How Does Stream Flow Change over Time?
ES1301  Controls on Discharge: Graphs III

The three graphs show discharge, temperature, and rainfall for the Colorado River below the Glen Canyon Dam in Arizona. Discharge was measured at Phantom Ranch in the Grand Canyon.

Water releases from Glen Canyon Dam are tied to demand for electricity produced by the hydroelectric power plant at the bottom of the dam. Recently, environmental scientists noted that the lack of natural floods below the dam was causing beach erosion and changing environments for native species in the Grand Canyon.

  !   Examine the graphs to interpret what was happening on the Colorado River. Use the information to answer the questions at the bottom of the page.

Data—USGS

9. What do you notice about the timing of the peaks of discharge and rainfall? What do you conclude from this relationship?

10. What relationship exists between temperature and discharge? What do you conclude from this relationship?

11. What do you think is responsible for the regular shape of the discharge peaks? Speculate on the cause of the major discharge peak at the end of March.


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