The hydrological problem of Saga area is governed by the fact that almost the area is below the Ariake sea level with the highest tide in Japan. Another problem is difficulty of supplying huge quantity of water for agriculture because of less water resources in Saga area. Therefore, open channel network system, Saga creeks, have been developed in this area. In this paper, an old system of water management on Saga creeks is described. The water management was a kind of integrated system by making use of function of Saga creeks such as drainage, storage. On the other hand, the main objective of modern and general water management is to protect flood damage caused by main river. The paper describes that, according to the modern concept, there has been many problems on drainage system in lowland especially in Saga area. Also, it is described that many factors to be cleared such as the drainage characteristic, time constant of design rainfall and the storage effect of channel network are examined. Finally, it is pointed out that the integrated water management system should be developed especially in lowland such as Saga area.