This project is being developed in the Metropolitan Region of Recife, the capital of the state of Pernambuco, and aims at the functional restoration of the coastal Beberibe aquifer, currently affected by a combination of critical factors: severe saltwater intrusion, chronic overexploitation, and unplanned urbanization. The Beberibe aquifer, formed by unconsolidated marine, fluvial, and aeolian sediments, represents a strategic source of groundwater supply for more than 3 million people. Its stratified structure and high hydraulic connectivity between layers make it extremely sensitive to imbalances induced by the decline in piezometric levels and lateral pressure from the Atlantic Ocean.
In recent decades, the exponential increase in unregulated water withdrawals, together with the impermeabilization of recharge areas and the loss of urban green spaces, has compromised the system’s ability to maintain its hydrochemical balance. As a result, the saltwater wedge has advanced inland, affecting sectors previously considered safe for urban, agricultural, and ecosystemic supply.
Faced with this scenario, the initiative proposes a multi-stage intervention grounded in scientific and operational foundations, combining Earth observation technologies (Sentinel-2, LIDAR, multispectral drones), high-resolution hydrogeochemical inspection campaigns, hydraulic sealing techniques adapted to tropical conditions, and applied bioengineering solutions such as managed recharge zones. These interventions act simultaneously on the physical vector (infiltration and groundwater flow) and on water quality, reducing the system’s vulnerability and enabling sustainable recovery.
From a methodological perspective, the project applies the water benefit accounting approach through the integration of VWBA (Volumetric Water Benefit Accounting) and WQBA (Water Quality Benefit Accounting) methodologies. This integration allows not only measuring the net additional volume of groundwater recharged (with baseline validation and permanence), but also verified improvements in critical quality parameters such as electrical conductivity, chlorides, nitrates, and turbidity.
Saltwater intrusion into the Beberibe aquifer represents a critical challenge for the water sustainability of Recife and its metropolitan area, as it is a phenomenon that alters natural hydrochemical balances in a dense urban context, climatically and geologically vulnerable. This coastal phreatic system, composed of sandy and silty sediments of marine and fluvial origin, has high permeability, high vertical connectivity between layers, and limited natural containment capacity against saline fronts. These characteristics make it especially susceptible to imbalances in hydraulic gradients.
The overexploitation of unregulated deep wells, many drilled without licenses or technical monitoring, has caused in various areas an inversion of the natural hydraulic gradient, favoring the rise of saline water toward previously protected extraction zones. This condition has worsened in areas such as Boa Viagem, Olinda, and Jaboatão dos Guararapes, where extractive pressure for domestic and industrial uses coincides with a progressive drop in piezometric levels.
Simultaneously, urban expansion has impermeabilized historically used recharge surfaces, drastically reducing effective infiltration and increasing contaminated surface runoff. Consequently, the natural renewal cycle of the aquifer is interrupted and its vulnerability to marine intrusion is amplified. In this context, abandoned, inactive, or illegal wells, without technical sealing or control, behave as open vertical conduits, allowing the unwanted mixing of waters of different quality and salinity, both upward and downward.
This hydrogeological degradation has multiple consequences: it compromises the quality of water available for human and productive supply; increases treatment costs; hinders planning for rational groundwater use; and drastically reduces the region’s resilience to droughts, water crises, or extreme events induced by climate change.
Facing this complex issue, the proposed solution is structured around a multi-component technical-operational strategy designed to address both structural causes and active degradation vectors. Actions are distributed across three main fronts:
Advanced diagnosis and technical characterization: A detailed mapping of the region is carried out using multispectral satellite remote sensing (Sentinel-2), infrared thermography, and drone flights equipped with LIDAR and multispectral sensors. This information is processed using GIS tools to identify hotspots of water risk, thermal depressions, changes in surface moisture, and topographic anomalies that may suggest the presence of active, abandoned, or decommissioned wells. Field validation is conducted through georeferenced inspections, sample collection, and measurement of key variables such as groundwater level, electrical conductivity, water temperature, and chloride concentration.
Hydraulic intervention and well sealing: Based on a hydrogeological risk index, wells whose morphology and location represent a higher probability of connection between contaminated layers are prioritized. The intervention is carried out using progressive sealing techniques with bentonite slurries, expansive cement mixtures, or polymeric resins, depending on depth, lithology, and structural collapse degree of the well. Each action is documented with technical sheets, satellite images, and geo-referenced work reports. This procedure cuts off unwanted vertical flows and eliminates contamination entry/exit vectors.
Implementation of managed recharge zones: In areas identified with hydrological potential, urban parks, green corridors, or non-urbanized peri-urban land, biofilters are built as semi-deep infiltration systems. These biofilters consist of a stratified combination of silica sand, washed gravels, activated carbon, geotextiles, and native vegetation adapted to wet soils (such as Cyperus, Heliconia, or Typha). Their function is to capture rain runoff, filter physical and chemical contaminants, and allow slow, regulated infiltration towards the water table. These structures are hydraulically modeled and monitored in real-time using flow sensors and automatic piezometers, which allows evaluating their performance and long-term impact.
