Spatio-temporal analysis of phosphorus concentrations in a North-Eastern German lowland watershed

Abstract

Study region: The Warnow River Basin, an agriculturally dominated lowland watershed in North-Eastern Germany with a considerable extent of artificial drainage. Study focus: We analyzed a 21-year data set (1990–2010) of dissolved reactive (DRP) and total phosphorus (TP) concentrations in surface waters to evaluate trends and seasonality of phosphorus (P) concentrations and pathways of P losses from soils. New hydrological insights for the region: Phosphorus concentrations were moderately spatially variable over the investigation period and mean DRP and TP concentrations ranged from 57 to 132 mg l−1 and 114 to 184 μg l−1 respectively. The mean annual DRP and TP loads ranged from 0.04 ± 0.01 to 0.15 ± 0.05 and 0.12 ± 0.05 to 0.27 ± 0.06 kg ha−1 a−1, respectively. We detected significant negative temporal trends of P concentrations and loads in the decade 1990–2000. In the 21st century, the TP concentrations and loads tend to increase moderately. The results underline the importance of baseflow for DRP export and storm flow events for TP export, and emphasize the importance of artificial drainage systems modifying the hydrological regime of soils and surface waters alike. The P export rates during storm events and the proportion of particulate phosphorus in artificial drainage systems should be monitored at a higher temporal resolution to obtain a comprehensive database necessary for developing management strategies to reduce P loads in agricultural used landscapes.

Keywords

• Catchment hydrology
• Dissolved reactive phosphorus
• Total phosphorus
• Artificial drainage
• Monitoring
• Sub-basin scale