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Flash floods cause severe natural disasters over the world generating property and infrastructures damages, poverty and loss of human life, among others. Mediterranean coastal watersheds are specially sensible to flash floods effects due to their typical drainage basin features (steep slopes, short concentration times, complex orography, etc.) and the high rainfall intensity typical of convective systems. In the present study, the temporal evolution of the hydrological answer in five Mediterranean (SE Spain) ravine basins with sizes from 10.2 km2 to 200.9 km2 were analysed. A sub-daily SWAT model was used at watershed scale to capture the complex hydrological dynamics. Five land use scenarios corresponding to no-urbanization (baseline), 1990, 2000, 2006 and 2012 were evaluated using GIS-based tools. Additionally, statistical significant differences among the studied scenarios were checked employing the Kruskal-Wallis and post-hoc tests based on Mann-Whitney test with BH correction. Our results show that flash flood risks have increased in the studied catchments due to changes in land uses, particularly affected by a large urban growth. Observed changes in soil uses have been important since the sixties of the last century, because of a high demographic and touristic pressure and specially the urban area has enhanced considerably during the last 22 years. Currently, some of these catchments present around 70% of their surface occupied by urban land uses with high population density producing curve number surpasses 85 and 90 levels. The hydrological response of the studied basins changed to higher flow rate peaks and shorter concentration times. Some discharges increased significantly from the baseline land use scenario (≈50 m3/s, 190 m3/s, 380 m3/s) to the most urbanised scenario (≈235 m3/s, 385 m3/s, 940 m3/s), respectively. These findings provide to urban planning policy makers very useful information in the face of flash flood effects, which have cost even human lifes in the studied ravine basins during last years. Financial support was provided partially by the University of Alicante, project GRE17-12. This study also has been conducted within the grant received from the Programa Nacional de Formación de Profesorado Universitario (FPU) conceded by the Spanish Ministry of Science to the first author.

Actualmente, las demandas hídricas se encuentran en continuo crecimiento lo que aumenta la presión, en cantidad y calidad, sobre los recursos hídricos disponibles a nivel global. Asimismo, la reducción proyectada de las aportaciones en régimen natural, consecuencia del cambio climático, supone un nuevo nivel de incertidumbre. Pese a errores todavía existentes, los modelos hidrológicos constituyen herramientas vitales para planificar y gestionar el recurso agua. Su correcta aplicación resulta esencial en áreas con elevado estrés hídrico (regiones áridas y semiáridas). La Demarcación Hidrográfica del Segura (DHS), sureste de España, presenta una de las mayores tasas de escasez y explotación intensiva de recursos hídricos en el contexto europeo y mundial. Este trabajo estima los efectos del cambio climático sobre los principales componentes del balance hídrico en la cuenca alta del río Taibilla (cabecera de la DHS). Dicha cuenca fue escogida al encontrase en régimen natural y ser actualmente primordial en el abastecimiento hídrico de numerosos municipios de la DHS y áreas contiguas. Para evaluar los mencionados efectos se ha implementado el modelo Soil and Water Assessment Tool (SWAT) calibrado con el algoritmo SUFI-2. La calibración y validación se realizaron con dos funciones objetivo (NSE y KGE) en el periodo con caudales observados (1996-2012). Las proyecciones de precipitación y temperatura proceden de los modelos climáticos globales (GCMs) bcc-csm1-1-m, MPI.ESM.MR y bcc. csm1.1, regionalizados con la técnica de Análogos, bajo los escenarios de emisión RCP4.5 y RCP8.5 (periodo 2010-2050). Los resultados del ajuste mejoran con NSE, con respecto a KGE, en las series de calibración y validación. En las próximas décadas, precipitación, escorrentía superficial y recarga de acuíferos muestran tendencias negativas mientras que la temperatura aumenta entre 1.5 °C y 1.7 °C. Pese a la incertidumbre existente, resulta evidente que las aportaciones disminuirán en la cuenca lo que supondrá un reto en la gestión del recurso agua para las autoridades locales. Los resultados obtenidos pueden ayudar a las autoridades locales en la toma de decisiones respecto a la planificación hidrológica y la lucha contra el cambio climático en la DHS. Así mismo, SWAT como herramienta de conversión lluvia-escorrentía, junto con los modelos y escenarios de cambio climático implementados, resultan válidos en un área de clima subhúmedo y semiárido pudiendo ser aplicados en otras regiones con una climatología similar. Currently, water demands are in continuous growth which increases the pressure, in quantity and quality, on the water resources available over the world. Likewise, the projected reduction of natural water inputs, due to climate change, represents a new level of uncertainty. Despite existing errors, hydrological models are important tools for planning and managing water resources. Their correct application is essential in areas with high water stress (arid and semi-arid regions). The Segura River basin district (DHS), southeastern Spain, has one of the highest scarcity rates and intensive exploitation of water resources in Europe and the world. This study estimates the effects of climate change on the main components of the water balance in the upper basin of the Taibilla River (the headwater of the DHS). This basin has been chosen because it is in natural regime and it is currently one of the main water supplies in many DHS municipalities and contiguous areas. In order to assess the mentioned effects, we used the Soil and Water Assessment Tool (SWAT) calibrated with the SUFI-2 algorithm. Calibration and validation were performed with two objective functions (NSE and KGE) in the period with availability of discharge data (1996-2012). The precipitation and temperature projections came from the global climate models (GCMs) bcc-csm1-1-m, MPI.ESM.MR and bcc.csm1.1, regionalized with the analogue technique, under the emission scenarios RCP4.5 and RCP8.5 (period 2010-2050). The adjustment results improved with NSE, with respect to KGE, in the calibration and validation series. In the future decades, precipitation, surface runoff and recharge of aquifers would show negative trends while the temperature would increase by between 1.5 °C and 1.7 °C. In spite of the existing uncertainty, it is evident that natural water inputs will decrease in this river basin. This will be a challenge in the water resources management for local authorities. The obtained results can assist local authorities at decision making regarding hydrological planning and the fight against climate change in the DHS. In addition, SWAT as a rainfall-runoff conversion tool, together with the implemented models and climate change scenarios, are suitable in an area with subhumid and semi-arid climate and can be used in other regions with similar climatology. El presente trabajo se enmarca parcialmente en el proyecto 19325/PI/15Ref concedido por la Fundación Séneca-Agencia de la Ciencia y la Tecnología (Región de Murcia, España). Adicionalmente, el primer autor agradece la financiación recibida del Programa Nacional de Formación de Profesorado Universitario (FPU) concedida por el Ministerio Español de Educación, Cultura y Deporte (MECD).

