This is an early example of a hydraulic power system and low pressure is a relative term. 300' would give water at 120 psi that would have been higher than the steam pressure used in most steam engines of the time. Hydrostatic head was later replaced by pumps producing higher pressures - typically 750 psi but up to 1100 psi in some hydraulic systems. The smaller tower is for a hydraulic accumulator that helps provide some reserve capacity in a pumped hydraulic power system.