Herramientas para la gestión de sequías y recuperación de costes que incentiven su uso eficiente y sostenible

Resumen

Droughts are natural phenomena that affect countries throughout the planet, albeit unevenly. The duration, magnitude and frequency are specific to each climate region and determine the impact on water resources and ultimately, the impact on the rest of water-dependent sectors (environment, society, economy). According to climate change projections, it is expected that they will become more frequent and intense as the 21st century progresses. This doctoral thesis assesses and develops different tools for improving drought management by providing: (1) a critical review of the strengths and weaknesses of European and Spanish water legislation and planning policies; (2) a critical analysis of the limitations and practical implications of applying the most recent 2018 Guadalquivir River Basin (GRB) Drought Management Plan (DMP), with a special focus on the methodological approach and operational framework; (3) a critical assessment of the real influence of the public participation and consultation process in shaping the 2018 GRB DMP; (4) a practical streamflow forecasting tool to support strategic water decisions; and (5) a hydro-economic methodology to provide transparency in the water cost recovery calculations and identify potential cross-subsidies among water users. At the EU level, droughts are succinctly dealt with in the Water Framework Directive (WFD 2000/60 / EC). In fact, the elaboration of DMPs is not compulsory but only recommended (by the 2007 EC Communication “Addressing the Challenge of Water Scarcity and Droughts in the European Union”) as supplementary documents of the River Basin Management Plans (RBMPs). On the other hand, even though there has been a significant improvement in developing drought data and management tools (EDR, EDII, EDO, WEI+, etc.) which are instructive and informative, there are still key challenges related to the practical integration and application of this information as well as its periodic upgrade (so that EU members could maximise their use in practice). In Spain, the preparation of DMPs is mandatory in line with art. 27 of Law 10/2001, of July 5, of the National Hydrological Plan. The first DMPs for all inter-community river basins were approved in 2007 and ten years later, these were revised and then adopted in December 2018. Important innovative aspects have been integrated such as the objective differentiation of droughts events (natural climatic events) from water scarcity situations (anthropic interaction with water resources) by setting out a different diagnosis system (indicators, thresholds and phases) and measures to deal with each phenomenon separately. The great advantage of this common methodology is that diagnosis results are comparable across all river sub-basins, and similar measures should be applied. This highlights not only the significant strides made by all River Basin Authorities (RBAs) in Spain towards the harmonization of technical procedures but also an effective intergovernmental coordination between all the organizations and processes involved at the political, technical, and institutional levels. Nevertheless, important technical aspects (such as the methodology applied to calculate the water scarcity thresholds) remain practically unchanged and hardly differ from those used over a decade ago in the first 2007 DMPs. At the GRB management level, significant deficiencies have been found in the 2018 DMP, including the following: (i) streamflow forecast models (or seasonal climate forecasts) are not used to improve drought management; (ii) specific technical, environmental, and economic assessments are not provided to support the proposed drought and water scarcity management measures; and (iii) a sound climate change assessment is not included. An alternative methodology to calculate the water scarcity thresholds has been proposed, and the benefits of using those in combination with streamflow forecasting tools have been demonstrated. Additionally, it was found that the public participation (PP) and stakeholder involvement process had, in reality, a negligible influence in shaping the 2018 GRB DMP. Only 8% of the total number of comments received was actually accepted. From this small proportion, the majority corresponded to typo, conceptual or calculation errors, while only a minority were related to improvements in the drought management strategy. This means that there was a very limited incorporation of the local knowledge and experience of participants, which highlights the absence of a truly inclusive participation strategy. Nonetheless, PP should proactively involve all interested parties at an early stage when it is still possible to alter the strategy. This could bring significant benefits, given that water users would thus assume more ownership and responsibility in the search for comprehensive solutions. To address one of the previously mentioned key technical deficiencies found in the 2018 GRB DMP, a practical and robust streamflow forecasting tool was developed to forecast monthly and annual streamflows within the current hydrological year. This innovative, user guided, and low-cost procedure combines the use of well-known regression analysis techniques, the two-parameter Gamma continuous cumulative probability distribution function and the Monte Carlo method. The results obtained from this model have demonstrated to be sufficiently reliable and robust to support strategic water decisions and build drought risk-reduction strategies. Additionally, this new tool is simple and can be easily used by non-technical experts such as authorities, decision-makers, managers or even water users. Therefore, it overcomes one of the major limitations associated with the use of this type of models. Another significant obstacle to achieving an efficient and sustainable use of water resources in Spain was the lack of transparency in water-cost recovery calculations (highlighted in the fourth European Commission report in 2015). A hydro-economic method has been developed to increase transparency in the water cost recovery calculations and identify potential cross subsidies among water users. This has been applied to the Upper Genil River case in the GRB. A tool has been created that calculates the Canon of Regulation (CR) for any year of the historical series under different assumptions. The results revealed that the household user pays an additional average annual cost of approximately €6,863 per cubic hectometre for having the theoretical priority of water use over the agricultural water user. However, this additional cost does not translate into a significant increase in the guarantee of water supply. The results obtained in this PhD thesis could be useful to water authorities, decision-makers, managers, policy-makers and water users in other similar drought-prone and water-scarce basins. These could also be considered during the revision of the WFD and Spanish Water Legislation, as well as in the development of the 3rd cycle RBMPs in the EU.