Some means for cutting off the water supply to the turbine are required to avoid wasteful
leakage when the unit is shut-down and dewatering is required to permit access for
maintenance of the connecting penstocks. Penstock gates at the intakes and inlet valves
adjacent to the turbine are provided for this purpose. The intake has a motor or hand lifted,
gravity lowered gate and valve, preferably with an automatic release operated by an excess
flow device if a burst occurs in a pipe line. When a tunnel and pipeline connect the reservoir
to the turbines, an additional valve may be provided at the junction of the tunnel and the pipe
line if the latter is long, and either this valve or the intake gate should be arranged for remote
closure in an emergency