Stiffness Patterns Research Articles

Hydro-Geochemistry and Water Quality Index Assessment in the Dakhla Oasis, Egypt

Water quality is crucial to the environmental system and thus its chemistry is important, and can be directly related to the water’s source, the climate, and the geology of the region. This study focuses on analyzing the hydrochemistry of specific locations within the Dakhla Oasis in Egypt. A total of thirty-nine groundwater samples representing the Nubian Sandstone Aquifer (NSSA) and seven surface water samples from wastewater lakes and canals were collected for analysis. Key parameters such as pH, electrical conductivity (EC), and total dissolved solids (TDS) were measured on-site, while major ions and trace elements (Fe+2 and Mn+2) were analyzed in the laboratory. The water quality index (WQI) method was employed to assess the overall water quality. Hydro-chemical facies were investigated using Piper’s, Scholler’s, and Stiff diagrams, revealing sodium as the dominant cation and chloride, followed by bicarbonate as the dominant anion. The hydro-chemical composition indicates that Na–Cl constitutes the primary water type in this study. This points to the dissolution of evaporates and salt enrichment due to intense evaporation resulting from the region’s hyper-aridity. In groundwater samples, the order of hydro-chemical facies is HCO3− > Cl− > SO4−2 > Na+ > Ca+2 > K+ > Mg+2, while in wastewater samples, it is Cl− > Na+ > SO4−2 > HCO3− > Ca+2 > Mg+2 > K+. When considering iron and manganese parameters, the water quality index (WQI) values suggest that most groundwater samples exhibit excellent to good quality but become poor or very poor when these elements are included. This study could prove valuable for water resource management in the Dakhla Oasis.

Groundwater quality prediction and risk assessment in Kerala, India: A machine-learning approach

Despite its critical importance for health, agriculture, and the economy, and its key role in supporting climate change adaptation, groundwater quality remains vulnerable to contamination and is often neglected until significant deterioration. The groundwater resources of Kerala, one of the southernmost states of India, are under escalating stress and scarcity, despite a high well density with 62% of the population relying on groundwater from approximately 6.5 million open wells. This study investigates the detailed hydrogeochemistry and predicts groundwater quality zones of the state using machine-learning techniques viz, extreme gradient boosting (XGBoost), support vector regression (SVR), artificial neural network (ANN) and random forest (RF) regression. The hydrogeochemical analysis reveals varying groundwater quality across the state. Among the different machine learning models, RF shows higher goodness of fit (R2: 0.922) with minimal prediction error (root mean square error: 6.29 and mean absolute error: 3.12). The predicted groundwater quality was validated using the spatially distributed stiff diagrams, visually representing water composition trends of each well. The very good, good, moderate and poor groundwater quality zones occupy 31.7%, 40.4%, 20.4%, and 7.4% of the state aligning accurately with the groundwater quality scenario of the state. Additionally, groundwater drinking risk assessment was conducted, considering that 7.4% of the state experiences poor-quality groundwater. Integrating groundwater quality maps with population data, the study assessed potential health risks due to consuming untreated water. Nearly 0.59 million people across 252 local self-government bodies (LSGs) are susceptible to consuming poor quality groundwater, which may pose potential health risks. This observation provides valuable insights for sustainable groundwater management and public health safeguarding and the findings of the present study are useful for achieving sustainable development goal (SGD) 6 (clean water and sanitation) and long-term groundwater management in Kerala.

Hydrogeochemistry of aquifers in the northern portion of the Lagoa Santa Karst Environmental Protection Area and surroundings, state of Minas Gerais, Brazil

The studied region, located in the central part of Minas Gerais state, Brazil, encompasses the northern portion of the Lagoa Santa Karst Environmental Protection Area (APA) and adjacent areas to the west. It is notable for harboring important karstic aquifers and archaeological and paleontological sites of global significance. The research aims to define the key parameters that characterize the waters of the aquifers, quantifying their most frequent maximum and minimum concentrations. For this purpose, water sampling and hydrochemical analyses were conducted at 51 water points. Hierarchical clustering analysis facilitated the association of samples with aquifer units. Utilizing Piper and Stiff diagrams, boxplot graphs, and proportional symbol maps enabled the classification of water and the determination of its hydrochemical signatures. All sampled waters are bicarbonated, with 87% being calcic. Waters associated with metacalcareous rocks exhibit higher concentrations of calcium (Ca2⁺), bicarbonate (HCO₃⁻), electrical conductivity (EC), total dissolved solids (TDS), and hydrogenionic potential (pH) compared to waters associated with non-carbonate rocks. Waters from the Lagoa Santa Member differ from those of the Pedro Leopoldo Member by higher concentrations of Ca2⁺ and HCO₃⁻ and slightly lower concentrations of sodium (Na⁺), magnesium (Mg2⁺), and silica (SiO₄2⁻). Non-carbonate waters related to granite-gneisses differ from those associated with metapelites by slightly higher concentrations of potassium (K⁺), sodium (Na⁺), silica (SiO₄2⁻), and barium (Ba2⁺). Additionally, hydrochemical variations have been linked to the regional groundwater flow (from west to east). The results obtained have enabled advancements in the hydrogeochemical understanding of the study area and can be valuable for comparative studies in other karst regions, contributing to more effective water resource management aimed at environmental conservation and water sustainability, a growing global concern.

