Urban areas can significantly alter the quality status of aquifers if appropriate strategies to prevent and detect groundwater contamination are not implemented in time. The prevention of groundwater contamination should be a priority due to its potential long-term impact on the environment and the high cost of remediation. For effective and sustainable groundwater management, it is crucial to proactively monitor a wide range of compounds to prevent their spread, progression and increasing concentrations. This study is one of the few to analyse the trends of various urban groundwater contaminants (nitrate, sulphate, hexavalent chromium, pesticides, PCE and TCE) from a groundwater management perspective. Characteristic trends are assessed using linear regression and the Mann–Kendall method, while significant changes in trends are determined using the Darken and Pettitt tests. The time span of the analysed trends covers the transition period before and after the implementation of the Water Framework Directive (2000/60/EC) and the Groundwater Directive (2000/60/EC). This study confirms the effectiveness of enforcement measures to protect groundwater quality, as evidenced by several statistically significant decreasing trends. On the other hand, this study emphasises the importance of intervention-targeted sampling campaigns and the reporting of raw analytical values according to the ISO 11843 series of standards. This approach is essential to detect upward trends in emerging contaminants at an early stage and prevent them from reaching levels that could negatively impact the economy or even jeopardise the safety of drinking water supplies.

A thorough understanding of the hydrologic mechanisms that control the movement of water through the soil is essential for developing effective stormwater management strategies. Infiltration is critical for determining the amount of water entering the soil and controlling surface runoff. Spatial and temporal variations in soil properties strongly affect infiltration rates, which underscores the importance of evaluating field-specific values for hydraulic conductivity, which are also highly dependent on the chosen measurement and evaluation methods. The objective of this study is to determine and compare soil hydraulic conductivity under dry conditions using two field measurement techniques, namely the double-ring infiltrometer (DRI) and the mini-disk infiltrometer (MDI). The results demonstrate the importance of performing multiple replicates of infiltration tests, especially during the dry season, as the initial dry surface caused deviations in hydraulic conductivity estimates for both methods used (DRI and MDI). Significant spatial variability was observed within the radius of the test replicates over short distances (<1 m). In addition, experimental infiltration curves for a selected site were used to evaluate and compare soil hydraulic parameters through infiltration modeling. In general, the Philip, Green-Ampt, and Smith-Parlange theoretical models showed a better fit to the experimental DRI data than the semi-empirical Horton model.

Urban areas are characterised by continuous emissions of particulate matter from multiple anthropogenic sources, which accumulate mainly on impervious surfaces such as roads, parking areas, and rooftops. During precipitation events, especially extreme rainfall, these accumulated contaminants can be mobilised and redistributed throughout the urban water cycle. This study examines contaminant mass balance and redistribution during extreme precipitation at the scale of the urban water cycle in the regional pilot-case aquifer. Understanding these processes is essential for evaluating the effectiveness and long-term risks of infiltration-based stormwater management.A multi-compartment sampling strategy is being implemented within an urban catchment to capture the key reservoirs and fluxes governing contaminant transfer within the system. Precipitation is sampled to characterise atmospheric washout, while street dust serves as an integrated record of contaminant accumulation on impervious surfaces. Surface runoff from sealed areas is monitored at gully pots, followed by sampling of water percolating through infiltration and filtration layers of the stormwater retention system. Groundwater quality is statistically evaluated at selected monitoring wells to assess aquifer response. In parallel, recharge inputs from the aquifer hinterland, including river infiltration, are characterised to constrain background groundwater conditions.Water samples are being analysed for physicochemical parameters and dissolved contaminants, while solid phases from precipitation, runoff, and dust are chemically, mineralogically, and morphologically characterised to identify dominant particulate contaminant carriers. These datasets provide the basis for developing a conceptual mass-balance model describing contaminant transfer across the air–surface–soil–groundwater continuum.Preliminary results indicate that a substantial fraction of contaminants mobilised during rainfall events is initially retained within soils and filtration media, thus limiting direct transfer to groundwater. However, this retention capacity is finite and strongly depends on contaminant loads, soil properties, and hydrological conditions. In areas affected by spatially localised industrial hotspots, extreme precipitation and associated leaching processes may act as effective triggers for contaminant release and downward transport once storage capacities are exceeded. These findings highlight the need to determine when soils and infiltration systems serve as effective buffers and when they facilitate contaminant transfer. This distinction is critical for evaluating the long-term performance of infiltration-based urban water management strategies and assessing groundwater vulnerability under climate change–related extreme precipitation regimes.