Methodologies of groundwater vulnerability assessment and spatial analysis of groundwater quality : comparison of methods under urbanization stress -

Abstract

This study is divided into two parts. The first part is titled “Assessment of methodologies for groundwater vulnerability to seawater intrusion along coastal and urban Areas”. It evaluates the performance of DRASTIC and EPIK, two commonly used groundwater vulnerability assessment models, using groundwater quality data by establishing water quality categories and cross-checking field measurements to that of simulated vulnerability levels. The results of this study show that the vulnerability levels in outcropping Karstic formations in Mount Lebanon and Anti Lebanon to be of high vulnerability with both used models. The extent of accuracy of the evaluation criteria for the water vulnerability assessment was limited by the accuracy of experimental measurements, the choice of analyzed parameters and model assumptions. The second Part is titled “Variation of the Spatial distribution of Groundwater Quality in Karstic aquifers under urbanization stress”. It evaluates the ability of different spatial interpolation methods to produce accurate groundwater quality maps using interpolation schemes. This study uses three different interpolation methods (IDW, Kriging, and Co-Kriging) with combinations of different semivariogram models and data transformation, producing 380 different combinations-scenarios. The study evaluated the accuracy of these scenarios using three validation approaches, (1) statistical indicators by Leave-One-Out cross validation method; (2) matching the results of measured and interpolated values based on established water quality categories, and (3) evaluating the accuracy relying on the results of groundwater vulnerability assessment (GVA). The results varied between cities and to the values of the measured parameters, and it also showed the different function of the two methods, which could not be used interchangeably.