WHERE DOES THE WATER GO IN THE SAN ANTONIO RIVER BASIN? OBJECTIVES Identify the San Antonio River Basin as a system that is a combination of systems Identify the San Antonio River Basin as part of the water cycle Describe the force that causes water to travel from the upper part of the San Antonio River Basin to the Gulf of Mexico and explain how water cycle processes cause the river to interact with its basin TOPICS Water cycle San Antonio River Basin Watersheds TEKS ALIGNMENT Grade 4 Science: 2D, 2F, 6A, 7C, 8B BACKGROUND MATERIAL This activity is most effective when it is done following a very similar activity called Where Does the Water Go in the Water Cycle? In that activity, students will receive a background about the different reservoirs through which water moves in the water cycle on a global scale: ocean, atmosphere, icecaps and glaciers, groundwater, and rivers, streams and lakes. They learn both about the relative amounts of water in each of these reservoirs and the processes by which water moves among the reservoirs. Students also learn that the water cycle is a system, which is made up of subsystems, sharing matter and energy. Grade 5 Science: 2D, 2F, 3A, 3C, 6A, 8B In this lesson, students learn about their local subsystem of the water cycle: the San Antonio River Basin. A basin, or watershed, is a system that is made up of a river, its tributaries and all of the surrounding land that drains water into them. The drainage area of the San Antonio River Basin is 4,180 square miles from the headwaters in Bandera County, to where it eventually flows into the Gulf of Mexico. But the San Antonio River Basin itself is a system that can be broken down into smaller units called subwatersheds. Each of the six major tributaries has its own watershed: Medina River, Leon Creek, Upper San Antonio River, Salado Creek, Cibolo Creek and Lower San Antonio River.
KEY TERMS Aquifer is an area where large amounts of water are stored underground in natural formations of sand, gravel or rock Basin is an area that includes a river, its tributaries and the surrounding land that drains water into them Headwaters are the place where a stream or river begins Hydrosphere is all place on Earth where water is found, whether it is liquid water, ice or water vapor Reservoir is a place where a substance, especially liquid water, is stored Residence Time is the length of time water spends in any part of the water cycle before moving to another part Spring is a place where water flows out of the ground and becomes part of a stream or river Subsystem is a smaller system within a larger system System is a collection of parts that act together to perform a task. The different part of the system share matter and energy as they work together Tributary is a smaller stream that flows into a larger stream Watershed is all of the land area that drains water into a common point, usually a lake, river or stream PROCEDURES A. Start by asking the students to reflect on what they know about the water cycle and briefly discuss its components and processes. Then ask the students if they know what a watershed is. Ask the students to look at Page 1 of their student sheets to study the different parts of the San Antonio River Basin, and discuss the related vocabulary with them. B. Divide the students in groups of four in order to play a game 1. Assign each student to one of the water reservoir bowls 2. Place or have the students place the following number of tokens into each of the bowls: a. Atmosphere = 3 b. San Antonio River MATERIALS Each team of students will need the following: 4 plastic bowls, each labeled with one San Antonio River Basin water cycle reservoir: atmosphere, groundwater, Gulf of Mexico and San Antonio River and its Tributaries 1 set of playing cards (made from the 20 Teacher Sheets printed front and back, laminated, and cut out) 200 toothpicks, pieces of macaroni, or other tokens Each student will need the following: One copy of Student Sheet 1 and 2
and its Tributaries = 8 c. Groundwater = 10 d. Gulf of Mexico = All remaining (about 170) 3. Point out to the students that the number of tokens in each bowl represents the relative amount of water in that reservoir 4. Have the students distribute the stack of cards so that each student gets all of the cards for their assigned reservoir. 5. Tell the students that each card represents a different process in the San Antonio River Basin subsystem 6. Starting with the Gulf of Mexico student, each player in turn draws a card from his/her stack and moves one token from his/her bowl to the appropriate bowl at the instructions of the card. For example, if the player who has the bowl labeled Gulf of Mexico draws a card that says evaporation into the atmosphere, the player will move one token from the bowl labeled Gulf of Mexico to the bowl labeled Atmosphere. If the drawn card is stay then the player will not move any tokens from the bowl until it is his or her next turn. 7. As the players move the tokens, they should draw arrows between the reservoirs on their Student Sheet 2 diagram. A different color can be used for each process in the water cycle. If a process occurs more than once, the students should draw a new arrow between reservoirs each time the process occurs. No arrow is drawn if the water molecule stays in place during that turn. 8. The game may continue until all 15 cards are drawn from each stack or for as long as desired. C. At the end of the game, lead a discussion with the students about what they observed by playing this game. GUIDING QUESTIONS Where does the San Antonio River begin and into what water body does it drain? From where does the name of our river basin come? From where do the names of the subwatersheds come? Can you explain why the San Antonio River Basin includes part of Bandera County even though the San Antonio River starts in Bexar County? What force causes water to flow? Do any tributaries flow through your county? EVALUATION Using Student Sheet 3, have the students list all of the things that they noticed about the movement of water between reservoirs of the water cycle as it relates to the San Antonio River Basin. Then have them list the ways that water gets into the San Antonio River and what happens to the water once it is in the river. Finally, have the students write a story in which they imagine themselves as a water molecule on a trip through the water cycle in the San Antonio River Basin. They should explain what happens to them as they travel from one place to another, where they finally end up, and whether their travels are over or they will have further adventures elsewhere.
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REFERENCES Black, P. E. 1996. Watershed Hydrology, Second Edition. Ann Arbor Press, Chelsea, MI. 449pp. Schlesinger, W. H. 1997. Biogeochemistry: An Analysis of Global Change, Second Edition. Academic Press, San Diego, CA. 588pp. U.S. Geological Survey. 1996. Groundwater Atlas of the United States: Oklahoma, Texas. U.S.G.S Publication HA 730-E. Wetzel, R. G. 1983. Limnology, Second Edition. Saunders College Publishing, Orlando, FL. 857pp.