Lunch seminar'Catchment-scale nutrient loads revealing biogeochemical stationarity under hydro-climatic variability'

Hydrological stationarity has been declared dead due to anthropogenic impacts. However, this presentation shows that the anthropogenic impacts also have contributed to an emergence of effective biogeochemical stationarity. Water-quality monitoring data from large catchments in the Mississippi River and the Baltic Sea Basins have been analysed consistently. The analysis reveals that inter-annual variations in exported loads for total-Nitrogen and total-Phosphorus are linearly correlated to corresponding variations in mean annual water discharge. The resulting flow-weighted nutrient concentrations remain then essentially constant in spite of wide inter-annual fluctuations in water discharge and hydro-climatic forcing. Such persistence can be attributed to a legacy of anthropogenic inputs generating long-term memory in catchments. These findings suggest that longer-term water-quality problems in surface and coastal-marine waters should be anticipated, and point to the need for adopting different types of pollution abatement measures and strategies than just the currently preferred ones.