Abstract
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 final objective of this study is to develop the integrated water management system for the Onga area. Water problem analysis is a first important step for analyzing water policy and the integrated management system. As a first step of this study, the water problems of the Onga River are analyzed based on the observed data of the water quality of the river for the last twenty years. It is clearly shown that eutrophication in the estuary reservoir takes place in summer season, especially in the low flow rate period. The BOD concentrations in the reservoir increase with the concentration of algae. Finally, the necessity of establishing the alternative concepts for the integrated water management is pointed out through comparing the existing water management in terms of water quality and quantity.
