In the Marina Baja region there is a tradition of fierce competition for water resources which necessitates the regulation of institutions in order to satisfy the interests of the different water users. The management of the water resources in this region is based on the water exchange between the different users with no legal modification of the water concessions. This situation requires continuous negotiation in order to maintain the balance between urban, tourism and the agricultural demand. In this article we define, describe and analyse the equilibrium model for water resources of the Marina Baja District using a simultaneous equations model (SEM). We analyse variables that influence the water management model through a simultaneous relationship between the above-mentioned demands in the region of the Marina Baja, using a methodology that directly links urban and irrigation demands and makes them relevant to one another from a socioeconomic point of view.

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One of the most controversial issues in recent years in water management has been finding a balance between available resources and water needs related to certain territories. The changes brought about by a new awareness over the need to preserve the environment, the social perception of the ownership of the river channels, the need for adjust financial costs arising from the waterworks and the compliance with European standards urgently require redesign of water supply policies in force at this time. The Júcar-Vinalopó water transfer, considered as an historic aspiration for many years in the region, has been regarded as a key element for solving the depletion of groundwater in a large area located in the southeast of the Iberian Peninsula, mainly for irrigation purposes. In this paper we present an approach to the economic aspects related to the implementation of the project, its investment and financing arrangements and the question of the subsequent management with the impact of the well-known "recovery cost principle", highlighting the current difficulties in carrying out projects of this size, due to severe limitations, as social and economic conditions of the transfer.

The International Water Association bets in its integrated management of water resource model (IWRM) toolbox for a management unit that covers the watershed. However, this point is debatable as there are models of IWRM implementation at the infra-basin level, or even, as in the case we present with this work, when there are several basins that interfere with a particular territory. The problems associated with the confluence of two or more basins in the same territory go through the difficulties in the management of the different resources and their allocation between different uses, especially when the resources are scarce to meet the total demands of water, which occurs in the areas of South-east Spain.Here, global demands are trying to articulate within two deficit basins (the Júcar and the Segura), with external contributions from the Tajo Basin (Tajo-Segura Transfer) and with non-conventional resources from the desalination of seawater. We will try to expose the state of the art at this time, and the alternatives that arise from an economic point of view. Attempts to solve this situation come from far away, even though on many occasions, the economic aspects have not been taken into account, giving rise to investment processes in infrastructures that, due to their costs and the refusal of the users to face them, have generated unstable equilibriums that different governments are incapable to solve.