A Study on Optimal Environmental Policy Measures Related to the Introduction of New Technologies to Improve the Water Quality of Lake Kasumigaura

Abstract

The quality of water in Lake Kasumigaura has been deteriorating since the 1970's by the pollution discharged from socio-economic activities of the catchment area. As a result of construction of a sewage system, and enaction of an ordinance to prevent the environment by the government, water quality of Lake Kasumigaura has improved to some extent, but the process of deteriorating is still continuing. Recently, many engineering groups are working to develop technologies in order to solve the problem.In this study, we analyze a dynamic optimal policy and evaluate new technologies to improve the water quality of the lake, considering both-the total ecological system in and around the lake and the situational changes over a certain period of time.We specify two sub-models (the ecosystem model and the socio-economic model) and one objective function (Regional GDP; GRP) in order to analyze the optimal policy to improve the water quality of Lake Kasumigaura. The ecosystem model describes how the amount of generation and flow of pollutants are changed and the extent to which it is abated by removal equipments in the lake and the rivers. The socio-economic model describes the social and economic activities in the catchment area and the relationship between the activities and the emission of pollutants. The optimal policies are derived so as to maximize the objective function subject to the structural equations which describe both the ecosystem and socio-economic system.The pollutants measured in this study are nitrogen, phosphorus and COD. These have been strongly affecting the deterioration of water quality.