Identification of Recharge Controls For Groundwater Aquifer System By Stable Water Isotopes

Abstract

A decrease in groundwater level, especially shallow groundwater, occurred in the residential areas, and Padjadjaran University of Jatinangor part of Manglayang slope, a volcanic region at West Java Indonesia. This is due to an imbalance between groundwater input and extraction. This research aims to compile data on physical characteristics of rock lithology containing groundwater, and identifying various layers of groundwater carriers. Groundwater samples were taken in the aquifer system at the study area of the Manglayang volcanic region, and analyses using the composition diagram method and chemical analysis were conducted. The old volcanic deposit was found based on geological mapping, hydrogeology, electrical sounding measure, and boring in the area at the distal and media regime. The tuff deposit with pale soil, young deposit product is dominant in the area where there are lava and lava dome that reached the peak. There are also three types of lava, which is basalt augite, basalt, and andesite. Springwater was found at the 650 – 800 mdpl elevation. It has the facies Ca, Mg HCO₃ (Calcium, Magnesium bicarbonate), and facies Mg HCO₃ (Magnesium bicarbonate). The area has a local groundwater flow system above the elevation of 900 MSL and an intermediate groundwater flow system below elevation 900 MSL. The study found water catchment area is located in two places, which are zone in the elevation 900 to 1100 m with local flow patterns and 1379 m to 1697 m   system intermediate. From these results, a zoning map can be developed based on the distribution of rocks and the sequences of rock formation. The study can also be utilized to determine the conservation zones' location based on the forms of delivery from each layer of rock.