Assessment of hydrological processes operating in a multi-layered sedimentary aquifer system in Saudi Arabia using integrated chemical and statistical approach.

Hydrochemical processes have a great influence on the groundwater quality especially in arid regions where groundwater is the single most important source of water supply. The present study was carried out in the Wadi Ad Dawasir region of Saudi Arabia. The objective of this study was to determine the processes influencing the groundwater composition in the region by integrated hydrochemical and statistical assessment. Hydrochemical data from 140 groundwater samples were interpreted using hydrochemical and statistical techniques. Evaporation, mineral dissolution, reverse ion exchange, and chloride/nitrate contamination from irrigation return flows were the main geogenic and anthropogenic sources influencing the groundwater composition. Principal component analysis was carried out to determine the component showing the maximum variability in the data. Two principal components were extracted. The first principal component representing gypsum dissolution and anthropogenic pollution (chloride and nitrate pollution from agricultural farms) was more pronounced in the western part of the study area whereas the second principal component representing silicate weathering process was more dominant in the eastern part. Total dissolved solid was found to be the single most important hydrochemical parameter showing the maximum variation in the analyzed data set. This study demonstrates that the loadings of the individual hydrochemical parameters in the extracted principal component and the component scores of the individual samples for each extracted principal component can be effectively used for determining the hydrochemical processes influencing the groundwater chemistry in an area.