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
BACKGROUND MATERIAL
 Water cycle
This activity is most effective when it is done following a very
 San Antonio River
similar activity called “Where Does the Water Go in the Water
Basin
 Watersheds
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
TEKS
ALIGNMENT
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
Grade 4 Science:
water cycle is a system, which is made up of subsystems,
2D, 2F, 6A, 7C, 8B
sharing matter and energy.
Grade 5 Science:
In this lesson, students learn about their local subsystem of the
2D, 2F, 3A, 3C, 6A, 8B
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
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
Subsystem is a smaller
system within a larger
system
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.
STUDENT SHEET 1
STUDENT SHEET 2
STUDENT SHEET 3
TEACHER SHEET 1
TEACHER SHEET 2
TEACHER SHEET 3
TEACHER SHEET 4
TEACHER SHEET 5
TEACHER SHEET 6
TEACHER SHEET 7
TEACHER SHEET 8
TEACHER SHEET 9
TEACHER SHEET 10
TEACHER SHEET 11
TEACHER SHEET 12
TEACHER SHEET 13
TEACHER SHEET 14
TEACHER SHEET 15
TEACHER SHEET 16
TEACHER SHEET 17
TEACHER SHEET 18
TEACHER SHEET 19
TEACHER SHEET 20
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.