An integrated multi-techniques approach for hydrogeochemical evaluation of ion exchange processes and identification of water types based on statistical analysis: Application to the Gaza coastal aquifer, Gaza Strip, Palestine

Abstract

Several approaches for ion exchange process (IEP) evaluation and water type identification have widely been developed during the last several decades. However, a lack of clear methodology to characterise IEP and water type remains a problem. In this paper, a novel hybrid approach is proposed to understand this deficiency, determine IEP accurately, identify hydrogeochemical facies precisely that characterise each hydrogeochemical signature of aquifer salinization and freshening, discriminate between humid and arid areas and investigate Ca2+/Mg2+ enrichment processes which may be accompanied with IEP and would have not explained using other conventional methods. This new method, termed IEP-SF-HA-WT, combines three techniques: hierarchical cluster analysis “HCA”, new hydrochemical analysis, and correlation analysis. It is applied on ten physicochemical variables for 214 municipal wells belonging to Gaza coastal aquifer system, Gaza Strip, Palestine to test its reliability and imputation ability.The results demonstrate that the new hybrid method performs well in discrimination between areas of reverse and direct IEP. It shows the dominance of IEP and the wide impact of reverse IEP as a result of the wide -ranging influence of seawater intrusion, saltwater up-coning and sewage inputs. .Similarly, it illuminates the impact of direct IEP and carbonate dissolution on the groundwater of the northern area. It reveals the predominance of Na–Cl (65.4%), Ca/Mg–HCO3/NO3 (15.9%), Na–HCO3 (8.4%), Ca/Mg–Cl (8%) and the existence of a unique Ca/Mg–NO3/HCO3 type (3.3%) in the northern area as a result of the influence of fertilizer inputs in this area. Moreover, it elucidates the humidity of the northern area due to rainfall recharge, irrigation return flow, and partially treated sewage infiltration. Therefore, the implication of this multi-beneficial approach can be widely used for precise and detailed hydrogeochemical evaluation of groundwater in the Gaza coastal aquifer system as well as for other similar aquifer systems elsewhere around the world.