Saline Water Intrusion Research Articles

Assessing the impacts of climate change on the vulnerability of coastal aquifers to the seawater intrusion

In most coastal areas, groundwater is affected by saltwater intrusion. Climate change effects, such as the sea-level rise and rainfall change are the climatic factors affecting the saltwater intrusion into groundwater. This study examines the vulnerability of the Abdan-Lamidan coastal aquifer to the intrusion of Persian Gulf saline waters under different hydrological conditions. First, the SIMCLIM model was used to calculate the regional sea-level rise of the Gulf under 24 future AOGCMs projections. The results showed that the increase in water level under the ensemble of AOGCM models and two RCP2.6 and RCP8.5 scenarios is 6.7 and 7.8 cm in 2050 compared to 2013. Then, the GALDIT vulnerability index was used to assess the vulnerability of the aquifer under the current condition and future scenarios. The results showed that parts of the aquifer that are currently at lower levels would be more vulnerable to sea-level rise in the future periods.

Hydrogeochemical assessment of groundwater and saline water intrusion along the coastal aquifer in Udupi region of Karnataka (southern India)

Hydrogeochemical assessment of groundwater and saline water intrusion along the coastal aquifer in Udupi region of Karnataka (southern India)

The effects of land subsidence and its mitigating measures on shallow groundwater salinization in the low-lying coastal plain of East Japan

Land subsidence in low-lying coastal regions results from geological and human factors, causing inundation during high tides. Mitigation measures, like pumping stations and ditch systems, aim to address this challenge. However, their impact on groundwater salinity near tidal rivers is understudied. Using a coupled surface-subsurface model, we investigate this issue in the lower Nabaki River region, Shirako Town, Japan. The simulation reveals adverse effects of pumping stations that induce intrusion of saline water from the tidal river into surrounding groundwater. While they are designed to prevent floods, these stations and ditches may inadvertently raise groundwater vulnerability to saltwater contamination. Despite 2D model limitations, it offers valuable insights into coastal groundwater dynamics and salinization. This study provides important information for policymakers and land managers to better understand the consequences of flood mitigation strategies on groundwater quality in vulnerable coastal areas.

Small-holder Fish Farming in the Upper Kuttanad and Brackish Water Villages of Alappuzha District, Kerala, India

In Kerala, smallholder aquaculture emerges as an alluring and significant part of rural lives, improving livelihoods and ensuring a sustainable supply of inland fish. One hundred and four smallholder fish farms were surveyed from the upper Kuttanad and brackish water villages of Alappuzha, the state's leading district for inland fish production. Personal interviews and questionnaires were employed to get primary data on species farmed, culture method, feed, and the challenges smallholder farmers faced. The most common fish species cultured in smallholder fish farms is Oreochromis niloticus (GIFT) (34%), followed by Etroplus suratensis (31%), Pangasius pangasius (15%), Anabas testudineus (6%), Channa striata (6%), Labeo rohita (4%), and Heteropneustes fossilis (4%). In the brackish water villages, 60% of the fish cultured are Etroplus suratensis. Eighty-one per cent of the farmers used ponds, 11% used biofloc, and 8% used cages. Sixty-six percent of farmers used commercially manufactured pellet feed, 21% poultry waste, 12% used food waste, and 1% live Black soldier flies. Fish cultured using the bio floc method are the most affected by the fungal disease, gill rot. Anabas testudineus cultured at high stocking density in bio floc showed tail-biting behaviour followed by bacterial infection. Fifty-one percent of farmers reported a lack of appropriate technical and financial aid from the government, including the withdrawal of subsidies for feed purchases. Even though the 2018 flood seriously affected the fish farms, only 8% of farmers reported the flood as a problem affecting their farms. The major challenges brackish water farmers faced were the intrusion of saline water from the nearby lake and the poaching of juvenile and mature fish from natural ponds. Apart from the monetary assistance provided by the government for starting farms under the "Jankeeya Matsya Krishi" Project, smallholder farmers should need additional help with insurance and subsidies to promote sustainable aquaculture.

