| Activity 3: Where does our water come from
? Objective: Students will learn that our water supply comes from surface and groundwater resources; they will learn about how the water cycle replenishes these resources and about their relative abundance. Methods: An overhead is used to present a comprehensive diagram of the water cycle, and a demonstration is used to help students visualize the relative abundance of surface and groundwater resources. Materials: water cycle diagram on an overhead transparency, overhead projector and screen, 3 clear jars 1. The water cycle is the sun-powered movement of water between the earth and the atmosphere. The steps of the water cycle include: Evaporation: the sun heats water on the Earth's surface, turning it into water vapor, which is water in its gaseous form. The water vapor enters the atmosphere. Transpiration: the movement of water from within the leaves of plants into the air . This is also a process powered by the sun, whereby water turns into vapor. Condensation: as water vapor rises, it cools, and returns to its liquid state, forming clouds. Precipitation: as clouds become saturated with moisture, water in the form of rain , sleet, hail, and snow, falls from the clouds in the atmosphere onto the earth. 2 . When water falls onto the earth, it may directly enter a surface water body such as a stream, river, lake, or ocean. Some may directly infiltrate into the ground. Some water that hits the earth becomes runoff; it flows over the ground until it eventually enters a surface water body or infiltrates into the ground. 3. Groundwater is water that is stored underground. An aquifer is the beds of sand, gravel, or rock that store and move ground water supply. It is not always level. It has ups and downs just as the land above has hills and valleys. 4. Aquifers lie on top of impervious layers of rock, which do not let water through. Clay and shale are examples of impervious rock. When an aquifer lies between two impervious layers, it is an artesian aquifer, because it is under pressure. A water table aquifer, on the other hand, is not under pressure, because it does not lie beneath an impervious layer. The top of a water table aquifer is the water table. 5. When a well is drilled into an artesian aquifer, the water gushes out because the well hole releases the pressure that the water is under... When a well is drilled into a water table aquifer, the water in the well does not rise above the water table, and thus a pump is used to get the water out. 6. Groundwater is replenished by rain that enters recharge areas. Water also flows freely between surface and groundwater. A spring is an area where , because of some geological phenomenon, the water table is above the surface of the land, and thus water flows out naturally from the ground. 7. Out of all the freshwater on the earth. 76% is tied up as ice in the poles and in glaciers 23.6% exists as groundwater 0.4% exists as surface water. Procedure: 1. Show students the water cycle diagram on the overhead. Discuss the movement of water through evaporation/transpiration, condensation, and precipitation. What provides the energy for this movement? In what parts of the cycle is water in liquid versus gaseous form? 2. Discuss surface versus groundwater, runoff, aquifers, wells, recharge areas, springs. What is the fate of water that hits the earth? What would happen to the water table if it didn't rain all summer? How would this affect streams, lakes, springs, and our aquifers, wells, and reservoirs? 3.Show students a glass jar full of water. Explain that it represents all fresh water on the earth. a. Pour out 76% into an empty jar, explaining that this represents all the water that is frozen at the poles and mountain tops. b. Pour out almost all the rest , 23.6%, explaining that this represents all the freshwater that is under the ground. c. The remaining drops.0.4%, represent all the fresh water in surface water bodies, including all our reservoirs. d. Of all our liquid freshwater, where is most of it found ?
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