I think you should probably look at your book for this, because clearly you are expected to come up with information from the book. We do not know what sorts of information you are supposed to put down.
After all, just based on this question, you could say that the answer is that 1) rivers are made up of water and 2) that the water in rivers runs downhill. Surely that's not what you're being asked.
A couple more important things about rivers, perhaps:
- All the water in a given area around the river drains into it. This means that runoff from agricultural fields can bring large amounts of chemicals into rivers.
- Rivers used to meander around, flooding their banks a bit here and there quite often. Now, they are forced into channels. When they overflow now, the results are much more catastrophic than before.
A river is a large body of water that flows over land in long channels. Rivers are formed when water from sources such as rain, melting ice, subsoil water ot other sources gets collected in narrow strips of low lying lands and flows further down to even lower lands. If a river does not find such strips of low lying land, the water of river accumulates where such barrier to its flow is encountered, forming lakes.Rivers drain its water in other rivers sea pr big lakes.
Rivers very greatly in size which is measured in terms of its length or in terms of rate of flow of water through it. The longest river in the world is river Nile in Africa. and the biggest river in terms of flow of water is the Amazon River in South America.
The various streams that flo from the source of a river are called its headwaters. At the end of the river is its mouth where it drains into another river, lake or an ocean. Headwaters has the highest elevation point along entire course of river, and the mouth has the lowest elevation.
Rivers are bodies of water that flow and run and can change direction over time. As the water travels through the river it changes the land formations surrounding the river by breaking down the sides of the land. Sediment is overturned by the force of the water. The turbidity of the river is measured to determine how much sediment it holds. Turbidity is the clarity of the water.
Rivers start at a source which could be an underground spring. Tributaries flow into the river and the river itself empties into a larger body of water such as the ocean or a lake.