Soil erosion by water
Water erosion is a natural phenomenon in which water removes and displaces soil particles and is often intensified as a result of human activity. Erosion is affected by the slope of the ground, climatic and weather conditions, vegetation cover, soil type, soil structure and tillage. In Finland, erosion is greatest outside the growing season at times of rain and snowmelt.
Water erosion from agricultural land is a key factor in deteriorating water quality and ecological status. Erosion material increases the turbidity and siltation of water bodies, and the erosion material carries with it nutrients and pesticides that cause eutrophication and deterioration of water quality. Erosion takes away the most fertile topsoil, impoverishing the soil of the fields, and at worst, large erosion can occur in the fields.
Water erosion of fields can be reduced, for example, by means of covering crops during winter and by leaving protection zones on the sloping slopes of water bodies. Direct sowing and light tillage methods also reduce erosion.
The erosion of Finnish fields calculated with the RUSLE model with the 2019 cultivation and operation data averaged 430 kg / ha / year and varied between 90-1280 kg / ha / year in different Finnish municipalities. The total erosion of the fields was almost one million tons. The previous erosion estimate has been made for 2016 and was 460 kg / ha / year at that time, but due to the development of data and calculation methods, the estimates for 2019 and 2016 are not fully comparable. According to the European Soil Data Center, Finland's erosion is the lowest in the EU (https://esdac.jrc.ec.europa.eu/content/soil-erosion-water-rusle2015), but despite this, especially the harmful effects of fine clay in Finnish waters are significant. The calculated municipality-specific erosion estimates are in the map and table on this page.
Description of the indicator
Soil erosion by water is one of the CAP impact indicators. The indicator aims to evaluate the risk of erosion by water and monitor the impact of preventive measures.
The water erosion indicator has been calculated in Natural Resources Institute Finland using the commonly used RUSLE (Revised Universal Soil Loss Equation) calculation model, which provides an estimate of the erosion indicator in tonnes / hectare / year. Estimates are based on long-term average precipitation, so annual weather variability has not been taken into account.