Improving the evidence-base for understanding and managing brownification of surface waters

Summary

Two decades of increasing dissolved organic matter (brownification) in many Swedish waters (1990-2010) has raised concerns about impacts on both drinking water supplies and aquatic ecosystems. Human actions can drive brownification via climate change, forestry and acidification/recovery. Countermeasures to control brownification in the forest landscape are contemplated. Conventional trend analysis methods, however, miss the fact that across much of Sweden, brownification stopped a decade ago. This highlights the need to better understand brownification and improve the evidence base for managing organic matter concentrations in surface waters. One key to this will be re-examining three decades of surface water monitoring data from across the country with non-linear methods supported by data on climate and land use to better resolve the role of different influences in space and time. A complementary approach will follow organic matter solubility at over 100 locations in hydrologically connected catchment source areas (mires, fens and mineral soils) over the same period. Both approaches will be supported by an innovative assessment of the hydrological connectivity of catchment organic matter sources based on new, high resolution mapping products. Stakeholders will be involved in the execution of the study to create a regionally resolved national assessment of the brownification to date and expected developments with and without countermeasures.

Brownification Climate Land Use Carbon