Interaction between surface and groundwater in the flooding of riparian wetlands: Biebrza wetlands case

The Biebrza Wetlands is located in a marginal-ice valley in north-eastern Poland and covers some 195 000 hectares in area. The most characteristic feature of the Biebrza River is flooding, which appears there almost every year. In the period 1999-2002, investigation of the flooding phenomena was carried out in order to understand the main processes involved in the inundation of the river valley and to combine them with characteristic vegetation patterns. The investigation used Landsat images, a hydrodynamic 1-D model of river and flood plain flow, and chemical analysis of flood waters. It was shown that river water is responsible for inundation of part of the valley only. Other parts of the valley were inundated by groundwater seepage or in situ snow melt. These observations agree with qualitative descriptions of water sources for the particular plant communities.