Stream valleys as wetlands

Wetlands as a component of discharge areas have been reduced to mere stream channels in the larger part of The Netherlands. The original shape and condition are described with help of data from the past and from some small remnants. The typical Dutch type of running water is the lowland stream, fed predominantly by rain and groundwater. Its nature is nutrient-poor in the upper course and eutrophying gradually downstream. The chemical composition of streamwater, the vegetation in the floodplain and the flora and fauna in the stream reflect this gradient. Some attention is paid to the amount and cycling of minerals and nutrients. It is shown that the input of nutrients is not a limiting factor for primary production, but under natural conditions light is limiting. Threats to stream wetlands are the composition of the precipitation, fertilization of the discharge area and water management measures such as draining and canalization. As a result perspectives for a qualitative recovery are unfavourable. Restoration of the shape of streams, however, is more prospective and several restoration programs are in execution.