Estimation of Groundwater Vulnerability to Pollution Based on DRASTIC and SI Methods: A Case Study of the Irrigated Area of Tadla Plain, Oum Errabia Basin, Morocco

Abstract

The aims of this study are the vulnerability assessment of an aquifer in a semi-arid environment, perimeter irrigated of Tadla plain. The vulnerability determined by two different methods: the DRASTIC and the SI methods. In the Drastic method, seven parameters of the model used to calculate the intrinsic vulnerability index and the vulnerability specific. The DRASTIC method gives two classes of vulnerability to pollution; the class of "low vulnerability", which is the most dominant as it covers a large area of 78.5%, and the "moderate" vulnerability with 21.5% of occupation. The SI method which relates to human activities, gives three vulnerability classes: the low vulnerability class, the moderate vulnerability class, which is the most dominant one as it covers almost the entire study area, and the high vulnerability class, with 11.5%, 85.3%, and 3.2% respectively. For the validation of the results obtained by the two methods, we use the concentrations of nitrate. These coincidence rates are satisfactory for both methods used; however, the specific method SI better assesses the vulnerability by nitrates.