Coastal Karst Research Articles

Isotopic study for evaluating complex groundwater circulation patterns, hydrogeological zoning, and water-rock interaction in a Mediterranean coastal karst environment

In this study groundwater provenance, circulation, and rock interaction processes have been assessed by cross processing the spatial distribution of chemical and isotopic signatures in freshwater with the hydrogeological features of the coastal karst carbonate aquifer of Murgia, located in the southeastern end of Italy, along the Adriatic Sea. Thanks to widespread groundwater quality monitoring (major, minor, and trace-element analyses) and multi-isotopic measures of O, H, Sr, and B, some assumptions about complex groundwater circulation patterns, hydrogeological zoning, and water-rock interaction have been drawn. Three sectors have been distinguished into the Adriatic side of the Murgia aquifer all fed by two main recharge areas located on the most elevated, inner side of the aquifer. Each sector is characterized by different groundwater circulation patterns, residence time, and hydrogeochemical features. The water samples collected into the western sector evidence a certain degree of water-rock interaction, which allows us to assume long groundwater flow paths and residence time. On the contrary, the eastern sector of Murgia has been proven to be characterized by short residence times and a possible direct freshwater contribution even in the downstream course due to the massive presence of karst forms. Herein, the isotopic analysis of the water samples does not provide evidence of water-rock interaction. Finally, in the third, central sector, water infiltrated at different locations mixes flowing through relatively long paths even though not sufficient to allow groundwater to gain the rock's isotopic signature.

Influence of submarine groundwater discharge on the nutrient dynamics of a fringing-reef lagoon

Study regionThis study investigates nutrient distribution and flux dynamics in a coral reef lagoon in Quintana Roo, Mexico, located on a permeable limestone coast of the Mesoamerican Barrier Reef System. Study FocusEmphasis is placed on submarine groundwater discharge (SGD) as a crucial contributor to nutrient pathways, including ammonium (NH4+), nitrate and nitrite (NOx-), hydrogen silicate (HSiO3-), hydrogen phosphate (HPO42-), and urea. Inputs vary with SGD magnitudes and sources and by proximity to active spring discharges. Groundwater multi-tracer analysis and multiple linear regression identify 226Ra as explaining NH4+ variability due to long-term groundwater processes, while 223Ra predicts NOx-, HSiO3-, and urea due to short-term inputs. No significant relationship was found between HPO42- and any radium isotope, indicating complex behavior in coastal karst aquifers. New hydrological insights for the regionThe findings highlight complex nutrient dynamics in coastal karst settings, with SGD-derived fluxes primarily consisting of dissolved inorganic nitrogen (DIN) and HSiO3-. Although lower in concentration, HPO42- and urea fluxes are significant compared to other karst environments. Radium isotopes distinguish between short-term and long-term, as well as new and recycled nutrient inputs. Groundwater inputs transport fresh nutrients to healthier reefs, whereas processed, recycled inputs were detected near degraded reefs. These insights are essential for understanding global nutrient cycles and coral health, particularly in the context of global change and anthropogenic disturbances affecting coral reef ecosystems.

Carbonate microfacies reveal how Asturian shell middens formed in the Mesolithic

The littoral platform of eastern Asturias (northern Spain) is a coastal karst modeled by the sea. During the Early Holocene, this landscape was exploited by successfully coastal-adapted hunter-gatherers. Intense coastal foraging resulted in accumulation of large amounts of shellfish in numerous karstic rockshelters. A century ago, the Count of Vega del Sella established the post-Paleolithic age of the Asturian shell middens, carbonate-cemented deposits hanging from the walls of karstic cavities. He argued that these were remnants from past shell accumulations filling up completely the rockshelters, as result of direct waste disposal, while the occupations occurred outside. Our geoarchaeological approach tested this long-lasting site-formation model with micromorphology and carbonate microfacies analysis of two sites: El Alloru and El Mazo. Novel outcomes are: 1) the carbonate cements correspond to calcareous tufa resulting from spring activity; 2) the deposits show a stratigraphic framework related to successive phases of debris accumulations and stasis; 3) tufa formation and accumulation of anthropogenic debris are syn-depositional; 4) biogenic and diagenetic cements reveal phreatic conditions. All these contradict a priori expectations from Vega del Sella's widely accepted model of anthropogenic mound constructions preserved in the currently cemented deposits. Microcontextual evidence suggest that shells were likely processed and produced also inside the rockshelters, which might have been used as occupation spaces as well instead of just for waste disposal, while the analyses exterior deposits at El Alloru also present occupational signs. This study also supports further evidence for higher water-table levels in the early Holocene at regional level, despite most caves show no signs of spring activity today.

