Assessment of groundwater suitability for irrigation in coastal-arid zone (Tunisian SE) using Analytic Hierarchy Process (AHP), GIS tools and water quality index

Abstract

In southern Tunisia especially in Gabes region, Irrigated agriculture is the major economic sector. The intensive exploitation of groundwater have been gradually rising, leading the water quality to deteriorate. To ensure sustainable development and preserve water, soil and land cover resources, a careful estimation of the irrigation water quality, which influence on the regional agriculture activities. The objective of this study is to investigate the irrigation water suitability based on hydrogeological; hydrochemical and analytic hierarchy approach (AHP) and water quality index (WQI). Results highlighted that TDS of the groundwater ranged from 0.4 to 7 g/L. The most abundant chemical species in the water were Ca2+, Cl−, SO42−, and Na+, with mean concertation of 460mg/l, 1320 mg/l, 1450 mg/l and 1200mg/L, respectively. The largest amounts were discovered along the shoreline and in deep aquifers embedded in cretaceous sediments. AHP has used as multicriteria decision analysis, to weighting groundwater quality criteria, and groundwater suitability for irrigation has been mapped. Based on the Quality index “WQI” the water samples are categorized into three types: excellent, acceptable, and worthless. A 45% of sampled water is not suitable for irrigation use. However, groundwater quality is increasingly poor towards the coastal areas and north of the study area. This study concluded that the method adopted in assessing the groundwater quality in arid coastal areas led to important results and could be helpful scholar to improve their research especially in similar areas. It can also assist decision makers in taking proactive solutions to protect and preserve groundwater resources from pollution risks.