Water ploblem analysis for water management of river area

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Many water problems in a river area, such as the shortage of water, water pollution etc., are occasioned by the urbanization and the increase of water demand in addition to agricultural water use. To solve these water problems, an integrated water management in the watershed both in terms of water quality and quantity is needed. The objective of this study is to develop the water management system for Onga and Chikugo areas. Water problem analysis is a first important step for analyzing water policy and the management system.First of all, the water problems of Onga and Chikugo River were analysed based on the observed data of the water quality of the river for the last twenty years.In this study, geographic information system, GIS, was used to discuss the framework for pollutant load analysis in both river areas. The pollutants density and/or distribution of non-point sources in these areas were demonstrated by using GIS data. It was clearly shown that eutrophication in the estuary reservoir takes place in summer season, especially in the low flow rate period.Secondary, the mechanism of water quality formation on nutrients in Onga River was studied.The relationship between the nutrients concentrations and the flow rate was used to discuss the mechanism of the water quality formation as well as the relationship between the nutrients load and flow rate. It was shown that the runoff process of precipitation that includes the eluviation of nitrate nitrogen in agricultural land affected the concentrations of nitrate nitrogen contained in the river water. Non-point source such as municipal wastewater seems to be a main pollutant source of ammonia nitrogen and phosphorus.Finally, the necessity of establishing the alternative concepts for the integrated water management was pointed out through comparing the existing water management in terms of water quality and quantity.