High-resolution seismic record of the Quaternary palaeoenvironments along a Dalmatian-type coast (Lošinj Channel, Adriatic Sea)

Coastal systems have changed considerably in response to Quaternary glacial–interglacial variability. Here, we offer the first detailed assessment of geomorphic features and late Quaternary sedimentation dynamics in the Lošinj Channel in the Adriatic Sea. The present study attempts to resolve the complex evolution of the environments by applying high-resolution seismic records that build upon sediment core data. Within this coastal karst basin, a significant amount of sediment accumulated during the Quaternary. Notably, the existence of several prominent erosional and depositional environments was revealed. We distinguished recurrent episodes of fluvio-lacustrine and marine sedimentation that probably occurred since Marine Isotope Stage (MIS) 6. The preserved record consists of erosional features and subparallel and oblique reflectors attributed to glacial periods (Seismic Units SU-II, SU-IV, and SU-V). Interglacial units are acoustically semitransparent and generally reflection-free (Seismic Units SU-I and SU-III). The mutual influence of sea level and climate change, sill depth, and karst hydrology enabled environmental changes in the Lošinj Channel. The area proves to be important for Quaternary studies because it contains a long sediment succession spanning at least the middle and late Pleistocene and Holocene. Our study has implications for the assessment of the long-term palaeoenvironmental evolution of similar coastal settings and reconstruction of the regional palaeogeography which is in turn crucial for understanding prehistoric human occupation and/or dispersal. This is one of the few well-preserved records in the Adriatic Sea that provides insight into submerged landscapes and sea levels since the penultimate glacial.

Mixing of endogenous CO2 and meteoric H2O causes extremely efficient carbonate dissolution

Karst corrosion of carbonate rocks by water with dissolved gases proceeds in most cases along two major scenarios: (i) meteoric water absorbs CO2 from soil and atmosphere, or (ii) ascending water of deep circulation carries with it dissolved endogenous gases, mainly CO2 and H2S. We have observed a peculiar variant where meteoric water absorbs ascending endogenous gases at a natural gas vent on a travertine mound in Slovakia. Carbonate dissolution's extreme effectiveness is demonstrated by mineralization of rainwater ponded at a gas vent, rising to 3.2 g/L of dissolved solids shortly after the rainfall. One liter of water ponded at the vent and mixing with the venting gas, dissolved up to 800 mg of calcium at a rate exceeding 5.8 mg/L·min. Limestone tablets placed at the vent show signs of significant corrosion, at rates up to 126 mm/ka. The rate is comparable to those in coastal karst, where freshwater is mixing with seawater and to those in sulfuric acid speleogenesis (SAS), both the highest hitherto known rates of karst corrosion in carbonates. The geomorphic effects of the process described are depressions on the surface of travertine near the vents of endogenous CO2. This type of corrosion seems to be universal and probably occurs everywhere where endogenous CO2 is exhaled to the surface from carbonate rocks.

