In a world increasingly defined by water scarcity, cities face an unsustainable paradox: drinking water is lost to the irrigation of green spaces, while reclaimed water, already treated and available, remains underused. Madrid is no exception. Every year, its parks and gardens consume millions of cubic meters of water that could come from a more circular, efficient, and resilient source. This project breaks that pattern: it transforms treated effluents into a safe, traceable water source for urban irrigation, relieving pressure on aquifers and anticipating a future of growing water restrictions.
The opportunity is clear: in the Madrid region alone, over 350 hectares of parks could be irrigated with reclaimed water. Each cubic meter reused means avoiding freshwater extraction that could instead support human consumption, agriculture, or environmental reserves. At the urban scale, this shift redefines public green areas, not merely as recreational spaces, but as active, circular climate infrastructure.
This project takes place in the municipality of Madrid, with an initial focus on public parks connected to reclaimed water distribution networks such as those of EDAR Sur and EDAR Butarque. Its strategic goal is twofold: to reduce the use of potable water in irrigation, and to consolidate a replicable model of water circularity for cities under increasing water stress. The solution builds on existing infrastructure, validated under Spanish reuse regulations (Royal Decree 1620/2007), and operates within a governance framework that ensures full physical, operational, and digital traceability of every cubic meter used.
Key actors include the Madrid City Council (urban green manager), Canal de Isabel II (reclaimed water system operator), landscaping and park maintenance companies, and a technical structuring partner aligned with the VWBA methodology. This project fulfills the principles of intentionality (aiming primarily to reduce water stress), additionality (this water would not have been reused otherwise), and traceability (direct, continuous measurement of substituted volumes), aligning fully with the Water Positive strategy and enabling verifiable benefits for ESG reporting, certifications, and institutional commitments.
Madrid faces a growing technical and strategic challenge: how to maintain its urban green infrastructure without compromising its fresh water resources. Pressure on reservoirs, combined with more frequent and prolonged droughts, demands a rethink of the water sources that sustain public parks and gardens. Reclaimed water from urban wastewater treatment plants, such as EDAR Sur or EDAR La Gavia, presents an immediate opportunity to substitute potable water with a safe, traceable, and reliable non-conventional source, without compromising landscape quality or public use.
This project reconnects irrigation systems to secondary reclaimed water networks, using proven technologies for conveyance, storage, and control already deployed in other Spanish municipalities. An estimated 400,000 m³ per year will be replaced in the first prioritized parks—equivalent to the annual consumption of more than 3,000 Madrid households. The benefits are immediate: reduced potable water use, enhanced climate resilience in urban landscapes, visible leadership in sustainability practices, and measurable Water Benefits under VWBA 2.0 method A-3 (volume provided from a new non-conventional source).
This transformation is made possible through coordination between the Madrid City Council, Canal de Isabel II, urban landscaping companies, and technical actors from the Water Positive ecosystem. The model is highly replicable and can be scaled to other districts and parks, leveraging existing infrastructure and adapting irrigation systems by zone. Cities, utilities, and service companies with ambitious sustainability targets can lead this transition and leverage it for ESG performance, reputational value, and alignment with emerging circular economy and water efficiency regulations.
The intervention consists of establishing a safe and efficient reclaimed water reuse system for urban irrigation, leveraging existing infrastructure and expanding its reach through advanced technologies. The main lines of action include:
This modular and scalable system allows adaptation to different demand conditions, locations, and water pressure, with the possibility of replication in other municipalities of the Community of Madrid. Additionally, by integrating the principles of circular economy, climate resilience, and environmental health, it represents a cutting-edge solution to face 21st-century challenges in densely populated cities like Madrid.
Applied Technologies: The project integrates advanced physical-chemical treatment technologies to ensure high microbiological quality of reclaimed water, without the use of chemicals. Processes such as advanced oxidation, which eliminates pathogens through highly oxidative reactions; hydrodynamic cavitation, which breaks cell structures through pressure changes; atmospheric plasma, which generates reactive species that disinfect water; and membrane ultrafiltration, which acts as a physical barrier to viruses and bacteria, are used. These technologies are complementary and ensure that the reclaimed water meets the required standards for urban uses such as public space irrigation
Monitoring Plan: It is structured over a digital network of online sensors and control points. It includes spectrophotometric equipment for E. coli and enterococci, amperometric probes for free residual chlorine, multiparameter sensors for physical-chemical quality (pH, turbidity, conductivity), and pressure and flow meters to ensure hydraulic integrity. These data are managed from a SCADA platform with smart irrigation algorithms based on meteorological conditions, evapotranspiration, and type of vegetation (Kc).
Partnerships: The project is structured around an inter-institutional collaboration network.
Participants include the General Directorate of Green Areas and Urban Trees of the Madrid City Council as the local operator; Canal de Isabel II as the reclaimed water supplier and technical support; companies specialized in non-chemical regeneration technologies (such as Geodesic and others with CE validation); and the Aqua Positive platform as traceability, validation, and volumetric water benefits (VWBs) accounting support. Integration with local universities is also considered for co-benefit evaluation and independent monitoring.
The project also includes a collaborative governance model, based on a technical-administrative consortium that regulates operational responsibilities, sanitary emergency protocols, and predictive maintenance. Regular training for operators, water quality validation protocols before point of use, and citizen awareness campaigns are established to strengthen public confidence. A pilot phase is planned in large parks such as Juan Carlos I or Valdebebas, where system performance will be validated, followed by progressive expansion to other districts such as Fuencarral-El Pardo, San Blas, or Usera.
The objective of this project is to transform water management in the urban green spaces of the municipality of Madrid through the safe reuse of reclaimed water from the city’s main wastewater treatment plants. This strategic intervention will replace the use of potable water for the irrigation of public parks with treated water that meets the microbiological and physicochemical requirements established by current regulations. The proposal is based on a circular model, integrating advanced regeneration technologies without the use of chlorine and a dedicated separate distribution network, ensuring traceability and sanitary safety at all times.
With an initial phase focused on large-scale parks and high-use density areas, the project is scalable and replicable across the entire municipal territory. Its implementation will reduce pressure on conventional water supply sources, contribute to the water balance of the Tagus River basin, decrease municipal operating costs, and strengthen public perception of the City Council’s commitment to sustainability and climate resilience. The project is fully aligned with the commitments of the European Green Deal, the objectives of Madrid’s Climate Change Adaptation Plan, and international water sustainability standards such as the AWS Standard and the principles of the CEO Water Mandate.
