Geography 110H
Fall 1997

Assignment 6
Due: Tuesday, Nov. 4
(Not yet edited for Fall 1998!)

Our topic is the hydrologic cycle and water resources, and for this assignment I would like to have you look at some aspect of the hydrologic cycle that relates local water resources to the global pattern of climates. There are numerous online resources providing information on runoff and streamflow; there are some that discuss flooding in general or particular floods that have occurred recently; there are others that discuss watershed studies or that discuss groundwater. I have provided some links below.

The assignment this time has two parts. For the first part, I am looking for you to focus on a case study of a watershed, an aquifer, or a particular body of water (i.e. a river or lake). There may be a particular environmental problem or research question associated with human interference in the workings of the hydrologic cycle

Examples could include the shrinking Aral Sea in central Asia; the depletion of the Ogallala aquifer in the high plains of the midwestern U.S.; the declining water levels in Mono Lake, California, and the resulting impact on rare and endangered species; the poisoning of the Kesterson Reservoir and of other areas in the Central Valley of California by increasing concentrations of selenium in irrigation return flow; the channelization of the Kissimmee River in south Florida and the subsequent project by the Army Corps of Engineers intended to restore the natural ecosystem; the decline of the Everglades in response to human alterations in the natural flow system and in water quality; deforestation and its impacts in (you pick the location); flood hazards and flood management on the Yangtze (or other rivers) in China.

Another option would be to select a particular river or river system and investigate its characteristics, including the size, shape, and underlying geology of the watershed, the pattern of flow observed over time, the physical characteristics of the channel system, and the effects of human activities on flow patterns or channel morphology. An atypical, but fascinating and well-documented example is the Colorado River in Grand Canyon (some links are listed below). Other examples might include (in no particular order; these are names that just came to mind) the Platte River, the Altamaha, the Savannah River, the Eel River or Redwood Creek in the Pacific northwest, the Huang Ho, the Rio Grande, the
Amazon River, the Ob and the Yenisei in Russia, the Irrawaddy, the Indus, the Ganges-Brahmaputra, the Yukon, etc. I haven't researched all of these and I don't know what information may be available on the web.

(look, for example, at the story about the experimental flood on the Colorado River in the Grand Canyon; or  look at one of the sites that discusses the fate of the Aral Sea in central Asia). Alternatively there may be a natural event, such as a flood or a drought, that illustrates something important about regional hydrology. In order to provide an appropriate context, make sure you have read through chapter 9, and I would recommend you also look at news reports 4 and 5 in chapter 14, as well as the section near  the end of that chapter on floods and river management. Put together a written synthesis of what you learned from the case study, and identify a couple of key research questions that remain to be answered.

For the second part, I want you to help in making a regional comparison of the relative amounts of runoff carried by different rivers. The total volume of water that flows down a river in a given year can be measured in cubic feet, cubic meters, acre-feet, or any other unit of volume. This water is derived ultimately from precipitation, and from our basic introduction to the hydrologic cycle we know that only a fraction of the water that falls as precipitation will actually appear in the stream as runoff. If we divide the total volume of streamflow by the total drainage area of the watershed, and if we convert units correctly, we can express the total amount of streamflow as an equivalent depth of runoff per unit area of the watershed, and we can express the number of inches or centimeters of runoff as a percentage of the total number of inches or centimeters that fall as precipitation over the course of the year. Your job is to select several watersheds from different climatic regions; to find both the total annual depth of precipitation and the total annual equivalent depth of runoff; and to calculate runoff as a percentage of precipitation. Compare your results from different watersheds and discuss why they look the way that they do.