According to the U.S. Geological Survey, most of that three percent is inaccessible. Over 68 percent of the fresh water on Earth is found in icecaps and glaciers, and just over 30 percent is found in ground water. Only about 0.3 percent of our fresh water is found in the surface water of lakes, rivers, and swamps. The use for the water in the world is for household drinking water. The ocean stores about 97 percent of the Earth's water; the remaining three percent is stored in glaciers and ice, below the ground, in rivers and lakes. Of the world's total water supply of about 332 million cubic miles of water, about 97 percent is stored in the ocean.
A<em> fish ladder</em> is also known as fish steps, fish pass or fishway.
It is built around waterfalls, dams and locks.
The purpose of building a fish ladder is to<em> facilitate the natural migration of diadromous fishes.</em>
A fish ladder helps the fish to pass through the barriers by leaping up or swimming through the low steps of the ladder and reach into the water on the other side.
Since, without the fish ladder the barriers will not allow the migration of fishes, it is essential to be built around the dams, waterfalls and locks.
Afferent nerve fibers carry signals from the somatic receptors to the posterior horn of the spinal cord or to the brainstem. So i beleive it is 4 but not too sure. Hope this helped a bit (:
