Why does water flow from river to sea but not backward?
In:
Think of the term sea level. Water always flows from high to low due to gravity. Land is always above the sea, therefore water on land will always flow to the sea.
Exceptions would be New Orleans, which is below the sea level, but kept dry by levys and dams.
On earth, there’s this force called gravity. Because the sources of rivers are at a higher elevation than the sea, gravity helps rivers flow towards the lower elevation of sea level.
It actually does to an extent. Any place where there is a river delta next to an ocean will be a mix of fresh and salt water.
However the ocean generally has to work against the gradation of the land, whereas most rivers are constantly propelled by the gradation of the land. In California, much of the drinking water from the Sacramento river gets “wasted” because it mixes too much with the salt water coming through San Francisco and the bay area…and the Sacramento delta is 50 miles from the ocean. There are plans in place to tunnel under the entirety of the delta to redirect more of the fresh water and prevent it from mixing with the salt water.
Latest Answers