EVALUATION OF WATER QUALITY FOR IRRIGATION PURPOSES IN ONIKITINBI VILLAGE, OGUN STATE, SOUTHWESTERN, NIGERIA.

The evaluation of groundwater quality is crucial for sustainable agriculture, as it is a primary water source for irrigation. This study discusses the results of examining the groundwater quality and its appropriateness for irrigation in Onikitinbi village, located in the Ogun waterside area of Ogun State, southwestern Nigeria. This was carried out using the irrigation water quality indices (hydrogeochemical and physio-chemical parameters). The indicators considered include the Magnesium Absorption Ratio (MAR), Kelly Ratio (KR), pH, Total Hardness (TH), Total Dissolved Solid, Stiff and Piper’s Diagram, and Kelly’s ratio. The values obtained were MAR (19.25 to 28.85%, mean of 6.95%), Kelly Ratio (0.11 to.016, mean of 0.13), and pH (6.83 to 7.08, mean of 6.95). Total Hardness (98 mg/L to 266 mg/L, mean of 183 mg/L) and Total Dissolved Solid (40 mg/L to 375 mg/L, mean of 207 mg/L). The Ca-HCO3 - and Ca-SO4 2- water types from Stiff diagram and Piper’s diagram shows that the water sample in the Onikitinbi are from freshwater and Industrial or agricultural sources respectively, while the Gibbs diagram suggests that the main factor controlling the water chemistry is the water-rock interaction. The calculated water indices indicate that the groundwater in the study area meets the required standards for agricultural purposes, specifically irrigation.

Hydrogeochemical Characterization of Groundwater of Field Y, Offshore Niger Delta

Hydrogeochemical analyses were carried out on groundwater samples in order to understand the hydrochemistry of the water. The results revealed that groundwater has a high electrical conductivity, which could be as a result of more chemicals dissolved in the water and total hardness observed in all samples shows that the water isn’t hard water. Major cations and anions were identified using Piper Trilinear diagram Durov diagrams and Stiff diagrams. The parameters studied include; Ph, Electrical conductivity, Temperature, Total Suspended Solid, Salinity as Chloride, Sulphate, Total Hardness, Total Hydrocarbon Content, Nitrate, Phosphate, Alkalinity, Calcium, Sodium, Magnesium, Potassium, Iron, Zinc. The major cations are: Sodium (Na+), Potassium(K+), Calcium (Ca2+), while the major anions are: Bicarbonate (HCO3–), Carbonate(C03–), Sulfate (SO4–), and Chloride (Cl–). TDS is the major physical parameter that is dominant in the Durov diagram, although the analysis in the Durov, Piper and Stiff diagram shows that Ca2+ and HCO3–, are the major cation and anion respectively which implies that the groundwater in the study area are Ca2+ and HCO3–. It was also observed that the quality of groundwater was suitable for domestic purpose and agricultural purpose.

ASSESSMENT OF GROUNDWATER SUITABILITY FOR IRRIGATION PURPOSES: A CASE STUDY IN MALAJOYE, EPE AREA, LAGOS, NIGERIA

Proper management of groundwater and surface water resources is crucial for a variety of reasons. The groundwater quality in Malajoye Village in Epe area was assessed by collecting samples from 8 dug wells to determine its suitability for irrigation due to the variability in quantity and quality of water available for irrigation in Nigeria. The fitness evaluation involved determining pH, conductivity, dissolved solids, alkalinity, as well as significant cations (Na+ , K+ , Ca2+, Mg2+) and anions (HCO3 - , Cl- , SO4 2- ). Of the 8 groundwater samples tested, 75% are classified as good water, while the remaining 25% are deemed unsuitable for irrigation. From these assessments, various irrigation quality parameters, including sodium absorption ratio, Kelley's ratio, residual sodium carbonate, and Mg hazard, were computed. Piper, and stiff diagrams shows the water type in the study area is freshwater while shoeller diagram indicates the water type is a combination of freshwater and seawater. The Gibbs diagram indicates water chemistry is primarily influenced by water-rock interaction, including mineral dissolution and chemical weathering. Evaluation of groundwater samples from the study area revealed that most of the water analysed is appropriate for irrigation use without endangering agricultural activities in Malajoye village, Epe, Lagos State.

