Combination of geostatistics and drastic model in assessing groundwater vulnerability to nitrate contamination

Abstract

Due to a rapid development of industrial and population growth in Malaysia, the demand for water has increased tremendously. This has caused the shortage of water supply and the new water sources have to be identified. Groundwater is one of the alternative ways. In the north eastern state of Kelantan, many people rely on the groundwater as their water resource. However, due to the uncontrolled development and human activities, groundwater is subjected to contamination by nitrate geochemical. This research is intended to assess this vulnerability by using a combination of geostatistical approach and a commonly applied model called DRASTIC (Depth, Recharge, Aquifer, Soil, Topography, Influence of the vadose zone and Conductivity). With Geographical Information System (GIS), each method is applied to produce the groundwater vulnerability maps. In geostatistical approach, the probability map is produced by using Kriging interpolation in order to predict a specific vulnerability of contamination risk. Meanwhile, the Weighted Overlay technique has been applied in the DRASTIC model to produce a vulnerability index map that shows the levels of vulnerability of the study area. The resultant maps are further combined to study the contamination pattern, in which case the nitrate concentration is taken as example. Then, the ground truthing of nitrate concentration tests are carried out to validate the reliability of the resultant maps. As a result, the pattern shows a positive relationship between the probabilility map and vulnerability index map. This indicates that the combination of these two methods has given a significant finding in assessing groundwater vulnerability to contamination