All rivers begin at a high point, whether from glacial melt that collects into streams, which slide down mountains to form large rivers or lakes at a high elevation. The water in rivers flows down away from these higher points and gathers momentum from water that joins from many other streams and rivers. Eventually all the water in a river will end up flowing in to the ocean. Along the way, rivers cause a massive amount of land erosion that can cut deep chasms into the land or carve larger paths for flow. Additionally, rivers provide the land with the essence that makes all life on earth possible -- water. The end of a river is called a "river delta" and it's a place high in nutrients as a result of all the minerals and soil rivers carry.
From outer space, it becomes clear that rivers are all connected to one another, looking like veins pumping blue blood throughout the Earth. The system of connected rivers is called a watershed. There are three types of watersheds: closed watersheds, open watersheds and multiple open watersheds. Closed watersheds empty their water into a inland body of water, such as a lake. Open watersheds gather water from one source that expels all of its water directly into the ocean. Multiple open watersheds empty their water into the ocean, which derives its water from many sources.
Rivers supply nutrients and water to all the ecosystems they flow through, which allows them to flourish with life. Rivers account for a large majority of wildlife such as fish, bears, eagles, herons, insects and more. Without the clean water that rivers provide, these animals and their habitats would not be possible.
Besides as a source for fresh water, people enjoy rivers for many recreational activities, such as fishing, canoeing and swimming. Rivers also carry away waste, storm water and pollution. These things directly influence the quality of water that animals and people depend on.
Farm ecosystems that are close to rivers cause damage since the large amounts of fertilizers and pesticides farmers use will end up draining into a river. These harmful substances dramatically alter the rivers' nitrate and phosphate levels, causing a large amount of algae to grow. The algae will deplete all the oxygen in a river quickly. This oxygen-deficient water flows downstream, directly affecting the lives of all animals and fish that depend on the river for sustenance. In addition, any harmful substances from sewage or industrial waste that is dumped into a river will flow downstream, affecting everything in its path.
When a river is polluted or mismanaged it affects the lives of all the animals that depend on it for food, shelter and water. Additionally, polluted rivers affect the lives of people too. Because salt water makes up 97 percent of the world's water and human population is constantly increasing at an exponential rate, protecting the remaining 3 percent is essential. Depleting fresh water supplies by heavily contaminating them with pollutants will affect the future well-being of human kind. Even though river water only makes up 0.2 percent of fresh water, because it is water in motion it has the capacity to carry harmful pollutants farther, affecting a larger amount of land and ecosystems.
