The intensification of agriculture as farming communities grew in size did not always produce a successful and sustainable economic base. At Ras an-Numayra on the Dead Sea Plain, a small farming community of the late fourth millennium BC developed a specialised plant economy dependent on cereals, grapes and flax. Irrigation in this arid environment led to increased soil salinity while recurrent cultivation of flax may have introduced the fungal pathogen responsible for flax wilt. Faced with declining yields, the farmers may have further intensified their irrigation and cultivation schedules, only to exacerbate the underlying problems. Thus specialised crop production increased both agricultural risk and vulnerability to catastrophe, and Ras an-Numayra, unlike other sites in the region, was abandoned after a relatively short occupation.

Hydrogeological research in coastal areas has gained considerable attention over the last decades due to increasing stresses on fresh groundwater resources. Fundamental groundwater flow and solute transport analyses remain essential for a concise understanding of the governing processes that lead to salinisation of fresh groundwater resources. However, the challenge of modern research is the application and quantification of these processes in real world cases. In this context, deltaic areas are amongst the most difficult study areas as they often have a complex groundwater salinity distribution. The Wadden Sea area in the northern part of the Netherlands is an example of such an area.

We quantified salt water intrusion and salinisation of groundwater flow systems in two representative case studies in the Wadden Sea area, using the density dependent groundwater flow and transport code M0CDENS3D. The results indicate that sea-level rise and autonomous processes will cause severe salinisation in the future, especially in the low polder areas close to the sea. In addition, we show that enhanced land subsidence due to salt exploitation accelerates this process. Salinisation can be mitigated to some extent by raising surface water levels in polders and by creating saline groundwater collection areas that maintain a low controlled water level.