Currently, water demands are increasing notoriously, spreading the pressure on available water resources around the world in both quantity and quality. Similarly, the expected reduction of natural water inputs, due to climate change, depicts a new level of uncertainty. Specifically, Southeast Spain presents water scarcity due to its aridity&mdash, irregular and scarce precipitation and high evapotranspiration rates&mdash, combined with the competition between several water demands: environment, agricultural dynamics, urban-tourist activities, and industry. The study area of this work is the most relevant functional urban area of Alicante province (SE Spain), where the administration of water management is carried out by a range of authorities at different levels as the consequence of a complex historical development of water governance schemes: at the national, regional, and local levels. This study analyzes 21 municipalities and proposes a conceptual model which was developed by including different origins of water inputs&mdash, surface resources, groundwater, desalination, wastewater reuse, or interbasin transfers&mdash, and water demands with information obtained from 16 different sources. Our main results denote a relevant water deficit of 72.6 hm3/year even when one of the greatest rates of desalinated water and reused wastewater in Europe are identified here. This negative balance entails restrictions in urban development and agricultural growth. Thus, presented results are noteworthy for the water policy makers and planning authorities, by balancing the demand for water among various end users and providing a way for understanding water distribution in a context of scarcity and increasing demand, which will become one of the most challenging tasks in the 21st century.

EMPORE project, co-funded by LIFE Programme (LIFE15 ENV/ES/000598), aims to demonstrate an innovative, cost-efficient and highly replicable technology for the removal of Emerging Pollutants (EPs) from European Waste Water Treatment Plants (WWTPs). In action, C2, a set of indicators to monitor the socio-economic impact of EPs removal, was developed. Framed in this action, a robust assessment of the social perception of these contaminants was performed in the South-East Spain, where the use of reclaimed water is widespread due to the structural water scarcity. An expert consultation by means of a survey technique was held from November to December of 2018 with a sample size of 114 cases. The survey focused on regulation, risk perception, technologies and socio-economic impact. A descriptive analysis of 19 variables was carried out. In general, the results suggest that the presence of EPs can be a significant risk and destabilization factor in the reuse of wastewaters. The impact of new regulations concerning EPs awakes uncertainty among water experts. Aspects such as the price of water free of EPs, treatment costs or the potential of different technologies to remove these compounds are sources of ambiguity. Nevertheless, experts believe new regulations on EPs will positively influence public health, social confidence or environmental sustainability, among others. It highlights that experts agree that the future of the reuse of wastewater passes through the combination of technologies. These findings provide water planning policy makers with very useful information in the water resources management of the South-East Spain because recent European laws can set new limits of emerging pollutants in waters. This project was produced under the co-finance of the European financial instrument for the Environment (LIFE) programme during the implementation of the project “LIFE EMPORE” (LIFE15 ENV/ES/000598). Pablo Aznar-Crespo and Antonio Jodar-Abellan acknowledge financial support received from the Spanish FPU scholarship for the training of university teachers. In the same way, this work has been conducted within the Cátedra del Agua of the University of Alicante (https://catedradelaguaua.org/).

