Groundwater Vulnerability to Seawater Intrusion in Parangtritis Beach, Yogyakarta Special Province, Indonesia
Faris Rizqi Imaduddin (1,3), Wahyu Wilopo(2*), Dewi Sekar Harum(2)

(1) Student Master of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta, 55281
(2) Department of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta, 55281
(3) Ministry of Public Works and Housing, Jakarta, 12110

Author Emails
*Corresponding author: wilopo_w[at]ugm.ac.id

Abstract

The consequences of increased tourism, population, and agricultural activities on groundwater exploration are concerning. The tourism industry in the Parangtritis Tourism Area has been growing. This growth has led to an increase in the number of hotels and tourists. The expanding population and the need for groundwater in agriculture have also contributed to a reduction in the potential groundwater content. Overusing groundwater can lead to various problems or negative impacts on groundwater resources, such as declining water tables and decreased water quality due to seawater intrusion. The effect of seawater intrusion on coastal areas is not to be taken lightly. It can hinder economic progress, endanger local culture, and contaminate groundwater sources. This study is of utmost importance as it aims to identify geological and hydrogeological conditions and pinpoint areas that are at risk of seawater intrusion in the study area. Surface geological conditions are observed, hydrogeology is mapped, and the GALDIT method assesses vulnerability to seawater intrusion in the study area. The results revealed a diverse lithology in the study area, including fine sand, coarse sand, sandy clay, floatstone, wackestone, andesite, andesite breccia. Based on the observations of 80 dug wells or boreholes, it was found that groundwater use in the study area was limited to an unconfined aquifer with a thickness reaching 101 meters. The results of the GALDIT index vulnerability show that the Parangtritis tourism area has a moderate to very high vulnerability class index to seawater intrusion. The area with very high vulnerability is primarily concentrated in coastal areas where extensive groundwater use activities cover 4,04% of the total study area. Additionally, high vulnerability levels cover 11,23% of the total research area, characterized by high hydraulic conductivity values in aquifers and dominated by settlements and agriculture in terms of land use.

Keywords: GALDIT, Seawater Intrusion, Parangtritis, Groundwater

Topic: Hydrology, hydrogeology, and geology engineering