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Water Storage Around the World

Background

Information:

> GRACE is the name of a pair of satellites that is measuring the
> gravity field of Earth. GRACE stands for Gravity Recovery and Climate
> Experiment. GRACE looks at problems in geophysics, oceanography and
> atmospheric science. Earth\'s diverse topography includes mountains,
> valleys, underground caverns, oceans and glaciers. Since gravity is
> directly related to mass, and different surface features contain more
> or less mass than others, slight variations in gravity exist across
> the surface of the planet.
>
> While tiny changes in gravity may be negligible when solving a basic
> high school physics problem, they can be a critical clue to
> understanding the structure of the solid Earth, ocean circulation, sea
> ice and sea-level rise, and fluctuations in the amount of water stored
> above and below ground.
>
> In the Arctic, for example, GRACE has found that the ice sheet that
> covers most of Greenland is shrinking. Measurements of decreasing
> gravity over the ice sheet, indicating a decrease in the ice sheet\'s
> mass, showed a loss of about 150 billion tons of ice per year between
> 2003 and 2006. Melting ice sheets and glaciers contribute to rising
> sea level worldwide. The melting Greenland ice sheet contributes about
> 0.3 millimeters per year to a rising global sea level. GRACE continues
> its measurements to understand whether this rate of sea level rise is
> increasing or decreasing.
>
> In Africa and Australia, decreases in gravity are evidence of drying
> river basins. GRACE not only measures changes in water above ground
> \-- in rivers, lakes and reservoirs \-- but also senses the amount of
> water stored in aquifers beneath the Earth\'s surface. This kind of
> information can enable better management of scarce water resources.
>
> The sources of global sea level rise (currently estimated to be about
> 1.8 mm per year over the last 100 years and about 3.3 mm per year over
> the last 15) are uncertain. Approximately 30 -- 60% of the measured
> sea level rise is believed to be from redistribution of mass from the
> continents to the ocean. The other portion is attributed to ocean
> warming. Gravity measurements from GRACE help discriminate between
> these sources through the continual monitoring of geoid changes, not
> only on global scales, but also on regional scales. Geoid means
> "earthlike" and defines the smooth shape that most closely
> approximates the true shape of the Earth with all its bumps, bulges,
> depressions, and divisions.
>
> **The Geoid -** When scientists discuss the gravity field and shape of
> the Earth, they often do so in terms of a surface called the geoid.
> This is the surface that most closely approximates sea level in the
> absence of winds, ocean currents, and other disturbing forces. The
> Earth\'s shape resembles an ellipsoid (its equatorial radius is about
> 21 kilometers (13 miles) greater than its polar radius) but it is not
> a perfect ellipsoid. Because of this resemblance, an ellipsoid is used
> to approximate the bulk of the Earth\'s shape, and departures from the
> ellipsoid are represented by the geoid elevation above or below the
> ellipsoid. The geoid can be as low as 106 meters (350 feet) below the
> ellipsoid or as high as 85 meters (280 feet) above.

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The Earth\'s Geoid

> The **Amazon River** of South America is the largest river in the
> world by volume, with a total river flow greater than the next top ten
> largest rivers flowing into the ocean combined.
>
> The Amazon River accounts for approximately 1/5 of the world\'s total
> river flow, and it has the largest drainage basin in the world. There
> was an ongoing dispute regarding its length and whether it was longer
> than the Nile; but, a joint study between the Geographic Association
> of Lima and the international scientific community finally concluded
> that the Amazon was longer than the Nile by approximately 400
> kilometers. Because of its vast dimensions, it is sometimes called
> *The River Sea*, and at no point is it crossed by bridges. In 1500,
> Vicente Yañez Pinzón was the first European to sail into the river.
> Pinzón called the river flow \"Río Santa María de la Mar Dulce\",
> later shortened to \"Mar Dulce\" (literally - sweet sea, actually -
> fresh-water sea).

