Preliminary study of isotope characteristics of groundwater in karst hydrogeology in Pacitan Regency, East Java

Abstract

The Pacitan Karst region is well known to be one of drought area in the Pacitan Regency during the dry season. Consequently, during the dry season, springs from karst system are required as a water source for the daily life. The appearance of these springs are a result and advantage of the karst terrain, which contains potential groundwater resources. The purpose of this study was to investigate the origin and characteristics of spring’s water in the Pacitan karst region based on its isotope concentrations. This research was conducted by collecting groundwater samples from springs, dug wells, bore wells, and rivers in Pacitan Regency and analyzing their 18O and 2H concentrations. Information on the source of groundwater is thought to be necessary for sustainable groundwater protection planning (conservation). According to the results of the investigation, there are four categories of isotope ratio distribution. The pattern of 18O and 2H concentrations in the samples around the Local Meteoric Water Line (LMWL) shows that groundwater originates from the same elevation of the catchment area from where rainwater falls and has the same characteristics as rainwater or meteoric water.