An experiment was carried out at our laborataries to investigate the flow through two pipes of same diameter fitted at the same height from water level inside of a water tank as shown. It is found the longer pipe line inside the water tank generates a higher speed resulting more powerfull flow. Flow in this pressure pipe develops due to gravitational accelaration on a horizontally flowing water column also, when it is an enclosed stream of flow. If this length is short it is not possible to develop the speed of an stream line.
A second experiment carried out with a coiled pipe line instead of a straight length. We found the similar effect for the same length. Accordingly we can device a hydro power booster pipe connected at sluice gate end. without extending the pipe to a distant location.
Thus the method can be diversified further to minimize the extending distance from hydropower dam, by giving a spiral shape to the pressure pipe as shown below.