In lowland landscapes rivers remain the most important refuges for biodiversity. Among the other aspects shaping functional diversity of riverine ecosystems, especially the ones that remain of low dynamic the processes of water exchange in the hyporheic zone are reported as critically important.
The 3D groundwater flow model based on FEFLOW (DHI) is focused on water flow calculations in hyporheic zone. The model covers the 4 km stretch of the Upper Biebrza River (Poland, Europe). This area remains one of the biggest consistent wetland areas of the European Union. This section of the river is characterized by its undisturbed river bed due to the ban on mowing and dredging since 1992 (part of Biebrza National Park). Automatic measurements of groundwater head in piezometers located in five transects (40 piezometers, time series covering 1 year with 3-hours frequency) combined with hydrological and meteorological data, were conducted to calibrate the model.
The new equipment, designed by authors for rivers with a thick peat sediment, was used to support the model verification process.
The model enables estimation of the velocity field and the water exchange flux between the river and aquifer in the hyporheic zone. Obtained results indicate the sections of the river which are characterized with a higher or lower intensity of water exchange between the river and the aquifer. Ecohydrological research of the riverine and riparian habitats conducted simultaneously to hydrogeological survey create the starting point for quantitative analysis of the relationship between changing status of these habitats and the dynamics of groundwater-surface water interaction.
Research was carried as a part of project OPUS No.2016/21/B/ST10/03042, funded by National Science Centre, Poland.