Soil subsidence
In many parts of the Netherlands, there is a slow, natural fall in ground level. This subsidence has various causes. In the past, natural subsidence was compensated by clay and sand deposited during the flooding of the major rivers. This was no longer possible, however, after dikes were built along the rivers. Another cause of soil subsidence is the commercial extraction of peat and clay. In the west of the Netherlands, these ground types naturally contain a lot of groundwater, and when that water is drained off, the soil subsides. In the Netherlands, groundwater has been drained off and pumped away for hundreds of years in order to use the land for agriculture.
A third cause of the soil subsidence is that peat is liable to oxidise when it lies above the water table. This is an important cause of subsidence in the peat meadows of the western Netherlands. Large-scale agriculture and the spread of cities have accelerated these processes of subsidence and oxidation.
Salinization of water resources
Salinisation of water resources occurs when (fresh) rain water infiltrates in relatively high areas. The (salt) water that was already present in the soil is then forced to move sideway to relatively lower lying areas, where it can reach the surface water. The surface water resources become unsuited for agricultural purposes, unless fresh water is added.
Dutch expertise abroad
In the Netherlands, the problems of land subsidence and salinization are interlinked to great extent . Dutch parties aim at sustainable management of coastal areas and have gained much experience that is relevant to similar areas abroad. Expertise also includes salinization of aquifers, use of brackish water as alternative resource and the use and management of subsiding land along rivers.
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Sources: Water in the Netherlands, 2004-2005, Facts and figures. Ministry of Transport, Public Works and Water Management, Nederland leeft met water, Rijkswaterstaat RIZA