Electrical Resistivity Techniques for Groundwater Studies in North-Western Part of District Hisar, Haryana, India

Abstract Haryana is one of the dominant agrarian states of India but salinity in the groundwater is one of the major concerns in the state. The salinity in groundwater is observed from top itself in the central part of Haryana consisting of Hisar, Jind, Rohtak, and Jhajjar districts. As a result, local inhabitants are facing severe problems with the nonavailability of fresh drinking water. In some places, shallow aquifers are having marginally saline water which is used by the local inhabitants in dry months. Groundwater even in shallow aquifers also becomes saline due to less rainfall and intrusion of saline water from lower layers. In some areas, the thickness of freshwater columns has been reduced significantly due to the excessive withdrawal of fresh water and intrusion from underlying saline groundwater aquifers. It is therefore pertinent to study fresh/saline groundwater interface to solve these problems on scientific basis. The geophysical methods especially electrical resistivity method has proved very useful for the estimation of fresh/ saline groundwater interface. The present paper deals with the findings of electrical resistivity survey conducted in Adampur and Agroha blocks of district Hisar, Haryana, India. Thirty-five Vertical Electrical Soundings (VES) were conducted in these areas for this purpose. The results indicate that the entire study area is occupied with marginally saline to highly saline groundwater. The study shows the presence of a thin layer of marginally saline groundwater almost uniformly distributed in the entire study area.

Surface oceanographic changes from ∼ 25,000 to 3500 cal yr BP in the eastern Arabian Sea

Multiproxy data of pteropods and planktic foraminifera from Core SK291/GC17 suggest significant surface paleoceanographic shifts from ∼25,000 to 3500 calibrated years before present (cal yr BP) in the eastern Arabian Sea (EAS). Increased values of the global ice-volume free stable oxygen isotope ratio of seawater (δ18Osw IVF) and stable oxygen isotope ratio in pteropod (δ18OH. inflatus IVF), as well as lower percentages of planktic foraminifer Globigerina bulloides from ∼22,000 to 18,000 cal yr BP, correspond to the weak Indian summer monsoon (ISM) during the Last Glacial Maximum (LGM). In the early Holocene, the EAS witnessed an increase in upwelling driven by strong summer monsoon winds, and a decrease in salinity corresponding with enhanced precipitation in the Western Ghats region. From ∼4800 to 4000 cal yr BP, including the 4.2 ka event, a prominent increase in the δ18OH. inflatus IVF values suggest an enhanced intrusion of the Arabian Sea High Saline Water (ASHSW) to the relatively deeper part of the mixed layer. In the same interval, the low representations of G. bulloides and thermocline dwelling planktic foraminifera indicate weakening of the coastal upwelling and a reduction in surface productivity due to weak ISM across the Arabian Sea, with more severe conditions in the EAS.

Safe water crisis and struggle of climate-vulnerable indigenous communities in southwestern coastal Bangladesh

Abstract This study was designed to unearth the beliefs, practices, and management of safe drinking water of Munda and Rajbangshi indigenous communities. To apprehend the safe drinking water-related behaviour and practice, the qualitative approach was followed where 20 in-depth interviews were carried out among the Munda and Rajbangshi communities in Shyamnagar and Kaliganj Upazila (sub-district) of Satkhira district, Bangladesh. Findings indicate that the intrusion of saline water due to climate-induced changes led to a scarcity of potable water for both communities in the last few decades. Despite the existence of centuries-old traditional practices of water purification, the indigenous communities, particularly women, were compelled to collect safe drinking water from, in general, distant sources as the other sources of water were contaminated with saline water. Despite their collective efforts, managing safe water sometimes, particularly in the rainy season, becomes impossible for these marginalized people as it costs a considerable amount of household income. To ensure their access to safe drinking water and to explore the underlying factors, whether social, economic, cultural or environmental, initiatives from both government and non-government organizations are required for a sustainable life for these unheard plain land indigenous communities in Bangladesh.

