Airborne Geophysical Investigation of Groundwater Resources in Northern Sumatra after the Tsunami of 2004

Abstract

The earthquake and the tsunami event on December 26th, 2004, caused not only the loss of life of a huge number of people and the destruction of houses, basic infrastructure and public facilities but also large scale salt-water intrusions and destruction of thousands of shallow water wells in the coastal region of the Province of Nanggroe Aceh Darussalam in northern Sumatra, Indonesia. The supply of a sufficient amount of potable water in all populated areas was complicated as many water pipes were broken by the earthquake and a huge number of dug wells were unusable after the tsunami. Furthermore, many new drillings were not successful in finding potable water due to the lack of information about local hydrogeological conditions. Therefore, the Indonesian and German governments set up a project dedicated to re-install the public life of the people living in the coastal regions of northern Sumatra. The focal point of this project was water assessment along the shorelines of Aceh about nine months after the tsunami. In order to get a fast overview on the remaining freshwater resources and to assist the Indonesian authorities such as the Directorate General for Geology and Mineral Resources (DGGMR), the National Development Planning Agency (BAPPENAS) and the Executive Agency for the Rehabilitation and Reconstruction in Nanggroe Aceh Darussalam Province and Nias Islands (BRR) as well as numerous aid organisations in finding suitable locations for drilling new water wells, it was decided to use airborne geophysics. The helicopterborne surveys including electromagnetics, magnetics and gamma-ray spectrometry were conducted by the airborne group of the German Federal Institute for Geosciences and Natural Resources (BGR) from August to November 2005. As the mineralisation of water correlates with its electrical conductivity and therefore freshwater and salt water can be distinguished in general, it was hoped that electromagnetic data would reveal freshwater resources not destroyed by the tsunami, particularly close to the populated coastal areas. The target areas (Fig. 1) of the German-Indonesian cooperation project HELP ACEH (HELicopter Project ACEH) were the city of Banda Aceh with the district of Aceh Besar on the north coast and the area on the west coast between the towns of Calang and Meulaboh in the district of Aceh Barat (Siemon et al., 2007). In addition to that, Coca-Cola Foundation Indonesia (CCFI) funded a further survey on the north-east coast around the town of Sigli in the district of Aceh Pidie (Steuer et al., 2008).