Water lift for a six-day border exercise
A company of 96 Rangers is deployed for a six-day border exercise at a post 40 km from the depot. The water scale is 3.5 litres per man per day for drinking and cooking, and the medical officer insists on a further 20 per cent on top of that figure as a reserve for washing and emergencies. One water bowser is available; it delivers 850 litres of usable water per trip. The round trip is 80 km at an average of 40 km/h, and each trip also needs 45 minutes for loading and 30 minutes for unloading. The bowser burns 6 litres of diesel per round trip and the depot holds 40 litres. The depot opens at 2200 hours and the first water must be at the post by 0600 hours. The quartermaster must confirm the plan to the adjutant before midnight.
1. Calculate the total water requirement, the number of bowser trips needed, and check the diesel and the 2200–0600 time window. State whether the plan closes.
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Water: 96 × 3.5 = 336 L per day; × 6 days = 2,016 L. Reserve at 20% = 403.2 L. Total = 2,419.2 L, rounded up to 2,420 L.
Trips: 2,420 ÷ 850 = 2.85, so 3 trips (2 trips give 1,700 L, short by 720 L).
Diesel: 3 × 6 = 18 L against 40 L held - sufficient, 22 L spare.
Time: each trip = 80 ÷ 40 = 2 h driving, plus 0.75 h loading and 0.5 h unloading = 3.25 h. Three sequential trips = 9.75 h. The window from depot opening to last light is 8 h (2200 to 0600).
The plan is short by 1.75 h: the bowser cannot complete three trips in the window. The water arithmetic closes; the movement plan does not. Report the two separately - a quartermaster who reports only "water arranged" has hidden the failure, and the post runs dry between the second and third lift.
2. On the morning of day 4, 24 extra men arrive and stay to the end of the exercise. Recompute the water position and say what it does to the movement plan.
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Extra demand: 24 × 3.5 = 84 L per day × 3 remaining days = 252 L; with the 20% reserve = 302.4 L, rounded to 303 L.
Headroom already in the plan: 3 × 850 = 2,550 L delivered against 2,419.2 L required = 130.8 L spare.
Shortfall = 302.4 − 130.8 = 171.6 L, so an additional movement is unavoidable. Options: a partial fourth bowser trip carrying about 200 L, or a smaller vehicle, or loading the extra onto the day-4 replenishment. Diesel rises to at most 24 L, still inside the 40 L held, so fuel is not the constraint - time is. A fourth solo round trip adds another 3.25 h, which no night window can absorb.
The sound decision is therefore not "send the bowser again" but "send the extra water on a lift that is already running": over-load the day-4 trip toward 1,000 L if the bowser can legally carry it, or add a second vehicle. Also check whether the 20% reserve can be partly released for washing while drinking water stays protected.
3. Recommend one measure to the quartermaster that fixes the time problem without breaching any constraint, and justify the choice.
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Recommendation: pre-position water at the post before the exercise begins, using a daylight lift, and keep the 2200–0600 window for topping up only.
Why this one: the binding constraint is time, not water, fuel or money. Three trips need 9.75 h and the window gives 8 h; no amount of careful driving recovers 1.75 h because the depot opening time is fixed. Pre-positioning moves one full 850 L load outside the window entirely, which removes roughly 3.25 h of in-window work and leaves two trips (6.5 h) comfortably inside 8 h.
Alternatives and why they are weaker: opening the depot an hour early buys only 1 h and needs authority the quartermaster does not have; cutting the reserve breaches the medical officer's instruction; a second bowser solves it but may not exist and takes longer to arrange than one daylight lift.
Report the arithmetic with the recommendation - 2,420 L required, 3 trips, 9.75 h against an 8 h window - so the adjutant approves a decision, not a favour.