihiko
• Format: Journal Article
• Language: Japanese
• Published: The Japanese Society of Irrigation, Drainage and Rural Engineering 25.10.2002
• Subjects: Geographic Information System; Multiobjective; Non-point source; Optimization; Pollutant load allocation; Total nitrogen; Watershed
• ISSN: 0387-2335; 1884-7234
• DOI: 10.11408/jsidre1965.2002.597

A method is developed to optimally allocate allowable pollutant loads from non-point sources in a watershed using multiobjective optimization theory and Geographic Information System (GIS). Using calculated values of flow length from each land management unit (LMU), which is represented by a grid of uniform size, to the outlet in the watershed, and assumed value of watershed-wide self-purification coefficient, a two-objective linear programming model is formulated. The objective function maximizes total allowable discharged pollutant loads from LMUs and promotes equal allocation of them in a selected sub-watershed, subject to constraints of effluent limitation at the outlet of the sub-watershed, relation among mean effluents from different types of LMUs, and minimum limit of effluent in each LMU. The model developed is applied to a sub-watershed of the Yasu river basin in Shiga Prefecture, Japan, in order to demonstrate the model's ability to determine optimum allocation of discharged loads of total nitrogen from various LMUs in the sub-watershed.