Seawater Intrusion Vulnerability Research Articles

Assessment of groundwater vulnerability for seawater intrusion using DRASTIC model in coastal area at Patuakhali District, Bangladesh.

Seawater intrusion is a growing concern for coastal regions in Bangladesh. Overexploitation of groundwater, low rainfall, a high rate of evaporation, rising sea level, cyclones, storm surges, and shrimp cultivation are the causes of seawater intrusion that polluted the groundwater near the coastal area. High values of EC, TDS, Na+, and Cl- ions in groundwater indicate the seawater intrusion. Piper's Trilinear and Durov diagrams of groundwater indicated that most gathered groundwater show predominantly Na-Cl-type of water. Based on the USSL diagram, it is observed that the salinity of the study area is medium to high and the alkalinity is medium to very high. Also, in view of the Wilcox outline, most of the samples in the area of interest are permissible to doubtful, and doubtful to unsuitable. Chloride is moderately correlated with Na+ (R2 = 0.590) and poorly correlated with (HCO3- + CO32-) (R2 = 0.128), which indicates seawater intrusion. According to a comparison of the levels of Fe and Mn in the groundwater of the study area with those recommended by the World Health Organization (WHO) and Department of the Environment (DOE), twenty-two out of thirty-one samples exceed the acceptable limit for Fe and thirty out of thirty-one samples fall within the acceptable limit for Mn. The calculated water quality index reveals that most samples are of low drinking water quality. The research area's poor water type is found in the north-central and southern parts. The WQI geographic variation map reveals that the study's water has a WQI of more than 100, making it unsuitable for consumption. The final seawater intrusion vulnerability map clearly identifies the moderate to highly vulnerable zone of the study area using DRASTIC index parameters. DRASTIC index parameters revealed that some portions of the northwestern part of the sample area show a moderately vulnerable zone. And the rest of the sampling area indicates the highly vulnerable zone.

Assessment of seawater intrusion vulnerability of coastal aquifers in context of climate change and sea level rise in the central coastal plains, Vietnam

Assessment of seawater intrusion vulnerability of coastal aquifers in context of climate change and sea level rise in the central coastal plains, Vietnam

A Numerical Approach to Evaluating Groundwater Vulnerability to Seawater Intrusion on Jeju Volcanic Island, South Korea

Seawater intrusion (SWI) is a critical issue for coastal aquifers, especially in islands where groundwater is the sole source of water supply. The objective of this study was to develop a straightforward approach to evaluating groundwater vulnerability to SWI, using a statistical method with spatial analyses applied to the four basins of Jeju volcanic island. In this study, five factors were parametrized, including hydraulic conductivity, groundwater level, distance from shoreline to wells, well depth and groundwater use. These parameters were spatially interpolated and correlated with groundwater electrical conductivity as a proxy for groundwater salinization, resulting in three parameters with significant relations: groundwater use, well depth, and groundwater level. Then, a numerical model for the SWI vulnerability assessment was constructed using ratings and weights, and by evaluating the vulnerability as weak, moderate and high with a numerical index. Regional conditions, including major land-use types, industrial activities, population and the degree of urbanisation, could affect parameters differently at each region. Based on the percentage of area with a high vulnerability, regions of Jeju Island followed the order of eastern > northern > western > southern, indicating that preventive measures for SWI and its influencing parameters could be applied more effectively in certain regions.

Design of groundwater monitoring network for coastal aquifers based on seawater intrusion vulnerability: A case study of Mandaue City, Philippines

Groundwater is an essential source of freshwater. However, this natural resource exhibits high vulnerability to contamination due to human activities and natural phenomena. Over extraction of groundwater and sea level rise have hastened seawater intrusion in aquifers that lie along the coasts. This has led to the accelerated deterioration of groundwater quality in coastal aquifers. Thus, there is an urgent need to develop tools to monitor groundwater resources. In this study, a framework of selecting priority areas for monitoring was applied to Mandaue City, Philippines. The monitoring areas were selected based on their vulnerability to seawater intrusion using the GALDIT-index. A collection of 77 initial public sites were investigated as potential locations of monitoring wells. The resulting network determined 45 priority areas located across the study area wherein monitoring wells should be located for the long-term observation of groundwater quality. These sites are composed of 28 from the initially investigated locations and 17 proposed sites which were determined to satisfy the required number of wells lacking in certain areas. The results of this study are intended to aid decision makers in creating groundwater management plans.

