Reply to "how to model water supply for dual tracks"

Here's a question or two, since we're talking about water supplies.  In the desert or other relatively dry areas, how would the RR find and pump water into the tanks, in quantities large enough always to be able to provide adequate amounts on an instantaneous basis?  Did they rely on gravity fed pipes from streams, or steam (?) powered pumps on very deep wells?  During droughts, did they replenish the tanks from rail cars filled with water? Or did they add tank cars to a train, if they thought that the water supply along the line might be inadequate?