The snowpack in mountain areas in semiarid catchments mitigate the peakflows during the wet season and provides water flow for the river and aquifer system during the usual dry season. However, the high insolation rates even in winter results in several accumulationablation cycles during the aseason, which enhances the sublimation fluxes (up to 20-35% of the snow water equivalent as an annual loss to the atmosphere in these regions). Whereas the annual precipitation does not show a clear trend in many of these catchments, on a seasonal basis a high increase of the torrential behaviour of the snow regime is observed; a higher occurrence and duration of dry spells, an impact on the amount of snowfall, and on the persistence of the snow pack, are the most common observations. This also impacts the hydrological planning and decision-making process: on one hand, there is an increase of the occurrence of peakflows close to the median value associated to snowmelt events during winter, that might overlap with heavy rainfalls; on the other, the shortest persistence of the snowpack can be caused by an enhanced sublimation, which reduces water storage volumes both in reservoirs and aquifers, and the summer recession flow and duration. The magnitude of this impact can vary significantly on an annual and seasonal scale, but it is the short scale regime which is mostly influenced, which affects the decision making process, and associated risk. Moreover, the skill of the global climate and hydrological models that provide seasonal or weekly forecasts is quite low in these mountain areas, since they are not capable to provide a good estimation of the precipitation volumen, especially as snowfall, nor of the snow persistence during dry spells. This project aims to analize the impact of the seasonal regime of the snow persistence on the water storage volumes and hydrographs in semiarid catchments. The final goa lis to provide the community with a methodology that generates an efficient information to assist the hydrological operability from observations and simulations available on quasi-real time. From satellite high resolution data on snow and vegetation states, and the antecedent flow/water level in control points, depletion curves for snow on different spatial scales will be generated; they will be the basis to develop operability diagrams for hydrological planning. The proposed approach is applied to reservoirs in the headwaters of Sierra Nevada, where the research team has been working for the past 15 years and runs a monitoring network snow-oriented. The transferability of the approach is tested in two additional sites, that share the occurrence of snow in a semiarid context, but located at very different areas from both the climate and hydrological point of view: Sierra de Cazorla (headwater reservoirs in the Guadalquivir River Basin) and the Teide (water inflows to underground galleries). The final result will be an innovative tool based on science but efficient on an operational basis to derive a decision tree for the management of water resources in the short and médium term, the verification of warranty criteria, and the improvement of their reliability.

The general objective of this proposal is to analyse the impacts of the intra-annual snow persistence regime on water storage and the generation of hydrographs in basins in semi-arid environments, with the ultimate aim of generating a methodology that provides effective information for decision-making at an operational scale in hydrological management, based on observations and simulations accessible in quasi-real time.

This methodology must i) improve the capacity to forecast the evolution of snow at a distributed scale with a spatial resolution appropriate to the characteristic heterogeneity of these areas, ii) incorporate quality information that allows its analysis in quasi-real time, and iii) establish a Bayesian monitoring system (based on antecedent states) of the evolution of the flow in these channels that allows decision-making in the short (daily-weekly) and medium term (weekly-one month) in the management of water resources.

To this end, in addition to the study area in Sierra Nevada, where the PI has been carrying out research on snow in Mediterranean basins since 2004, two new study areas similar in terms of the occurrence of snow in semi-arid environments but with different conditions in terms of meteorological and hydrological regime, and their vegetation cover, are proposed: Sierra de Cazorla, studying fluvial inputs in a selection of headwater reservoirs in the Guadalquivir basin, and Teide, assessing infiltration inputs to selected control points in the underlying underground gallery network.

The study of snow in Mediterranean regions from the analysis of the physical processes that interact is a line of great scientific interest in areas of civil engineering, associated with the hydrological and hydraulic management of water systems, as well as in areas of ecology and environmental conservation, as it is the physical basis of morphological and ecological processes affected by the hydrological regime associated with snow in high mountain areas. The impact of this line on the technical management capacity in basins affected by snow is very high; guaranteeing the availability of water resources is a major social and economic conditioning factor in mountain basins or basins with headwaters in these areas. On the other hand, the impact of global warming makes these regions vulnerable due to the effects on the activities on which they base their economy, and their evolution is a reflection of their future migration towards higher latitudes. Recreational and sporting activities in the snow, rural tourism, the operation of mini-hydroelectric power stations, the management of water resources downstream, agriculture and tourism in areas supplied by reservoirs, etc. depend on the presence of snow and its spatial and temporal evolution.

Knowing with precision the state of the snow and its persistence in the short and medium term, and anticipating with limited uncertainty its most probable evolution in order to forecast in the short, medium and long term the impact on the fluvial regime of high mountain rivers and receiving watercourses is a relevant result of this Project. From this it will be possible to evaluate the planning of water resources and the operation of associated structures, and if necessary correct or propose advanced plans for adaptation to global warming. Obtaining hydrological operability diagrams based on the persistence of snow also provides a useful tool for the preparation of hydrological plans and their updating in the next planning cycle (2022). The study areas are environments subject to the consequences of high hydrological variability, with recurrent droughts and occasional (Andalusian basins) or frequent (Tenerife) water scarcity problems, and an economic sector based on the availability of water for tourism or intensive cultivation.

Likewise, the inclusion of specific data sources for snow variables in these environments, including the latest high spatial resolution sensors, is crucial in these regions of great spatial heterogeneity; their coupling to simulation tools contributes to Social Challenge 5 of the H2020-EU programme, Climate Action, Environment, Resource Efficiency and Raw Materials and other national and international strategies (see point 2.2 of section 1).

The objectives set are hot scientific challenges in specialised fora, with great reception in the best scientific journals in this area. The participation of the Project, where appropriate, in scientific networks of international institutions of the highest prestige in this field means a high impact on the results to be achieved due to their contrast with other regions of the world with similar conditions, and projects the activity and collaboration of the Project abroad (see following points). On the other hand, the results will be transferred to different public bodies with competences in hydrological management, and private bodies related to energy generation in mini-hydroelectric power stations, as well as to the managing bodies of the National Parks in which the high mountain areas studied are located.

The plans for the dissemination and internationalisation of results, and for transfer, guarantee the global impact of this project and are described below.

María José Polo Gómez (UCO) – Responsible Researcher

María Cristina Aguilar Porro (UCO) – Researcher

Axel Ritter Rodríguez (ULL) – Researcher

Fco. Javier Bonet García (UCO) – Researcher

Rafael Pimentel Leiva (UCO) – Researcher

Claudia Notarnicola (EURAC) – Collaborator

Rayco Marrero Díaz (ULL) – Collaborator

Pedro Torralbo Muñoz (UCO) – Collaborator

Elena Herrera Romero (UCO) – Collaborator

Fco. Javier Herrero Lantarón (UCO) – PhD Researcher

Javier Aparicio Ibáñez (UCO) – FPI MINECO Researcher

The research team proposes a four-level dissemination of results, in parallel to the inclusion of the work, experimental data files and calculation algorithms generated, on the PAIDI TEP248 River Dynamics and Hydrology Research Group website at the UCO, www.uco.es/dfh, and other international open access repositories. Internationalisation also has a fundamental support in the activity that the PI develops as coordinator of the International Working Group of the Panta Rhei 2013-2022 initiative of the International Association of Hydrological Sciences (IAHS), Water and Energy Fluxes in a Changing Environment (WG), with the participation of the international researcher of the Project, and Vice-President of the International Commission of Remote Sensing (ICRS-IAHS).