Warnow River Basin
What is the reduction potential of various P-filters on the total phosphorus concentrations in a river basin? Rostock University (UROS) used a long-term dataset (1991-2015) to analyze the temporal development of dissolved reactive phosphorus (DRP) and total phosphorus (TP) in surface waters of the Warnow river basin and to simulate the potential of various P-filters on the P load in the river.The Warnow river basin - and its sub basins - (3041 km²) is located in north-eastern Germany, it is agriculturally dominated and 18% of the fields are tile-drained. Data indicate that DRP- and TP- concentrations decreased drastically in the 1990s and target values according to EU-WFD and national laws are mostly achieved nowadays. Nevertheless, according to the Baltic Sea Action Plan (BSAP), Germany has to reduce annual P loads into the Baltic Sea by 110 ton.
Broken down to the Warnow river basin, Rostock University calculated a reduction requirement of 13 ton P/y meaning a required P load reduction of 26%. The eco-hydrological Soil and Water Assessment Tool (SWAT) was employed to estimate the reduction effect of P filters in tile-drained areas on the overall P load.
Hydrology and P loads in the Warnow river basin were simulated using a multi-site calibration and validation approach. It was found that the main P sources in the catchment are groundwater (72%) and tile-drainage water (23%). P originating from surface runoff accounts for 5% only.
Fig. 2: Total Phosphorus (TP) sources (pie chart) and annual TP loads of the river Warnow basin based on observed (black bar) and simulated (red bar) data. The blue bars indicate TP loads due to different P-filter settings.
The Warnow river basin - and its sub basins - (3041 km²) is located in north-eastern Germany, it is agriculturally dominated and 18% of the fields are tile-drained. Data indicate that DRP- and TP- concentrations decreased drastically in the 1990s and target values according to EU-WFD and national laws are mostly achieved nowadays. Nevertheless, according to the Baltic Sea Action Plan (BSAP), Germany has to reduce annual P loads into the Baltic Sea by 110 ton.