River Systems

A river is different from a lake because water is moving down a river. A river has feeder streams emptying into it. These feeder streams are called tributaries. The water in these feeder streams comes from rain, snow melt and ice melt. If the water does not soak into the ground it runs off. Gravity causes the water to run down hill. The land area that this water runs off of is called the rivers' watershed.

Water that runs into a river could and often does carry a lot of materials. As the water runs off the land it dissolves a lot of materials such as; soil, sand, and organic materials that are carried by the stream. The materials carried by the stream is known as Stream Load. All of this material plus the water moving down the stream in a given time is called Discharge. There is a life cycle in a river which is different than the life cycle in a lake. There are places in a river where the water moves faster and places where the water slows down. Faster water can carry more sediment but when the water slows down it drops some of its load.

All the above conditions set up differing environments along the course of the river that living things must be able to adapt to or they do not survive. Flowing water systems are Open systems meaning much material enters the river through runoff. A major energy source for rivers is the organic matter (dead plants and animals) that is carried into the river. A river has changing conditions as you move from the headwaters down to the mouth. So, it would seem logical when looking at a river to assume you would find different organisms at different locations along the river channel.

Rivers are different ecosystems from lakes, one way being rivers are more heterotrophic. The flowing water does not allow for the production of larger plants. Because of this there is much less primary production in a river. The main producers are algae and mosses. Zooplankton, worms, clams, and insect larvae are some organisms that make up the first order consumers. Many of these consumers rely heavily on the organic materials that run off the lands around the river. Fish, amphibians, and some reptiles are some of the second and third order consumers.

Assignment One: You are to define the following terms by searching the internet or using some other source.

Delta Downstream Flood plain
Headwater lentic lotic
meanders periphyton pool
riffle upstream watershed

Internet sources for definitions:

http://commpres.env.state.ma.us/content/glossary.e asp

Assignment Two: You are to draw a picture of a river and on the river draw pictures of some of the organisms you would find in that stretch of the river. Describe the conditions under which each organism lives. You must have at least 6 different organisms.

There are a number of different uses for rivers. Some of which are; boating, fishing, and swimming. A number of different communities use the river as their source of drinking water.

Assignment Three: You are to describe the bad effects that boating and fishing could have on the water in the river.


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