Published on: 19.1.2021
Information produced by Finnish Environment Institute
Climate change increases water pollution

While the ecological status of Finnish lakes and coastal waters is mainly good, they are polluted by runoff from land. Climate change may worsen this problem.
Climate change will affect water quality and aquatic environments in many ways, and all of its consequences cannot yet be predicted.
An obvious result of climatic warming is that lake and sea waters will also warm up, which will change their natural conditions. Bacteria and algae may become more abundant, and the oxygen content and mixing of water layers may be altered. Aquatic ecosystems will additionally be affected by the shortening of the annual period of ice cover.
Worse still, increasing precipitation and heavy rains, in particular, will carry more solids and nutrients into water bodies, boosting eutrophication. This problem is exacerbated by the fact that a larger share of precipitation in winter will come as rain and fall on bare ground. Nutrient leaches can be restricted, however, for instance by developing better farming practices.
While the increasing nutrient influx and eutrophication may cause stronger algae growth and widespread oxygen depletion, waters may also be affected by other harmful substances which the increasing amount of rain releases from the soil.
More frequent floods may present an additional risk for lakes and rivers locally by eroding shores and transporting large volumes of sediment. The worst-case scenario is a fluvial flood that exceeds the capacity of sewers and pumping stations, making it necessary to release untreated wastewater straight into a watercourse.
Drought in summer may also have an adverse effect on water quality by reducing flow rates and increasing lake retention times, which may result in oxygen depletion in deep areas.
Image: © Mikko Suonio, Vastavalo