Carbon in the river system

This Carbon Update explains a link between the processes of the carbon and water cycles. Terrestrial soils are one of the most significant stores in the carbon cycle. Soil erosion by water into the river system is an important route by which carbon can be lost from this store

The Isar River in Germany swollen with flood water that has carried soil particles in runoff

Globally, there is around two to three times as much carbon stored in soils as there is in the atmosphere.Estimates suggest that this could total up to 2,500 gigatonnes of carbon. Many terrestrial environments act as carbon sinks, which means that they are accumulating more carbon over time (the amount of carbon in the store is increasing). However, some terrestrial environments act as sources of carbon, meaning that they are losing carbon over time.

This carbon can be lost in a variety of different ways, through different pathways and processes. The movement of carbon from one store to another is known as a carbon flux. Some carbon is lost from the soil to the atmosphere through respiration, and some is lost to the fluvial (river) system. In the UK, the main type of carbon which enters the river system from the soil is organic carbon, which means that it is derived from living organisms. This organic carbon can be in particulate or dissolved forms.