CHARACTERIZATIONS AND CLASSIFICATION OF FORMATION WATER PRODUCED IN OILFIELDS

Formation water known as oilfield wastewater, produced water, associated water and brine; which generated in great volumes in onshore and offshore oil and gas production. As more and more world major oilfields mature, more water begins to be produced from oil producers because of aquifer encroachment and/or water injection. The evaluated characteristics of offshore oilfield produced water in oilfields is very important for petroleum engineering industry from both upstream and downstream activities, as well as is essential for both environmental assessment and reservoir management. This study has been conducted on two oilfields namely Sarir and Nafora for oil producing wells to distinguish the characterizations of the produced water. Also, the water characteristics are investigated in five gathering centers in Sarir oilfield. The study included the analysis of sixty water samples to determine the physiochemical characterizations. The data obtained from the chemical analysis were used to classify formation water and to determine the environmental deposition using Sulin's system. The results revealed that the type of formation water in both two fields are belonging to CaCl2 type and deep marine environment. The Stiff diagrams of the studied formation water of Sarir field were constructed for five gathering centers and compared with different patterns of Stiff diagrams. Most of the studied water exhibits a similarity of these patterns, but some of them show slightly deviation, this may be attributed to the type of formation and the source of brine.

Hydrogeochemical Evaluation of Surface and Groundwater in Haditha Area, Al-Anbar Governorate, Western Iraq

This research deals with the study of the hydrochemical characteristics of surface water and groundwater to assess the quality of water and its suitability for different uses in the Haditha region. Thirty –Two samples were collected in July 2022,6 samples were taken from the Euphrates River and 17 samples from wells were analyzed. In this study, main cations ( Ca2+, Mg2+, Na+, and K+) and anions (Cl-, SO4, HCO3),Total dissolved Solids(TDS), pH, Electrical conductivity(EC), and Temperature(T) were studied. The results show that the water types are mainly earth-alkaline water with an increased portion of alkalis with prevailing SO4 and Cl according to Piper and Stiff diagram. The results of the water quality index (WQI) show that surface water are suitable for drinking while the groundwater is not suitable except for W1, W13, W15, W16 and W17. The classification of water for irrigation purposes according to the Sodium Adsorption Ratio and Residual sodium carbonate showed that the ground and surface water in this region is excellent and good quality according to Permeability Index. Irrigation water quality based on sodium ion percentage indicates that all samples belong to the permissible category for groundwater except for W1, W11, and W16, while Surface water is good quality for irrigation. Finally, the absence of management and low discharge, are the primary reasons for the continuous deterioration of water quality.

Presentation and use of a new diagram to determine the facies and the origins of water: The 3rd Parfait-Hounsinou diagram

To determine the origin of groundwater mineralization, it is often necessary to produce Piper or Schoeller-Berkaloff or Stiff or Durov diagrams, to calculate the Revelle index or the basic exchange index.In this new method, the Reports rCl−rHCO3−+rCO32−, rSO42−+rNO3−rHCO3−+rCO32−, rNa++rK+rCa2+ , rMg2+rCa2+ and rNa++rK+rCl− are represented by 5 points on the 3rd Parfait-Hounsinou diagram which makes its interpretation faster than the interpretation of the Scholler-Berkaloff and Stiff diagrams which have 7 and 6 representative points respectively. The 3rd Parfait-Hounsinou diagram is more precise and gives more information than the diagrams of Piper, Scholler-Berkaloff and Stiff on the origin of the mineralization of water. The Parfait-Hounsinou table makes it possible to identify the facies and the origin of the mineralization of an infinity of water samples. The 3rd Parfait-Hounsinou diagram and the table of Parfait-Hounsinou were used to study the waters of 44 wells in the town of Abomey-Calavi in Benin and the results obtained were compared to those results obtained using the Scholler-Berkaloff and Stiff diagrams. The Parfait-Hounsinou table and the 3rd Parfait-Hounsinou diagram showed that 79.22% of the waters studied have a sodium potassium chloride facies, 13.63% of these waters have a sodium potassium bicarbonate facies, 2.27% of these waters have a sodium potassium sulfate facies and 2.27% of these waters have a calcium sulfate facies. They revealed that for 86.63% of the well water studied, clay minerals capture the Ca2+ and Mg2+ ions present in groundwater and release Na+ and K+ ions into the water in exchange. They also revealed that there is seawater intrusion in 4.54% of the waters studied, all located in the coastal village of Togbin. The results obtained during this study confirm those obtained previously in the study area using multiple methods. The novelty brought by the 3rd Parfait-Hounsinou diagram and the table of Parfait-Hounsinou is that they are more precise and make it possible to obtain more information on the facies and the origin of the mineralization of the water samples than the diagrams of Piper, Schoeller-Berkaloff, Stiff and Durov.

