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Exploring STREAMS

Streams are important habitats for dozens of plants and animals, from single-celled algae to medium sized fish. Use the handouts to learn about and explore streams and the creatures that live in them.

Stream Basics

Streams are also called creeks or brooks.

Streams are places where the ground surface is low enough that it intersects the water table, the place where the ground is saturated with water. This ground water is what provides the base flow for a stream, the water that flows even if it hasn't rained for a while. Streams are also places where rain water that doesn't soak into the ground collects and flows downhill. If there is too much rain water for the ground to absorb, it can cause a stream to be flooded.

Each stream is a home to animals and plants specialized to live in the particular conditions of that stream. The four most important conditions are how fast the water flows, what the bottom is made up of (mud, sand, or rocks), how clear the water is, and how regular the stream flow is.

Streams have three different sections, riffles, pools, and runs. A riffle is where the water is shallow enough to tumble over the rocks. Riffles are important because when the water tumbles over rocks it picks up oxygen from the air, and even animals living in water need oxygen.

diagram showing a riffle, pool and run

Pools are deep places where the water looks still. Pools are important because they are a refuge for animals when there is so little rain, the stream no longer runs on the surface.

Runs are places where the water is too deep for a riffle, but too shallow for a pool. Runs are important for smaller fish to keep them from being eaten by big fish that live in pools.