Identifying spring recharge areas using stable isotope and geophysical methods: A case study of the Ababi Mountain Region, Bali, Indonesia

Abstract

Identifying spring recharge areas is essential for water resource conservation. This study aimed to determine the recharge area of Ababi Spring, Indonesia, using stable isotope, vertical electrical sounding (VES), and audio magnetotelluric (AMT) methods. Rainwater and spring water were sampled at 211–978 m locations above sea level. Hydrogen and oxygen isotope ratios revealed that spring water originated from a higher elevation source. The relationship between oxygen isotope composition and elevation was used to estimate the spring recharge elevation as 2,118-2,137 m above sea level. VES and AMT methods generated geoelectrical profiles depicting subsurface water flow from recharge to discharge zones, confirming the elevated recharge area. Additional isotope analysis of 1,514 m altitude rainwater supported the prediction model. This multidisciplinary approach combines hydrochemical and geophysical techniques to enable more reliable delineation of groundwater recharge areas than single methods. Determining the Ababi Spring recharge zone facilitates targeted conservation efforts for this vital water resource. Further work should investigate geochemical evolution along subsurface flow paths.