Estimated Time: Two forty-five minute class periods
Indicator(s) Core Learning Goal 1:
1.4.6 The student will describe trends revealed by data.
1.4.9 The student will use analyzed data to confirm, modify, or reject an hypothesis.
Indicator(s) Core Learning Goal 2:
2.2.2 The student will explain the role of natural forces on Earth.
Student Outcome(s):
The student will be able to describe the structure of the hydrosphere quantitatively in terms of reservoirs, fluxes.
Brief Description:
In this lesson students will
revisit the water cycle to model the earth's water reservoirs and fluxes.
Background
knowledge / teacher notes:
All of the earth's water is contained in the system we call the hydrosphere. The subsystem include the oceans, frozen water in glaciers and the ice caps, and other water such as groundwater, and the water vapor in the atmosphere. Wherever water occurs may be considered water's "reservoir." The biggest reservoir- the oceans hold 97.25% of the earth's water.
|
The
Earth's Water Reservoirs |
||
|
Reservoir |
Volume
(km3) |
%
of Earth's water |
|
Oceans |
1,320,000,000 |
97.21 |
|
Glaciers |
29,200,000 |
2.15 |
|
Ground water and soil moisture |
8,417,000 |
0.62 |
|
Lakes and Rivers |
230,000 |
0.017 |
|
Atmosphere |
13,000 |
0.001 |
|
Plants and Animals |
< 10,000 |
< .00075 |
|
Total |
1,357,870,000 |
100 |
|
Water
Fluxes on Earth |
|
|
Process |
Volume
of water moved (km3/year) |
|
Precipitation into oceans |
385,000 |
|
Evaporation from oceans |
425,000 |
|
Precipitation onto continents (precipitation that becomes ground water) |
111,000 (16,000) |
|
Evaporation and transpiration from continents |
71,000 |
|
Transport of atmospheric water vapor from ocean areas to continental areas |
40,000 |
|
Flow of surface, and groundwater into oceans |
40,000 |
|
Total
Flux / Year |
1,072,000 |
For the Exploration activity, it is necessary to define an area in which water flexes will be measured. A flux is defined as a process that moves material form one reservoir to another at a particular rate. Use a local topographic map to trace the boundaries of a drainage basin to be used.
Lesson Description: Lesson 1A
|
ENGAGE |
Ask students to estimate how much water they might use in a typical day. Some figures are: shower- 20-30 gallons, tub bath - 30-40 gallons, flushing standard toilet- 3 gallons, machine wash one load of clothes- 20-30 gallons. Education Elements: SCIENTIFIC ILLUSTRATION Picture of the water cycle http://ga.water.usgs.gov/edu/watercyclegraphic.html BACKGROUND INFORMATION The water cycle. |
|
EXPLORE |
Review with students the diagrams they completed of the water cycle in Unit I. or create a new systems diagram of the water cycle. Include the reservoirs (groundwater, water from lakes, rivers, oceans, and atmosphere as well as plants and animals) and the fluxes or processes that move water. (see above) On a local scale, the water cycle can be described by a hydrologic budget equation that accounts for all the water that enters and leaves a given area. Ask students to write a word equation that balances the water budget in their region. Use the information on the water cycle to write the hydrologic budget. Education Elements: BACKGROUND INFORMATION, STUDENT ACTIVITIES, LINKS Water Science for Schools—This excellent site contains links to interactive challenges, images, facts, data sets, graphic organizers, extensions, and a navigation guide to facilitate use of the site. |
|
EXPLAIN |
Calculate the fraction of the Earth's water that moves each year. (total fluxes/total volume in reservoirs). Use the data from your system diagram. Journal Write: What does the data show about the inflow and outflow from the oceans? Calculate the water that enters and leaves the atmosphere each year. Is there a balance? Explain. Education Elements: GLOSSARY; BACKGROUND INFORMATION USGS Introduction to hydrology and hydrologic definitions http://water.usgs.gov/wsc/glossary.html |
|
EXTEND |
How much time does water spend in a given place or reservoir? Use the equation Residence time = reservoir size / total outflow to determine the average residence time for water in each of the reservoirs. GT/Honors Apply the hydrologic budget to your area. Things to think about: Use a topographic map to determine your drainage area and calculate the area of the basin. Determine the volume of precipitation for a calendar year Determine the monthly evaporation data and extrapolate for the calendar year. Calculate the volume of water leaving the basin as stream flow. Determine the unaccounted for water. Education Elements: DATA SETS; LINKS; BACKGROUND INFORMATION Surf Your Watershed http://cfpub1.epa.gov/surf/locate/index.cfm SCIENTIFIC ILLUSTRATION Global water reservoirs, fluxes, and turnover times. http://www.ess.uci.edu/~reeburgh/fig8.html |
|
EVALUATE |
Journal Write: Explain the earth's water budget in terms of
reservoirs and fluxes. GT How does
the local water budget compare to the global water cycle in terms of
reservoirs and fluxes? |
Materials:
Resources:
John
Wiley and Sons, Inc. (1999). Laboratory Manual to Accompany The Blue Planet An
Introduction to Earth Systems. Water: we'll meet again. pp. 79-84.