Three-dimensional hydrodynamic modelling of saltwater ingression and circulation in a Brackish Lake Shinji, Japan

Lake Shinji is a mesohaline lake that has intermittent saline water intrusion from its east coast connection of Ohashi River. This intrusion is often in the shape of a very thin layer that moves along the Lake bottom and stayed at the center due to bowl shape bathymetry of the Lake having maximum depth at the center. To elucidate the intrusion mechanism a 3-D hydrodynamic model (EcoPARI) was employed in a hindcast mode covering the year 2012 from the beginning of January to the end of September. Initially, the core emphasis was given to the vertical turbulence diffusion model and optimum model parameters were determined to accurately simulate the hydrodynamics. It was highlighted by the numerical simulations that alteration of one model constant, which is the multiplying coefficient of Richardson number, “α”, is influential instead of altering all the constants to tune the turbulence model. The possibility of using differential model constants for temperature and salinity was also tested and it helped in the improvement of simulations. Finally, the performance of the model was also assessed under extreme weather conditions and a historical upwelling event was simulated. The model was able to reproduce the intrusion in the summer months as well as the upwelling event in September due to strong westerly winds caused by a nearby passing typhoon.

River Morphological Stability of Juana River based on Sediment Transport

Juana River is a river located in the north of Central Java. The downstream part of the Juana River flows into the North Java Sea. Problems with the Juana River include drought during the dry season and flooding during the rainy season. In addition, saline water intrusion makes it difficult for communities to access raw water. Flooding in the Juana River is caused by land use changes in the upper reaches of the river, the presence of a large number fishing boats anchored downstream, flooding in the lower reaches, and the relatively gentle slope of the Juana River. Currently, the Ministry of Public Works and Housing (Kementerian PUPR) is undertaking the construction of normalization, dam raising, and rubber dams in the Juana River. This study aims to analyze the stability of the Juana River. The analysis in this study uses the regime method to obtain the dimension of stability in the Juana River. The analysis in this study uses the regime method to obtain the dimension of stability in the Juana River. The results of the stability analysis in the Juana River found that the depth and slope parameters in the Juana River were unstable while the width parameters in the Juana River were stable. This research is useful to provide input to the Central and Regional Governments in planning and implementing river management in the Juana River.

Numerical investigation of mixed physical barriers for saltwater removal in coastal heterogeneous aquifers

Saltwater intrusion is a prevalent global environmental issue that detrimentally impacts coastal groundwater aquifers. This problem is exacerbated by climate change and increased groundwater abstraction. Employing physical barriers proves effective in mitigating saline water intrusion. In this study, a validated numerical simulation model is utilized to assess the impact of aquifer stratification on the effectiveness of mixed physical barriers (MPBs) and their response to structural variations. Additionally, the performance of MPBs was compared with that of single physical barriers in a laboratory-scale aquifer. Three different configurations were replicated, comprising two stratified aquifers (HLH and LHL) and a homogenous reference aquifer (H). The results demonstrate that MPBs are efficient in decreasing the saltwater penetration length in the investigated cases. The reductions in penetration length were up to 65% in all cases. The removal efficacy of residual saline water for MPBs exceeded that of the subsurface dam by 2.1–3.3 times for H, 2.1–3.6 times for HLH, and 8.3 times for LHL conditions, while outperforming the cutoff wall by 38–100% for H, 39–44% for HLH, and 2.7–75% for LHL. These findings are of importance for decision-makers in choosing the most appropriate technique for mitigating saline water intrusion in heterogeneous coastal aquifers.

