Impact will differ from one area to the next
Water supply from rivers is unavailable in many elevated parts of the Netherlands. Consumers fully depend on precipitation and groundwater. Consequently, such areas are more prone to water shortages, resulting in drought stress. Drought stress occurs when the soil dehydrates to a point that inhibits plant evaporation. Drought stress may cause part of the plant or the entire plant to die. In agriculture, drought stress can reduce crop yield. Drought-intolerant crops include, e.g., vegetables, potatoes, and beetroots. Drought stress also has a severe impact on the natural environment: local extinction of species, a higher risk of wildfire, pools and brooks running dry. Furthermore, a severely dehydrated soil will hamper water infiltration. During torrential rain, this may lead to waterlogging.
Drought can add to soil subsidence. As a result of less water in the soil, the soil will compact. This process is referred to as “shrinkage”. Once more rain starts to fall, part of the soil may expand again, but a part will remain compacted. The latter is referred to as “settling”. The compaction will cause the soil to subside. An additional process is peat oxidation. When groundwater levels fall, peat will be exposed to oxygen. Peat that comes into contact with oxygen will decay and disappear. As a result, the soil will subside even more. Furthermore, this process will release a great deal of greenhouse gases. Soil subsidence due to drought may also cause subsidence and cracks in buildings, roads, and dykes. In addition, drought can cause problems in wooden foundations. Many older houses in clay and peat areas are founded on wooden poles. These poles must remain submerged in water to prevent rotting and mould through exposure to oxygen. Drought may result in such foundations running dry. This will cause pole rot and subsidence. The Foundations Risk Maps map narrative of the Climate Impact Atlas shows the areas that are at risk of foundation damage.
Low-lying parts of the Netherlands can be supplied with water from rivers and other freshwater sources, such as Lake IJsselmeer. However, this supply also has its limitations. This is one of the conclusions from the stress test conducted in the IJsselmeer region. In dry summers, water requirements will increase, whilst river discharges will be low. Water shortages will cause an additional problem in the coastal provinces: salinisation. Salinisation – the accumulation of salts in groundwater and surface water – occurs when saline sea water travels further inland in times of drought and low river discharges. Salinisation poses problems for various functions that depend on fresh water, such as the drinking water supply, but also for bulb growing, agricultural areas, and the industry. In addition, fish and plant species habitats will shift, whilst salinisation can also be harmful to certain types of nature. Salinisation also occurs in the major rivers, such as the Rhine and the Meuse. Consequently, the problem extends beyond the coastal areas.
Water shortages and salinisation are increasing in the low-lying Netherlands
In the low-lying Netherlands, it is becoming harder and harder to keep enough fresh water available during dry summers. Climate change means less water flows through the rivers in summer. At the same time, we need more fresh water, for example to combat salinisation. The Sea Level Rise Knowledge Programme (Kennisprogramma Zeespiegelstijging) shows that sea level rise makes this problem worse. From about 0,5 metres of sea level rise, a dry summer will require twice as much river water to keep salt-sensitive polders as fresh as they are now. That water can then not be used elsewhere. We can limit salinisation with measures, but we cannot prevent it everywhere. That is why, in some places, we must learn to live with saltier water.