Not sure I agree. That task was "quantity surveying, estimating, and arithmetic" not mathematics. A mathematician would have proved for all cities and terrain

Not sure I agree. That task was "quantity surveying, estimating, and arithmetic" not mathematics. A mathematician would have proved for all cities and terrain topologies there's a critical viscosity of liquid above which it is impossible to effectively drain them, along with an estimate of the lower bound of that viscosity. <grin>