Appraisal of urban growth impacts on seawater intrusion vulnerability using GIS-based modified GALDIT-U model: a case study of Kozhikode coastal stretch, Kerala, South India

We investigate the potential vulnerability to seawater intrusion into the aquifers along the Kozhikode coastal stretch using the modified GALDIT (GALDIT-U) model from an urbanization perspective. Urban growth impact (expansion of the impervious surface) was added as an additional input parameter in the GALDIT model, and the analyses were performed using GIS. The results indicated that the area of 16.84 km2, found within the proximity of urban settlements and eroded shorelines along with the Kozhikode, Beypore, Kadalundi, and Faroke, falls under very high vulnerability to seawater intrusion with vulnerability index values ranging 24.82 to 29.82. In the southern sector, the area of 16.84 km2 between Elathur and Beypore also falls within very high vulnerability zones. Similarly, the area of 37.01 km2 in Quilandi, Faroke, Puthiyankadi, Panniyankara, and the east sector of Kozhikode municipality is seen as high vulnerability zones with the vulnerability index values ranging 19.84 to 24.82. Seawater intrusion estimated under moderate vulnerability zones is found to occupy 47.85 km2 (vulnerability index values 14.88 to 19.84). The low and very low vulnerability zones cover 65.07 and 48.07 km2, with the vulnerability index values ranging 9.92 to 14.88 and 4.96 to 9.92, respectively. When cross-validated using major hydrochemical parameters, the results indicate a strong correlation between the vulnerability index classes and groundwater physicochemical parameters. The sensitivity analysis carried out indicated that the distance from the shoreline (D), impacts of urban growth (U), and depth to groundwater table above sea level (L) to be highly influencing parameters for seawater intrusion vulnerability in the coastal stretches. The modified GALDIT-U model shows reliable accuracy for estimating and demarcating seawater intrusion vulnerability zones and could act as an efficient tool in the sustainable management of coastal aquifers in an urban environment.

Use of GALDIT model and HFE-Diagram to assess seawater intrusion vulnerability in West Nile Delta, Egypt

Use of GALDIT model and HFE-Diagram to assess seawater intrusion vulnerability in West Nile Delta, Egypt

Development of Seawater Intrusion Vulnerability Assessment for Averaged Seasonality of Using Modified GALDIT Method

Climate change and anthropogenic activities are necessitating accurate diagnoses of seawater intrusion (SWI) to ensure the sustainable utilization of groundwater resources in coastal areas. Here, vulnerability to SWI was assessed by classifying the existing GALDIT into static parameters (groundwater occurrence (G), aquifer hydraulic conductivity (A), and distance from shore (D)) and dynamic parameters (height to groundwater-level above sea-level (L), impact of existing status of seawater intrusion (I), and aquifer thickness (T)). When assessing the vulnerability of SWI based on observational data (2010–2019), 10-year-averaged data of each month is used for GALDIT dynamic parameter for representing the seasonal characteristics of local water cycles. In addition, the parameter L is indicated by the data observed at the sea-level station adjacent to the groundwater level station. The existing GALDIT method has a range of scores that can be divided into quartiles to express the observed values. To sensitively reflect monthly changes in values, the range of scores is divided into deciles. The calculated GALDIT index showed that the most vulnerable month is September, due to relatively low groundwater level. The proposed method can be used to apply countermeasures to vulnerable coastal areas and build water resources management plan considering vulnerable seasons.