Properties and Mechanisms of Seawater Exchange in Marian Cove, King George Island, West Antarctic Peninsula

AbstractThe Antarctic Peninsula is one region that has recently experienced warming substantially more rapidly than the global mean over the past 50 years. Marian Cove is located in the South Shetland Islands connected to the Bransfield Strait via Maxwell Bay between King George Island and Nelson Island. In this study, we identified properties and mechanisms of seawater exchange in Marian Cove from multiple hydrographic surveys and a single bottom‐mounted mooring installed at the entrance to Marian Cove. Regardless of the season, the mean current velocity profiles at the entrance to Marian Cove were constant because of the influence of tidal forcing. Wind was the primary force that determined the variation in surface current; in response, a countercurrent occurred near the bottom area. We estimated salt transport to understand what effects Maxwell Bay′s saline water intrusion has on the Marian Cove environment. When the daily easterly wind was at its maximum of 18.5 m s−1, the salinity could increase to 7.20 × 10−4 g kg−1 in 1 day. In addition, the average freshwater residence time in Marian Cove for the quantitative evaluation of seawater exchange was approximately 9 days. However, the freshwater residence time was reduced to less than 2 days when there were extreme easterly winds.

Technology Focus: Water Management (December 2023)

What is new about water scarcity? We hear about climate change; rivers drying up, resulting in tracks of dinosaurs that lived 113 million years ago surfacing at Dinosaur Valley State Park in Texas; people walking miles for a gallon of water; millions dying each year from water-borne illnesses; glaciers melting; and freshwater aquifers becoming more vulnerable to saline water intrusion. United Nations researchers predict a 20% decline in renewable water resources for every 1°C rise in the world average temperature. For most of us, this is daily news and we have heard it for many years now. How can the individual, the industry, corporations, and global society wake up to the reality of a drying last well and collectively act to extend life on Earth for another million years? The first commercial natural gas well was drilled in 1821, and the first oil well was drilled on 27 August 1859. In 2022, global oil production was approximately 93.9 million B/D and natural gas produced was approximately 4.1 trillion m3. On average, between 2 and 5 bbl of water are produced for every barrel of oil and 260 bbl of water for every million cubic feet of natural gas. The older the fields, the higher the water generation. We are talking roughly 300 million–600 million bbl of water generated per day, and, in the last nearly 200 years, technology and corporate citizenship could succeed in recycling or reusing a meager 3 million–6 million BWPD (approximately 1%). It is acknowledged that political leadership, front-ending innovation, and financing for domestic and commercial viability are essential. In the “quadilemma” between industrialization, agricultural demand, urbanization, and the needs of human and livestock for water, political and financial levers tilt toward industrialization. Hence, industrialization typically carries the blame for causing the water crisis across the continents, but it also creates and shepherds the innovation and introduction of a plethora of technologies and tools that enable intelligent use of water, intuitive approaches to conserve it, and implementable practices that preserve the watershed and prolong the life of aquifers. Desalination, which is still seen as a breakthrough and technology’s most practical solution to alleviate the water crisis, is still expensive when compared with tapping surface water or groundwater. Other smart and superior technologies are evolving, but their success is intrinsically linked to acceptance and adaptation. Once that happens, the lowering of remediation cost eventually will occur. This, complemented by the ease of implementation and reliability, will drive the success of water management and move the 1% of produced-water reuse to a much greater amount. In this issue, I selected three papers for publication that discuss three different established and emerging approaches that explore cost-effective ways to “move water from the Martian poles to the people.” Recommended additional reading at OnePetro: www.onepetro.org. SPE 213239 Sustainable Ion-Exchange Resins for Produced-Water Treatment by Madina Baltaeva, Aramco Innovations, et al. SPE 215061Increased Oil and Reduced Water Production Using Cyclonic AICDs With Tracer-Monitoring Applications in Peru’s Bretaña Norte Field by L. Acencios, PetroTal, et al.

Impacts of climate change and coastal salinization on the environmental risk of heavy metal contamination along the odisha coast, India.

