Groundwater management is a very important subject in the environmental field. This paper analyzes groundwater system of Saga plain respecting to hydrogeological and geochemical aspects. Saga plain is located in the west of Kyushu Island of Japan. The groundwater seriously affected by over-pumping and land subsidence was observed from 1960 and it is estimated that occurred from 1957. Groundwater level varied seasonally by pumping amount and precipitation. According to the geological properties of Saga plain, aquifers was simplified as a one-layer aquifer model. A two-dimensional model was adopted to simulate the fluctuation of groundwater level.
Saga plain is a typical lowland area. Land subsidence due to over-pumping is the most serious problem in Saga plain. Since 1957, the maximum accumulation of subsidence reached 110cm. At present, the land subsidence is still serious with maximum subsidence of 20–100mm per year in the southwest area of the Saga plain. Observations showed that the land subsidence was closely affected by the fluctuation of groundwater level what was corresponding to amount of pumping. The measurement of land subsidence was made initially in 1960, and still continues today. In order to prevent the land subsidence, pumping restriction was put into effect in 1974. Even after the restriction, land subsidence continued. In addition, salt-water intrusion, that probably due to over-pumping, also occurred in this area. It is therefore important to consider both the development and the protection of groundwater resource. Generally properties of groundwater depend on regional influence. Water quality and quantity are not only affected by the recharge and soil utilization, but also by the surrounding geological conditions that is considerable as the reservoir of groundwater. This study analyzes the groundwater system of Saga plain respecting to hydrogeological and geochemical respects.
Saga plain is an alluvial deposit plain.