Vulnerability assessment of seawater intrusion in coastal aquifers of southern Bangladesh: Water quality appraisals

Overexploitation of groundwater, sea level rising, shrimp cultivation, etc. are the main causes of seawater intrusion in the coastal aquifers which is a growing concern around the globe. So to evaluate the seawater intrusion in the coastal aquifers of southern Bangladesh (Paikgachha, Khulna), water quality parameters such as pH (7.75–8.82), EC (371–5320 µS cm−1), TDS (182–2790 mg L-1), salinity (0.1–2.8 ppt), Na+ (14.8–1376 mg L-1), K+ (2.71–19.4 mg L-1), Ca2+ (33.2–192 mg L-1), Mg2+ (25–138 mg L-1), Cl- (18.2–3168 mg L-1), HCO3− (205–840 mg L-1), and CO32− (6.22–149 mg L-1) for 20 composite water samples, along with the hydro-geo-physical entities were utilized. Additionally, groundwater quality distributions were also appraised for identifying the suitable water sources for drinking and irrigation. Most of the sampling sites possessed mainly NaCl-type groundwater where Na+ and Cl- contents were 2–6 times higher than the recommended limits. Indices-based calculations indicated that only 35% of the sampling sites can provide good quality drinking water whereas groundwaters from >50% of sampling sites were unsuitable for irrigation. Statistical approaches reveal the potential seawater intrusion with trivial evidence of carbonate mineralization. Distributions of seawater intrusion vulnerability among the studied area were specified by the GALDIT index. The central (30%), southern (25%), and northern (45%) parts were identified as high, moderate, and low vulnerable zones, respectively due to saline water. Thus, considering the heterogenic distribution of seawater intrusion vulnerability among the studied unconfined aquifers, more intimate and detailed groundwater investigations are required on a periodical basis to explore water for drinking and irrigation.

Estimating Soil Water Susceptibility to Salinization in the Mekong River Delta Using a Modified DRASTIC Model

Saltwater intrusion risk assessment is a foundational step for preventing and controlling salinization in coastal regions. The Vietnamese Mekong Delta (VMD) is highly affected by drought and salinization threats, especially severe under the impacts of global climate change and the rapid development of an upstream hydropower dam system. This study aimed to apply a modified DRASTIC model, which combines the generic DRASTIC model with hydrological and anthropogenic factors (i.e., river catchment and land use), to examine seawater intrusion vulnerability in the soil-water-bearing layer in the Ben Tre province, located in the VMD. One hundred and fifty hand-auger samples for total dissolved solids (TDS) measurements, one of the reflected salinity parameters, were used to validate the results obtained with both the DRASTIC and modified DRASTIC models. The spatial analysis tools in the ArcGIS software (i.e., Kriging and data classification tools) were used to interpolate, classify, and map the input factors and salinization susceptibility in the study area. The results show that the vulnerability index values obtained from the DRASTIC and modified DRASTIC models were 36–128 and 55–163, respectively. The vulnerable indices increased from inland districts to coastal areas. The Ba Tri and Binh Dai districts were recorded as having very high vulnerability to salinization, while the Chau Thanh and Cho Lach districts were at a low vulnerability level. From the comparative analysis of the two models, it is obvious that the modified DRASTIC model with the inclusion of a river or canal network and agricultural practices factors enables better performance than the generic DRASTIC model. This enhancement is explained by the significant impact of anthropogenic activities on the salinization of soil water content. This study’s results can be used as scientific implications for planners and decision-makers in river catchment and land-use management practices.

An optimization method coupled the index-overlay method with entropy weighting model to assess seawater intrusion vulnerability.

