Policies & regulation for saline intrusion
In the Netherlands, management of saline intrusion is a shared responsibility (PDF) of the Ministry of Infrastructure and Water Management and water boards. Nationally, measures to manage saline intrusion are outlined in the Delta Programme and National Water Programme 2022-2027 (PDF). The implementation of these measures often lies with water boards and can differ strongly per region. Moreover, regulations on saline intrusion are closely linked to the management of sea level rise, drought, subsidence, and heat.
Managing saline intrusion
Besides measures that are specifically aimed at minimising the impacts of saline intrusion on sectors, more broader measures can be implemented. In the Dutch estuary, river water plays a key role (PDF) in managing salinisation. One method is by creating counterpressure, where river discharge pushes back against intruding sea water, preventing saline intrusion. Additional measures to manage (PDF) saline intrusion include optimizing the lock regimes, and installing salt traps or bubble screens.
To manage saline intrusion into polders via groundwater, available freshwater is used to flush away saltwater (PDF). Currently, the total flushing demand (PDF) of the Dutch polders is 20 cubic metres per second (m3/s). With projections of rising sea levels, this demand can increase substantially: to around 50 m3/s with 0.5 metres of sea level rise, 100 m3/s with 1 metre, and as much as 350 m3/s with 3 metres.
It is important to note that the freshwater used to flush away saltwater cannot be used for other purposes. This can lead to challenges, especially in combination with drought and heatwaves. In the future, projections of higher drought risk (PDF), more frequent and longer heatwaves, and sea level rise can further limit freshwater availability to manage saline intrusion. Moreover, water demand Is likely to increase in the future (PDF) due to population growth and urbanisation. With limited freshwater available, saline intrusion is difficult to manage and its impacts will likely increase.
To manage the projected future sea level rise and associated increase in saline intrusion, the Dutch government outlines scenarios for future adaptation in the Freshwater Delta Plan 2022-2027 and the Sea Level Rise Knowledge Programme. These strategies focus on exploiting opportunities to retain and store freshwater, efficient water level management, and development of knowledge and optimisation solutions to ensure effective long-term water management.
Sectoral policies & regulations
Agricultural measures
Potential adaptation options are being studied to manage salt intrusion in agricultural production. In the Netherlands, saline pilot farms are used to test how existing, commonly cultivated crops respond to increased chloride concentrations in water. These trials focus on determining tolerance levels, duration of exposure, and the conditions under which crops can continue to grow.
Drinking water
The drinking water sector (PDF) explores alternative water sources for drinking water production, such as brackish groundwater. Brackish groundwater can be desalinised to make it suitable for consumption. This process is technically feasible, but it has clear downsides. It requires large amounts of energy, leads to water losses, and produces a residual waste stream in the form of concentrated salt load that also needs to be managed. Some utilities are also exploring seawater desalination which likewise also involves high energy use and residual waste products.
Other strategies explored by the drinking water sector (PDF) include new abstraction locations and optimisations in operational management. Measures include creating freshwater buffers for dry periods, both above ground in surface water reservoirs or in the subsurface via managed aquifer recharge, although permits for this may be time-consuming.
Industrial measures
Many industrial cooling processes already make use of saline water. However, installations that currently depend on freshwater are vulnerable to salt intrusion. One possible measure is to replace freshwater-dependent installations with systems that can operate using saline water. This approach requires extensive technical adaptations and investment. Another option is to desalinate saline water for industrial use. While effective, desalination is energy-intensive and therefore increases operational costs.
Nature
Water and nature managers take targeted measures in several areas to partially restore natural fresh–salt transitions. These measures are often aimed at improving ecological functioning rather than eliminating salinity altogether. A key focus is on enhancing migration opportunities for migratory fish species. This is achieved, for example, through the construction of fish passages that allow species to move between freshwater and saline environments.
