Saltwater intrusion increasingly jeopardizes groundwater in low-lying coastal plains worldwide, where the combined effects of sea-level rise, land subsidence, and hydraulic regulation further exacerbate aquifer vulnerability and threaten the long-term sustainability of freshwater supplies. To move beyond sparse and fragmented piezometric observations, we propose “integrated coastal supersites”: wells equipped with multiparametric sensors and multilevel piezometers that couple high-resolution vertical conductivity–temperature–depth (CTD) profiling with continuous hydro-meteorological time series to monitor the hydrodynamic behavior of coastal aquifers and saltwater intrusion. This study describes the installation of two supersites and presents early insights from the first monitoring period, which, despite a short observation window limited to the summer season (July–September 2025), demonstrate the effectiveness of this approach. Two contrasting supersites were deployed in the coastal plain between the Brenta and Adige Rivers (Italy): Gorzone, characterized by a thick, laterally persistent aquitard, and Buoro, where the aquitard is thinner and discontinuous. Profiles and fixed sensors at both sites reveal a consistent fresh-to-saline transition in the phreatic aquifers and a secondary freshwater lens capping the confined systems. At Gorzone, the confining layer hydraulically isolates the deeper aquifer, preserving low salinity beneath a saline, tidally constrained phreatic zone. Groundwater heads oscillate by about 0.2 m, and rainfall events do not dilute salinity; instead, pressure transients—amplified by drainage regulation and inland-propagating tides—induce short-lived EC increases via upconing. Buoro shows smaller water-level variations, not always linked to rainfall, and, in contrast, exhibits partial vertical connectivity and faster dynamics: phreatic heads respond chiefly to internal drainage and local recharge, with rises rapidly damped by pumping, while salinity remains steady without episodic peaks. The confined aquifer shows buffered, delayed responses to surface forcings. Although the monitoring window is currently limited to 2025 through the summer season, these results offer compelling evidence that coastal supersites are reliable, scalable, and management-critical relevance platforms for groundwater calibration, forecasting, and long-term assessment.

Saltwater intrusion poses an increasing threat to groundwater sustainability in coastal aquifers worldwide, where relative sea-level rise, climate variability, and drainage management jointly alter groundwater recharge and flow regimes. To properly understand these forcings and implement effective management strategies, adequate monitoring approaches are required. However, conventional regional monitoring networks, typically based on sparse and infrequent measurements, often fail to capture these coupled dynamics, complicating the development of regional models and long-term assessments.This study presents the design and first observations of an integrated coastal “supersite” monitoring framework implemented in strategic areas of the coastal plain between the Brenta and Adige rivers (northern Adriatic coast, Italy), within the SWAMrisk project. The region hosts a multi-layer aquifer system composed of a shallow unconfined aquifer and several deeper confined units, separated by discontinuous silty–clayey aquitards, and is heavily modified by a dense network of drainage channels and pumping stations that regulate groundwater levels. Two supersites were established at Gorzone and Buoro, characterized by contrasting hydrostratigraphic settings and located next to pumping stations hydraulically connected to tidally influenced drainage networks. Each supersite integrates three multilevel piezometers equipped with fixed-depth conductivity–temperature–depth sensors, periodic high-resolution vertical electrical conductivity (EC) profiling, surface-water level monitoring in canals and pumping stations, and information from nearby meteorological and tide-gauge stations.Despite the limited initial observation period (July–September 2025), the combined approach reveals consistent and site-specific fresh–saline groundwater structures and dynamics. Both sites exhibit vertically layered systems, with small fluctuations in groundwater level and pronounced vertical variability in EC. A persistent freshwater cap above more saline groundwater was identified in both aquifer systems. At Gorzone, where a thicker and laterally continuous aquitard promotes hydraulic isolation, the upper confined aquifer remains relatively fresh (~2.3 mS/cm) and stable, increasing to ~12 mS/cm at depth. The phreatic aquifer shows EC values rising from ~2 to 18 mS/cm in the upper part, driven mainly by pressure perturbations associated with tidal propagation and drainage management. At Buoro, a thinner and discontinuous aquitard allows partial vertical connectivity, resulting in faster phreatic responses to local recharge and pumping, and subtle, delayed confined-aquifer responses linked to inland rainfall. Here, the phreatic aquifer hosts a thicker fresh-to-brackish lens (~3–10 mS/cm), stabilizing at ~15 mS/cm near its base, while a thin freshwater lens (~2 mS/cm) caps the confined aquifer and rapidly transitions to saline conditions (~24 mS/cm) at depth.These observations support a dual-forcing conceptual model in which short-term groundwater and salinity fluctuations are dominated by local mechanical controls, whereas longer-term stratification and freshwater preservation in confined aquifers are governed by regional recharge and density-driven processes. The results demonstrate that integrated coastal supersites provide a robust, scalable, and management-relevant platform for improving process understanding, model calibration, and adaptive management of coastal aquifers under climate change and increasing human pressures. Research funded by the Interreg Italy–Croatia 2021–2027 Programme, Project ID: ITHR0200479—SWAMrisk “Subsurface Water Monitoring and Management to Prevent Drought Risk in Coastal Systems”.

