EarthLabs > Drought > Lab 6: Drying of the American West > 6C: Can the River Continue to Meet Demand for Water?

Drying of the American West

Part C: Can the River Continue to Meet Demand for Water?

  1. Go to the Bureau of Reclamation's Colorado River Water Use webpage. This table is a record of the amount of water used by states and Mexico by year since record-keeping began in 1906. Scroll through the table to see if you can get a sense of how water use has changed over time.
  2. Visit the Bureau of Reclamation FAQ site to learn more about the Colorado river system and the dams.
  3. Download this spreadsheet file (Excel 23kB Jul21 08) of the Colorado River water use data. Open it in Microsoft Excel or a similar spreadsheet program.
  4. Select appropriate columns of data and generate an X,Y (Scatter) graph to show Arizona water use by year. Repeat for the other two states and Mexico. On your graphs, add linear trendlines or 10-year moving averages to smooth the data and interpret the trends.

Checking In

  • Describe the trend of water use in the states of Arizona, California, Nevada, and the country of Mexico.
  • How does water use in the states compare to the natural flow of the Colorado River (see graph in Part B) over the same time period?

Stop and Think

9. Calculate the percent increase in AZ water consumption between the years 1906 and 2008.
10. Based on the data in this section, describe what do you think will happen if the consumption of Colorado River Water continues to grow at its present rate. Have we reached the carrying capacity of the watershed? Explain your reasoning.

Do reservoirs prevent or merely postpone a water crisis?

  1. Go to the Earth Observatory Article, Drought Lowers Lake Mead. Skim the article and view before and after images of the dramatic changes in the water level of the reservoir named Lake Mead.
  2. Move your cursor on and off the first satellite image in the article to activate the rollover that shows the change in area covered by the reservoir between 2000 and 2003.
  3. Scroll down to the high-resolution images and compare how the shoreline and islands changed between the images.

Checking In

  • How might the change in water levels affect you as a recreational boater? Give a specific example, naming features that are labeled in the pair of images.

Stop and Think

Imagine a half-full bathtub that is being filled by tap water at the same time as the drain is open, letting water out. Depending on the balance of water coming in and going out, the water level in the tub could get higher or lower. Compare the Lake Mead reservoir to your mental picture. Rivers flowing into the reservoir are like the tap water going into the tub and water flowing out from the dam is like water flowing down the drain.

11. Given that long term changes in climate are reducing inflows into the reservoir, and that outflows through Hoover Dam are growing to meet demand by an increasing population, what is the projected result in the reservoir? What would you need to know in order to predict the date of the result?
12. Based on data you examined in this lesson as well as other sources, do you think that reservoirs in arid lands prevent or merely postpone water shortages?

Optional extension

View this graph of Historical Lake Mead water levels and describe the trends that you see.

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