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Department of Geography, University of Victoria
GEOGRAPHY 370: HYDROLOGY – Spring 2019
Instructor: Dr. Matthew Asplin
Laboratory Assignment 3:
Water Vapour, Energy, Evapotranspiration and Groundwater
71 marks
Date Assigned: B01 (Feb 11
th
), B02 (Feb 14
th
)
Due Date: B01 (Mar 4
th
), B02 (Mar 7
th
)
In this lab you get a chance to work through some of the equations that we have encountered in
this course so far pertaining to water vapour, energy budgets, evapotranspiration and
groundwater.
Use a spreadsheet, calculator or scripting for the calculations. In this lab
assignment, you do not have to show all of your work, but you must provide enough sample
calculations that we can follow your methodology and you can demonstrate that you know where
your answers came from.
Learning Outcomes:
1.
Students will become familiar with equations in this course pertaining to water vapour
transformations, energy budgets, and estimates of evapotranspiration
2.
Allow students the opportunity to become comfortable with equations and calculations in
excel or equivalent analysis software (if desired)
Background Information and Some Equations
Additional supporting and equation information can be found in your textbook and may be helpful
as you work through this assignment.
Pressure and Weight
The mean pressure of the atmosphere at sea level is (1013.25 mbar or
101.325 kPa or 1013.25 hPa or 101,325 Pa or 101,325 N m
-2
or 101,325 kg m
-1
s
-2
).
Pressure,
P
equals force acting over an area,
A
. The force of the atmosphere is due to the weight of air,
mg
(
m
=
mass,
g
9.8 m s
-2
= the acceleration of gravity). Hence the pressure of the atmosphere can be
written as:
Since we know
P
and
g
at sea level, the mass of a column of the atmosphere 1 m
2
in area is
P
/
g
=
m
/
A
10
4
kg m
2
.
It is useful to work with vertical columns of air (or water) since we often want to
solve for “depth” of water, in cm or m.
Density
(
) is mass (
m
) divided by volume,
V
and is usually expressed with the units of kg m
-3
A
mg
=
P
/
.