Politécnica de Madrid

'Water reuse for irrigation contributes to more sustainable management'

ETSIAAB professor Irene Blanco coordinates a project for studying the potential in Spain of an alternative to 'reduce pressure on water resources, extend the supply guarantee, and bring about nutrient discharge reduction.'


The threat posed by climate change to a future with less water prompts research into non-conventional water resources. Reclaimed water for agricultural irrigation is an option on the table. Analysing these alternative source potentials in Spain, and their social, economic and environmental effects, is the goal of the 'RECLAMO' research project (an acronym for 'The contribution of water REuse to a resourCe-efficient and sustainabLe wAter manageMent for irrigatiOn'). It is coordinated by Irene Blanco, professor at the Escuela Técnica Superior de Ingeniería Agronómica, Alimentaria y de Biosistemas (ETSIAAB) and researcher at the Centro de Estudios e Investigación para la Gestión de Riesgos Agrarios y Medioambientales (CEIGRAM). The team comprises agronomists, hydrologists, chemists and agricultural economists, mainly from the Universidad Politécnica de Madrid (UPM).

Question: Reduce, reuse and recycle. The circular economy strategy also works for a resource such as water.

Answer: Indeed. Water plays a vital role in moving from linear economic systems to more circular models. Climate change is causing quantity and quality water to decrease. Here, the circular economy is in search of new formulas for more sustainable water management. Water reuse for irrigation contributes to more sustainable management and is one of the circular economy instruments. The extraordinary potentials of water reuse have recently aroused great interest. Particularly in scarcity areas, it has become a strategic alternative to reduce pressure on water resources, extend the supply guarantee, and bring about nutrient discharge reduction.

Q.- Farmers and consumers may be suspicious of crop irrigation with water from treatment plants. Is it a well-founded distrust?

A.- Public health risks represent a significant obstacle to reclaimed water widespread use. Many countries have developed strict regulations on the subject, which require expensive legal requirements. The European Commission has recently adopted Regulation No 2020/741 on minimum requirements for water reuse, applicable from June 2023. It includes chemical and biological parameters to ensure that reclaimed water is safe for agricultural irrigation. Besides, farmers remain reticent because water reuse is more energy-intensive than conventional surface and groundwater sources. Reused water production costs have been borne mainly by the managing bodies of the treatment plants. However, according to the Consolidated Text of the Law on Water, farmers, as the end-users, should bear these costs. The willingness to shoulder these costs is expected to increase when the right signals are sent to users in terms of the actual water cost and the need to achieve environmental and economic sustainability of water management.

Q.- The main aim of the project is to explore the potential of reclaimed water for irrigation in Spain. How is the analysis conducted?

A.- The project will combine quantitative and qualitative modelling tools to analyse reclaimed water for irrigation and its real potential. Quantitative modelling is based on agronomic-hydrological-economic model development and application. These models boost the study of complex spatial and temporal relationships between water resource availability and demand and the implications of water reuse for irrigation. Qualitative modelling involves systems analysis and future scenario (climatic and socio-economic) development. It also serves to develop roadmaps to promote this resource. Interest groups co-design these models and scenarios. The aim is to support decision-making and better target priorities for water reuse for irrigation. The project relies on a multidisciplinary team with extensive experience in agricultural economics, hydraulics, agronomy and water chemistry and treatment.

Q.- Two field case studies are planned, in Ciudad Real and Murcia.

A.- We have selected two case studies to show very different contexts of water reuse for irrigation. On the one hand, we will work in the upper Guadiana basin (Ciudad Real). This area has some success cases but minimal experience in water reuse. This internal basin, where intensive irrigation was carried out at the end of the 20th century, led to the overexploitation of the water bodies Mancha Occidental I and Mancha Occidental II, formerly known as Aquifer 23, and the degradation of the Tablas de Daimiel wetlands. Reclaimed water for irrigation instead of groundwater abstractions could help deal with pressure on water bodies and wetlands, contributing to sustainable management of resources if ecological flows are maintained. In addition, the project will study the case of the Segura basin (Murcia), the most significant example of urban wastewater treatment and reuse in Europe. In this water-deficient area, water flows from water reuse are vital for agricultural produce. Reuse could increase the net available volume of water resources, particularly in coastal regions that discharge directly into the sea. We consider that the analysis and comparison of the two case studies will help identify barriers and opportunities related to the promotion of water reuse for irrigation in Spain.

Sand filters for treated water before it is discharged into the irrigation network. 'Los Auriles' irrigation community facilities (Tomelloso, Ciudad Real, Spain).

Q.- What are the barriers that hinder the better use of wastewater?

A.- As I mentioned earlier, public health, financial and economic barriers. But also, technical obstacles related to wastewater treatment, infrastructure development (adaptation of conduction systems) and irrigation techniques (devices used to reduce crops' exposure to pathogens). Besides, environmental barriers might lead to adverse impacts produced by water reuse on the environment, arising from salts, heavy metals and pathogens with negative effects on plants, animals and soil. We can also mention regulatory barriers linked to the concession framework, governance, and the difficulty of interpreting regulations and restrictions related to quality criteria. Finally, obstacles linked to the perception and social acceptance of reclaimed water for agriculture. Society is not, in general terms, aware of the potential for water reuse in Spain and the rigidity regarding the applicable regulatory framework in terms of quality and irrigation management.

Q.- What role the public administrations have in this context?

A.- Public administrations lead on firmly towards water reuse for irrigation at the national and European level. The New Circular Economy Action Plan of the EU and the Spanish Circular Economy Strategy show the way to water reuse as a priority area for action. The Spanish proposal is to review the current regulatory framework, based on Royal Decree No 1620/2007. In the lead-up to this process, Spain chooses to adopt the ambitious DSEAR Plan, the Spanish acronym for National Plan for Treatment, Sanitation, Efficiency, Saving and Reuse. This plan will fit the new parameters and procedures defined in the new European legislation (Regulation No 2020/741) to be incorporated into the third hydrological planning cycle for 2021-2027, providing the necessary legal certainty for consumers and end-users.

Q.- A program oriented towards the so-called societal challenges from The State Research Agency is funding the project. Is it fair to say that one of the major challenges for Spanish agriculture is adapting to a major future water scarcity problem?

A.- Absolutely. Spain is one of the driest countries in Europe, and it is expected to be one of the driest countries in the world by 2040. Concerning the impacts of climate change in Spain in the next 50 years, the picture looks terrible. Temperatures are likely to rise by up to 2.5 degrees, and rainfall could fall by 10 per cent. According to the European Union, legislative changes and planned investments in water reuse will allow a six-fold increase in the annual volumes reused by 2025. This evolution could alleviate the pressure on water resources and avoid direct water abstractions from surface and groundwater sources by up to 5 per cent. However, it is not only the environmental benefits; this activity is a creator of wealth and green jobs. A 1% increase in the growth rate of the water industry in Europe could create between 10,000 and 20,000 new jobs.