Civil Engineering - Hydraulics - Discussion

Surge tank is a water storage device used as pressure neutralizer in hydropower water conveyance system to resists excess pressure rise and pressure drop conditions. A surge tank (or surge drum or surge pool) is a standpipe or storage reservoir at the downstream end of a closed aqueduct, feeder, dam, barrage pipe to absorb sudden rises of pressure, as well as to quickly provide extra water during a brief drop in pressure.

This is shown in the impulse turbine when the penstock after surge will provide the surge can control the pressure in penstock indirectly its control the water hammering effect also.