Coastal aquifers are characterized by a mixing zone with freshwater–saltwater interactions, which have a strong relationship with hydrological forcings such as astronomical and storm tides, aquifer recharge and pumping effects. These forcings govern the aquifer hydraulic head, the spatial distribution of groundwater salinity and the saline interface position. This work is an empirical evaluation through time-series analysis between aquifer head and groundwater salinity associated with the sea-level dynamics and the aquifer recharge. Groundwater pressure, temperature and salinity were measured in a confined aquifer in the northwest coast of Yucatan (México) during May 2017–May 2018, along with precipitation. Cross-correlation and linear Pearson correlation (r) analyses were performed with the data time series, separating astronomical and meteorological tides and vertical recharge effects. The results show that the astronomical and meteorological tides are directly correlated with the aquifer head response (0.71 < r < 0.99). Salinity has a direct and strong relationship with the astronomical tide (0.76 < r < 0.98), while the meteorological tide does not (r < 0.5). The vertical recharge showed a moderate correlation with the aquifer head (0.5 < r < 0.7) and a nonsignificant correlation with the groundwater salinity (r < 0.5). In this study, the sea level (r > 0.7) is a more important forcing than the vertical recharge (with 0.5 < r < 0.7). Empirical relationships through time-series analysis and the separation of individual hydrological forcings in the analysis are powerful tools to study, define and validate the conceptual model of the aquifer.

The Ring of Cenotes (RC) extends along the edge of the Chicxulub crater, in the limestone platform of the Yucatan Peninsula (YP), where groundwater shows two preferential flow paths toward the coast near Celestun and Dzilam Bravo towns. The objectives of this study were to describe the regional hydrogeochemical evolution of the groundwater in the RC, and its association with the dissolution/precipitation of the minerals present along its pathway to the ocean. These objectives results were obtained by: (a) characterizing groundwater hydrogeochemistry; (b) calculating calcite, dolomite, and gypsum saturation indexes in the study area; and (c) developing a hydrogeochemical model using PHREEQC (U. S. Geological Survey) inverse modelling approach. The model predictions confirmed that there are two evolution pathways of the groundwater consistent with the preferential flow paths suggested in a previous regionalization of the RC. On the western path, where groundwater flows towards Celestun, marine intrusion influences the hydrogeochemical processes and represents a risk for the freshwater. On the eastern path, where groundwater flows toward Dzilam Bravo, rainfall has an important effect on the hydrogeochemical processes, evidenced by a higher concentration in sulfates during droughts than during rainy periods. Then, monitoring of marine intrusion and phases dissolution in the RC is highly recommended.

Springs are common features on the Yucatán coast. They can discharge either under the sea (submarine) or inland in coastal lagoons and wetlands. Previous observations of a coastal lagoon located on the northern Yucatán Peninsula (La Carbonera) reported sea water intrusion on a spring that discharge on a coastal lagoon (lagoon tidal spring). The saltwater intrusion occurs when the tide is at its lower level, which is the opposite to what has been reported for submarine springs in the Yucatán Peninsula. In this study, the hydrodynamics of the spring is analyzed and the driving forces controlling the seawater intrusion are identified and discussed. Time series of water levels, salinity, and velocity measurements in the lagoon, the aquifer, and the spring are analyzed by means of tide component decomposition and cross-correlations analysis of the tide signals. Results show that the main driving forces causing the intrusion are the density differences and pressure head gradients, and the mechanisms influencing the driving forces driving those differences are the tides, the friction in the lagoon, and the confinement of the aquifer; other mechanisms are discussed to present a complete idea of the complexity of the interactions between the coastal aquifer, the coastal lagoons, and the sea.

Coastal zones are crucial ecosystems supporting significant biodiversity and pertinent socio-economic activities. However, anthropogenic development contributes to socio-environmental complexities, particularly public water supply threats caused by climate change. This research presents a case study on the north-western coast of Yucatan, Mexico, which models potential saltwater intrusion in groundwater for multiple projections of sea level rise and recharge change due to climate change and its implications for the public water supply of the regional population and ecosystem. For this purpose, a previously calibrated and validated numerical model is employed, adapting its boundary conditions, keeping its calibrated hydrogeologic parameters, and considering the 2040 and 2100 climate change projections. Simulation results show that under these projections, significant saltwater intrusion may occur, reducing freshwater thickness due to increased salinity in groundwater and a loss of freshwater sources resulting from brackish-saline wedge intrusion. These scenarios are of particular concern as freshwater in this coastal region is the main source for public water supply and for freshwater input in coastal ecosystems. Moreover, this study underscores the susceptibility of karstic aquifers to salinization, especially in the face of rising sea levels, given their unique hydrogeological characteristics and substantial responsiveness to marine forcings. In spite of the uncertainties in global climate change predictions, this study enhances our understanding of the dynamics of these unique aquifers, and presents future saltwater intrusion projections that offer valuable technical insights to design and implement pertinent and resilient coastal aquifer management strategies.

Tracer hydrology in Latin America and the Caribbean has made significant progress in recent decades, largely through the sustained support of the International Atomic Energy Agency (IAEA). Current practises show water stable isotope applications and precipitation‐groundwater monitoring at the core of most networks, providing valuable insights into recharge mechanisms, groundwater to surface water connectivity, pollution tracking, and climate variability. Despite these advances, critical challenges persist, including short and fragmented monitoring records, limited capture of extreme events, restricted data accessibility, and persistent barriers related to funding, analytical capacity, and weak policy integration. Improving science communication emerges as an urgent need to transform technical findings into actionable knowledge that informs decision‐makers and empowers communities. Opportunities exist to build on IAEA's legacy by sustaining long‐term networks, diversifying tracer applications, mobilising citizen science in monitoring efforts, expanding modelling and laboratory capacity, and advocating for FAIR data sharing across end‐users. Strengthened collaboration across the region, improved communication, and deeper policy engagement can elevate tracer hydrology into a pillar of regional water governance and hydro‐climate resilience.