The greatest similarity between fresh and salt water is that both are basically the same chemical – water, although the contents of other materials dissolved in it differ. Both contain some amount dissolved chemical in it though the quantities vary. Both form different links in the water cycle of the nature. Both are homes to aquatic life. Difference: Salt water contains much higher quantities of dissolved chemicals as compared to fresh water. This higher concentration of chemical also raises the density of salt water above that of fresh water.
Plant and animals living in two types of water bodies are different. Salt water is found only as large standing bodies of water. Most of these are in form of seas and oceans, although though some lakes including very large ones considered to be sea also contain salt water. Fresh water is found in standing bodies of water called lakes, as well as running water as in rivers and streams.
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Fresh water is available in many other forms such as in rain, and ice caps in the poles and in very cold places. However no fresh water is found in seas and oceans.
Fresh water is used for drinking as well as many industrial processes. However salt water is generally not suitable for most of the industrial use except for cooling. On the other hand salt water is used as a source of some chemicals, particularly common salt. Freshwater does not yield any such chemicals. Comparing Fresh water and ocean water, each has their differences. Most notable is animals living in each. The animals that live in the Salt “ocean” water would not survive in fresh water for an extended length of time. Same holds true for fresh water animals.
However there are a few species that have adapted and can live in both. Some Salt water animals have also evolved to live in Fresh water. Humans cannot drink ocean water without dying. The salt in it dehydrates you to the point you die of thirst. In order to drink ocean water you have to desalinate it in one of many ways. Boiling it being one way. Ocean water also contains every natural element on the planet. If we could find a way to mine the water that is cost effective, we would have a lot more resources. Ocean water freezes at 26 degrees F and fresh at 32.
While only 6 degrees difference in water terms that is huge. It prevents a vast amount of the oceans from freezing over in the winter, of course global warming has helped with that. As for your comment of only 3% of the worlds oceans is fresh water, it is very true. While there is a lot of surface area of fresh water the oceans are miles deep. The deepest point on Earth is approx 35,000ft below sea level or about 6. 75 miles down. Many of the deepest lakes only hit about 2000 to 3000 ft deep. Also when you compare the surface area of the fresh water bodies comparies to the oceans there isn’t much.
The great lakes between Canada and the USA contain 20% of all fresh water on the planet. That is enough water to cover the entire USA with 9. 5 feet of water. When compared to the oceans that isn’t much. So don’t be surprised. Fresh water is lighter than salt water. Therefore, fresh water “floats” on top of salt water. This principle becomes extremely important when considering the drilling of a well in order to tap into the ground water of any island. The weight of the rain water that percolates into the ground depresses the salt water beneath it forming a profile that has the appearance of a lens.
This is called the Ghyben-Herzberg lens. The principle of this relationship was discovered independently by a Dutch scientist named Baden-Ghyben and a German scientist named Herzberg. The underground boundary that separates the fresh water layer from the salt water is not a sharp boundary line. In reality, this boundary is a transition zone of brackish water (fresh/salt mixture). This is caused by seasonal fluctuations in rainfall, tidal action, and the amount of water being withdrawn either by humans or by natural discharge. Fresh water has a density of 1. 0 while salt water has a density of 1. 025.
From this, you can see that salt water is slightly heavier than fresh water. The ratio between the two is 41:40. The formation of the Ghyben-Herzberg lens has a profound effect upon the availability of fresh water on an island. This principle essentially states that for every foot of ground water above sea level there are forty feet of fresh water below sea level! The mathematical formula for the fresh to salt water relationship is: hs = hf / es – ef where hs is the depth of fresh water below sea level, hf is the depth of fresh water above sea level, es is the density of salt water, and ef is the density of fresh water.
Using the common density figures for fresh and salt water the formula can thus be simplified into hs = hf / . 025 Understand that this applies only to fresh ground water that is sitting directly on an intruded body of salt water. It has no meaning on a large island where an inland body of ground water may be confined by layers and dikes of lava rock. On islands that are largely composed of dense lava rock, little if any salt water intrudes very far into the underlying rock structure. It is generally only in shoreline regions that salt water intrudes into the cracks, crevices, and loose rock spaces.
On low, small islands that are largely composed of coral or other porous materials, salt water intrusion into the underlying interior is quite common. The drilling or digging of wells on these islands and especially on along the shoreline must be done with care. Going too deeply will penetrate the transition zone and result in salt water infiltration and the contamination of the fresh water in the well. I have seen such a well dug in solid lava rock along the shoreline in the Ka’ u District on the island of Hawai‘i. This well was located a few feet above the high tide line approximately a hundred feet from the ocean.
The opening was rectangular, about 3 1/2 feet wide, and 6+ feet long. On one end a set of stairs had been cut into the rock allowing one to walk down five or six feet to the level of the well water. This well was unused as there are no dwellings or settlements in the immediate area. In fact, the area was considered to be “range” land where a few head of cattle managed to find enough to eat in this dry, desert-like environment. The size and construction of the well indicated that at one time it may have served a considerable number of people and possibly even an old Hawaiian village. Unfortunately the well had been abandoned and neglected.
It contained a fair amount of decaying leaves and grass. There was also a considerable amount of broken glass from beer bottles that had been thrown against the interior sides of the well. This was probably done by shore fishermen who frequented the area from time to time and used the well as a convenient trash dump during evening camping parties. Nonetheless, the well serves as an excellent example of the Ghyben-Herzberg lens’s importance to the availability of fresh water in a place where one might think that none can be found. I already had listed some differences of salt water versus fresh water so here are some similarities;