Assessing the Vulnerability of Groundwater to Pollution Using DRASTIC and VLDA Modelsin Halabja Saidsadiq Basin, NE, Iraq

Abstract

Abstract:Groundwater plays important roles as one of the essential source of water supplies of the studied area. Consequently, it needs to be prevented from contamination. In this study, two methods have been examined, namely DRASTIC (depth to groundwater, net recharge, aquifer media, soil map, topography, impact of vadose zone and hydraulic conductivity) and VLDA (vadose zone lithology, land use patterns, depth to groundwater and aquifer media) to model a map of groundwater vulnerability for contamination of the basin. The standard DRASTIC vulnerability maps classified the basin of four vulnerability index zones: very low (34%), low (13%), moderate (48%) and high (5%). While the VLDA model classified the area into four categories as well: low (2%), moderate (44%), high(53%) and very high (1%). The results demonstrate that there is a significant dissimilarity in the rate of vulnerability. Validation of the constructed maps is required to confirm the validity of the theoretical sympathetic of current hydrogeological conditions. In this study, nitrate concentration analysis was selected as a contamination indicator to validate the result. The nitrate concentration of two different seasons (dry and wet) was analyzed from (30) watering wells, considerable variations in nitrate concentration from dry to wet seasons had been noted. Consequently, it points toward that groundwater in the HSB (Halabja Saidsadiq Basin) is capable to receive the contaminant due to suitability of overlies strata in terms of geological and hydrogeological conditions. Based on this confirmation, the result exemplifies that the degree and distribution of vulnerability level acquired using VLDA model is more sensible than that attained from the standard DRASTIC method .In addition, the DRASTIC models need to be modified based on the land use pattern, which clarifies the role of human activity on the vulnerability system.

Assessment of Groundwater Vulnerability to Pollution Using VLDA and COP Models in Halabja Saidsadiq Basin, Iraq

“…To assess the groundwater vulnerability, the new corresponding weights in HSB were proposed using sensitivity analysis method [6]. Based on the result of sensitivity analysis, the proposed weights used for VLDA model measured as 8.2, 4.8, 5.2 and 4.8, and after normalization, the weight is 0.357, 0.209, 0.226 and 0.209, respectively [10].…”