In the agricultural heart of Lleida, where the land has sustained an economy based on intensive production for centuries, the water crisis is becoming undeniably clear. Pesticide contamination, stemming from decades of conventional agricultural practices, has exposed the fragility of rural water systems. In 2022, the herbicides metolachlor and terbuthylazine exceeded legal limits in the water supply of 25 municipalities in Les Garrigues, leaving more than 20,000 people without safe drinking water for months. What seemed at first a local incident is, in fact, a reflection of a global challenge: the accelerated depletion and contamination of freshwater caused by unsustainable practices.
Globally, more than 4 billion liters of clean water are lost each day to diffuse agricultural pollution. Europe allocates over 60% of its freshwater resources to agriculture, and in Spain, 45% of groundwater bodies already show traces of pesticides or nitrates, threatening the health and future of entire rural communities. This context reveals not only environmental risk but also an urgent opportunity to redefine how we produce food and manage water resources.
The Les Garrigues Water Regeneration Initiative, located in the Ebro Basin, one of the most strategic in the Mediterranean and a water source for more than 3 million people, seeks to transform the local agricultural model into a benchmark for regenerative water management. Through the deployment of biofiltration, phytodepuration, and sustainable agrochemical management, it aims to return more clean water to the environment than it withdraws, restoring the ecological and social functions of the water system.
Its strategic goal is twofold: to protect public health and to restore hydrological integrity, proving that agricultural productivity can coexist with ecosystem preservation. Beyond decontamination, the project redefines the relationship between production and water, generating verifiable benefits under the Volumetric Water Benefit (VWB) framework and adhering to the principles of additionality, traceability, and intentionality outlined by the Water Positive approach.
The regenerated water volume will equal the annual consumption of more than 1,000 households, while pesticide reduction is projected to reach 90% in the Utxesa reservoir. This collective effort, led by the Catalan Water Agency (ACA), local cooperatives, universities, and technology providers, positions Les Garrigues as a living laboratory of European water innovation.
What began as a contamination crisis is now a catalyst for transformation: an opportunity to prove that every drop can be regenerated, and that the transition toward resilient agriculture is not only possible but necessary and profitable.
The technical challenge facing the region is diffuse contamination of water sources by persistent herbicides, a phenomenon that directly affects public health and hydrological stability. The Les Garrigues Water Regeneration Initiative introduces a paradigm shift from reactive management to an integrated strategy of prevention, regeneration, and traceability, grounded in science, innovation, and multi-sector collaboration.
Centered around the Utxesa reservoir, the project implements a hybrid system of advanced phytodepuration, agricultural biofiltration, and smart reuse of treated water. This green-gray infrastructure combines subsurface-flow wetlands with biofilters using activated carbon and natural zeolite, optimized to remove metolachlor and terbuthylazine with over 90% efficiency. Treated effluents are reused for low-water-demand crops, closing the loop and easing pressure on local aquifers.
The regenerated water volume will reach 150,000 m³ per year, equivalent to the domestic consumption of more than 1,000 households, while the reduction of pesticides and organic matter will restore surface and groundwater quality in the Utxesa system. Environmentally, the project will prevent indirect CO₂ emissions associated with emergency bottled water logistics, reducing up to 400 tons of CO₂e annually.
Direct benefits include water regeneration for agricultural and domestic use, reduced chemical toxicity, replacement of harmful inputs, and biodiversity recovery. Operationally, it enhances rural resilience and strengthens participating companies’ social license to operate by delivering measurable results under the VWBA: “Green/Gray Infrastructure + WASH” classification.
This initiative is made possible through cooperation among the Catalan Water Agency, the Catalan Forest Technology Center, local agricultural cooperatives, and technology partners specializing in biofiltration and digital monitoring. Together, they form a participatory governance model ensuring full traceability, each liter regenerated is verifiable and certifiable as a Volumetric Water Benefit (VWB).
The model is replicable in other Mediterranean basins affected by diffuse pollution, such as the Segura or Júcar, and scalable through corporate water neutrality programs. Companies in agri-food, energy, or retail sectors with ESG commitments will find in this solution not only compliance but leadership in environmental stewardship. Acting now is not only strategic but urgent: each uncontrolled agricultural season releases thousands of liters of persistent pesticides. This project turns that liability into regenerative value, returning clean water, reputation, and resilience to the territory.
