The aim of this paper is the economic valuation of the water shortages in the irrigated agriculture in the Segura river basin. The methodology consists in the modelling of the water resource system, using the DSS Aquatool-Optiges, and the irrigated activities, by means of mathematical programming. This work includes the policy scenarios proposed in the Spanish Water Planning Law for the years 2009, 2015 y 2027. The results show that the increment in urban water demands in the successive scenarios is translated to a higher water deficit in the irrigated agriculture; even higher in 2027 due to climate change. The direct economic impact on the agricultural sector varies from 237 €/ha for an average year in terms of water availability, to 1.925 €/ha for the more unfavourable scenario. Finally, the contribution of the Tagus-Segura Transfer has been estimated in 253 million euros per year.