Author(s): Shigeya Maeda; Toshihiko Kawachi
Linked Author(s):
Keywords: Optimization; Wasteload allocation; River water quality management; Nonpoint source; Uncertainty; Geographic Information System
Abstract: A method is presented to evaluate the level of river water quality management using a multiobjective optimization model, ε-RO model, and a Geographic Information System (GIS). The GIS can help delineate catchment boundaries influencing a diagnosed section of a polluted river, find outfalls of wastewater, and estimate discharge and COD (Chemical Oxygen Demand) load with a land use map and elevation data. A framework of robust optimization is employed to develop the optimization model where temporal variation of hydro-environmental scenarios can be treated stochastically. Calibration of a finite element model for COD and dissolved oxygen transport in the river of interest is required to identify some scenario components. Objectives defined in the ε-RO model are to maximize total allowable COD load and to keep river water quality around the standard values. Wastewaters from nonpoint sources (NPSs) such as agricultural land and city are treated as controllable in the optimization model, so that it can provide more strategic COD load allocations to both PSs (point sources) and NPSs than our earlier model. Application of the ε-RO model to Yasu River, Japan, illustrates evaluation of the current level of water quality management by comparing with noninferior solutions in regard to total allowable load and in-stream water quality. The diagnostic results reveal that an optimal allocation exists which upgrades the river water quality even if both PS- and NPS-born COD loads are increased.
Year: 2005