Climate change and the increase of population pose challenges to ensuring suitable water supply in water-scarce regions. This work presents a comparative analysis of the water-supply approaches adopted in Los Angeles, Southeastern Spain, and Sydney. Results show a decrease in per-capita water use in the period 2000–2020, which reflects an improvement in water conservation. Social factors in the domain of hydropolitics and economic efficiency explain the divergence of water policies adopted. The adaptation to water scarcity and growing population in three regions of developed countries located in different continents sheds light on challenges facing the achievement of water security worldwide.

Sewage management is a key issue within circular economy and climate change scenario. Ensuring water supply is a challenge on a global scale. Numerous projects for potable water reuse (indirect or direct) are carried out in different parts of the world. This territorial study analyzes the situation of sewage in the Campo de Cartagena – Mar Menor region (Southeastern Spain), an area with semi-arid Mediterranean climate with structural scarcity of water and high competition for the uses of water. With data provided by ESAMUR, the evolution of its performance, use of reclaimed water and the presence of pollutants at the entrance and exit of the STPs are examined. It concludes that the concentrations of parameters contemplated in Directive 91/271/EEC are met regardless of the greater or lesser presence in the inlet flow. It is convenient to advance with potable reuse pilot projects and greater investments.

La comarca del Campo de Cartagena – Mar Menor es un área de características semiáridas con sequía estructural y donde la carestía de agua ha sido constante en la historia, suplida mediante trasvases de agua y recursos no convencionales. El estudio realiza un análisis del consumo de agua potable, diferenciando entre consumo en alta y consumo en baja, para conocer el rendimiento de la red, y se formulan unas estrategias y líneas de actuación prioritarias para mejorar la seguridad hídrica de la comarca. Se han tomado datos de la Mancomunidad de Canales del Taibilla, de las empresas municipales de abastecimiento y de los Ayuntamientos de la comarca. Los resultados muestran la evolución de las fuentes de abastecimiento, y se extrae, entre otros, que los rendimientos han mejorado y que es clave la adaptación frente al cambio climático, diversificar la oferta de recursos e implementar nuevas tecnologías, así como mejorar las redes de distribución y avanzar en la concienciación social para conformar un territorio resiliente. Este trabajo sirve como modelo para caracterizar y mejorar la situación del abastecimiento de agua en otros medios semiáridos de similar problemática.

Semi-arid and arid regions are characterized by their water scarcity, which leads territories to seek ways of increasing the water resources available to meet their demands (urban, agricultural, industrial, leisure and tourism, etc.). For this reason, this article proposes the term “wastewater use basin”; the concept of the “wastewater use basin” is presented as a working unit of a smaller scale than traditional river basins, which allows for a better management of the water collected in the sewerage network and rainwater of urban agglomerations. It is a geographically-focused proposal for the integrated management of wastewater and stormwater that ends up in a wastewater treatment plant for treatment and reuse. The study area is located in the southeast of the Iberian Peninsula, Spain; specifically, the Campo of Cartagena-Mar Menor district (Murcia) and Vega Baja district (Alicante). The results show the trend behaviour of rainfall in the Segura river basin in recent episodes of torrential rainfall. There is a clear tendency for these episodes to occur in the coastal and pre-coastal areas, so that the water does not reach the headwaters where the reservoirs are located. For this reason, the proposed concept includes the area of the basin that would be formed by the wastewater and rainwater collectors which, in short, are intended to be treated in a treatment plant for subsequent reuse. The calculations made on the basis of the capacity of the environmental tanks executed and projected amount to four cubic hectometers which could be added to the hydrological planning of the Segura basin. In conclusion, the collection of rainwater allows the incorporation of an additional volume of water that complements and increases the resources offered by the treatment plants in the hydrological planning. It also serves as a measure of adaptation to climatic extremes (droughts and floods) and to the effects of climate change, supporting a circular management of the use of resources.

The Commonwealth of the Taibilla Channels (MCT) supplies drinking water to most of the Southeast of Spain, an area with a semi-arid Mediterranean climate with a structural shortage of water. With the data of this organism, a study of water consumption in the XXI century (2000-2019) is carried out, in terms of the distributed volume and the origin of each water resource. The evolution of the contributions to the water mix of surface water, transferred water and desalination are analyzed. It is emphasized that the supply of the resource has been diversified and that it is necessary to maintain it, in parallel with the improvement of the distribution networks and socio-environmental awareness.