Sötvatten

Sötvatten, or freshwater, refers to water with low concentrations of dissolved salts, typically suitable for drinking, agriculture, and most terrestrial life. In scientific terms, freshwater is water whose salinity is low enough that it is regarded as non-marine, usually defined as less than 0.5 practical salinity units (psu) or about 0.5 g/L of dissolved salts. Freshwater is distinct from brackish and seawater.

Natural sources include rivers, lakes, groundwater, and wetlands, as well as ice and snow in glaciers and polar regions. Together these sources form the global freshwater system and participate in the hydrological cycle through evaporation, precipitation, infiltration, and runoff. Globally, about 2.5 percent of Earth's water is freshwater, with the majority stored in groundwater and ice caps, and only a fraction readily available in rivers and lakes.

Humans depend on freshwater for drinking, cooking, sanitation, agriculture (irrigation), industry, and energy production. The distribution of freshwater resources is highly uneven, leading to regional water stress in many areas.

Ecological importance: freshwater bodies host diverse ecosystems, provide habitat for fish and invertebrates, and support nutrient cycling and climate regulation.

Threats include pollution, over-extraction, habitat alteration, invasive species, and climate change, which can reduce quality and availability. Management approaches emphasize sustainable use, watershed protection, pollution control, wastewater treatment, and integrated water resources management to ensure reliable freshwater supplies.