Investigation of the Aral and Salton Seas

Lesson Plan:

Overview
 The Salton Sea , located in Imperial County of Southern California, is a saline lake that was formed in a large basin (called the Salton Trough) created by releasing bend of the San Andreas fault. In modern times, the Salton Trough became a lake in 1891, but dried up within a year. It began to form again in 1893. In 1905, the Colorado River was diverted into the Salton Trough to create the Salton Sea. The Salton Sea was originally a fresh water lake. The Aral Sea , located in Uzbekistan and Kazakstan (both countries were part of the former Soviet Union), is historically a saline lake. It is very much like the Salton Sea of Southern California, except much larger. The Aral Sea was also formed in a basin formed by a releasing bend of a strike slip fault. The Aral Sea and the Salton Sea are both prime examples of dynamic environments. The Aral Sea is considered a true environmental disaster, but most students do not think this could ever happen in the United States, much less in their own back yard. By making students aware that the Aral and Salton Seas share many similarities, we hope that students will become more environmentally conscious. It may be too late to "save" the Aral Sea, but there is still hope to prevent the ecological collapse of the Salton Sea.

Similarities between the Salton (SS) and the Aral (AS) Seas

  • Recent major environmental changes that were caused by humans.
  • Potential dangers from military toxins/wastes.
  • Loss of fisheries due to human-caused environmental changes.
  • Sea water that is polluted by sewage, pesticides, defoliants, selenium (SS), agent orange (AS), and DDE (SS).
  • Salinity at near-fatal (SS) or fatal (AS) level for sea-living organisms.
  • Salinity levels that are still on the rise.
  • Major source of airborne particles (dust) for their respective regions.
  • Cotton growing regions.
  • Closed systems, with no outlet except for evaporation.
  • The health of animals and people in the areas have been negatively affected.
  • Long history of natural cycles of drying up and re-establishing bodies of water.
  • Political issues are encountered when trying to deal with the environmental problems. Issues concerning the Salton Sea need to be addressed by the United States and Mexico. Aral Sea issues need to be addressed by five independent Asian countries; Uzbekistan, Kazakstan, Turkmenistan, Tajikistan and Kirghizstan.
  • We have a good supply of space shuttle images of both regions.
  • Except for scale, the regions are very similar. The environmental problems of the Aral Sea are more advanced than those of the Salton Sea. If the environmental issues surrounding the Salton Sea are not dealt with, it will advance to a similar state to that of the present Aral Sea.

    Goals:
    Understanding closed systems and how human actions can change natural systems.

    Central Question:
    What would happen to a body of water in a closed system if its incoming water supply was reduced or cut off?

    Materials for each team:
    Internet access
    Other resources:
    Worksheets
    Diagrams of the Aral and Salton Seas
    Atlases and maps
    rulers and calculators

    Setting the stage:
    Begin with a class discussion about the water cycle and closed hydrologic systems. Do the students understand why a body of water wouldn't have an outlet?

    Exploration/Investigation
    Working in teams, split the class into two groups. Have half of the class concentrate on the Salton Sea, half on the Aral Sea. Use atlases, rulers and calculators to estimate the dimensions of the bodies of water. Add a scale bar to the respective diagram. Make sure that the students note what year the atlas was published. Why might that be important?

    Go to the respective web sites:
    Aral Sea
    http://VisEarth.ucsd.edu/VisE_Int/aralsea/index.html

    What is a "closed system"?
    What are the names of the rivers supplying the water to the Aral Sea? Where is the original source of this water? What naturally occurring global conditions could cause the Aral Sea to increase in volume? What naturally occurring global conditions could cause the Aral Sea to decrease in volume? Currently we are in an interglacial period (a warming period.) What would be happening to the Aral Sea if it were in its natural state? Why? Do we have any other evidence of this?
    Why is the Aral Sea decreasing in volume? Is this decrease in volume on a major or minor scale? Predict some of the effects of the decreasing volume of the Aral Sea on the surrounding environment. Would animal life be affected? Humans? Plants? Climate?
    Go to link Navigate the Aral Sea.
    Use the colored circles to add information about the Aral Sea to your Aral Sea diagrams. Be sure to check the orientation of the diagram to the orientations of the images.
    What is the major source of employment in the Aral region? What used to be the major source of employment in the region? Can you use the images to determine the local climate? For instance, note the number of months that there is sea ice covering some portion of the Aral Sea. What is the latitude of the Aral Sea? Is this similar to the latitude where you live? They grow cotton in the Aral Sea region. Where in the United States do they grow cotton? What are the latitudes of these areas? Are you surprised to find cotton growing near the Aral Sea? Why?
    Make a list of the environmental issues facing the region. What are some of the ways that you would suggest to help solve some of the environmental predicaments of the region?
    Were there any images that you especially liked? Did you find any of the images surprising? If so, how?

    Salton Sea
    http://VisEarth.ucsd.edu/VisE_Int/aralsea/SaltSea_intro.html

    What is a "closed system"? What are the reasons that the Salton Trough is a closed system? What are the names of the rivers supplying the water to the Salton Sea? Is there any other source of water entering the Salton Sea?
    Have you read any newspaper or magazine articles about the Salton Sea? If so what specific topics did they address?
    What is grown in the Salton Sea region? Does the agriculture in the area create any environmental concerns/problems? Do any organisms live in the Salton Sea?
    What is the recent history (since 1900) of the Salton Trough? What is the more ancient history of the Salton Trough? What is the name of the fault that is responsible for creating the basin that contains the Salton Sea? The Salton Trough is below sea level, so why hasn't it been inundated by the ocean (from the Gulf of California)? Originally, the Salton Sea was fresh water. How did the water become saline? Is the salinity of the Salton Sea a problem?
    Pollution:
    What are some of the pollutants found in the Salton Sea?
    What are some ways that you would suggest for helping to save the Salton Sea? How would you deal with the problem of increasing salinity? How would you deal with the problem of increasing pollution?

    Bringing it together:
    Class discussion
    Have groups give short presentation about their respective sea to enlighten the other half of the class. Have a discussion to determine the common issues faced by both the Aral and Salton Seas. List these on the blackboard. List issues that are unique to each region.

    Assessment:
    Diagrams of the regions
    Questions

    Background:
    All background information is contained in the web pages.
    http://VisEarth.ucsd.edu/VisE_Int/aralsea/index.html
    http://VisEarth.ucsd.edu/VisE_Int/aralsea/SaltSea_intro.html

    Activity Sheets:
    Diagram of Aral Sea
    Diagram of Salton Sea