A third of the world’s population live in coastal areas. Lower river discharges and sea level rise make these areas particularly vulnerable to salinisation. The problem will get worse in the future as a result of changes in the climate and weather. Salt will penetrate further and further inland via rivers and groundwater, threatening our food security and biodiversity. The United Nations has therefore launched a campaign to make policymakers and decision-makers aware of this risk.
Salinisation has major long-term effects. The ecosystem changes, drinking water becomes scarce, and agriculture is no longer possible. More and more businesses and people leave the area. With our knowledge of the water and subsurface system, we can predict these effects and help to prevent them.
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Encroaching seawater due to sea level rise, flooding or saline seepage can make the important stocks of fresh groundwater increasingly brackish. And where land has been reclaimed, much of the soil and groundwater can also be saline. Freshwater stocks will be depleted faster here. Particularly in areas where there are no other sources of fresh surface water, this can lead, for example, to agriculture being impossible in the long term. Where there are rivers in an area, then freshwater discharge is likely to decrease in the future. In both cases, the sustainable use of fresh groundwater is becoming increasingly important. It does help to use fresh groundwater sparingly and only when high-quality water is needed. Other functions may be able to use brackish water (in some cases after desalinisation). Infiltrating clean rainwater is another solution, particularly if there are periods with enough precipitation. Changes in land use can also allow rainwater to sink into the ground. We are studying these solutions at home and abroad, and providing the information needed to enable these transitions.
Fresh and salt water meet in estuaries: the ecology and spatial planning adapted accordingly. But sea-level rise, storm surges, water shortages and falling river discharges allow the salt water to penetrate further and further inland. That has an adverse effect on drinking water supplies, agriculture and nature. Salinisation can be prevented with a combination of water management and engineering structures such as dams and locks. That infrastructure has direct economic consequences such as longer waiting times at locks, and also long-term consequences for the ecology. Tackling salinisation with water management costs fresh water. If dry periods get longer, users will have to adapt to match their water demand to supplies.
With our knowledge of the water and soil system, Deltares can answer questions from water managers about how to tackle the salinisation of surface water. For example, in the case of flushing with fresh water, how much flushing is needed, and how should the water be brought in to meet the demand for water? What impact will diverting that water have on other water users and the ecosystem? These are short- and long-term questions. Because we have a range of experts in our organisation, we can provide integrated answers with the broad scope required. We think sustainable solutions are important, as in the case of wetland restoration to reduce salt levels.
Hydraulic structures such as dams, locks and weirs play an important role in water management. Engineering structures can allow salt into the system. For example, sea locks allow large amounts of salt water to enter a canal along with a ship. Innovations to prevent this can be tested in our lock facility. The systems for the sea locks in IJmuiden and Terneuzen were tested here.
But weirs, sills and dams can also be used to keep out salt water. Our computer models help to forecast the effects of these measures.