The Amazon basin, the largest drainage basin in the world, covers an
area of some 6,915,000 square kilometers (2,670,000 sq mi), or some 40
percent of South America. It gathers its waters from 5 degrees north
latitude to 20 degrees south latitude. Its most remote sources are found
on the inter-Andean plateau, just a short distance from the Pacific
Ocean.

The area covered by the water of the River and its tributaries more than
triples over the course of a year. In an average dry season 110,000
square kilometers (42,000 sq miles) of land are water-covered, while in
the wet season the flooded area of the Amazon Basin rises to
350,000 square kilometers (135,000 sq mi). At its widest point the
Amazon River can be 11 kilometers (7 mi) wide during the dry season, but
during the rainy season, when the Amazon floods the surrounding plains,
it can be up to 45 kilometers (28 mi) wide.

The quantity of fresh water released by the Amazon to the Atlantic Ocean
is enormous: up to 300,000 cubic meters per second in the rainy season.
Offshore of the mouth of the Amazon, potable water can be drawn from the
ocean while still out of sight of the coastline, and the salinity of the
ocean is notably lower two hundred kilometers out to sea.

Objectives: To observe the amount of water in the Amazon River Basin.

Standards: Science: Unifying Concepts & Processes: Science as Inquiry;
Physical Science; Earth & Space Science Math: Computation & Estimation;
Measurement

TEKS: 4.11B

7.14A

8.12B

Vocabulary: Sea Level River Basin Potable Water Geoid Ellipsoid

Materials: Maps of the World

Colored Pencils

Rulers

Engage: Using a large map, have the students find South America, the
Amazon River, and the Amazon River Basin. Have the students identify on
the GRACE map
(http://www.csr.utexas.edu/grace/publications/water_litho.pdf) the area
covered by the Amazon River Basin. Note: This is a large file and
requires extra time to download.

Teacher asks: "What do you think causes the Amazon River Basin to vary
in the amount of water stored?" Students will write down their
predictions. Teacher will show the GRACE Amazon River Basin lithograph
titled, "Science Serving Society: Water Management."
<http://www.csr.utexas.edu/grace/publications/water_litho.pdf>. Students
will record what they observe in journals.

> Teacher asks: "What do you notice about the Amazon River Basin from
> January 2004 to April 2004? What do you think is happening?" Students
> record responses in journals.
>
> Discuss results of the map observations and review the vocabulary
> terms "river basin" and "sea level". Discuss facts about global
> warming.

Explore: Part 1. Distribute copies of the GRACE map
<http://www.csr.utexas.edu/grace/publications/water_litho.pdf>.

> Have the students complete the following, writing answers in journals
> as needed:

1.  Use a blue map pencil and outline the Amazon River Basin.

2.  Identify the scale on the GRACE map. How high is the water level in
    the Amazon River Basin?

3.  Have students answer each of the following questions using complete
    sentences!

-   Calculate the amount of water in the Amazon River Basin.

-   Calculate the area of a football field.

-   If we put the amount of water in the Amazon River Basin onto a
    football field, how deep would the water be?

> Part 2. Students will use the GRACE map
> (<http://www.csr.utexas.edu/grace/publications/water_litho.pdf>) and
> online maps (links below) to complete the following assignment :
>
> 1\. How high is the water level in the Mississippi River Basin?
>
> 2\. Using the following maps, if the water level rose in the
> Mississippi River Basin by the same amount as in the Amazon River
> Basin, identify 5 cities that would be under water.

[http://nationalatlas.gov/dynamic/dyn_relief.html#](http://nationalatlas.gov/dynamic/dyn_relief.html)

<http://nationalatlas.gov/natlas/Natlasstart.asp>

Explain: Review answers to Explore activity. Students are to answer
"Why" did this happen. Scientists have no definitive results to explain
the level of sea rise, but they do believe that the sea level is rising
3 -- 6 mm each year. Does this affect the Amazon River Basin? What do
you think caused the month-to-month changes?