Climate change-mediated rise in sea level and storm surges, along with indiscriminate exploitation of groundwater along populous coastal regions have led to seawater intrusion. Studies on groundwater salinization and heavy metal contamination trends are limited. Present study investigated the heavy metal contamination, associated risks and provided initial information on the impacts of groundwater salinization on heavy metals along the coastal plains of Odisha, India. Total 50 groundwater samples (25 each in post- and pre-monsoon) were collected and analysed. Concentrations of Fe (44%), Mn (44%), As (4%) and Al (4%) in post-monsoon and Fe (32%), Mn (32%), As (4%), B (8%) and Ni (16%) in pre-monsoon exceeded Bureau of Indian Standards (BIS) drinking water limits. High concentrations of heavy metals (Fe, Sr, Mn, B, Ba, Li, Ni and Co) and high EC (>3000 μS/cm) indicated that the groundwater-seawater mixing process has enhanced the leaching and ion exchange of metallic ions in central part of the study area. Multivariate statistical analysis suggested leaching process, seawater intrusion and agricultural practices as the main heavy metal sources in the groundwater. 4% of samples in post- and 16% in pre-monsoon represented high heavy metal pollution index (HPI). Pollution indices indicated the central and south-central regions are highly polluted due to saline water intrusion and high agricultural activities. Ecological risks in the groundwater systems found low (ERI <110) in both seasons. Children population found more susceptible to health risks than adults. Hazard index (HI > 1) has shown significant non-carcinogenic risks where Fe, Mn, As, B, Li and Co are the potential contributors. Incremental lifetime cancer risk (ILCR >1.0E-03) has suggested high carcinogenic risks, where As and Ni are the major contributors. The study concluded that groundwater salinization could increase the heavy metal content and associated risks. This would help policymakers to take appropriate measures for sustainable coastal groundwater management.

INTERROGATING THE EFFECTS OF SAND MINING: A CASE STUDY OF AGILA DISTRICT, ADO LOCAL GOVERNMENT AREA, BENUE STATE, NIGERIA

This study is of believe that Illegal acts and discerning sand excavation/mining has become arisk to the ambiances. While theresearchrelied on personal geological observation on the mining sites, qualitative data were used from secondary literature. Using Agila’s river and coastal mining sites as a case study, the study revealed that it sparks to diversifications in river channels ways, physical ecosystem and food webs. As well it speeds up the river’scurrent and eventually eroding the river banks. Destroying the soil profile and removing the flora reduces the population of animals and eliminates habitat both the surface and subsurface resources. Sand dunes has played a vital aspect role in stoppage against heavy storms, erosion causes by some agents of transportations like winds, waves or floods. Numerous tiny habitants that are a component of the marine and coastal food chain and whose removal would pose some hazards to some other species rely on them for existence. The water tables in the surrounding areas decline as a result of sand mining, drying out the drinking water wells on the river embankments. Turbidity rises at the mining site as also the aquifers near the shore are affected by saline water intrusion. Sand mined areas loose scenic beauty, it emits radiation reliant on the component minerals, dust pollution, emits vibration/noise and it damages roads and some infrastructures. This researchinspected and reviewed the sand mining impacts on river, dune, marine, hydrological, biological and sociological environments with some case studies of the study area.

Using TODIM decision method to control saltwater intrusion by numerical simulation approach (study area: Nowshahr-Nur aquifer)

Over-pumping of aquifers and lack of planning for the water resources, and allocation system in coastal aquifers, in addition to minor problems, disturb the ecological balance. This type of exploitation reduces the groundwater level and the hydraulic gradient in the coastal strip and, due to the higher density of saline water, includes the invasion of saline water and salinization of groundwater resources. Due to population growth, migration, drought, and over-pumping in the southern part of the Caspian Sea, this issue has disturbed the balance of groundwater resources, and most of the coastline has been associated with increasing solute concentrations. Accordingly, in this study, using the SEAWAT code, the intrusion of saltwater in the Nowshahr-Nur aquifer has been simulated, and the results analyzed, which showed that in the current situation, saline water intrusion spreads a wide width of 862 m from the aquifer. To control the current situation of saline water invasion in the coastal strip, seven treatment strategies were simulated and the TODIM decision-making method was used to prioritize. For this purpose, four criteria of economic, social, environmental, and groundwater level improvement were selected for decision-making and weighed by hierarchical analysis. The weighting results showed that the criterion for improving the groundwater level with a weight of 0.311 is the most important. Based on the weighting of the criteria, the strategies were prioritized and the results showed that a 20% reduction in aquifer abstraction by combining the construction of an underground barrier was selected as a solution to control the invasion of short water. The results of this solution showed that 317 m of saline water backflow will arise in the Nowshahr-Nur aquifer.

