lowland area has faced many water problems such as flood, drainage, water pollution, saltwater intrusion, etc. Generally, an integrated water management system is needed to solve these problems in the lowland area, both in terms of water quantity and quality. The main objective of this study is to develop the integrated water management system for Saga lowland. A comparative study between the water management systems in the Netherlands and Saga lowland is carried out. The Policy Analysis of Water Management for the Netherlands (PAWNp roject) is reviewed to clear the concept of integrated water management in lowland. The water system in Saga area is evaluated from the view point of flood control and drainage by using a computer model. Main conclusions of this study are as follow;1) New concept for water management/control system should be developed in Japan.2) Drainage system planning in Saga lowland has been limited by flood control system of the main river, in terms of design period and capacity.3) Open channel network with some facilities such as storage ponds, pumping stations, etc. are an efficient water system in lowland.4) Policy analysis of water management especially for lowland should be conducted to develop the integrated water management.
Generally, an impermeable plate has been used as the substratum of rotating biological contractors (RBC). In this study, ‘wire nets’ are used for the permeable substratum of RBCs. As a result, the following findings were elucidated : (1) The substrate removal rate of the permeable substrata is higher than that of the impermeable ones due to bio-mass existing in the space of the substratum and the increase of bio-film thickness. (2) The stable treatment performances are attained in case of short- and long-term change of loading. (3) After detaching bio-film from the substratum, the substrate removal rate of the permeable substratum is not decreased by reactivating of the remained bio-film. Concluding from the above results, when permeable substratum is used in RBCs and any detachment is occurred on the bio-film, the detachment face retrieves a new bio-film surface. Dominant microorganisms in the deep bio-film can be activated. Then it is predicted that the substrate removal rate increases more than the one in the impermeable substratum.
There is an important need in lowland such as the Saga Plains to study on integrated water management. Open channel, network in Saga is necessary for drainage, irrigation and drinking water etc. Recently, however, water pollution is a serious problem in the channel network. This study is carried out to research on property of water quality in the channel systems in Saga and to develop numerical water quality model for water management in hydraulic network systems. The major transport processes for the modeling are shown to be eutrophication and sedimentation. A numerical model for the simulation of one-dimensional unsteady flow and water quality in channel systems is newly developed. Simple tests are carried out to show the possibtlity of the presented model.
