As part of PHISHES, an experimental biofilter has been installed and tested in a small sub-catchment near the village of Chyšná (Martinice u Onšova). The 2.6 km² catchment, located within the Martinický creek stream basin, was chosen for its mix of forest and active agricultural land, including areas with functional drainage systems.
The project addresses water quality in small catchments impacted by farming. A key component of the experiment is a newly constructed in-situ biofilter with a total volume of 7.5 m³, composed of biochar and woodchips. This active, natural filter is designed to bind and remove substances—primarily nitrogen and phosphorus from fertilization, as well as other chemical metabolites transported by ground and surface waters.
A detailed monitoring campaign was conducted from November 4-6, 2025, strategically timed after a significant autumn rainfall event. This event was expected to generate higher runoff and pollutant loads from the surrounding agricultural lands.
Water flowing through the catchment was measured at the newly installed monitoring profile, downstream the biofilter.
Researchers expect the chemical analysis of the samples (taken upstream and downstream of the biofilter) confirm that the biofilter successfully captured a some or significant portion of the pollutant load. This experiment aims to validate the use of active, simple (low-complexity), nature-based biofilters as a practical solution to reduce contaminant inflow from some of selected agriculture fields into the strategic Švihov water reservoir.
Experimental catchment during the monitoring period, following recent autumn agricultural activities.