Human exposures to multiple water sources in the southwestern coastal region of Bangladesh: water quality, pollution sources, and preliminary health risks appraisals.

The coastal areas of Bangladesh have poor accessibility to fresh drinking water and the groundwater is not suitable for drinking, cooking, and other domestic uses due to high levels of salinity and potentially toxic elements. The current study focuses on understanding of the distribution of some physicochemical parameters (temperature, pH, EC, TDS, and salinity) and chemical elements (Fe, Mn, Zn, Ca, Mg, Na, K, Cu, Co, Pb, As, Cr, Cd, and Ni) with health perspective in drinking water from the southwestern coastal area of Bangladesh. The physicochemical properties of the water samples were examined with a multiparameter meter, while the elemental concentrations were analyzed using atomic absorption spectrometer. Water quality index (WQI) and irrigation indices were utilized to determine the drinking water quality and irrigation feasibility, respectively, whereas hazard quotients (HQs) and hazard index (HI) were used to assess the probable pathways and the associated potential risks to human health. The concentrations of some toxic elements in measured samples were relatively higher compared to drinking water guidelines, indicating that ground and surface water are not apt for drinking and/or domestic uses. The multivariate statistical approaches linked the source of the pollutants in the studied water body mostly to the geogenic origin including saline water intrusion. WQI values ranged from 18 to 430, reflecting excellent to unsuitable categories of water quality. The assessment of human health risks due to exposure to contaminated water demonstrated both carcinogenic and non-carcinogenic health risks in the exposed residents of the study area. Therefore, appropriate long-term coastal area management strategies should be adopted in the study region for environmental sustainability. The findings of this research will be supportive in understanding the actual situation of fresh drinking water in the area for policymakers, planners, and environmentalists to take effective necessary measures to ensure safe drinking water in the study area.

Past and future freshwater availability scenarios and their impact on the Indian Sundarbans ecosystem and fisheries

Abstract The Indian Sundarbans is considered one of the zones of highest vulnerability in the world in terms of climate change. About 4.43 million people living in the Indian Sundarbans face a lack of freshwater availability due to the erratic behaviour of monsoon rains, frequent cyclonic storms, intrusion of saline water, and other factors, all of which affect the fisheries and agriculture activities of this area. In this study, estimates of freshwater availability through past and predicted future rainfall and evapotranspiration change scenarios in the Sundarbans are presented. Due to the lack of high-quality in-situ data, various sources of gridded rainfall and evapotranspiration data were used. Between 1948 and 2010, half of the 19 administrative blocks showed a decreasing trend of monsoonal rainfall while the rest showed an increasing trend. Freshwater availability showed a decreasing trend during the monsoon season over different blocks of the Sundarbans, which is a matter of great concern for fisheries and agricultural activities. Statistical downscaling was used to generate future rainfall and evapotranspiration scenarios, using coarse resolution Global Climate Models from the Coupled Model Intercomparison Project phase five for a smaller area like the Sundarbans. Downscaled Global Climate Models project an increasing trend in future monsoon rainfall in both RCP 4.5 and RCP 8.5 emission scenarios. The increasing rainfall can trigger excessive run-off and flooding, which would in turn affect aquaculture infrastructure and damage lentic aquaculture productions across the Sundarbans. However, increased rainfall may expand the flood plain area and extend the feeding grounds of fish. Hence, the impact of rainfall change is quite unpredictable. Proper adaptation techniques may be required to harness the positive impacts while preventing negative effects.

