Geochemical Evolution and Groundwater Flow System in Batujajar Groundwater Basin Area, West Java, Indonesia

Abstract

DOI:10.17014/ijog.7.1.87-104Batujajar and its surrounding areas, situated in the west of the Bandung Basin, are geologically composed of various Tertiary rock formations with complex fold and fault systems. Springs and drilled wells in sandstone aquifers, tuffaceous sand, and tuffaceous breccias mark the development of their aquifer systems. This study aimed to determine the characteristics of the hydrogeochemistry by analyzing major ions and stable isotopes (18O and 2H) of thirty-four hydrogeological objects. The groundwater flow pattern in this area is controlled by northwest-southeast lineament, as indicated by the emergence of springs along the transition zone between areas with high and low lineament density. In order of dominance, the groundwater facies are as follows:Ca-Mg-HCO3>Ca-HCO3>Ca-Na-Mg-HCO3>Na-Ca-HCO3. Hydrochemical evolutions were detected from the change of cations from Ca2+ to Mg2+ and then Na+, and this is believed to be the product of cation exchange and dissolution of silicate minerals. However, evolutions toward anion changes were not apparent yet, meaning that HCO3- ions still prevail, or in other words the groundwater flow system is local. Nevertheless, the geological and hydrogeochemical analyses, along with the relative compositions of stable isotopes, revealed that the groundwater had three systems, namely shallow, intermediate, and deep groundwater flows; all of which were segmented in three subgroundwater basins (Sub-GWB). Aquifer systems with shallow to intermediate groundwater flow were found in Sub-GWB-A, Sub-GWB-B, and Sub-GWB-C, while the other ones with deep groundwater flow system were identified in Sub-GWB-B and Sub-GWB-C.Fracture system has an important role as a connector between recharge system in hilly areas and discharge system in plain areas.

Geological Trap Controlling the Residence Time of Groundwater in Assessment of Exploitation Zone for Its Sustainable Resources Case Study: The Slope of Karang Mount, Banten Province, Indonesia

“…Water as the filling fluid moves following the geological setting of an area with its dynamics (García-Gil et al, 2023). The interaction of water and rocks along with the geological setting is indicated by the quality or the chemical content of the water (Suhendar et al, 2020;Gebeyehu et al, 2022). Meanwhile, groundwater is a dynamic substance that follows nature laws, and flows depends on the head of pressure and temperature as well as hydraulic gradients.…”

Groundwater Recharge Area Based on Hydrochemical and Environmental Isotopes Analysis in the South Bandung Volcanic Area

“…Determination of the recharge area elevation from isotope can be performed using natural isotope methods, namely δ 2 H and δ 18 O isotope in water molecules [2,21]. Water-rock interactions, evaporation, mixing, water origin, and accompanying processes are known by comparing the isotopic composition of water with reference [3,16]. The altitude effect and the amount of rainfall can be used to find the relationship between the isotope composition of rainwater and the altitude of a recharge area [27].…”

“…The abundance of δ 2 H and δ 18 O molecules in water is not measured in absolute ratio but in terms of their relative abundance to a standard. The relative abundance of the HD 16 O molecule is called the relative abundance of deuterium (δ 2 H), and the close lot of H 2 18 O is called the δO 18 . The relative mass of δ 18 O and δ 2 H in water molecules is measured relative to an international standard SMOW (Standard Mean Ocean Water).…”

“…Groundwater genesis can be seen from the composition of groundwater, and the processes occur when passing through aquifer media [9]. Research on hydrochemical and stable isotopes in hydrogeological systems at Bandung-Soreang and Batujajar Groundwater Basin has been widely carried out by several researchers [6,[11][12][13][14][15][16][17]. Previous isotope research for groundwater recharge in the Bandung Basin has been carried out based on groundwater type.…”