New modelling results from the Koprzywianka River basin within the PHISHES project highlight significant changes in river-roundwater exchange, supporting ongoing drought mitigation and water quality management in southern Poland.
The activities in the Koprzywianka River pilot address water shortage issues in a catchment characterized by complex hydrogeological conditions and variable surface water-groundwater interactions. The main goals include assessing impacts of point source and aerial pollution, evaluating adaptation measures related to soil treatment and agricultural practices, and developing mitigation strategies for heavy metals concentrations monitored in streams.
Figure 1 – Soil types in the Koprzywianka catchment
Figure 2 – Land use classes of Koprzywianka catchment
Model development and retention measures
In the first months of the project, a MIKE SHE model was developed and calibrated for the Koprzywianka catchment as part of the Polish national drought mitigation plans to counteract water shortages. A range of technical actions aimed at increasing retention in the catchment area was examined, including partial restoration of the river channel, revitalization of floodplains and meanders, and increasing channel retention by repairing existing weirs.
Preliminary analysis showed that these actions are too small and localised to significantly affect hydrodynamic conditions at catchment scale and can only increase channel retention locally. Continuous riverbed revitalisation was therefore analysed – by modifying roughness coefficients in the riverbed – and enabling unrestricted flow between the channel and groundwater.
Simulations of the impact of these actions – conducted for the period from 1 January 1986 to 29 June 2009 – indicate that exchange between groundwater and surface water in the riverbed changed. The total amount of water flowing into the riverbed decreased by about 35%, due to an increased amount of water replenishing groundwater resources through seepage from the channel. The absolute amounts of stored water are relatively small – few millimeters per year – and distributed along the riverbed.
Figure 3 – Water sampling and gauging points
Monitoring and next steps
Monitoring of surface water quality at three locations – ongoing since October 2024 until October 2026 – will continue with particular emphasis on relationships between water levels, discharge rates and pollutant concentrations, mainly heavy metals, especially during high water events. Additional monitoring points near mining sites and exploitation areas are under consideration. Continuous recording of water levels and discharges will be realised, and model validation based on water quality data gathered until the end of 2025 is expected.