Drought-Induced Salinity Intrusion Affects Nitrogen Removal in a Deltaic Ecosystem (Po River Delta, Northern Italy)

In the summer of 2022, the Po River Delta (Northern Italy), a eutrophication hotspot, was severely affected by high temperatures, exceptional lack of rainfall and saline water intrusion. The effect of saline intrusion on benthic nitrogen dynamics, and in particular the N removal capacity, was investigated during extreme drought conditions. Laboratory incubations of intact sediment cores were used to determine denitrification and DNRA rates at three sites along a salinity gradient in the Po di Goro, an arm of the Po River Delta. Denitrification was found to be the main process responsible for nitrate reduction in freshwater and slightly saline sites, whereas DNRA predominated in the most saline site, highlighting a switch in N cycling between removal and recycling. These results provide evidence that salinity is a key factor in regulating benthic N metabolism in transitional environments. In a climate change scenario, salinity intrusion, resulting from long periods of low river discharge, may become an unrecognized driver of coastal eutrophication by promoting the dissimilatory nitrate reduction to ammonium and N recycling of bioactive nitrogen within the ecosystem, rather than its permanent removal by denitrification.

Groundwater and pore water inputs to the Bay of Bengal supported by geochemical tracers: Example from Tamil Nadu and Pondicherry, East Coast of India

Submarine groundwater discharge (SGD) and Saline water intrusion (SWI) are the two major processes that influence coastal aquifers resulting in severe water stress. It is essential to characterize groundwater dynamics and discriminate geochemical characterization to understand both approaches. The present study investigates the zones influenced by SGD and SWI along the coastal aquifers of Tamil Nadu and Pondicherry. Pore water (PW) and groundwater (GW) samples were collected during the monsoon season at low tide and analyzed for major ions adopting standard procedures. Hydrogeochemical characterization of water samples revealed by the piper, ionic ratio, ionic delta (Δmi), and seawater fraction (fSea) plots suggest that the PW samples, irrespective of location and GW samples in specific areas, were attributed to SWI, while the remaining samples suggested SGD. The average chloride-attributed SGD flux calculated for PW was 23.45 × 10−7 L cm−2 S−1 and for GW, 0.58 × 10−7 L cm−S−1. Higher fluxes observed in PW suggest seawater recirculation as the primary mechanism, and GW samples were found to be influenced by fresh, recirculated, and saline intrusions. Overall, the northern parts of the study region were influenced by freshwater discharge. However, the central and southern parts of the study regions were influenced by mixed RSGD and SWI water types. The present work suggests locations influenced by fresh, recirculated, and saline water zones that can benefit the stakeholders in planning strategies to identify proper aquifer recharge and suggest ideal pumping scenarios to sustain groundwater resources.

Application of statistics to correlate groundwater chemistry with land use on O'ahu, Hawai'i.

This study compiles commonly available groundwater chemistry data from the Pearl Harbor Sole Source Aquifer (SSA), Hawai'i-O'ahu's primary drinking water source-and applies hierarchical clustering analysis (HCA), principal component analyses (PCA), piper diagrams, and box plots with geospatial analysis to better define groundwater regions and correlate groundwater chemistry in those regions with land use. Groundwater in this aquifer recharges and flows through chemically similar soil and rocks, such that anthropogenic activities are a primary influence on the chemical variability of the aquifer's differing regions. Our analyses link specific chemical species in groundwater to land use/cover categories: urban, agriculture, and natural and anthropogenically-induced saline water intrusion. To create distinct statistical groupings with different groundwater chemistry compositions, it was important that the suite of parameters used in the statistical analysis do not covary. In our case, Cl- covaried with several major ions; however, by including F-, alkalinity, and SiOx that do not covary with Cl- in the covariance matrix, we produced improved spatial grouping of HCA clusters and stronger affinities to land use designations. Results show that dominant groundwater chemistry changes with land use along flow paths. These results pertain to areas where groundwater flows from conservation land in high recharge areas of O'ahu's mountain ranges to urban and agricultural land use regions: groundwater retains its source characteristics until about 3-6km into agricultural and urban zoned lands. Ultimately, this study outlines a simple method for water quality regulators to use groundwater chemistry to identify risks of target contaminants based on land use.