Abstract: A drainwater/sewage treatment installation for producing electrical power and for regulating waterflow in a drainage network is provided. The installation comprises at least a first reservoir, at least a second reservoir below the first reservoir and conduits connecting the reservoirs. The invention combines a drainage network having a pumped energy storage hydroelectric station and at least a two reservoir system wherein the second reservoir is connected to the drainage network in order to be able to serve as a temporary storage facility for the purpose of spreading out peaks in the flow rate of rain water in the drainage network.

Abstract: For the purpose of effecting a quasi-permanent raising of the normal water level of an impounded reservoir and thereby augmenting its storage capacity except during the passage of major floods, the invention consists of rigidly fixing to the sill of the spillway a water level raising means comprising at least one vertical plate capable of resisting the water loads when spilling moderate heads (for discharging the floods of shorter recurrence intervals) but bending at its lower portion where it is fixed to the sill at a predetermined head not higher than the maximum water level in order to discharge larger floods.

Abstract: For the purpose of effecting a quasi-permanent raising of the normal water level of an impounded reservoir and thereby augmenting its storage capacity except during the passage of major floods, the invention consists of installing on the sill of the spillway a water level raising means comprising at least one heavy element, the said means or water level raising elements being capable of resisting the water loads when spilling moderate heads (for discharging the floods of shorter recurrence intervals) by virtue of their own weight but breaching by overturning at a predetermined head corresponding to a level not higher than a predetermined maximum water level in order to discharge larger floods.