Improving fresh groundwater supply—problems and solutions

Many coastal regions in the world experience an intensive salt water intrusion in aquifers due to natural and anthropogenic causes. The salinisation of these groundwater systems can lead to a severe deterioration of the quality of existing fresh groundwater resources. In this paper, the characteristics of variable-density groundwater flow and the concept of an interface between fresh and saline groundwater are introduced. Problems associated with these groundwater resources are discussed, such as upconing of saline groundwater caused by excessive overpumping and salt water intrusion caused by global mean sea level rise. Possible human activities to compensate and control the salinisation of coastal aquifers are presented. Most countermeasures appear to be expensive, laborious and should be taken in time. Finally, the effect of lowering piezometric heads on the salinisation of the subsoil is illustrated in a Dutch aquifer system.