The aim of the State Water Societies (SWC) is the construction of works that have been considered necessary by the public Administration and in that the users are arranged to participate. They are public companies that have been constituted by Law 13/96, of 30 of December, of Fiscal Measures, Administrative and of the Social Order in Spain. Its objective is "the construction, conservation and operation of works and infrastructures realted to the regulation of the hydraulic resources, their conduction, purification and desalination, and to the cleaning and purification of residual waters". The financing of works is carried out with governmental capital and private, although the participation of the public sector is superior of the private one. One of the main reasons that justifies the existence of the societies is the necessity to reduce the public deficit. At the same time, it is valued that the consumers are arranged to participate in some form in the construction of works. The SWC have less than three years of existence, the reason why it is ventured to make another valuation of his activity that the merely enterprise one. Nevertheless, he is interesting to explain his origin, to raise his performance within the framework of the Spanish hydraulic policy and to know his financing. The appearance of SWC in the Spanish hydraulic sector has positive and negative effects on the economic agents: consumers, companies and public sector, which will be detailed. Also, its paper in the sector will be analyzed within the framework of the hydrologic planning