Perpustakaan Digital ITB

An aquifer may be defined as a formation that contains sufficient saturated permeable material to yield significant quantities of water to wells and springs. Aquifer system in Semarang city basin is mainly divided into two different types including unconfined aquifer with an average depth of 3 – 18 meters and confined aquifer with an average depth from 50 – 90 meters. Urbanization and industrialization processes cause groundwater in Semarang city area to be overexploited to meet the needs for domestic and industrial use. As a result, the aquifer system in Semarang city is being partially damaged. Damaged aquifer has the lower possibility to store the water because its void, porosity and hydraulic conductivity are reduced dramatically. Damaged aquifer also intensifies water scarcity and affects the water security in the future. There is a difficulty in estimating water table decline due to the limited on-site groundwater data. Luckily, there is correlation between water table decline and land subsidence from existing publications in several places across the world. While aquifer damage can be estimate from water table decline value. The correlation is used as an alternative to do inversion to calculate water table decline from land subsidence data. Therefore, this research is to create two mathematical models for estimating water table decline. Model 1 is built based on the field data of groundwater in Semarang in correlation with land subsidence data and Model 2 is built by using the correlation data from existing publications. The research shows that Model 1 and Model 2 well represent for the correlation between land subsidence and water table decline in Semarang city basin. The two models give the similar resulting water table decline. Consequently, the two models can be used interchangeably. Moreover, Model 2 can be also used for other places in the world in consideration of VS30 similarity. According to water table decline value estimated by both Model 1 and Model 2, more than 70 percent of the aquifer system of Semarang city basin will be damaged and very damaged in 2050 if there is no action taken to stop the subsidence phenomenon.