Seawater intrusion poses a serious threat to coastal areas around the world. The purpose of this study was to develop a comprehensive approach to assess the vulnerability of saltwater intrusion. The powerful decision-making technique GALDIT was firstly selected, and its inherent weights are the origin of the subjective method. The entropy method was then integrated to reasonably determine the objective weight of this basic structure. Furthermore, to balance conflicts between subjective and objective methods, game theory was intruded upon. The result of the sensitivity analysis showed a correlation coefficient between the effective weights and theoretical weights of the normal method, entropy theory, and game theory of 0.66, 0.89, and 0.94, respectively. Meanwhile, the best correlation coefficient between the vulnerability indices and the values of 38 monitoring wells was obtained by the game model. Finally, the optimal weights of G, A, L, D, I, and T were 0.096, 0.153, 0.220, 0.320, 0.150, and 0.061, respectively. The study area was finally classified into regions with high, moderate, and low vulnerability, accounting for 11.4%, 24.9%, and 63.7% of the area. The paper included that the optimization of GALDIT through game theory gives a more accurate assessment of the groundwater vulnerability to seawater intrusion.

Seawater intrusion vulnerability evaluation and prediction: a case study of Qeshm Island, Iran

Abstract Seawater intrusion is one of the most serious issues to threaten coastal aquifers. Tourian aquifer, which is selected as the case study, is located in Qeshm Island, Persian Gulf. In this study, first the vulnerability of the region to seawater intrusion is assessed using chloride ion concentration value, then by using the autoregressive integrated moving average (ARIMA) model, the vulnerability of the region is predicted for 14 wells in 2018. The results show that the Tourian aquifer experiences moderate vulnerability and the area affected by seawater intrusion is wide and is in danger of expanding. It is also found that 0.95 km2 of the region is in a state of high vulnerability with Cl concentration being in a dangerous condition. The prediction model shows that ARIMA (2,1,1) is the best model with mean absolute error of 13.3 mg/L and Nash–Sutcliffe value of 0.81. For fitted and predicted data, mean square error is evaluated as 235.3 and 264.3, respectively. The prediction results show that vulnerability is increasing through the years.

The SIVI index: a comprehensive approach for investigating seawater intrusion vulnerability for island and coastal aquifers

Seawater intrusion is a major groundwater quality management issue for islands and coastal aquifers. In this paper, a new comprehensive index called the SIVI index has been proposed to assess the vulnerability of these aquifers to seawater intrusion. The index consists of eight parameters including: surface area of the aquifer affected; the intensity of intrusion; its seasonal variation; its evolution; aquifer type; the hydraulic conductivity of the aquifer; the height of groundwater levels above sea elevation; and distance of the aquifer from the coast. The SIVI index considers both the dynamic and intrinsic characteristics of the region to evaluate seawater intrusion vulnerability. The new index was applied to the Tourian aquifer located in Qeshm island in the Persian Gulf. The results show that the aquifer locally has a high vulnerability (SIVI index 0.54) to seawater intrusion as currently an area 9.5 km2 of the aquifer is in danger of being salinized. The presented SIVI classification method can be used to analyze vulnerability of aquifers and management of groundwater resources in any coastal region.

Application of GALDIT in Assessing the Seawater Intrusion Vulnerability of Jeju Island, South Korea

Seawater intrusion (SWI) is a major environmental threat to groundwater resources in coastal regions. GALDIT is an index-based SWI vulnerability model that is increasingly being used in many parts of the world to identify regions that are vulnerable to various types of SWI based on six major parameters. In this study, we conducted a vulnerability assessment of Jeju Island to SWI based on several years of collected groundwater level data and hydrogeological values where the objectives of the study were to visualize the distribution of recent SWI, to increase the reliability of the GALDIT assessment method by improving current GALDIT techniques, and to respond effectively to diagnoses of SWI on Jeju. To improve the GALDIT assessment method to fit the Jeju model, the possibility of electrical conductivity was explored instead of standard GALDIT parameters that represented the existing impact of SWI. Improvements to the GALDIT vulnerability assessment method made it clear that groundwater became increasingly vulnerable to SWI in the existing high-vulnerability group. The results of this research may be used to develop a quantitative index for rational decision-making on policies and suggest the need for further improvements in groundwater management, with a stronger focus on easing groundwater use.

