Water intake installation comprising a suction basin from which a pumping station supplies water to a cooling circuit, and a suction tunnel that supplies water to the suction basin so as to maintain a sufficient water level. The water intake installation furthermore comprises a system for supplying additional water, able to supply water to the suction basin from an emergency water reserve. The system for supplying additional water comprises a water duct connecting the suction basin to said emergency water reserve and an obstructing device able to open the water duct if the water level in the suction basin drops in a way defined beforehand as being abnormal. Nuclear power plant comprising such a water intake installation, especially suitable for establishment on a coastline vulnerable to tsunami flooding.
