ASSESSMENT OF AQUIFER SUSCEPTIBILITY DUE TO EXCESSIVE GROUNDWATER ABSTRACTION; A CASE STUDY OF YOGYAKARTA-SLEMAN GROUNDWATER BASIN

Abstract

Yogyakarta-Sleman groundwater basin is one of productive groundwater basins in Indonesia. The groundwater basin is built by unconfined sand-aquifer system. Since the early 1980’s many schools, universities and hotels have been developed in this area to support education and tourism activities, and since the beginning of 2000’s the number of buildings has increased significantly. The development has resulted in a rapid rate of land use and population changes with the consequence of increasing groundwater pumping. Measurement results show that the rate of groundwater table degradation exceeds 0.5 m/year at some districts underlain by the groundwater basin. Because of this condition, it is necessary to assess the susceptibility of the aquifer to negative impacts due to the excessive groundwater pumping. The assessment was conducted by overlying factors such as aquifer response characteristics, aquifer storage characteristics, thickness of the aquifer, depth to groundwater table and distance from the sea. The assessment results show that the excessive groundwater abstraction to the aquifer has caused moderate to high susceptibility. It means that the groundwater pumping activities on this groundwater basin should be managed and controlled.