Elaborate: Students will answer: "What is the amount of change in the
water storage of the Amazon River Basin on a month-to-month basis in
2004? Why is this important? Graph the results.

Evaluate: Using the information gained from the lesson, students will do
one of the following:

1)  Record in cartoon form what happened to a family living on the
    Amazon River in January and again in April of 2004.

2)  It is May 2004. Write a story for the local newspaper about the
    Amazon River Basin.

3)  Interview a grandparent or other elderly individuals and have them
    describe what the weather was like when they were young. How has it
    changed? Relate this information to what was learned in this lesson.
    Write up the results.

Electronic: Students will develop a Powerpoint presentation that
hypothesizes and describes the future effects of global warming.

Teacher

Resources:
[http://nationalatlas.gov/dynamic/dyn_relief.html#](http://nationalatlas.gov/dynamic/dyn_relief.html)

> This is a fun application that shows elevation in the Continental US.
> A student can simply mouse over the map to isolate areas of less than
> 500 feet in diameter to visualize coastal vulnerability in continental
> US. The application requires free Shockwave plug-in.

<http://nationalatlas.gov/natlas/Natlasstart.asp>

> This can be used to query for the elevation of a hometown. A student
> can zoom to a map feature, and can use the map key and elevation
> information to analyze sea level rise. It is also possible to link
> TerraServer for (old) aerial photography & USGS topographic maps or
> Google Earth (<http://earth.google.com/>) for elevation information.\
> \
> DEFINITIONS:
>
> [Sea Level]{.underline} - the level of the surface of the ocean
> relative to the land, halfway between high and low tide, used as a
> standard in calculating elevation
>
> Here are a couple of examples of links that may be used:
>
> http://[www.climate.org/topics/sea-level/index.html](http://www.climate.org/topics/sea-level/index.html)
>
> <http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml>
>
> <http://pubs.usgs.gov/fs/fs2-00/>
>
> [River Basin]{.underline} - the land area surrounding one river from
> its headwaters to its mouth; the area drained by a river and its
> tributaries
>
> <http://earthobservatory.nasa.gov/Study/WeighingWater/>
>
> <http://www.nature.com/nature/journal/v444/n7119/full/444562a.html>
>
> [Potable Water]{.underline} -- water of a quality suitable for
> drinking
>
> <http://nasascience.nasa.gov/earth-science/applied-sciences/national-applications/water-management>
>
> [Geoid]{.underline} - means "earthlike", defines the smooth shape that
> most closely approximates the true shape of the earth with all its
> bumps, bulges, depressions, and divisions; surface that most closely
> approximates sea level in the absence of winds, ocean currents, and
> other disturbing forces
>
> <http://www.ngs.noaa.gov/GEOID/geoid_def.html>
>
> <http://www.esri.com/news/arcuser/0703/geoid1of3.html>
>
> <http://terraetl.blogspot.com/2007/10/geoid-equipotential-description.html>
>
> [Ellipsoid]{.underline} - Since the Earth is in fact flattened
> slightly at the poles and bulges somewhat at the equator, the
> geometrical figure used in geodesy to most nearly approximate the
> shape of the Earth is an ellipsoid of revolution. The ellipsoid of
> revolution is the figure which would be obtained by rotating an
> ellipse about its shorter axis. An ellipsoid of revolution describing
> the figure of the Earth is called a reference ellipsoid
>
> <http://69.17.46.181/manifold/manuals/5_userman/mfd50The_Earth_as_an_Ellipsoid.htm>
>
> [Global Warming]{.underline} - an increase in the Earth\'s atmospheric
> and oceanic temperatures widely predicted to occur due to an increase
> in the greenhouse effect resulting especially from pollution
>
> <http://www.ncdc.noaa.gov/oa/climate/globalwarming.html>
>
> <http://www.nrdc.org/globalWarming/>
>
> *Lesson contributed by GRACE Outreach Teach*

*Gravity Recovery and Climate Experiment*

> <http://www.csr.utexas.edu/grace/>