The project follows an integrated, phased approach ensuring both operational efficiency and long-term environmental sustainability. The first phase involves installing subsurface-flow constructed wetlands and natural biofilters, using zeolite and activated carbon to remove metolachlor and terbuthylazine through biological and physicochemical processes. These hybrid systems can treat up to 410 m³ per day, restoring water quality before it reaches the Utxesa reservoir. Conventional treatment plants and ultrafiltration membranes were evaluated but were dismissed in favor of nature-based solutions for their lower operational costs, self-purifying capacity, and ecological benefits.
The second phase promotes sustainable agricultural management, introducing integrated pest control, progressive substitution of herbicides, and vegetative buffer strips that reduce runoff by 60%. IoT soil moisture sensors, smart flow meters, and digital traceability platforms ensure compliance with VWBA principles, no double counting, additionality, and temporality. The system self-adjusts filtration parameters based on hydrological variability, maintaining continuity even during drought periods.
Operational risks such as filter clogging, nutrient overload, or pump failure are mitigated through redundancy systems, remote alarms, and active contingency plans. Preventive maintenance, microbiological monitoring, and sensor calibration occur quarterly under shared governance between authorities, cooperatives, and technical staff. Climate variability risks are reduced by modular wetland designs adaptable to flow changes and resilient native vegetation.
Long-term resilience is ensured by technological flexibility and community participation. Continuous monitoring feeds a regional data system that identifies contamination trends and facilitates replication in other basins. Expected results include the regeneration of over 150,000 m³ of clean water per year, 90% improvement in chemical quality, 400 tCO₂e avoided, and restoration of 12 hectares of natural habitat.
The project follows an adaptive, phased delivery that makes performance transparent at every step and locks in permanence of benefits. It blends nature-based infrastructure with digital control, and it is executed in stages so the system can learn and scale without service disruption.
Phase 1, Diagnosis, Design, and Baseline (Months 0–6). A full pre‑construction baseline is established across quantity and quality. Flow, COD, TSS, nutrients, and pesticide loads (metolachlor, terbuthylazine) are characterized upstream and downstream through composite 24‑hour samples and grab samples in peak season. A hydrologic and pollutant‑load model (SWAT/Mike SHE) defines the without‑project counterfactual using a 3‑year climatic normal. Health and service indicators (days of potable‑water advisories, emergency bottled‑water logistics) are also recorded. The engineering design is validated with hydraulic simulations and pilot column tests on zeolite and activated carbon media to determine hydraulic loading rate (HLR ~0.15 m/d) and hydraulic retention time (HRT 36–48 h).
Phase 2, Construction and Installation (Months 7–18). Subsurface‑flow constructed wetlands and modular biofilters (zeolite + GAC) are built, with diversion channels to stabilize inflows. Each treatment train has metered inlets/outlets (ultrasonic flowmeters with totalizers), V‑notch weirs for calibration, and isolation valves for maintenance. Instrumentation includes multi‑parameter probes (turbidity, EC, DO, ORP), UV254, nitrate ISE, and auto‑samplers; a weather station records rainfall/ET. All assets are georeferenced and connected to a SCADA platform. Nominal capacity is 410 m³/day, with a turndown ratio of 50–120% and seasonal surge to ≈550 m³/day by bringing standby cells online. Target removals: >90% for metolachlor/terbuthylazine, COD <25 mg/L, TSS <15 mg/L, DO >6 mg/L.
Phase 3, Commissioning and Validation (Months 19–24). Progressive wetting of cells and media conditioning precede performance testing under varying flows. Sensors are calibrated; alarm thresholds are set for turbidity, UV254, EC, DO, and flow variance. A 90‑day validation run compares monitored results to the baseline and the modeled counterfactual, producing the first with‑vs‑without VWBA calculation: Volume Treated, Volume Improved, and mass removal (g of pesticide removed). An independent accredited laboratory performs weekly LC‑MS/MS analyses for pesticides during this phase.
Phase 4, Continuous Operation and Monitoring (Months 25–36). The system operates under a preventive and predictive maintenance plan: quarterly media inspection, reed harvesting once per year, backflushing where applicable, and media replacement intervals (GAC: 18–24 months; zeolite: ~36 months, based on breakthrough curves). Real‑time KPIs include water regenerated (m³), removal efficiencies (%), energy intensity (kWh/m³), downtime (hours), and CO₂e avoided (t/year). The SCADA issues instant alarms (SMS/e‑mail) for out‑of‑spec events and executes automatic fail‑safe bypass to protect downstream users. Monthly performance reports are submitted to ACA/CHE; semi‑annual internal audits and annual third‑party VWBA/WQBA verifications confirm benefits and claims.
