Sequía y escasez en la Demarcación Hidrográfica del Segura, impactos económicos, déficit hídrico y alternativas de gestión

Resum

Drought is an increasingly recurrent phenomenon in the world, especially in the Mediterranean area, as climate change forecasts indicate. This situation generates a reduction in rainfall recorded and, therefore, a decrease in water resources to meet the socioeconomic and environmental needs of the areas that suffer from it. Despite these drawbacks, droughts are temporary and cyclical, and through the activation of measures, enables the adverse effects to be anticipated and mitigated, allowing the maintenance of activities linked to the availability of water. The case of the Segura River Basin is special, located in southeast Spain, it is one of the areas most affected by droughts at a national and European scale; but it also has a structural shortage of resources, which means that, even under a business-as-usual scenario or years without drought, not all the demands of the basin are met, generating a continuous deficit situation, which mainly affects irrigated agriculture, one of the main economic drivers of the region. And this happens despite having developed an integrated management model of both conventional resources, endogenous and exogenous from the Tagus-Segura transfer, and non- conventional, from reuse and desalination. On the one hand, a specific study of the drought that occurred in the Segura Hydrographic Confederation during the period 2015-2019 has been carried out in this research. For this purpose, the procedure for stating the drought has been analyzed, supported by the Special Drought Plan approved in 2007, based on drought status indicators, which determine the activation of measures which would enable the mobilization of extraordinary resources to compensate for the depletion of natural resources. It should be noted that, in 2018, the revision of the Drought Plans was approved, which updates the drought indicators established in 2007, defining differences between situations of prolonged drought and temporary shortages, which determine the declaration of extraordinary drought. A comparison between both methodologies has been implemented in the work, which has allowed differentiating the detection capacity of drought and shortage situations, showing that, by using the new methodology, the period of extraordinary drought would have been reduced. On the other hand, an analysis of the economic impacts associated with irrigation has been developed, accounting for variables as production value or net margin, both linked to the units of agricultural demand and established by the Hydrological Plan of the Segura Hydrographic Confederation, based on the availability of resources versus economic values. To this end, the average value of these economic variables was first established, thus determining the economic impact of the structural shortage, and then analyzing each of the years of drought. These estimations are based on the irrigated area and remote sensing studies carried out annually by the Segura Hydrographic Confederation, which make it possible to find out the water applied by type of crop in each of the demand units. The results show both a reduction in the value and in the net margin as a consequence of the insufficient volumes from the Tagus- Segura water transfer, which has been aggravated by the years of drought. Finally, after the analysis of the drought period, the water deficit for the new planning cycle 2022/27 has been obtained, quantifying the supply of water resources which has been weighed against the demands that must be supplied annually. This balance shows the insufficiency of water resources, caused mainly by the drop in the volume of resources transferred from the Tagus to the Segura basin, which is significantly lower than the maximum volume approved. This deficit situation, far from being reduced, is bound to become larger due to further reductions of transfers from the Tagus-Segura, even considering the implementation of new measures to increase the mobilization of non-conventional resources ⎯mainly desalination⎯, which would not manage to reduce the structural deficit situation of the Segura River Basin.