What is the salinity of fresh water?
In fresh water the concentration of salts, or salinity, is nearly zero. The salinity of water in the ocean averages about 35 parts per thousand (ppt). The mixture of seawater and fresh water in estuaries is called brackish water and its salinity can range from 0.5 to 35 ppt.
After years and years of river inflow and evaporation, the salt content of the lake water built up to the present levels. The same process made the seas salty. Rivers carry dissolved salts to the ocean. Water evaporates from the oceans to fall again as rain and to feed the rivers, but the salts remain in the ocean.
- Get to know estuaries with this two-minute video. Estuaries and their surrounding wetlands are bodies of water usually found where rivers meet the sea. Estuaries are home to unique plant and animal communities that have adapted to brackish water—a mixture of fresh water draining from the land and salty seawater.
- Now as we know the vast majority of rivers are freshwater but they contain salt to a minimal degree since in the travel of rivers to the oceans they pick up mineral solids and deposit them in the ocean. Now there are a few exceptions to this that produce saltwater rivers, streams, and creeks.
- The 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 atmosphere and material from the sea and land over which the rain bearing clouds have traveled.
- The new Aquarius map reveals predominantly well-known ocean salinity features, such as higher salinity in the subtropics, higher average salinity in the Atlantic compared with the Pacific and Indian oceans, and lower salinity in rainy belts near the equator, the northernmost Pacific Ocean and elsewhere.
- The Dead Sea has a salinity of 33.7 per cent. This is almost 10 times saltier than ordinary seawater. If you evaporated a litre of Dead Sea water, you'd have around 250g of salt left behind, and in the whole of the Dead Sea there are about 37 billion tonnes of the stuff.
- There are parts of the ocean where hardly any rain falls but warm dry winds cause lots of evaporation. This evaporation removes water – when water vapour rises into the atmosphere, it leaves the salt behind, so the salinity of the seawater increases. This causes the seawater to become denser.
Updated: 7th December 2019