Browning of waters is related to reduced acid deposition rather than climate warming

The scientific magazine Nature published an article this week about unexpected effects of acid precipitation and water quality, based on research carried out at the Norwegian Institute for Water Research (NIVA) in collaboration with other scientific institutes in several countries. New research results show that increased humus content in water is associated with reduced acid precipitation, and not due to climate change as earlier presumed.

The future trend of humus content in water is of strong public interest. Drinking water purification facilities that take in humus-rich untreated water have to remove the humus by an array of physical and chemical processes before the water can be distributed to consumers. Thus, the humus content in untreated water is important for the costs of water treatment and for water quality as well.

NIVA is a programme centre for an international programme for monitoring water quality related to acid precipitation, (ICP Waters) under the Convention on Long-Range Transboundary Air Pollution (UN-CLRTAP). The Nature article is based on an analysis of the database of ICP Waters that includes 522 lakes and rivers in Norway, Sweden, Finland, Great Britain, the USA and Canada.