Mechanisms, configuration typology, and vulnerability of pumping-induced seawater intrusion in heterogeneous aquifers

Coastal aquifers are vulnerable to seawater intrusion due to excessive groundwater pumping. Most research on salinization vulnerability considers homogeneous aquifers, forming the basis of management guidance. However, geologic structure can be highly heterogeneous, with preferential flow paths and low-permeability barriers that complicate flow and salt transport processes under pumping conditions. Here we use a series of variable-density groundwater flow and salt transport models with geostatistical representations of heterogeneity to illustrate characteristics of vulnerability in heterogeneous and homogeneous aquifers. Simulations showed that in homogeneous aquifers, salinization patterns were simple and related only to the hydraulic properties. In heterogeneous aquifers, salinization rates and patterns were much more complicated, and related to pumping location and depth, aquifer geometry, and geologic connections between pumping location, landward boundaries, and saline groundwater. An intrusion configuration typology approach was developed for both homogeneous and heterogeneous aquifers. The configuration approach was applied to heterogeneous aquifers of low, medium, and high geologic continuity, and vulnerability was assessed. The probability-based assessment was able to characterize the impact of pumping locations and rates in heterogeneous aquifers, considering different types of intrusion. The results showed that groundwater vulnerability to salinization was sensitive to pumping distance to the coastline for low-continuity aquifers and to pumping depth for high-continuity aquifers. The analysis provides new insights into the relationship between land-sea geologic connections and seawater intrusion vulnerability. The configuration approach plus probability-based assessment can be a starting point for large-scale aquifer characterization and more sophisticated groundwater management, including vulnerability assessment and optimization of pumping location, depth, and rate.

Seawater intrusion vulnerability in the coastal aquifers of southern India-an appraisal of the GALDIT model, parameters' sensitivity, and hydrochemical indicators.

An appraisal of seawater intrusion into the coastal aquifers is one of the major issues for groundwater resource management. The GALDIT model applies to the analysis of multiple parameters using systematic GIS techniques for mapping and assessment of seawater intrusion vulnerability. It demarcates the mapping of potential vulnerability that shows a higher vulnerability to seawater intrusion in various parts of the coast and the estimated vulnerability index value of 7.50 and 9.64. An area of 33.0km2 spread in the low-lying coastal area comprising estuaries, salt marshes, and saltpans shows the high vulnerability condition with an estimated vulnerability value of 6.42-7.50. An area of 73.20km2 spread over coastal and alluvial plains experiences moderate vulnerability (temporal salinity in the groundwater sources) with an estimated vulnerability index value of 5.46-6.42. Aquifers underlying coastal uplands (hard rock formations) and some parts of accretionary beaches (2.05km2) are relatively protected fresh groundwater sources, wherein the estimated vulnerability index is 4.55-5.46. The vulnerability mapping of the GALDIT model using hydrochemical analysis of primary groundwater parameters such as TDS, Cl-, HCO3, and Cl-/HCO3 ratio is validated. Higher concentration of TDS (2637-4162mg/l) and Cl- (1268-2347mg/l) is taken for the areas falling under higher vulnerability to seawater intrusion, especially in the placer mining sites and coastal areas facing erosion. Similarly, the groundwater sources of the low-lying areas including estuaries, salt marshes, saltpans, and backwater were noted to have higher values of Cl-/HCO3 with a rationality of 9.87-12.18. Hydrological facies shows the highest concentration of NaCl in the groundwater sources within the proximity of eroded beaches, saltwater bodies, and sand mining areas. A hydrochemical facies evolution (HFE) diagram represents the hydrochemical facies of groundwater elements that shows an intrusion of seawater into the coastal aquifers underlying the very high vulnerable zones. Higher bicarbonate concentration (233-318mg/l) is noticed in the upland areas and some parts of dunes and accreted beaches, sandy coasts, and uplands. Vulnerability analysis reveals that those areas near saltwater bodies and eroding coasts are prone to lateral and vertical diffusion of saltwater. The geodatabase developed through such modeling studies can help in planning and developing activities for sustainable groundwater resource management in coastal areas.

