Units of
pressure and energy occur frequently in environmental applications.
These applications include the measurement of hydraulic head as
pressure, evaluation of hydrological systems as energy (energy balance
equations for flow, solutes and thermal systems). These properties can
be measured in a variety of units, including the ones in the following
calculators:
Pressure
Input:
Units:
Output:
Units:
Energy
Input:
Units:
Output:
Units:
Example:
Pressure head measurements were taken by a consultant at your
current site 30 years ago. You are interested in the changes
in the head at the site since then. The measurements you have
taken are in the units of Pa, and the old measurements were in
pounds per square feet. One of the old measurements is 2.5
lb/ft2, and your recent measurement was 135 Pa. How much has
the pressure head changed in the past 30 years?
Using the calculator you should find that 135 Pa = 2.81 lb/ft2 OR
2.81 lb/ft2 = 134.54 Pa so the pressure head has not changed
significantly.
There are many resources
available for more information on unit conversions. For this
newsletter the following textbooks were used:
Freeze, R.A. and Cherry,
J.A. (1979). Groundwater. Published by Prentice Hall, New
Jersey.
Fetter, C.W. (1994).
Applied Hydrogeology, Third Edition. Published by Macmillan
College Publishing Company, Inc., New York.