Recent records of thermohaline profiles and water depth in the Taam ja’ Blue Hole (Chetumal Bay, Mexico)

Coastal karst structures have been recently explored and documented in Chetumal Bay, Mexico, at the southeast of the Yucatan Peninsula. These structures, recognized as blue holes, stand out for their remarkable dimensions within a shallow estuarine environment. Particularly the Taam Ja’ Blue Hole (TJBH), revealed a depth of ~274 mbsl based on echo sounder mapping, momentarily positioning it as the world's second-deepest blue hole. However, echo sounding methods face challenges in complex environments like blue holes or inland sinkholes arising from frequency-dependent detection and range limitations due to water density vertical gradients, cross-sectional depth variations, or morphometric deviations in non-strictly vertical caves. Initial exploration could not reach the bottom and confirm its position, prompting ongoing investigation into the geomorphological features of TJBH. Recent CTD profiler records in TJBH surpassed 420 mbsl with no bottom yet reached, establishing the TJBH as the deepest-known blue hole globally. Hydrographic data delineated multiple water layers within TJBH. Comparison with Caribbean water conditions at the Mesoamerican Barrier Reef System, reef lagoons, and estuaries suggests potential subterranean connections. Further research and implementation of underwater navigation technologies are essential to decipher its maximum depth and the possibilities of forming part of an interconnected system of caves and tunnels.

Coastal karst aquifers and submarine springs: what future for their water resources?

This paper is intended to be a reminder of a series of scientific works whose origin is largely attributable to G. de Marsily, without attempting to make an exhaustive overview of submarine springs and coastal karst aquifers. The main results show that coastal karst aquifers with their submarine outlets and the possibility of natural seawater intrusion are particularly fragile and must be studied and managed with appropriate tools. For the coming decades, the evolution of the climate as results from the IPCC scenarios leads us to question the effects of the increase of sea level on this coastal resource, and the effects of frequent and severe droughts, added to an increase in withdrawals from aquifers caused by the coastalisation of the population. Cet article a pour objectif de rappeler une série de travaux scientifiques dont l’origine est largement attribuable à G. de Marsily, sans chercher à faire un tour d’horizon exhaustif des sources sous-marines et des aquifères karstiques côtiers. Les principaux résultats montrent que les aquifères karstiques côtiers avec leurs exutoires sous-marins et la possibilité d’intrusion naturelle d’eau de mer sont particulièrement fragiles et doivent être étudiés et gérés avec des outils appropriés. Pour les décennies à venir, l’évolution du climat telle qu’elle résulte des scénarios du GIEC nous conduit à nous interroger sur les effets de l’augmentation du niveau de la mer sur cette ressource côtière, et sur les effets de sécheresses sévères et plus fréquentes et de la montée du niveau marin, ajoutés à une augmentation des prélèvements dans les aquifères causée par la littoralisation de la population.

Assessing the impact of climate change on a coastal karst aquifer in a semi-arid area

This study investigates the potential future state of a coastal karst aquifer located in the Salento peninsula of southern Italy, examining the impact of climate change. After a historical and future overview of the climate in the study area, an analysis of meteorological indices (SPIs and SPEIs) and groundwater levels (GWLs) during the historical period revealed a strong correlation between them. Then, straightforward linear regression models were applied to establish relationships between SPIs/SPEIs and GWLs for the analysed wells. To estimate future SPIs and SPEIs, an ensemble of regional climate models was used, and estimates of GWLs until the end of the century were obtained by incorporating these projections into the regression models. Two emission pathways, the RCP4.5 and the RCP8.5, were considered in the analysis. The results based on SPIs suggest no significant changes in future GWLs across all wells. However, when considering also temperature through the use of SPEIs, a general decline in groundwater levels is expected, with the decrease being more pronounced under the RCP8.5.

