The Hydrologic Cycle
The water on planet Earth is not new. Water is constantly in motion changing from a vapor (gas) to a liquid (rain) to a solid (ice, snow). It travels continuaily from the earth to the atmosphere as seen in the hydrologic cycle.
During this cycle, water evaporates from the ground, vegetation (transpiration), and other bodies of water (lakes, rivers, streams, etc.) lt travels through the atmosphere as a vapor where it cools and condenses. The droplets join together to form clouds. Rain falls back to the earth from these clouds, feeding the earths surface and making it possible to support plant life. Lakes, streams, and rivers are fed by these rain waters. Underground cavities, called aquifers, catch some of the rain water as it seeps into the soil. Soil moisture, which is part of the water which has been absorbed into the soil, is taken up through the root of vegetation and is transpired from the leaves. The water from these sources is heated by the sun and returns to the atmosphere as a vapor. Thus water is constantly traveling from the ground to the atmosphere and back to the ground.
The hydrologic cycle has no beginning or end but is a constantly moving system. No water is ever lost or gained in this cycle for it simply returns to the earth in one form or another. This cycle plays a major role in determining climate and types of vegetation so what effects this cycle at any point can have long lasting effects.
Objectives
-
1. Children will learn about the water cycle through simple experiments and hands-on activities.
Materials
Felt pieces cut out in the shape of a raindrops, mountain, river and clouds.
Procedure
-
1. Ask the children how many things they do which include the need for water.
-
2. Ask the children what forms water comes in other than a liquid.
-
3. Discuss with the children how we get rain.
-
4. Ask them where does the water that falls from the clouds come from.
-
5. Where does this water go after it falls?
-
6. Use your felt pieces to tell the story of the water cycle.
-
7. Let the children follow a raindrop through the cycle using a teacher made or store bought activity sheet.
-
8. In their eco-journals, allow the children to draw and write about the Hydrologic cycle, following a raindrop through the cycle. They may want to give their raindrop a name.
Extended Activity
Allow the children to retell the story of the Hydrologic Cycle using the felt pieces and a flannel board. Write the story parts on large sheets of paper using a magic marker. Divide the children into small groups and let them illustrate the story. Combine the pages to create a class big book.
More Activities
-
1. Discuss conservation of water in the home and at school.
-
2. Place a 1/2 gallon jar in the water holding tank of the toilet to save 10% of the water with each flush.
-
3. Have the children make a check of the faucets in the home and at school and report leaks to the proper people.
-
4. Encourage the children to shut the water off while brushing their teeth.
-
5. Discuss helium filled balloons. Tell the children that they deflate and sometimes end up in the ocean. Explain how they quickly lose their color and can look like jelly fish. Whales and sea turtles eat them and starve to death because the balloons block their intestines.
Forests and Other Vegetation
Once the United States was covered with forests which covered most of the country. Forests at one time grew so thick that a person would not walk through them. With the arrival of the European settlers and the development of land for cultivated crops, farms, towns and cities, these forests were cut down and the land cleared. Cultivated crops now replace those areas where natural plants once grew. Alaska and Hawaii are the only two states which still have a substantial amount of their natural vegetation.
Types of Forests
The kind of forest found in an area is determined by the climate, soil and topography of the region. Natural forest will maintam itself in a relatively fixed, self regulated condition for extended periods of time. The size and height of the plants in a forest control the type of vegetation which will grow on forest floor. Forest fires and harvesting of trees by lumber companies may cause a forest to change from one type of tree to another.
Tree Groups
Based on the type of leaf and climate forest in the United States have been divided into the following group.
Deciduous trees are found usually in the eastern United States. They are broadleaf trees with a wide, flat leaf. Their wood is hard and their seeds are enclosed in some type of covering. These trees include the oak, maple, and popular.
Coniferous trees are found in the more northerly forests of the United States. Coniferous trees have needles or scale shaped leaves and are called evergreens. Much of the softwood yielded in the United States comes from the Douglas fir forest of the Pacific Northwest. The seeds of the coniferous trees are found between the scales of the cones produced by these trees. Coniferous trees include the pine, fir and spruce.
Palm trees flourish in warmer climates, including some desert areas of the United States. Since they do not have branches, the leaves grow right out of their trunks.
Many plants and animals are dependent on trees for food and shelter. A small elm tree can be home thousands of different species of plants and animals. Birds survive on the insect population they find in the trees while animals build their homes in these same trees.
The natural growth pattern of a forest is more acceptable for animal life than a man made forest. Forest planted by man tend to have trees of the same age and are planted too close together. Trees thus planted are called tree plantations. The size and closeness of the trees block out light and deters the growth of ground plants. The thick clusters of needles and leaves that fall discourages the growth of new trees. Dead trees, which in a natural setting, would rot and become home to insects and fungi are cleared away. Thus the biological diversity which would exist in a natural forest does not exist.
People also need trees for survival. Trees give us the wood we need to build houses, to make furniture and instruments, and many other things. We heat our homes with the wood from trees. In some countries, the only fuel people use is wood. Trees provide us with fruits, spices, and nuts. Paper is made from trees. Trees help to lessen the amount of dust in the air by capturing it in their leaves. They take in carbon dioxide and release oxygen which is necessary for all life. The roots of trees act as a glue, holding the soil in place.