The present invention relates to a water supply method for water culture of a large quantity (large amount) of crops disposed in multiple layers in a vertical direction in a greenhouse. Water from an upper water reservoir (tank) arranged as a first layer in the greenhouse firstly flows down and is supplied, via a supply pipe, to a water supply container arranged as a second layer in a horizontal direction below the water reservoir. When the firstly flowed down water reaches a predetermined water level within the water supply container, the water secondly flows down and is supplied to a culturing container arranged as a third layer in a horizontal direction below the water supply container, via a plurality of water outlets arranged at the same height. When the secondly flowed down water reaches a predetermined water level within the culturing container, the water thirdly flows down and is drained to a water drain container via water outlets. The thirdly flowed down water fourthly flows down into a lower water reservoir arranged below the water drain container, via water outlets arranged identically to those of the culturing container, such that the fourthly flowed down water is collected in the lower water reservoir is supplied to the upper water reservoir (tank) by means of an automatic pump. An automatic water supply system repeats the above-described processes to reuse the drained water.La présente invention concerne une méthode dalimentation en eau pour culture hydroponique dune grande quantité de produits agricoles placés verticalement sur plusieurs niveaux dans une serre. Leau dun réservoir supérieur constituant un premier niveau dans la serre sécoule premièrement vers le bas et alimente, grâce à un tube dalimentation, un récipient dalimentation en eau constituant un deuxième niveau dans une direction horizontale en dessous du réservoir deau. Lorsque leau sétant écoulée premièrement vers le bas atteint un niveau prédéfini dans le récipient dalimentation en eau,
