Physical Soil Parameter and Resistivity Profile in the Vadose Zone: Preliminary Result of Groundwater Recharge Study

^{1, 2, 3} Graduate program in Mining Engineering, Institut Teknologi Bandung (ITB), Indonesia
⁴ Meteorology Department, Institut Teknologi Bandung (ITB), Indonesia
⁵ Geological Engineering, Universitas Padjajaran, Bandung, Indonesia
^* Hydrogeologist, PT. Tirta Investama, Jakarta

^* Corresponding author: trezahyd@gmail.com

Abstract

In tropical-volcanic-dominated areas, such as Java Island in Indonesia, aquifer recharge is highly impacted by rainfall intensity and soil characteristics. The first stage of recharge begins with the soil surface's response to rainwater until it percolates to the deep layer. The primary objective of this research was to study groundwater recharge processes from the soil surface to deep percolation in the volcanic deposit at the northwest flank of Mount Pangrango, West Java, Indonesia. The present study also includes the 2D geoelectrical survey results combined with the soil core drilling. A vertical undisturbed soil profile 4 to 4.5 meters deep was drilled to determine parameters such as soil water content, total porosity, permeability, organic content, and soil texture. Results from core drilling activities confirmed that resistivity values are in the range of 80 to 360 ohm.m, which is related to wet soil layers at 1 to 4 meters below the surface. It is found that the most significant difference between organic and mineral soils in terms of resistivity value is that of organic content. Depth and radius of Pinus merkusii and Melia azedarach tree according to resistivity and soil drilling result confirmed at 2.5; 4.5 meter and 0.9; 2.2 meters respectively. By profiling these factors, the behavior of water movement may be better described, allowing the net recharge rate from rainwater to the water table in the unsaturated zone to be estimated.