if rivers run into the sea and the sea has a tide why are rivers 'fresh' water not salt water?

Answer 1

If you're asking why doesn't the sea push upstream during a tide, it's because the fresh water from the river is moving with more force than the sea pushes with. Kind of like if you put a garden hose in a bucket of salt water. As long as the hose is turned on and flowing, the salt water won't get into the hose.

Also, the greater distance from a sea, the higher the river's elevation. Therefore it is too high above sea level to be reached by a tide.

Hope this is what you meant by your question.

Answer 2

The flow of the river into the sea as the tide is going out means that the fresh water is stronger,relatively, than the sea water. When the tide comes in the salt water manages to push up stream a little. Where the great Mississippi pours into the sea the sea is actually fresh water for many miles out.

Answer 3

Rivers form from water collected by the land that runs downhill and follows the path of least resistance. They go downhill until they reach some obstruction or a sea or ocean. Oceans already occupy the lower places on the earth's surface so cannot move uphill to mix with the rivers. The oceans' tides do not move the water's edge that much to have a significant effect on this. River estuaries are affected by the ocean tides and are a mix of salt and freshwater i.e. less concentrated salt water.

Answer 4

All the earths rivers run to into the sea, carrying with all that "fresh" water are small amounts of minerals including small amounts of salt. Once all this "fresh" water reaches the oceans and the seas, these minerals are now concentrated. Sodium Chloride or salt is non-detectable by the human taste buds in concentrations less than 250-300 ppm(parts per million). The salt is there in the fresh water, you just can't detect it.

Answer 5

The level difference between low tide and high tide water is only a few feet. Hence high tide water cannot run for a long distance upstream along a river. The river water is a mixture of saline and fresh water till the distance, upto which high tide water reaches. This is the delta region, and we get a reversible flow of water in rivers and distributaries there. Further upstream, the water flow is only towards downstream direction and river holds only fresh water.

Answer 6

In large river basins (like the Amazon) the volume of water going out to the sea is so huge that it has been said that you could get a bucket of "fresh" water over 100 miles out in the Atlantic Ocean. Not actually tried it.. but theoretically very possible.

Answer 7

London's river - the Thames - is tidal all the way through central London (all through the tourist-y bits) right up to Teddington lock - about 35 miles (IIRC) inland.
at the lock, the river is almost pure :-) fresh river water

as you travel down river, through london and out to sea, the water becomes more salty and less 'fresh'.
the mix of fresh/sea water, at any individual place along the route, would be dependant on the tides and other rivers/streams mixing with the central flow

Answer 8

Rivers and streams are made up of rainwater.

The basic water cycle shows that rain clouds are formed by the evaporation of salt water( the sea ) and the salt and minerals in the sea are left behind, as they do not evaporate, the clouds then come in land, and give rain, which is salt free, to form the rivers.

The cycle goes on.

Answer 9

the part where the river meets the sea is a mix of fresh and salt water for this reason.

Answer 10

The ocean—the seas—are made up of 96.5 percent pure water. The remaining 3.5 percent is made up of 75 other elements. Six elements are responsible for 99 percent of the sea's saltiness. They are: chloride, sodium, sulfur, magnesium, calcium, and potassium. Most of the saltiness comes from the compound sodium chloride (ordinary table salt).
Where do the elements come from? The wearing away of rocks on land. As rock erodes, rivers carry the salts and other minerals to the ocean. Volcanoes and undersea springs also release salts to the ocean.