Sample Computation. As a first step, you will need to accumulate the necessary background data for making your
calculations. In the following scenario, you are the water section NCOIC of an S&S Company. The company commander
briefed you on the Operation Plan (OPLAN). Your section is to provide water support for a light infantry division of 12,000
personnel (a medium force deployment). The operational environment is hot/arid. Water quality is saline with total dissolved
solids (TDS) at 35,000 milligrams per liter and a water temperature of 30€C. Water source availability is plentiful. The force
will be in the field for several weeks. The ration policy will be B-Ration, MRE, and B-Ration. You will therefore provide
sustaining water support to this force. There is no NBC threat. The CO of the division has determined that laundry/showers
will be allocated at 2 showers and 15 pounds of laundry per soldier per week. Estimated water resource back-up requirement
is none. You have four 3,000-GPH ROWPUs, two E-5 team chiefs, eight at E-4 and below. Your mission is to establish two
water points with two 3,000-GPH ROWPUs at each water point.
Consumption Factor. As a second step, you need to determine the purification production requirement (or consumption
factor) for each echelon to be supported. For example, in the previous scenario, the echelon to be supported is a division of
12,000 personnel. Table 1-1 contains the information identifying the medium force deployment at a division level.
Then, you will derive the final consumption factor through a process of locating the necessary components on the Army
By cross matching the first line on the table labeled Universal Unit Level
Force Echelon/Command Level Table.
Consumption with the environmental columns to the right under the titles Hot/Arid/Sustaining, the first factor is 7.90 gallons.
The next factor comes from the line labeled Level I and II Medical. It adds an additional factor of 0.4 gallons to the previous
number for a total of 8.3 gallons. In addition, the OPLAN calls for showers and laundry operations under the same
environment. The line labeled Central Hygiene... is cross matched to the environmental columns titled Hot/Arid/Sustaining
where you locate the factor of 9.8 gallons. By adding all three of these numerical values (7.9, 0.4, and 9.8), the result is 18.1
gallons per man per day as the total daily consumption factor per soldier. This factor can be rounded to 18 gallons per man
Calculating Total Daily Requirement. To get the total daily requirement for the support force multiply the total force
personnel of 12,000 by the daily consumption factor of 18 gallons (12,000 x 18 =) results in 216,000 gallons per day. The
next step is to determine the shortfall, if any, which is the number of gallons short of the total necessary per day to sustain the
force given the full capacity of the equipment designated for the mission.
Determining Shortfall. To determine the shortfall, it is necessary to first calculate the production capacity of all the
ROWPUs at your command to determine the daily water production rate and then subtract that result from the total daily
requirement. The difference between the numbers will be the shortfall if the result is lower than the total daily requirement.
To determine the total production flow, however, you will first