Various thoughts and travels
Nice old truck. Bet it starts right up (firemen are famous for their well maintained equipment).
My guess is it's used for hauling water. Or could that tank be used for fertilizer?
My guess is its mission is now hauling water for whatever might need water where there's no water source. Like mixing farm chemicals out in a field, putting out grass fires, watering livestock, etc.
It does look as though it's being used for hauling water.