The transfer of agricultural land into tidal salt marches will affect the groundwater system, like head levels, infiltration / seepage fluxes, and salinity distribution for both the tidal area and the adjacent area.
The restoration of tidal areas will cause:
- an increase of the average water level since the water level will change from polder water level (usually 1 to 3 m below sea level) to average sea level;
- increase of hydraulic heads in the subsoil;
- an increase of the infiltration of salt water. Effects will propagate outside the tidal area via the hydraulic heads in the aquifer(s).
Concerning the groundwater system in and outside these new tidal areas, the following three research questions were formulated:
- What is the effect of the new tidal area on the groundwater system in the adjacent agricultural area and is the implemented mitigation measure SeepCat compensating the effects properly?
- What is the tidal propagation in the aquifer below the tidal area?
- What is the effect of the tides on the salinity of soil and groundwater in the tidal area?
Data and methods
The data and the methods that have been used for the evaluation of the groundwater processes are all described in the Perkpolder progress reports:
- Perkpolder tidal restauration, one year after realisation, draft progress report, Boersema, M., J. van der werf, P. de Louw, T. Ysebaert, T. Bouma, Centre of expertise Delta Technology, 27 november 2016.