Dear Colleagues,

In nature, urban groundwater propels many processes, including climatic, geological, geomorphic, geochemical, ecotoxicological, and hydraulic processes, sustaining several ecological purposes and services. Urban development has a profound impact on hydrological systems. Additional issues concerning water resource sustainability and hydrological cycle comprehension are added to by urbanization. The anatomy of the urban underground is constituted by an intricate network of pipes, conduits, channels, galleries, storm sewers, and other structures that alter the hydraulic conductivity of geomaterials. In addition, the release of compounds from urban infrastructure alters the chemistry of the surrounding environment and affects water quality. Urban streams (some of them also being channeled and shallow buried) receive dissolved and particulate chemical loadings from runoff, sewer connections, direct discharge from other waterways, and interactions with groundwater. The chemistry of urban runoff tends to be dominated by material associated with or accumulated on impervious surfaces, such as heavy metals and deicing salt from roadways. Sewage treatment plants are typically designed to remove some, but not all human-produced compounds and suspended material from water. Consequently, these urban buried features act as favorable pathways for the fluid flow of urban-sourced contaminants into groundwater resources. In addition, ground surfaces are generally covered and perceived as virtually impervious (e.g., buildings, asphalt, concrete, or brick). Today, environmental pressures affect urban groundwater systems, which are faced with increasing urban pressure, overexploitation, contamination/pollution issues, and climate variability.

A paradigm shift based on holistic management is required to design sustainable water systems. Consequently, an urban water framework must be based not only on sustainable technical–scientific studies but also on socioeconomic, cultural, heritage, and ethical challenges.

This Special Issue emphasizes the presentation and discussion of key studies, model-urban and peri-urban areas, new methods, original papers, and review articles that describe the current state of the art on the challenges and emerging fields related to the mapping, characterization, assessment, mitigation, and protection of sustainable groundwater systems, water–ground interactions, and water resources in urban areas.

Potential topics in urban areas include but are not limited to the following: hydrogeological mapping, hydrogeochemistry, isotope hydrology, hydraulics, water resources, groundwater engineering, and modeling. Other emerging fields in urban studies are most welcome, such as: urban GIS mapping, geovisualization, and UAV techniques; urban hydrogeomorphology and planning; rural hydrogeology and small-scale water resources management; hydrotoponymy, historical cities, and cultural heritage; smart cities and groundwater; cities, water security and services; and groundwater ethics and urban areas management.

Prof. Dr. Helder I. Chaminé
Prof. Dr. Maurizio Barbieri
Prof. Dr. Maria José Afonso
Guest Editors

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• urban hydrological cycle
• groundwater GIS mapping for urban areas
• urban hydrogeochemistry and isotopic hydrology
• urban hydraulics and hydrodynamics
• urban groundwater recharge
• urban groundwater, planning, and engineering
• urban conceptual models and numerical modeling
• integrated water resources management for urban areas
• geochemical change
• ecotoxicology, geomicrobiology, and hydrobiology studies in urban environments
• environmental risk assessment for urban areas
• urban groundwater and geohazards
• uncertainty, variability, and climate change impacts in urban groundwater systems
• ethics, environment, society, and groundwater for urban areas