Sweden has over 90 000 lakes and 300 000 kilometres of streams and rivers. Therefore Sweden is relativly rich in lakes in relation to its territory. The lakes vary from clear mountain lakes, brown forest lakes,nutrient poor to lakes very rich in nutrients,these often found on muddy soil in farmland areas. The richness of species depend on the status of nutrients but also on the proximity to sea, size and shape. Along rivers and streams we find localities with high variation of species, the highest variation of species one can find in the transition between land and water. These habitats also play a significante role in the distribution of certain species of flora and fauna living along the lake shores or in the lakes.

Human activities have an effect on lakes and rivers, both physically when water levels are changed, and chemically through acidification and eutrophication. Sweden has since long worked towards better water quality and today work is also being done to improve the physical environment around lakes and rivers.