LONG TERM PERPECTIVES FOR WATER MANAGEMENT IN DRAINED PEATLANDS; EXPERIENCES IN PEAT-POLDER SYSTEMS IN THE NETHERLANDS

摘要

In the Netherlands, many peatlands were drained since the 16~(th) -17~(th) century and used for peat extraction and dairy farming. Since then the rate of land subsidence rates varies between 3 mm - 2 cm per year, depending on local conditions. This requires regular adaptation of water management and hydraulic infrastructure. Different stages of water system (or polder) development can be distinguished. Awareness of the actual stage of development in a drained peatland site enables to predict the next stage in its development. This recognition allows a better decision making on required adaptation strategies such as continuation of the actual agricultural land use, adaptations in agricultural zoning (see Rahmadi et ah, 2011) or transformation into e.g. restored wetlands (Schouwenaars, 2011). Based upon historical analyses of water management in the peatland polder systems in the Netherlands, trends in development are described. A typology is presented which may serve to identify the actual stage of development of peatlands after drainage. Drainage will continuously require adaptation measures and creates an increasing dependency on human interventions to reduce risks for flooding. The technical infrastructure becomes more complex and fragmented and the costs for water management increase gradually. The presented typology allows a better understanding on the actual stage of development of a drained peatland at a given site. It also gives a tool to predict the future stages in development.