Numerical definition
Fresh water can be defined as water with less than 500 parts per million (ppm) of dissolved salts.
Other sources give higher upper salinity limits for fresh water, … 展开

Saline water in oceans, seas and saline groundwater make up about 97% of all the water on Earth. Only 2.5–2.75% is fresh water, including 1.75–2% … 展开

The increase in the world population and the increase in per capita water use puts increasing strains on the finite resources availability of clean fresh water. The response by 展开

• Limnology – Science of inland aquatic ecosystems
• Properties of water – Physical and chemical properties of pure water 展开

The original source of almost all fresh water is precipitation from the atmosphere, in the form of mist, rain and snow. Fresh water falling as mist, rain or snow contains materials dissolved from the 展开

Water is a critical issue for the survival of all living organisms. Some can use salt water but many organisms including the great majority of higher … 展开

Human uses
Uses of water include agricultural, industrial, household, recreational and environmental activities.
Global goals for conservation 展开