Euro-limpacs Deliverables

ABSTRACT - DELIVERABLE 99

Report on the first year of sampling lowland streams

Climate change will, amongst others, result in a increase in precipitation. This increase will be most significant in winter. Not only the overall precipitation will go up also the intensity of severe rain showers will increase in both winter and within dry summer periods. Consequently the discharge pattern in lowland streams will become more irregular with floods and dry periods. To study the effects of these expected disturbances in discharge we took a reverse example.

The stream Springendal is situated on the glacier hill ridge of Ootmarsum (province of Overijssel, The Netherlands). A few decades ago, the stream still was in a near natural condition. From the second half of the former century on, land use intensified in the infiltration areas of the upper catchment. This resulted in a disturbed hydrology and eutrophication. Especially, the disturbed hydrology impoverished the stream community and caused the stream to cut itself into the landscape causing a drying and acidification of the stream valley. Inundations with nutrient rich stream water caused nearby stream valley areas to become more eutrophic. This pre−restoration phase is comparable with the situation in about 50 years due to climate change.
In the late nineties several restoration measures were undertaken. These measures aimed to reduce both discharge dynamics and eutrophication. The post−restoration phase is taken as the current situation before climate change will have its impact.

To evaluated the effects of restoration, two approaches were initiated:
i) Large scale measurements of hydrology and morphology took place over the whole stream length (large spatial scale of kilometres) in 1995 and 2004 (large time span of years).
ii) Small scale measurements of hydrology and morphology took place at six sections in the catchment (small spatial scale of metres) over three periods of four to five weeks (small time span of days).

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