The river-delta system of the Neretva, located in the southeastern Adriatic Sea, confronts the simultaneous influence of basin-driven processes and coastal oceanographic conditions, which together exert dominant control over the land-sea interaction and the balance between surface-water and groundwater regimes across the delta. River Neretva Delta represents the largest cultivated agricultural area (4500 ha) along the Croatian coast and it is increasingly exposed to climate change and reduced freshwater availability, which intensifies salinization through saltwater intrusion. Since the 1960s, the delta area has been significantly transformed from its natural state into an intensively cultivated landscape, primarily via the extensive implementation of melioration infrastructure. Up to date, after the preconditions for agriculture have been met, no significant improvements to the melioration system’s operating regime have been implemented, nor has novel infrastructure been introduced, although a clear decline in both freshwater quality and quantity is evident.This study aims to highlight the adverse effects of climate change, relying on datasets obtained via several cross-border collaboration programmes. Initially, monitoring was focused on capturing groundwater salinity and related volumetric features in the area. As an add-on, a monitoring infrastructure has been implemented to ensure insight into surface-water quality and quantity parameters. Since the Neretva River has been identified as a dominant boundary condition for the hydrological and hydrogeological setting of the delta, the estimation of the freshwater discharge has been significantly improved to ensure the real-time information on freshwater availability and on upstream penetration of the seawater wedge, which can infiltrate through the riverbed and feed the aquifer with saltwater. In addition to the onshore monitoring network, further activities led to the installation of subsea piezometers to support offshore groundwater characterization, sampling, and the collection of Rn222/226 datasets.Results obtained revealed several emerging trends. With ongoing sea-level rise, the impact of saltwater intrusion on freshwater availability is evident at both seasonal and short-term timescales. Land subsidence analyses highlight a steady trend with minor spatial variability. Upstream freshwater discharge is regulated by hydropower plants in operation, thereby reducing freshwater availability during the dry season. Even though the phreatic aquifer is sensitive to external conditions, deeper lithological units appear comparatively insensitive, reflecting the dominant influence of the Adriatic Sea and a persistent lack of freshwater throughout the hydrological year. Considering climate change-induced effects, this study indicates a deterioration of the water quality and highlights the associated challenges for water management.Research funded by the Interreg Italy–Croatia 2021–2027 Programme, Project ID: ITHR0200479—SWAMrisk “Subsurface Water Monitoring and Management to Prevent Drought Risk in Coastal Systems”.

The Mediterranean region is increasingly affected by water scarcity, land degradation, and desertification processes driven by unsustainable land management practices and climate change, with significant impacts on agricultural sustainability and food security. In this context, Neglected and Underutilized Species (NUS), due to their adaptability to marginal and degraded environments and low input requirements, represent a viable option for enhancing agroecosystem resilience while contributing to sustainable land management and restoration efforts. In this study, a harmonized geospatial database at the scale of the Mediterranean basin was developed by integrating over 30 abiotic parameters, including soil properties, topography, vegetation, land cover, and climate indicators. Freely available global datasets were harmonized at a consistent spatial resolution and reference system and used to derive a set of key indicators that support cost-effective, large-scale assessments of soil health and climate stress over extensive areas. Both historical climate observations and CMIP6 future projections under SSP2-4.5 and SSP5-8.5 scenarios were considered.Using internationally recognized classification standards and unsupervised clustering techniques, we performed a spatial zonation of abiotic environmental conditions by first classifying each individual parameter according to threshold-based schemes indicative of soil functional limitations or climate-induced stress. These classifications were subsequently integrated through a linear combination of the parameter-specific classes to jointly assess cumulative environmental constraints. This approach enabled the spatial identification of areas where an increasing concentration and severity of unfavourable conditions correspond to higher levels of land marginality and degradation susceptibility, and thus potential suitability for sustainable, low-input NUS cultivation across the Mediterranean basin.This comprehensive dataset supports evidence-based land-use planning and climate-adaptation strategies, providing a foundation for scaling NUS cultivation to enhance ecosystem resilience and agricultural productivity under changing environmental conditions. The resulting database further underpins the development of decision-support tools for sustainable land-use planning and climate adaptation in Mediterranean agroecosystems.This work was conducted in the framework of the project VENUS - “ConVErting marginal lands of the Mediterranean basin into productive and sustainable agroecosystems using low water demanding Neglected and Underutilized Species” funded by the PRIMA programme (Grant Agreement No. 2312) supported by the European Union’s Horizon 2020 research and innovation programme.