The objective of this work is to show which would be the economic benefits for the agriculturists when the water is assigned by a market. The agriculturist receives a water quantity and under a scheme of decentralized market he decides to sell or to buy water according to a benefit function. In addition, the mexican institutional frame that governs the allocation of the water in agriculture is analyzed, putting special emphasis in the possibilities that exist at the moment for the operation of the water in a market. In order to calculate the possible benefits derived from the operation of the market, a neoclassic technology was constructed to a model supposing and hoping that the price that would reach the water in a hypothetical market was the result of a process of walrasian auction. A calculation with values of the district of irrigation of the Yaqui and Coast of Hermosillo was made, for which they had to become strong supposed on the form of the technology and supposing null costs of transaction. The conclusion is that positive benefits derived from the commerce of the water through a market would exist, although it must be clarified that the obtained results are only indicatives, due to they are not had considered the production functions that the technologies used in the agricultural production represent, nevertheless is considered that the proposed model is the suitable one.