Each of these lines of action is accompanied by a participatory governance strategy involving local authorities, water companies, research centers, and community organizations, ensuring sustainability, territorial appropriation, and synergy among stakeholders.
The project implementation is organized into five consecutive phases, with differentiated and overlapping activities that ensure comprehensive technical control of each component:
Phase 1 – Remote Diagnosis (Months 0 to 2): Initial cartography is developed using multispectral Sentinel-2 images, digital elevation models, and thermal remote sensing. Risk maps are generated and linear structures, thermal anomalies, and changes in NDVI index are identified. Municipal geographic information system databases and CPRM hydrogeological cartography are incorporated.
Phase 2 – Field Validation (Months 2 to 4): Wells are physically inspected, their structural status is determined, piezometric records are taken, and water samples are extracted for certified laboratory analysis (chlorides, EC, nitrates, turbidity, heavy metals). Permanent control points are installed to establish the baseline quality and water table level.
Phase 3 – Intervention Design (Months 3 to 5): Sealing plans for wells and hydraulic design of recharge zones are prepared. Constructive parameters, materials, expected flows, vegetation coverage, and construction schedules are defined. Key performance indicators (KPIs) and regulatory requirements for environmental permits are established.
Phase 4 – Construction Execution (Months 6 to 10): Progressive technical sealing of wells is performed with volume and resistance control, according to ABNT standards. Biofilters are constructed at selected sites with sensor instrumentation for flow, observation wells, and automatic weather stations. Each intervention is documented with full traceability (well ID, material volume, tightness test results).
Phase 5 – Continuous Monitoring and Reporting (Months 10 to 24): A real-time monitoring network connected to a digital platform records piezometric level, EC, temperature, accumulated infiltration, and precipitation. Quarterly external audits are conducted and verified water benefits are reported on Aqua Positive. The VWBA approach is applied using the formula:
Meanwhile, the WQBA approach quantifies the percentage improvement in water quality by reduction of measured pollutants compared to initial concentrations, validated by an external lab and maintained for three consecutive quarterly cycles.
In the Metropolitan Region of Recife, one of the most densely populated urban centers in northeastern Brazil, the coastal Beberibe aquifer faces severe deterioration due to saltwater intrusion, historical overexploitation of wells, and progressive soil impermeabilization. This aquifer, which supplies more than three million people, has a stratified structure and high hydraulic connectivity, making it particularly vulnerable to imbalances induced by ocean pressure and falling piezometric levels.
The project “Groundwater Guardians – Recife” proposes an integrated intervention aimed at restoring aquifer functionality, recovering its recharge capacity, and improving stored water quality. The strategy is based on a combination of remote monitoring technologies, high-resolution hydrogeochemical diagnosis, technical sealing of critical wells, and the installation of managed recharge zones through nature-based solutions.
The methodological approach combines two complementary frameworks: Volumetric Water Benefit Accounting (VWBA) to quantify induced additional recharge, and Water Quality Benefit Accounting (WQBA) to measure actual improvements in parameters such as chlorides, electrical conductivity, and nitrates. Both approaches include external verification and digital traceability via platforms like Aqua Positive.
Project actions are deployed in five phases: remote diagnosis using satellite imagery and drones; field validation with piezometric measurements and chemical analyses; technical design of hydraulic works and green infrastructure; execution of progressive well sealing and biofilter construction; and finally, continuous monitoring with IoT sensors connected to a digital analysis platform. Throughout the process, compliance with key performance indicators (KPIs) is ensured, and local governance mechanisms are established with participation from environmental authorities, universities, water operators, and communities.
The project is located within the hydrogeological unit of the Beberibe aquifer, crossing municipalities such as Recife, Olinda, Paulista, Jaboatão dos Guararapes, and Cabo de Santo Agostinho. This area has been identified by the Brazilian Geological Service (CPRM) as highly vulnerable to marine salinization due to its interaction with estuarine bodies, urban density, and low natural recharge capacity.
From a sustainability perspective, the intervention directly contributes to the Sustainable Development Goals: it improves public health (SDG 3), ensures access to clean water (SDG 6), drives innovation in resilient infrastructure (SDG 9), strengthens climate adaptation in urban environments (SDG 11 and 13), restores degraded ecological functions (SDG 15), and fosters inter-institutional partnerships (SDG 17). Additionally, it enables the generation of Positive Water Credits (PWCs) as an instrument for environmental valuation and climate financing.
This advanced hydrological restoration model has replication potential in multiple coastal basins in South America under water stress, consolidating a technical, participatory, and results-oriented governance approach.
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