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.

En el sureste de España se sitúa la Demarcación Hidrográfica del Segura, afectada por un escenario de déficit estructural, como consecuencia de contar con una precipitación muy baja —la menor del continente— y que, ante los escenarios de cambio climático, puede agravarse durante los próximos años. Esta situación de escasez ha requerido la combinación de recursos de diversos orígenes, que pueden clasificarse en los naturales y los no convencionales, que intentan alcanzar en conjunto un grado satisfactorio de atención de las demandas, principalmente en las más importantes por su volumen, como son el regadío y el abastecimiento. El objetivo principal del presente estudio es el análisis detallado del déficit mediante la información recogida por la planificación hidrológica, identificando aquellas áreas donde se concentra esta anomalía y que coinciden en gran medida con las zonas regables del Trasvase Tajo-Segura. Como objetivo secundario, se plantean las alternativas que permitan la movilización de nuevos recursos que consigan aumentar la oferta actual, específicamente, aquellos procedentes de la desalinización. Para ello, será necesaria la ejecución de nuevas infraestructuras, que ya contempla la planificación actual, pero que pueden añadir nuevos condicionantes, esencialmente económicos, motivados por los sobrecostes sobre el ya elevado precio del agua desalinizada y que cuestionaría la viabilidad económica del sector agroalimentario dependiente de este insumo fundamental.

Throughout history, the Segura River Basin, located in the south-east of the Iberian Peninsula, has suffered from countless drought periods. They have largely been managed as occasional episodes of crisis through the reduction of the resources applied or the mobilisation of extraordinary resources. Recently, the phenomena of drought and water scarcity have been incorporated into Spain’s national hydrological plan. This has given rise to an improvement in their diagnosis and management and enables us to learn about how climate change affects their frequency and intensity. Agriculture is highly relevant in the basin, comprising mainly irrigated crops that represent more than 80% of total demand for a net area of more than 260,000 ha. There is an undeniable connection between this sector and the availability of water and in periods of drought, such as the recent episode in the Segura River Basin (drought declaration in the territorial area of the Segura River Basin through Royal Decree 356/2015 of 8 May), the reduction in the availability of water generates a significant impact on the agricultural sector. Therefore, by analysing the production value and net margin generated in the agri-food systems, both the values established in the 2015/21 Hydrological Plan and those estimated in the drought period 2015–2019, we seek to assess the economic impacts generated, as knowing the direct effect on the agricultural sector will enable us to quantify the opportunity cost resulting from not being able to apply 100% of the resources demanded.

Urban areas are currently experiencing rapid growth, which brings with it increases in the population, the expansion of impervious surfaces, and an overall jump in the environmental and hydrological impact. To mitigate such an impact, different strategies proposed to tackle this problem often vary; for example, stormwater tanks, the reuse of wastewater and grey water, the installation of equipment to reduce water consumption, and education-based approaches. Consequently, this article presents the simulation and evaluation of implementing infrastructure options (stormwater harvesting, reuse of industrial waters, water-saving technology in residential sectors, and reuse of water from washing machines) for managing urban water in two urban catchments (Fucha and Tunjuelo) in Bogotá, Colombia, over three periods: baseline, 10 years, and 20 years. The simulation was performed using the software Urban Volume Quality (UVQ) and revealed a possible reduction in drinking water consumption of up to 47% for the Fucha Catchment and 40% for the Tunjuelo Catchment; with respect to wastewater, the reduction was up to 20% for the Fucha Catchment and 25% for the Tunjuelo Catchment. Lastly, two scenarios were evaluated in terms of potential savings related to water supply and sewage fees. The implementation of strategies 3 and 6 insofar as these two strategies impacted the hydric resources. Therefore, there would be a significant reduction in contaminant loads and notable economic benefits attributable to implementing these strategies.