Origin of Groundwater in Kawung Carang Cold Spring, Sumbang District, Banyumas Regency, Central Java

Abstract

The occurrence of several springs around Slamet Volcano raised questions regarding their origin. Many studies have been conducted to understand the origin of hot spring water around Slamet Volcano. Meanwhile, there has not been any research on the origin and hydrogeological system of cold spring water around Slamet Volcano. Kawung Carang Spring is one of cold spring water that occurs on the southern flank of Slamet Volcano. It is situated in a quaternary volcanic deposit of Mt. Slamet formation. Field observation was conducted to identify local geological conditions and hydrogeological systems in the research area. Isotopic analysis was performed to help understand how to delineate the recharge area. This study used a physical-chemical analysis of Kawung Carang cold spring water and the ratio of deuterium (2H) and 18O stable isotopes to interpret its groundwater origin. The results of the analysis informed that the origin of Kawung Carang spring water was local meteoric water. The hydrogeological system was an unconfined aquifer that consisted of a lahar deposit on the top of a volcanic breccia layer. The physical-chemical characteristic of groundwater around the Kawung Carang cold spring shows low electric conductivity (EC) and total dissolved solids (TDS) values. EC and TDS values of groundwater vary from 92 to 253 μS/cm and 46 to 126 mg/L indicating that groundwater has a short time in water-rock interaction process and comes from shallow depth aquifer. Furthermore, the signature of stable isotopes of δ18O and δ2H shows the elevation of the Kawung Carang cold spring recharge area ranges from 386.08 to 441.37 meters above sea level in the northwestern part of the research area.