Nowadays, water demand is increasing continuously, which raises the pressure on available water resources around the world, in both quantity and quality. Moreover, the projected decrease of natural water inputs due to climate change denotes a new level of uncertainty. In particular, the south-east of Spain suffers from water deficit due to its aridity – irregular rainfall and high evapotranspiration rates – together with the competition between existing demands: environment, agricultural dynamics, urban-tourist activities and industrial sector. The study area is located in the Alicante province (SE Spain), where the administration of water management is carried out by several authorities at different scales as a result of a complex historical evolution of water governance schemes, at the national, regional, and local levels. This case study is focused on 21 municipalities and draws a conceptual model which is performed considering the different origins of the water inputs – surface resources, groundwater, desalination, wastewater reuse or interbasin transfers – and water demands with data from 16 different entities. The main results depict a general water scarcity of 72.6 hm3/year generating restrictions in urban growth and agricultural development. These findings provide useful information on water planning policymaking in order to face the shortage of water resources in a context of growing demand. This work was partially supported by the project Life Empore (Life15 ENV/ES/000598) coordinated by the University of Alicante and by the project Asesoramiento y Asistencia Científico-Técnica en la elaboración del Plan de Acción Territorial de Alicante y Elche coordinated by the UTE Cercle and Jornet Llop Pastor companies and the University of Alicante. In the same way, this work has been conducted within the Cátedra del Agua of the University of Alicante (https://catedradelaguaua.org/).

The province of Alicante (SE Spain) is the fourth most populated region in Spain, with 1.9 million inhabitants. Additionally, tourism is one of the most important industries of the region since the sixties of the last century. Tourism industry attracts more than 3.4 million tourists and 14.5 million overnight stays per year, mainly in summer. Urban development has expanded as a consequence of that demographic pressure, mainly in the coastal areas. At present time, there are examples of watersheds with ephemeral streams where more than half of the complete area is occupied by urban soil. This urban development has increased the existing high hydrological hazard, since the hydrological answer of watersheds to a precipitation event has moved to higher flow rate peaks and shorter concentration times. Urban planning policy makers have to face that problem urgently since the main climate features of this geographic area are the very intense and localized rainfalls, which fall specially in the months of September, October and November. Then, the ravines beds, which remain dry during the majority of the year, are forced to lead high amounts of water in a clear case of flash floods. In the present study, we analyse the temporal evolution of the hydrological response of a small watershed as a consequence of the urban growth. Hydrological dynamics were accomplished with the ArcGIS tool and the SWAT hydrological model. Changes in soil uses have been analysed through GIS- based tools, with soil use coverage information for the different study periods. Main results show that study area (Amerador watershed) has duplicated its urban area since 1990 (31.62 ha) to 2012 (61.07 ha) increasing the risk of flooding in a coast urban zone with low runoff thresholds (0 l/m2–7.5 l/m2) and discharges that reach 190 m3/s. Financial support was provided partially by the University of Alicante, project GRE15-19. This study also has been conducted within the grant received from the Programa Nacional de Formación de Profesorado Universitario (FPU) conceded by the Spanish Ministry of Science to the first author.

Nowadays, the south-east of Spain has several problems of water supply due to high agricultural, urban, industries, and so one water demands. In addition, this sensible area has limited precipitations, high temperatures and evapotranspiration rates. At the same time, in many places, the urban growth has been poorly organized. Usually, some areas are subjected to the effects of flash floods caused by heavy and concentrated rainfalls. In this work, we analyse the evolution of the floodable park “La Marjal” (Alicante, SE Spain) since its construction two years ago as a solution to reduce the mentioned problems. This floodable park, the first constructed in Spain and the second in Europe, cost 3.3 M€ and presents a total water volume of 45,000 m3. The park gets to avoid typical flash floods in San Juan urban area and provides storage of water to reuse it in irrigation of urban parks and gardens, countries, street cleaning, and other uses. Financial support was provided partially by the Fundación Séneca-Agencia de la Ciencia y la Tecnología, project 19325/PI/15. This study also has been conducted within the grant received from the Programa Nacional de Formación de Profesorado Universitario (FPU) conceded by the Spanish Ministry of Science to the first author.

The issues of wastewater treatment and the reuse of water are of great importance, especially in areas where the shortage of conventional resources is a structural problem, as it is in the case of Spain. Wastewater reuse is a valid mechanism to avoid problems derived from droughts and water scarcity. It allows access to water resources in areas with water restrictions and to prevent futures scenarios, due to it being expected that water consumption will double by 2050 over the world. Thus, the likelihood that this unconventional, strategic resource would become scarce is unquestionable, particularly in cases where water planning and exploitation systems prioritize the preservation, protection, and improvement of water quality, as well as the sustainable and efficient use of natural resources. This paper shows how wastewater treatment and reuse are linked, as the reuse of wastewater is associated with a previous regeneration, and both of them are essential tools for maximizing environmental outcomes, as called for in the European Union Directives. This research was funded partially by the projects GRE17-12 and Life Empore (grant number: Life15 ENV/ES/000598) coordinated by the University of Alicante. Antonio Jodar-Abellan acknowledges financial support received from the Spanish FPU scholarship for the training of university teachers. In the same way, this work has been conducted within the Cátedra del Agua of the University of Alicante (https://catedradelaguaua.org/).