Phase 5, Evaluation, Communication, and Improvement (Month 37 onward). A rolling annual review compares operational data to the counterfactual using climate‑normalization. Findings trigger process adjustments (cell rotation, HLR/HRT tuning), media optimization, and firmware updates. A five‑year technology refresh roadmap ensures the system remains best‑available‑tech while keeping OPEX ≤ target €/m³.
Measurement and Data Integrity. Inline sensors log at 1–5‑minute intervals; lab verification follows a weekly cadence during Year 1 and monthly thereafter. Synoptic pesticide campaigns run at seasonal peaks. Wetland condition is tracked via remote sensing (NDVI) and fixed‑point photography. Lysimeters quantify infiltration where relevant. All data carry time stamps, asset IDs, and geolocation; audit logs are immutable. Data are retained for ≥10 years to support verification and regulatory reporting.
Control and Traceability. Physical traceability is ensured through metered boundaries at each inlet/outlet and unique asset tagging. Digital traceability runs on the SCADA/IoT platform with role‑based access, automated QA/QC, and export of signed data packages. A cryptographic ledger can be enabled for claim assurance when buyers require enhanced provenance. Deviations auto‑generate incident tickets, root‑cause analyses, and corrective‑action plans. Claims follow VWBA Step 6 with documented additionality, intentionality, and no double counting.
Governance, Roles, and O&M. Operations are led by a qualified operator (24/7 duty phone) under a service‑level objective of ≥95% uptime (target 98%). The asset owner (municipality/mancomunitat) approves annual plans and budgets; ACA/CHE oversee compliance; a third‑party verifier audits annually; cooperatives and community representatives sit on a basin committee for transparency. Water‑use agreements prioritize regenerated water for environmental flows and essential services, then for low‑demand irrigation, aligning with permits and plans. A spare‑parts inventory (critical spares ≤48‑hour replacement) and an emergency response plan (spill, contamination spike, flood) are in place. EHS protocols cover vector control, confined‑space entry, and public safety.
Permanence and Financing of Benefits. A dedicated O&M reserve and insurance cover extraordinary events; long‑term service contracts lock performance obligations and verification costs. The project’s benefits are reported as outputs (m³ treated/regenerated; ha restored), outcomes (quality improvement; advisory‑days avoided), and impacts (public health, resilience, biodiversity), all tied to SDGs and basin plans. This closes the loop between engineering delivery, regulatory compliance, and credible Water Positive claims.
The Les Garrigues Water Regeneration Initiative, Ebro Basin is an integrated water regeneration project combining ecological engineering, digital monitoring, and shared governance to solve structural pesticide contamination. The intervention centers on constructed wetlands and agricultural biofilters using zeolite and activated carbon in subsurface flow systems that mimic natural purification processes. Treatment occurs in three stages: primary sedimentation, biological filtration, and bioadsorption. Operational capacity reaches 410 m³/day, regenerating over 150,000 m³ of clean water annually. Compliance: EU Water Framework Directive, ISO 14046, and WHO water quality guidelines.
The project was chosen over MBR or physical-chemical treatment alternatives for its energy efficiency, low carbon footprint, and rural landscape compatibility. Equipped with IoT sensors and a SCADA system, it monitors flow, turbidity, conductivity, and dissolved oxygen in real time. Data are digitally recorded and verified per VWBA 2.0 principles.
By reducing 90% of pollutants, restoring clean water, and ensuring secure supply for 25 municipalities, it turns crisis into regeneration. Results: 150,000 m³ water regenerated, 400 tCO₂e avoided, 12 ha wetlands restored. COD <25 mg/L, herbicides <0.05 µg/L, dissolved oxygen >6 mg/L.
Strategically, it adds value to the Water Positive roadmap, aligning with SBTi for Water, NPWI, and Agenda 2030. It reinforces corporate ESG reputation, offering measurable, verified, and transparent impact. Its replicability spans Mediterranean and global agricultural basins, adaptable through modular nature-based technology and community participation.
The final impact is both hydrological and social: increased clean water availability, aquifer relief, climate resilience, green job creation, health improvements, and community empowerment. Symbolically, it reaffirms that water regeneration is not a future option but a present necessity, proving that innovation and collaboration can restore water, protect life, and drive a truly regenerative economy.
