Are You Getting Thirsty?

Student Worksheet - An Introduction to Drought as an Ecosystem Stressor

Refer to the following Web pages for answers to the questions below: – Climate TimeLine Drought Tutorial – Climate Science, 10 year time scale – Climate Summary, 100 year time scale – Climate History, 1000 year time scale – North American Drought Variability Table

  1. What is a hydrograph?
  2. What was the most destructive climate-related event during the 20th century?
  3. What happened during the early 1940s that caused the deaths of 3 million people in China?
  4. What were four possible reasons for the Ancient Pueblo (“Anasazi”) people of Mesa Verde to abandon their homes in Colorado and migrate south to New Mexico and Arizona?
  5. What evidence is there for a relation between climate and the collapse of the classic Mayan culture?
  6. What climatic events coincided with the disappearance of the Roanoke Colonists?
  7. How do estimates of PDSI based on tree-rings compare with PDSI values calculated from actual measurements with scientific instruments?
  8. What effects in the southern U.S. and Pacific Northwest would be expected during a La Niña event?
  9. Droughts in mid-1950s in the western U.S. were the motivation for what human activity?
  10. Refer to Maps 1, 2, and 3 on the “CTL and Drought - Part 3” page ( Here’s how you can use NOAA’s “Climate Diagnostic Center’s Monthly Mean Compositing Page” ( to decide which of these maps corresponds to the periods 1934-1939, 1954-1956, and 1985-1995:
  11. On the Climate Diagnostics Center page:

    • select “Palmer Drought Severity Index” from the pull down menu next to “Variable?”;
    • select “Dec” from the pull down menu next to “Ending month”;enter “1934” and “1939” in the boxes next to “Enter a range of years”; and
    • Click “Create Plot”.

    Compare the resulting map to Maps 1, 2, and 3 to decide which map corresponds to the 1934 – 1939 period. Repeat these steps for the other time periods.

  12. Refer to the “North American Drought Variability” Table ( Click on the animation graphic to display the “Reconstruction of Past Drought Using Instrumental and Tree-ring Data” window, and use the playback tools to find answers to the following questions:
    1. In which years between 1770 and 1800 was the coast adjacent to the area that is now the Channel Islands National Marine Sanctuary subjected to an extreme drought (PDSI = -4.0 or less)? See the map of National Marine Sanctuary sites at or to locate the Channel Island NMS.
    2. According to instrument measurements, in what years during the first half of the 20th century was the area adjacent to the Channel Islands National Marine Sanctuary exposed to extremely wet conditions (PDSI = 5 or more)?
    3. According to instrument measurements, in how many years during the “Dust Bowl” drought (1930 - 1939) was the coast adjacent to Gray’s Reef National Marine Sanctuary exposed to lower-than-normal precipitation (PDSI less than 0)?
    4. Read the introductory page about the Tijuana River National Estuarine Research Reserve at What do you think this estuary would have been like in 1990?
  13. Here’s how you can obtain a hydrograph that will give you an idea about freshwater inflows to the Grand Bay National Estuarine Research Reserve (Jackson County, Mississippi).
    • Refer to the Climate TimeLine Data Access page (
    • Click on “Find Your Place from NGDC.”
    • Click on “U.S. Counties.”
    • Choose “U.S. Stream Gauges” from the “Select” pull down menu on the left of the page.
    • Type “Mississippi” and “Jackson” into the “State Name” and “County Name” boxes. Click “Select Data.”
    • The program should return two Stream Gauge Stations that match the search criteria. Click on “Pascagoula River At Graham Ferry, Ms”.
    • Select “Surface Water in the “Data Category” pull down menu at the top of the page.
    • Select “Time Series: Monthly statistics” in the “Available data for this site” pulldown menu.
    • A new window should appear; click the box next to “Discharge, cubic feet per second,” and set the date range to “From: 1994-01” “To: 2006-12,” then click “Submit”
    • You should see a table of monthly streamflow beginning in 1994.
      1. What was the maximum monthly mean streamflow recorded?
      2. What was the minimum monthly mean streamflow recorded?
      3. In general, at what time of the year are streamflows at their maximum?

  14. The Padilla Bay National Estuarine Research Reserve is located in the Salish Sea near Mount Vernon, Washington. The Salish Sea is a large estuary fed by many fresh water sources including the Fraser and Skagit Rivers. What was the longest period of time since 1950 that the peak flow from the Skagit River did not reach 100,000 cubic feet per second?
  15. Hints:

    1. If you don’t enter a county in the fourth step (above) the program will return a list of all stream stations in the specified state.
    2. Consider selecting one of the other options under the “Available data for this site” pulldown menu instead of “Surface-water: Daily streamflow.”


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