Research on salinisation processes in the province of Zeeland
The fresh water resources in the groundwater system of the coastal province of Zeeland are at present jeopardized by various causes. Floods, droughts, eutrophication and salinisation of the ground and surface waters are some pressing topics. Moreover, sea level rise and climate change threaten the groundwater system even more. Water management in the province should anticipate on these changes. The province has initiated a study to get a better insight in the salinisation processes in the top system. The main goal is to analyse what measurements are effective in mitigating the salinisation of the water system. Special attention is given to the so-called rainwater lenses in agriculture plots. Agricultural crops depend on these shallow vulnerable water systems which float upon brackish groundwater and vary over the season in thickness.
Impact of the 26-12-2004 Sumatra Tsunami on freshwater resources on islands.
The Sumatra Tsunami has affected many fresh groundwater resources in the low-lying coastal zones in the north-eastern part of the Indian Ocean (Gulf of Bengal). Figure 3 gives a sketch of possible impacts on freshwater resources in coastal aquifers. Questions can be asked about how serious the impacts of the floods on fresh groundwater resources are; about how harmful they are from a drinking water point of view; and about how long it takes before the contaminated freshwater resources are clean again for consumption.
By analyzing several possible situations in the subsoil that may have occurred, we have tried to describe the relevant processes of salt water intrusion in the coastal aquifers by means of conceptual models (figure 4b and 4c). The main hypothesis is that sea water that flooded the land may have intruded into the subsoil, causing density driven flow through salt water fingers (figure 5).
Factors of importance are:
• Disturbance and reduction of the freshwater lens by the subsurface pressure wave.
• Local geometry of the inundated areas.
• Duration of sea water standing on the land.
• Leaching of salts from the soil.
• Local weather conditions during the coming months.
