Salt intrusion in Coastal and Lowland areas of Semarang City

Over a long term, Semarang Coastal and Lowland areas have experienced salt water intrusion. This condition is accelerated due to land subsidence, sea level rise and groundwater exploitation. The purposes of this research paper were to highlight the salt water intrusion from 1995 until 2108 based on well log measurement and MODFOW numerical modeling in Coastal and Lowland of Semarang City. Sea level rise projection also was considered for salt intrusion projection in the future. MODFLOW was used to compute the groundwater flow field, MT3D for the salt transport, and ArcGIS Environments for coherent geographic visualization. A calibration of the model was conducted based on observation best match. The results obtained illustrate the development of a forward onshore sea salt water intrusion since 1995. It also showed the 2008 recorded sea water intrusion and provide groundwater sea water contamination projection for the years 2018 until 2108. Moreover, fresh water distribution near the coast in previous years developed into brackish water then into saline groundwater. Result showed the movement of saline groundwater from coastline to landward years by years from 2018, 2028, 2048, 2068, 2088 and 2108 following high hydraulic conductivity area. Salt intrusion was also driven by future sea level rise which result to the increase of the fresh water front forward move.