Freshwater

Freshwater is water with low dissolved mineral content, typically with salinity below 0.5 grams per liter (much less than seawater). It occurs naturally as rivers, lakes, streams, wetlands, groundwater, snow, and ice, and as atmospheric moisture. It is essential for life, human consumption, agriculture, and industry.

Globally, freshwater accounts for a small share of Earth's total water. Roughly 2.5 percent of all water is freshwater, most of which is locked in ice caps and deep groundwater. Only a small fraction is readily accessible in rivers, lakes, and shallow groundwater, making freshwater a finite and unevenly distributed resource.

Freshwater is often categorized by its position in the hydrological cycle. Surface freshwater includes lentic systems (lakes, ponds) and lotic systems (rivers, streams), as well as wetlands. Groundwater resides in aquifers and supplies wells and springs. Seasonal freeze–thaw processes in high latitudes also store freshwater as snow and glaciers.

Its uses are wide ranging: drinking water, sanitation, irrigation, industry, and energy production. Freshwater ecosystems support diverse organisms and contribute to nutrient cycling, flood control, and recreation. Many species depend on clean, well-oxygenated water and habitat diversity.

Threats include pollution, eutrophication from nutrients, over-extraction of rivers and groundwater, habitat loss, invasive species, and climate change altering precipitation patterns and temperatures. Management emphasizes water quality protection, sustainable allocation, watershed approaches, and, where necessary, treatment and desalination to augment supplies.