1-4. Water Supplies. There is usually no time to search for the best water when troops are
in combat. Units must take whatever is available and purify it as needed. Reconnaissance
personnel are responsible for helping commanders locate adequate water supplies.
Engineers use the capacity-of-source (quantities) formula to determine the volume of
streams, wells, or springs and the dimensions of lakes, with their rate of outflow. The
amount of water that passes a point in 1 minute is calculated as shown in the example in
Figure 1-11. The quantity of water is recorded on the reconnaissance overlay in conjunction
with a critical point symbol. Critical point symbols and their uses are discussed later in this
subcourse.
Q=
A x V x 48,000
6m
where
Q
= flow in liters per minute
2m
A
= cross section area of stream flow in square meters
V
= velocity of the water in meters per second
48,000 = conversion and correction factor
4m
top width + bottom width
A = depth x
=
Cross section area of a stream
2
6 4
2x
= 2 x 5 = 10 square meters
30m
5 ft
2
Point B
AB (m)
5m
Point A
V=
=
= 0.2 meter per second
10 sec
time (sec)
10 sec
Q = 10 x 0.2 x 48,000 = 96,000 liters per minute
Figure 1-11. Example of Capacity-of-Source Formula
1-9
EN 5622
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