Water quality for different uses in the main groundwater bodies of the Guadalquivir River Watershed, Atlantic Basin, Spain

This work was made to asses the groundwater quality in relation to agricultural uses and/or public supply in the main groundwater bodies (GWB) of the Guadal-quivir River Basin (southern Spain) according to the recommendations of the Water Framework Directive. The study was made for both carbonate and sedimentary-rock/alluvial GWBs of the Basin in order to detect variations in the groundwater quality as a function of the hydrogeological functioning, among others. Groundwater samples were collected from selected and representative wells and drills in each GWB. The results obtained from the analyses of major ions, pH, SC25 and nitrate reveal that the groundwater in carbonate aquifers is suitable for both agricultural and domestic uses according to the FAO classification. The quality of water from sedimentary-rock and alluvial GWBs is medium for agricultural purposes and inappropriate for human supplies in most cases due to excessive content of chloride, sulphate and nitrate. The use of well-known hydrochemical indicators such as SAR, RSC or Gibb's ratio allowed us to predict groundwater quality in the main GWBs of the Guadalquivir watershed. Therefore, this methodology proves to be a useful tool to correctly manage and find strategic water reservoirs in an area that is going to be particularly threatened by climate change in the near future.