Long-term erosion resistance of grouting curtain in coastal karst fracture area

To study the long-term erosion resistance of grouting curtain in coastal karst fracture areas, a long-term erosion resistance test is performed using a self-designed grouting curtain accelerated erosion test system at different accelerated erosion ages in a specific water pressure environment. Results show that the ion-diffusion depth in grouting-reinforced bodies follows the exponential function growth law with increasing erosion age. The grouting curtain deterioration in coastal karst areas occurs within 1–1.5 years. The damage pattern of grouting-reinforced bodies shows a brittle–ductile–brittle transformation trend. The compressive strength, elastic modulus, and peak strain of the grout curtain show a trend of first increasing and then decreasing, conforming to the normal distribution law. In addition, analyses of the pore structure, hydration products, and cementation characteristics of the slurry–rock interface reveal that the erosion products, Friedel salt, AFt, and CaSO4·2H2O, change the slurry microstructure. This shows the effect of filling and compacting in the early stage, swelling and cracking damage in the later stage. In particular, the porosity and proportion of harmful pores in the slurry first decrease and then increase, and cracks form and expand at the slurry and slurry–rock cementation surface.

Effects of global and climate change on the freshwater-seawater interface movement in a Mediterranean karst aquifer of Mallorca Island

Karst aquifers are globally prized freshwater sources, posing a significant preservation challenge. These aquifers typically exhibit dual or even triple porosities, encompassing matrix, fractures-fissures and conduits, rendering them highly responsive to variations in chemical characteristics and hydraulic head. In coastal regions, these aquifers often possess extensive subsurface conduit networks intricately linked to the rock matrix, facilitating groundwater discharge into the sea. Therefore, they display acute sensitivity to seawater intrusion, swiftly reacting to changes in precipitation and pumping regimes. This makes them exceptionally vulnerable to short-term meteorological fluctuations and long-term climate change. Their high heterogeneity leads to uneven penetration of the freshwater-seawater interface, causing rapid seawater intrusion inland over significant distances. The Mediterranean region, characterized by water deficit and water stress, faces strong impacts from climate change, featuring a warming atmospheric trend exceeding the global average, along with diminished rainfall exacerbating water scarcity. Increasing water demands for agriculture, urban development, and the growing tourism industry, because of global change, are worsening water stress. Our primary research objectives were analyzing the environmental consequences of global and climate change on seawater intrusion in Mediterranean coastal karst aquifers, with a focus on the role of the double-flow model, thus contributing to the understanding of the processes involved. To achieve this, we selected a study region on Mallorca Island in the western Mediterranean, where a karst aquifer system discharges into the sea. We employed various study methods, notably hydrochemical techniques and multi-isotopic analysis, encompassing the examination of 2H and 18O isotopes in water, 87Sr/86Sr ratio, Sr and B concentrations, and δ11B in water. A key finding is the rebound effect, wherein aquifers recontaminate due to solute molecular back-diffusion following cessation of extractions and the retreat of marine intrusion, providing insight into the impact of climate and global change on Mediterranean karst aquifers.

Past and Present Drivers of Karst Formation of Ciénega de El Mangle, Panama

Tropical coastal karst areas represent dynamic, fragile, and biodiverse environments. Central America’s karst regions have been scarcely studied, with most of the research focused on the northern part of the region and on several larger cave systems. The coastal carbonate zones of the Central American region represent a unique karstic landscape, which, so far, has been insufficiently studied. Therefore, in this paper, we aim to describe the (i) landscape geomorphology and (ii) chemical conditions that define Ciénega de El Mangle in Panama as a distinctive karstic site. Carried geomorphological mapping and the characterization of karstic features have resulted in the identification of the different karstic forms and processes that are present within this unique karstic area. Considering that the chosen karstic study area is located in a marine–coastal fringe on the periphery of a lagoon, it is affected by a combination of several factors and processes, including seawater intrusion (through sinkholes), the formation of conchiferous limestone (CaCO3), and NaCl precipitation related to efflorescence. Due to the seasonally humid tropical climate, the chemical weathering processes are intense, thus forming alkaline soils that are hindering the development of mangrove vegetation. The geomorphology of the area results from intense evaporation combined with an influx of brackish groundwater, due to which a landscape has evolved in the marine–coastal strips, of seasonal tropical climates, that exhibit saline beaches, known as a littoral shott. In total, 24 karstic microdolines have evolved within the shott, of which six represent domical geoforms formed by gradual evaporitic precipitation, while seven other geoforms represent active karstic sinkholes filled with brackish water. These results are key for understanding the past and present climate interactions and conditions that have led to the formation of tropical karst environments.

