Evaluation model of policy scenarios for basin-wide water resources and quality management in the tone river, Japan

The objective of this study is to evaluate the conceptual scenarios of various water resources and quality management on the same level of policy decisions for optimizing river basin management. First, the water and pollutants balance model in the upper reaches of the Tone River is proposed. This model has the following characteristics: (1) Water quantity and quality at various target points of the rivers are estimated simultaneously, with a statistical evaluation for the uncertainty of hydrological events; (2) The management scenarios include selection of water savings in domestic use, reservoir construction, the expansion of sewerage coverage and so on. Several interesting results supporting policy making are obtained as follows: (1) Fifteen percent reduction in domestic use is sufficient as a substitute for new reservoir; (2) the expansion of sewage coverage in the upper reaches has large effects on reduction of BOD and COD, but the nutrient removal process should be introduced in sewage treatment plants for reduction of TN and TP.