Physics B Hydrostatic Pressure: Dams
Instructions to students:
It may be scary when a levee breaks, but what about a dam!!! Dams, even more than levees, are
subject to tremendous force due to hydrostatic pressure. This pressure is variable, since often the
reservoir
behind the dam is raised and lowered at different times during the year. In order to insure the safety of the
public, much design work has to go into the development of safe dams. The hydrostatic pressure (or
hydrostatic “head”) changes tremendously with water depth. A dam that is safe under certain conditions
can be unsafe when the water rises, even though the height of the dam is sufficient to contain the rising
waters.
Engineers who build high dams, such as Hoover or Norris dam, use special techniques to insure
that forces on the dam do not result in failure of the dam. Often, the surfaces of dams are curved.
You are on a TVA Educational Outreach committee, and the mission of your committee is to
educate the public about the TVA dams in your region. The Discovery Channel will film your presentation
and present it to the viewing public.
a) What is the shape of a really high dam, such as the Hoover dam?
b) What hydrostatic pressure is Hoover dam subjected to?
c) Closer to home, what dams are in the TVA system, and what hydrostatic pressure head must they
withstand?
d) What ranges in water depth (and hydrostatic pressure) must a nearby dam, such as Norris Dam,
withstand? How does this compare to Hoover Dam?
e) What is the history of the TVA system? Why was it built? How did TVA affect the decision of
the US government to build Oak Ridge at its current location?
Your team should consist of several experts.
The Chief Engineer and Commander, US Army Corps of Engineers: You lead the effort, and
coordinate the work of your team. You also coordinate the presentation during filming by the
Discovery Channel.
TVA Engineers: You are experts on hydrostatic pressure and the design of dams. You take the
lead on the dam design.
The historian: You research, and present, the history of the TVA system. What were the reasons
for the creation of the Tennessee Valley Authority?
Your team is to put together a presentation of its findings for the Discovery Channel. Clarity of
presentation and correct facts are of utmost importance. The presentation should include
A historical analysis: TVA through the decades.
Diagrams: A diagram (or maybe a model) of a high dam.
Calculations: The hydrostatic pressure must be calculated, as well as the change in hydrostatic
pressure during different seasons of the year. Why is the reservoir depth changed?
A presentation: The Discovery Channel will film your presentation – so look sharp!