Groundwater depletion and salinity intrusion have deepened concerns over the long-term reliability of freshwater resources across Bangladesh, stimulating increased attention to the role of Managed Aquifer Recharge (MAR) in strengthening water security. The review examines the development, implementation, and performance of MAR across two distinct hydrogeological settings: the Barind Tract in the northwest, where groundwater levels are rapidly declining, and the coastal zone in the southwest, where salinity limits access to freshwater. The study evaluates the development of MAR practices in Bangladesh and synthesizes evidence on the effectiveness of major MAR techniques, including Rainwater Harvesting Systems (RWHS), Aquifer Storage, Transfer and Recovery (ASR/ASTR), and Induced Bank Filtration (IBF). RWHS installations, which rely on rooftop and stormwater capture, typically recharge shallow aquifers ranging from 140 to 1,070 m 3 /year. ASR/ASTR systems using treated pond or surface water achieve recharge capacities of up to 3,600 m 3 /year, although their performance is influenced by water turbidity, filter clogging, and aquifer properties. IBF systems provide substantially larger recharge volumes, reaching up to 31,200 m 3 /day where permeable riverbank sediments permit efficient infiltration; however, their effectiveness is reduced in areas with thick clay layers. Findings highlight the dominant role of geological variability in determining the suitability and long-term performance of MAR interventions. The study emphasizes the need for site-specific hydrogeological assessments, operational monitoring, and coordinated strategies that integrate technology, policy support, financing mechanisms, and community participation. Strengthening these elements is essential for enhancing groundwater sustainability and improving resilience in drought-sensitive and salinity-prone regions. • MAR in Bangladesh has evolved irregularly across regions and technologies. • Most MAR initiatives have been implemented through foreign-funded projects. • MAR suitability varies across Barind and coastal zones due to diverse geology. • MAR techniques show contrasting recharge capacities and operational constraints. • Sustainable MAR requires site-specific assessment with strong local capacity and policy support.

Coastal aquifers serve as a lifeline for agriculture, drinking water and ecosystems. However, they are increasingly under threat worldwide from seawater intrusion, primarily driven by excessive groundwater extraction, intensified land use, population growth, and climate change, including sea-level rise. This study applies an integrated, multi-seasonal hydrochemical and isotopic approach to assess groundwater and surface water quality in the Metaponto coastal plain (southern Italy). Groundwater and surface water were sampled seasonally over one year and analysed for major ions, trace metals, stable isotopes (δ 18 O, δ 2 H), and radioactive isotopes ( 3 H, 14 C), supported by hydrochemical diagrams, ionic deviation analysis, seawater fraction (f sea ), and multivariate statistics. Electrical conductivity in groundwater ranged from freshwater values (<1,000 μS/cm) inland to >10,000 μS/cm in coastal and deep wells, with maximum seawater fractions reaching ∼0.41. Hydrochemical facies evolve from Ca–HCO 3 inland to Na–Cl dominance near the coast, reflecting salinization driven by seawater mixing and cation exchange. Stable isotopes indicate predominantly meteoric recharge, while enriched δ 18 O and δ 2 H values (up to −2.5‰ and −15‰, respectively) in coastal and deep groundwater reflect evaporation and saline mixing. Tritium (≤0.5–4 TU) and radiocarbon ages (<1,500 to >10,000 years BP) reveal a vertically stratified aquifer, with modern shallow groundwater overlying confined paleo-groundwater. Despite elevated salinity, Heavy Metal Pollution Index (HPI) values remained low (≈10–15), indicating negligible metal contamination. These results demonstrate that groundwater quality degradation in the Metaponto coastal aquifer is primarily controlled by salinization rather than metal pollution and highlight the value of integrated hydrochemical–isotopic tools for identifying aquifer vulnerability and supporting sustainable groundwater management in coastal plains. • Integrate methods to identify processes causing groundwater quality degradation. • Reveal inland-to-coast salinity shifts with seasonal and depth-specific variations. • Differentiates mixing and reactive processes using f sea and ionic deviation analyses. • Apply δ 18 O, δ 2 H, 3 H, and 14 C to assess recharge sources and aquifer stratification. • Reveals isolated paleo-groundwater (>10,000 yrs) beneath a vulnerable coastal aquifer.

Saltwater intrusion into freshwater systems, intensified by climate change and anthropogenic activities, poses multifaceted challenges in coastal Bangladesh. This study investigates how thirty years of peer-reviewed research has addressed these challenges, asking: What are the dominant themes in salinity-related research in Bangladesh, and how do they interconnect? Guided by a combination of systems thinking, socioecological resilience, knowledge mapping, and boundary work frameworks, this study presents a comprehensive systematic scoping review of research on coastal salinity in Bangladesh, aiming to map the breadth of existing literature and examine the interconnections among key research areas. Following PRISMA 2020 guidelines, 231 relevant studies were identified from Scopus and Pubmed. Abstracts were independently coded and categorised into 14 thematic areas, including agriculture, health, livelihoods, water management, climate, ecosystems and pollutants. Co-occurrence analysis using ATLAS.ti 25 revealed significant thematic overlaps and interactions. Among the themes, crops, human health, and livelihoods emerged as the most dominant, reflecting the direct and immediate impacts of salinity on food security, well-being, and economic stability. From these themes and co-occurrence measurements, this scoping review discusses salinity’s drivers, its co-contaminants, and its impacts on ecosystems, land use, livelihoods, communicable and non-communicable disease and agriculture, as well as the diversity and efficacy of water management strategies. By mapping peer-reviewed research on salinity in coastal Bangladesh, this scoping review offers a holistic and integrated perspective spanning public health, socioeconomic, agricultural and ecosystems research. It provides a structured foundation for future research, guiding scholars in contextualising their inquiries, identifying knowledge gaps, and selecting appropriate analytical frameworks. In particular, the study discusses three complementary frameworks (socioecological systems, vulnerability, and just transition) that collectively address the multifaceted and complex challenge of salinity intrusion in coastal Bangladesh. • Saltwater intrusion in water harms health, agriculture and ecosystems in Bangladesh • Comprehensive interdisciplinary review maps salinity research and thematic overlaps • Analysing themes and co-occurrence in 231 studies spanning 30 years using Atlas.ti • Crops, health, and livelihoods themes dominate, with complex thematic interactions