Limitations of GALDIT to map seawater intrusion vulnerability in a highly touristic coastal area

Coastal aquifers are susceptible to seawater intrusion, especially touristic areas where the overexploitation combined with the agricultural use of groundwater represent a severe issue for water management. GALDIT methodology was applied as a management tool to identify and prevent salinization of the aquifer. GALDIT methodology needs six input parameters: groundwater occurrence (G), aquifer hydraulic conductivity (A), groundwater head above sea level (L), distance from the shore (D), impact of the existing status of seawater intrusion (I), and thickness of the aquifer (T). Then a contour map is created using three degree of vulnerability: high, medium and low. The higher vulnerability zone ranges from 40 to 550 m towards the mainland with the rest of the aquifer characterized by medium vulnerability. The main problem affecting the selected field site is the large water requirement during the summer period due to the touristic activities, but the correct use of surplus water collected in the winter can overcome this problem. This study demonstrates that further investigation on groundwater hydrochemistry and on water demand trends from the different activities impacting the field site should be implemented, in order to guarantee environmental and touristic development sustainability.

A fuzzy multicriteria categorization of the GALDIT method to assess seawater intrusion vulnerability of coastal aquifers

Groundwater constitutes the primary source of fresh water for >1.2 billion people living in coastal zones. However, the threat of seawater intrusion is widespread in coastal aquifers mainly due to overexploitation of groundwater. In the present study, a modified fuzzy multicriteria categorization into non-ordered categories method was developed in order to modify the standard GALDIT method and assess seawater intrusion vulnerability in a coastal aquifer of northern Greece. The method is based on six parameters: groundwater occurrence, aquifer hydraulic conductivity, groundwater level, distance from the shore, impact of the existing status of seawater intrusion, and aquifer thickness. Initially, the original method was applied and revealed a zone of high vulnerability running parallel to the coastline and covering an area of 8.6km2. The modified GALDIT-F method achieved higher discretization of vulnerability zones which is essential to build a rational management plan to prevent seawater intrusion. The GALDIT-F approach also distinguished an area of the aquifer that is influenced by geothermal fluids. In total, twenty-five categories were produced corresponding to different vulnerability degrees according to the initial method (High, Moderate, Low) as well as the area influenced by geothermal fluids. Finally, a road map was developed in order to adapt management strategies to GALDIT-F categories and prevent and mitigate seawater intrusion. The proposed management strategies of the coastal aquifer include managed aquifer recharge (MAR) implementation, reallocation of existing wells, optimization of pumping rates during the hydrological year, and a detailed monitoring plan.

A national inventory of seawater intrusion vulnerability for Australia

Abstract Study region Twenty-eight coastal aquifer case study areas across Australia. Study focus Seawater intrusion causes degradation of groundwater resources in coastal areas. The characterization of seawater intrusion is difficult and expensive, and there is therefore a need to develop methods for rapid assessment of seawater intrusion as part of large-scale screening studies in order to guide future investment. We use a steady-state analytic approach to quantify seawater extent and propensity for change in seawater extent under different stresses, in combination with findings from a previous qualitative investigation, which relies on a data-based assessment of regional trends. New hydrological insights for the region The combination of methods identified areas of highest risk to SWI including unconfined aquifers at Derby (WA) and Esperance (WA), and confined aquifers at Esperance (WA) and Adelaide (SA). The combination of analytic and qualitative approaches offers a more comprehensive and less subjective seawater intrusion characterization than arises from applying the methods in isolation, thereby imparting enhanced confidence in the outcomes. Importantly, active seawater intrusion conditions occur in many of Australia’s confined coastal aquifers, obviating the use of the analytical solution, and suggesting that offshore groundwater resources provide significant contributions to these systems.

Peer review report 2 On “A national inventory of seawater intrusion vulnerability for Australia”

Peer review report 2 On “A national inventory of seawater intrusion vulnerability for Australia”

Peer review report 1 On “A national inventory of seawater intrusion vulnerability for Australia”

Peer review report 1 On “A national inventory of seawater intrusion vulnerability for Australia”