Increasing water demand, climate change and rising relative sea-levels all contribute to salinisation in coastal areas, leading to shortages of freshwater for drinking water, agriculture, industry, nature and (urban) water management. This forces us more and more to turn to expensive alternative solutions for freshwater supply, such as desalination (seawater) and the transport of scarce freshwater over long distances. Moreover flooding is also a growing concern.
Because of this set of problems, the business climate in coastal areas is becoming less and less attractive. The use of freshwater surpluses after their temporary storage in the subsurface, and the use of upwelling brackish water, are currently still seen as small-scale initiatives that can only be applied by end-users at a local level. And the linking opportunities for water management are still hardly taken advantage of. This is why, in 2016, COASTAR (COastal Aquifer STorage and Recovery) was created: a framework of action for a robust freshwater supply through the large-scale, organised use of the subsurface for the storage and supply of freshwater, with benefits for the management of the entire water system.
The COASTAR concept was systematically and critically researched and developed within the TKI project on the basis of three concrete cases: Waterbank Westland (dry feet and sufficient irrigation water), brackish water abstraction Polder de Noordplas (source for drinking water and remedy against salinisation of surface water), and brackish water abstraction Solleveld (extension of freshwater lens and alternative freshwater source). The case studies focussed on the subsurface and the technology, but also on costs and benefits, financing and organisation.
The final outcome of the TKI COASTAR project is a roadmap for a COASTAR implementation programme in the region of The Hague-Westland-Rotterdam. The roadmap also provides a model for other areas in the Netherlands and for coastal areas worldwide. During the COASTAR conference on 18 May 2018, the Water Authorities, water utilities, knowledge institutes, Arcadis, the Province of South Holland, and the greenhouse horticulture sector committed themselves to the further development of COASTAR. The first step involves setting up a knowledge programme for COASTAR with the aim of further elaborating the concepts and testing them out in practice. The ultimate objective – as part of the Delta Programme Freshwater Plan – is to provide the basis in 2020 for well-founded decisions for future, large-scale implementations.