The Upper Guadiana basin, in Spain, presents important conflicts between the agricultural sector and the environment due to their competence for water resources. The high development of irrigation has led to the over-exploitation of the aquifers, which are the main source of water in the area, and to the loss of wetlands of high ecological value. The River Basin Authority (RBA) has recently designed a new water management plan which included a group of measures aimed at reducing water consumption. Our objective is the development, with the active participation of the stakeholders, of a decision support system composed of an economic model and an object-oriented Bayesian network, used to evaluate the trade-off between agricultural economy and the environment that the different water management measures would have at different scales. Results obtained show that attaining a reasonable probability to recover the aquifer level requires, at the same time, a high enforcement capacity of the RBA to make farmers comply with water restrictions and a high price paid by the RBA for the irrigation rights. Compliance with water restrictions leads, however, to certain losses in farm income, especially in small vineyard farms, unless additional measures are taken to compensate those potential losses.