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

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