Identification of Subsurface Water Flow Using Gradient Horizontal Gravity Data in Tanjung Priok and Koja, North Jakarta

The presence of saline or salt water in the Jakarta groundwater aquifer is still widely debated by various geologists and groundwater experts. This study intends to identify the cause of the high salinity of groundwater at Tanjung Priok and Koja, North Jakarta. The First Horizontal Derivative (FHD) method of gravity data is applied to identify the direction of subsurface fluid flow. It is also supported by groundwater sample data and self potential (SP) data. The direction of fluid flow on the FHD contour map is indicated from low to high FHD value. From gravity data, Bouguer density values obtained in the study area were 2.12 gr/cm3. This study focuses on surface aquifers so that it is necessary to separate regional and residual anomalies. The results show that the direction of fluid flow is from north to south, there is a high FHD value that is distributed around the coordinates (709000, 9322000) which may indicate as the salt depositions of sea water intrusion.