How diverse are the mountain karst forests of Mexico?

Tropical forests on karstic relief (tropical karst forest) are among the most species-rich biomes. These forests play pivotal roles as global climate regulators and for human wellbeing. Their long-term conservation could be central to global climate mitigation and biodiversity conservation. In Mexico, karst landscapes occupy 20% of the total land surface and are distributed mainly in the southeast of the country, along the eastern slope, and in the Yucatan Peninsula. Within each of these areas, the following types of karst occur: coastal karst, plain karst, hill karst, and mountain karst (low, medium, high). Mountain karst cover 2.07% of Mexico's land surface and are covered by tropical rainforests, montane cloud forests, and tropical deciduous forests. These are probably one of the most diverse biomes in Mexico. However, the mountain karst forests of Mexico have received little attention, and very little is known about their diversity. Here, we evaluated the vascular plant species richness within the mountain karst forests of Mexico. We assembled the first, largest, and most comprehensive datasets of Mexican mountain karst forest species, from different public databases (CONABIO, GBIF, IBdata-UNAM), which included a critical review of all data. We compiled a list of the families, genera, and species present within the mountain karst forests of Mexico. Taxa that best characterize these forests were identified based on their spatial correlation with this biome. We explored biodiversity patterns, identifying areas with the highest species richness, endemism centers, and areas of relatively low sampling intensity. We found that within the mountain karst forests of Mexico there are representatives of 11,771 vascular plant species (253 families and 2,254 genera), ca. 50% of the Mexican flora. We identified 372 species endemic to these forests. According to preliminary IUCN red list criteria, 2,477 species are under some category of conservation risk, of which 456 (3.8%) are endangered. Most of the Mexican mountain karst forests have been extensively explored and six allopatric, species-rich areas were identified. Compared to other regions in the world, the mountain karst forests of Mexico are one of the most diverse biomes. They contain more species than some entire montane systems in Mexico such as Sierra Madre Oriental, and Sierra Madre del Sur. Also, the mountain karst forests of Mexico are most diverse than similar forests of South America and Asia, even if considering the effect of different sampling areas. The fact that mountain karst forests are embedded in areas of high biotic diversity, probably contributes to their great floristic diversity. Thus, the mountain karst forests of Mexico are an important source of diversity and shelters a large percentage of the Mexican flora.

Impact of connected conduit on pumping-induced seawater intrusion in a coastal karst aquifer

IntroductionCoastal karst aquifers face the risk of seawater intrusion due to groundwater development. Based on the conceptualization of Woodville Karst Plain (WKP), this study investigates the effect of karst conduit and pumping conditions on the aquifer vulnerability and pumping security.MethodsAccording to the purposes of this study, two cases are considered: one with conduit and one without. Salinization levels are compared between two cases, considering pumping rates ranging from 50 to 200 m3/day and various pumping locations throughout the on-shore region.ResultsThe results reveal that the aquifer with conduit is more susceptible to seawater intrusion at low pumping rates, whereas both scenarios experience significant salinization at high pumping rates. Specifically, in the non-conduit case, contamination is most prevalent when wells are located in the middle of the aquifer, while in the conduit case, pumping from inland areas poses high vulnerability. Moreover, conduit case and non-conduit case display different regions for pumping clean water. At low pumping rates, both cases show saline water being pumped from wells near the shore, and clean water is obtained from inland wells. At high pumping rates, the non-conduit case allows for clean water extraction from wells situated further inland, while in the conduit case, no wells within the entire aquifer are deemed safe.DiscussionThe analysis and findings of this study offer valuable insights for the management of groundwater in coastal karst aquifers, encompassing vulnerability assessment, selection of pumping locations, and determination of pumping rates.

