Two waterboards are responsible for the water quality and quantity within a polder area of 20,000 ha, called Alblasserwaard and Vijfheerenlanden, in the low-lying part of the Netherlands. On average, the polder area lays 1m below sea level and water is pumped out of this polder area into the surrounding river system. In the summertime, water from the rivers is used to keep water levels up to the required levels (in the polder areas).
Branches of the river Rhine are the north and south border of the Alblasserwaard and Vijfheerenlanden. Dikes protect the area from river flooding. The climate changes are expected to lead to sea level rise, more intensive rainfall and increasing peak river discharges in the winter period and decreasing river discharges in summer time.
Analyses show that the climate change in combination with the land subsidence of the peat soils in the polder areas will have a great impact on the drainage capacity. Draining of excess water becomes problematic due to lower land level and higher water levels on the river system on which the excess water has to be pumped, which in turn implies increased head.
The traditional way to solve these problems is to enlarge the canals (discharge capacity) and to increase the pumping capacity but this will lead to enormous costs (considering construction of additional pumping capacity and enlarging canals.
An alternative approach is to create more space in which water can be temporally stored during periods with excess rainfall. However there is a scarcity of space in the densely populated Netherlands. Instead of competing with other interests for the limited remaining space in the area, a possible solution lies with integrating with the other interests: multifunctional use of the limited space.
A process was set up, in which all parties claiming space (agriculture, recreation, town planning, etc.) in the area were invited to discuss the water issues, focusing on the extra buffer space needed for the water system. In several sessions, it was discussed, under which conditions water storage could be combined with other land use: examples included storing water in recreational lakes, temporally storage of water on meadows, etc.
The result of this process is a framework plan, indicating the extra room needed for water and giving leads for multifunctional use. An open planning process was introduced, in which all parties claiming space could get acquainted with the future water problems on the one hand, and on the other hand could give their views on how to solve them through multifunctional use of the limited space.
In the coming years, this framework plan will be worked out in detailed plans and implemented. The financial arrangements will be worked out for each plan, clear is that the involved parties (including the water manager) have to participate.
Until now, water boards did not play an active role in spatial planning. Spatial plans were made and the waterboards were asked to adapt the water system according to the needs of the plan. An open planning process allows water managers to play an active role in the spatial planning in order to get the extra space needed for the water system.
The practical outcomes will be assessed after full implementation of the project.
Importance of the case for IWRM
This case shows that the additional water needs can be integrated in the spatial planning through an open planning process, which, if implemented in a correct way, will provide a sound basis for solving the future impacts of climatic change.
It shows that the problems related to the expected climatologically changes inwater systems can be solved in a sustainable way, not only depending on costlytechnical solutions.
Photo credit: Bert Heymans