Quantification of phosphorus retention efficiency by floodplain vegetation and a management strategy for a eutrophic reservoir restoration

This paper presents an ecohydrological approach to the reduction in the phosphorus load transported by the Pilica River into a lowland reservoir in the central region of Poland. The research was carried out on a 26.6 ha section of the river floodplain where vegetation was the important component accumulating phosphorus (P) in plant tissues. Quantification of P accumulation in plant tissues and retention efficiency by plant communities in the floodplain were analyzed in order to develop a vegetation management strategy that would enhance river self-purification. A Digital Terrain Model (DTM), a location–altitude map, an inundation model of the floodplain, and a map of the distribution of plant communities were used to evaluate the capacity of the floodplain to retain P.In summer, the biological potential for phosphorus retention in the floodplain was estimated to be as high as 255 kg P. However, this potential can be increased by planting fast-growing patches of willow. Therefore, covering 24% or 48% of the entire floodplain (identified by DTM analysis) where are suitable hydrological conditions for growth and cultivation of willows may increase this accumulation to 332 or 399 kg P, respectively. In the long run, an appropriate management strategy (cutting and removing the biomass from the floodplain) should favor a decrease in nutrient transport downstream.