The history of water law and water administration in the New World is based on roman and more especially on iberian law experiences, so are the fueros or the siete partidas. The development of water law in the hispanic world during the colony age -especially appointed in the summary of the supreme indian law from 1681- inhered the creation of a new juridical tendency with the so-called mercy of water rights (merced de aguas) which were given by the crown to private men. With the begin of chilean republic age until the codification of national chilean water law (1951, 1969 and 1981) the influnce of these water using rights (derecho de aprovechamiento) changed according to the different political sceneries (liberalism, socialism, neoliberalism). Actually there is a debate in modifying the water rigths due to a variety of conflicts, principally caused by the private use of a scarce ressource.