First insights into an exceptionally deep blue hole in the Western Caribbean: The Taam ja’ Blue Hole

Coastal karst formations may remain unexplored by the global marine scientific research community. Knowledge provided by fishermen coupled with scientific research on karstic formations prompted us to explore the geomorphometric and physicochemical features of a submerged blue hole in the large tropical estuary of Chetumal Bay in the southeastern coast of the Yucatán Peninsula, Mexico. Differently from the well-known literature on cenotes in the Yucatán Peninsula, no references are made to blue holes in the region. Sampling and surveying of the blue hole were conducted in September 2021 by scuba, echosounders, CTD profilers, and the collection of water samples. This study revealed a previously unknown maximum water depth for the Taam ja’ Blue Hole, as it is now named, of 274.4 meters below sea level (mbsl), making it the second deepest known blue hole in the world. The Taam ja’ Blue Hole has a nearly circular shape at its surface, encompassing an area of ~13,690 m2. The sides of the blue hole are steep, with slopes >80° that form a large conic structure covered by biofilms, sediments, limestone, and gypsum ledges. The blue hole mouth locates at ~4.5-5.0 mbsl, at which water properties change significantly with temperature and salinity gradients of 4.9°C/m and 9.8 PSU/m, respectively. Hydrographic profiles show a stratified water column inside the blue hole consisting of a hypoxic layer (5-20 mbsl), a chemocline (50-80 mbsl), and an anoxic layer (>110 mbsl). Evaluation of anions and cations indicated that the water inside corresponds mainly to that of diluted seawater.

Investigating compound flooding in a low elevation coastal karst environment using multivariate statistical and 2D hydrodynamic modeling

Miami-Dade County is vulnerable to flash, pluvial, fluvial, coastal and groundwater flooding due to its low-elevation karst morphology. Despite considerable advances in understanding the impact of compound flooding events by considering major flood drivers (precipitation, river discharge, and coastal surge), little is known regarding the severity of groundwater hazards in this region. This study links a multivariate statistical analysis with a coupled physically-based 2D hydraulic model to estimate the flood hazard in the Arch Creek Basin located in North Miami. A bivariate copula analysis was used to capture the joint probability of key flood drivers with predefined water table thresholds to set-up the flood modeling conditions. Results demonstrate the high vulnerability to extreme precipitation events compared to coastal surge in the study area. Similarly, groundwater flooding is relevant in shallow water table environments, as it influences the severity of flood hazards in terms of flood inundation depth, extent, and damage to the built environment. This research demonstrates that groundwater flooding is a latent risk that should be incorporated in flood hazard mapping in regions susceptible to high water tables and sea level rise.

The Transboundary Approach to Landscape Geointerpretation: Challenges in Interpretive Planning and Geoconservation

The paper introduces the transboundary approach for landscape geointerpretation using a karst landscape (NW Dinaric Karst) as an example. It proposes geointerpretation that focuses on attractive geoheritage themes that are unique to a karst landscape, such as “duality” of the landscape (surface and underground landscape), geodiversity and geohistory of explorations. Four representative karst landscape types are presented in two neighbouring countries, Slovenia (SI) and Croatia (HR): low karst (Karst Plateau/SI), contact karst (UNESCO site Škocjan Caves/ SI), high alpine glacial karst (Gorski Kotar/HR) and coastal karst (Island of Krk/HR). The transboundary geointerpretation approach is based on an interpretive planning process, which was conducted through participatory workshops with local people and stakeholders and resulted in one interpretive master plan and four permanent exhibition plans. The key phenomena and themes for permanent exhibition plans were identified and used as the basis for the establishment of off-site karst interpretive centres and on-site polygons. The karst heritage was interpreted by using Freeman Tilden’s basic principles of interpretation. The presented approach and the interpretive infrastructure provide a good basis for further geoconservation projects, as well as for geopark designation. Its transferability and further geotourism applications are discussed.

