It does seem like a lot, but not so much when you consider that every member of personnel actually doing those man-hours needs water, just as surely as they nee

It does seem like a lot, but not so much when you consider that every member of personnel actually doing those man-hours needs water, just as surely as they need a salary - and unlike the salary, the water has to be shipped out. In the desert a person can easily drink a gallon a day, not to mention all the other uses of water on a base. That's nearly 5 kilos of supplies per person per day. Most personnel are not firing ordnance, flying planes, or driving dozens of miles every single day - but they will all go through water like clockwork.