Simulated Short- and Long-Term Deformation in Coastal Karst Caves

The self-balanced pressure arch theory is an important basis for excavation support in karst caves, but it is difficult to quantify the empirical theory in coastal areas. In addition, the rheological effects of karst strata could pose a hazard to engineering. Therefore, this study investigated the rheological mechanism under the self-balanced pressure arch effect, and we proposed a mesoscopic unit rheological model for clay minerals in a water-rich environment. With the discrete element method (DEM), we realized the numerical modeling of the rheological model. Then, the proposed model is validated by a case study of foundation excavation in the coastal karst area of China. The mesoscopic mechanical characteristics of caves considering the influence of pressure arch are analyzed. The results show that the self-balance of the caverns mainly lies in the mesoscopic mineral strength and local stress. With the rheological controlled model, the final predicted convergent deformation of the foundation has an error of less than 10% compared with the field monitoring data. In this study, we can quantitively describe the self-balance effect of the pressure arch surrounding the caves and reveal the rheological mechanism. The proposed model can be applied to similar engineering with careful calibration and provide safety guidance.

Saltwater Intrusion of Coastal Karstic Aquifer on the Example of the Boljkovac Water Supply Pumping Station near Zadar, Croatia

Numerous coastal karst springs of the Mediterranean region have problems with salinization. Salinization usually occurs during summer dry periods as a result of long droughts and excessive pumping for water supply. The Boljkovac water supply pumping station has slightly increased parameters that indicate the possibility of salinization during the dry summer periods, but the main salinization occurs post heavy rains which appear after long dry periods in the fall, winter, and spring. Due to the occasional occurrence of salinization, continuous monitoring of the aquifer by depth was set up at the piezometric well drilled near the water supply pumping station. The results of the monitoring were analyzed in relation to external factors that can negatively affect the disruption of the labile dynamic balance of salt and fresh water. The analyzed external factors are the pumping rate for the water supply, the amount of precipitation, surface flow and the interaction of surface water and groundwater, as well as the sea level changes. In Croatia, and the wider Mediterranean area, there are a large number of springs and water wells that have the same or similar problems, so the results of this analysis can be used in designing monitoring and setting up management systems for these coastal aquifers.

A homogeneous approach in modeling a coastal karst aquifer

A homogeneous approach in modeling a coastal karst aquifer

The Influence of Seasonal Recharge and Groundwater Pumping on the Seawater Intrusion in a Coastal Karst Aquifer

Wu, X.; Xu, Z.; Xu, Z.; Hu, B.X.; Chang, Q., and Hu, Y., 2022. The influence of seasonal recharge and groundwater pumping on the seawater intrusion in a coastal karst aquifer. Journal of Coastal Research, 38(4), 785–794. Coconut Creek (Florida), ISSN 0749-0208. Groundwater resources in the coastal karst aquifers are threatened by long-distance seawater intrusion. The severity of groundwater contamination can be affected by hydrologic and anthropogenic factors, including rainfall conditions and pumping situations. A better understanding of these factors' control on the seawater intrusion is critical for their vulnerability estimation and aquifer management. The aquifer salinization, pumping safety, and the vulnerability of inland springs were examined by a synthetic-modeling work in this study. Different pumping locations, pumping rates, the comparison of dynamic seasonal recharge (DSR), and steady-state recharge (SSR) were considered in this study. Several time-based metrics were developed to estimate the aquifer vulnerability and water quality. The results show that the distance of pumping location to the shoreline significantly impacts seawater intrusion. The near-shore pumping leads to lower aquifer contamination while higher salinity in pumped water, and the inland pumping causes more aquifer salinization with cleaner pumped water. In addition, aquifer, pumping water quality, and inland spring are more vulnerable to seawater intrusion under the DSR condition than SSR condition. The difference of aquifer salinization between DSR and SSR condition increases with pumping rate from 50 to 150 m3/day and then decreases from 150 to 200 m3/day, which shows a threshold pumping rate in comparing DSR and SSR conditions. The insights from this work provide essential suggestions for groundwater simulations and related management decisions.