Hydrogeochemical characteristics of groundwater in Baleendah - Soreang, South Bandung, West Java Province

The Baleendah – Soreang area is part of the southern part of the Bandung Soreang Groundwater Basin, constructed by volcanic activity. Regional development in the Baleendah – Soreang area can decrease groundwater quality, influenced by natural and anthropogenic factors. Groundwater hydrogeochemical analysis is important in environmental management studies. This study aims to determine groundwater’s physical properties and hydrogeochemical facies in this area. The groundwater hydrochemistry analysis, determined by analysis of Stiff diagrams and Piper diagrams, shows that the groundwater in the area is classified as freshwater and has intermediate groundwater flow. In addition, the groundwater quality is affected by some anthropogenic activities.

Geology and Groundwater Quality Analysis for Clean Water and Irrigation of Sanga-sanga District, Kutai Kartanegara Regency, East Kalimantan Province

The research locations are in two sub-districts, namely Sanga-Sanga District, Samarinda City and Palaran District, Kutai Kartanegara, East Kalimantan Province The research method used in this study is geological mapping, then laboratory analysis. The well water sample data used is 2 sample water which is considered to represent the research area. Geological conditions in the study area there are 3 rock units where the rock units of the oldest are the Sanga-sanga sandstone unit, the Bantuas sandstone unit and alluvial deposits. For geomorphological units, it is divided into 6 forms, namely the eroded hill unit, the remaining hill, the Alluvial Plain, swamp, river body, disposal and mine opening. Based on the results of the piper diagram analysis Groundwater is included in the type of magnesium bicarbonate with carbonate hardness (secondary alkalinity) > 50% groundwater is dominated by alkaline soil (Ca + Mg) and weak acids (CO3 + HCO3), and based on the results of the stiff diagram analysis, the research area is included in the type of calcium carbonate (CaHCO3) and Magnesium Carbonate (MgHCO3). The assessment of groundwater quality for irrigation purposes concluded that the analyzed sample could be used as irrigation water.

ANÁLISIS HIDROGEOQUÍMICO DE LA CALIDAD DE AGUAS SUPERFICIALES EN UNA ZONA MINERA EN EL FLANCO OESTE DE LA CORDILLERA OCCIDENTAL DE LOS ANDES

This study used the hydrogeochemical properties of surface waters surrounding a mining project in Peru to compare them with the environmental quality standards established in Supreme Decree 004-2017-MINAM, focusing on category 3 for vegetable irrigation and animal drinking. Physical-chemical, inorganic, microbiological and parasitic parameters were evaluated in lagoons and springs. The results determined the presence of slightly alkaline deposits with a pH of 9.59 and slightly acidic deposits with a pH of 5.33, as well as deposits with high content of iron, manganese, and zinc. To ensure the reliability of the chemical analysis, an ionic balance of the main dissolved cations and anions was performed. The Piper diagram determined the predominant calcic sulfate waters, as well as the presence of a calcic bicarbonate water deposit. On the other hand, the Stiff diagram determined sulfate (SO42-) as the predominant ion. This study concludes that the different stations comply with the environmental quality standards, although deposits with high levels of iron, manganese, and zinc were found in surface waters. Different treatments were determined to control pH levels and to decrease the amount of such ions present.

The 1st method Parfait-Hounsinou used for the detection of saltwater intrusion in groundwater

This study presents the 1st method Parfait-Hounsinou, a method that makes it very easy to detect saltwater intrusion in groundwater. The method relies on the commonly sampled ion concentrations. This method involves several steps, namely: Chemical analyzes to determine the concentrations of majors ions and TDS in groundwater, production and study of the spatial distribution of chemical parameters in groundwater (TDS, Cl−…), delimitation of a probable area of saltwater intrusion in groundwater and the production and the study of spie chart where area of pie slices represents ions contents or group of ions content in the groundwater sample of the probable area of the saltwater intrusion in groundwater and radius length represents the Relative Content Index. The method is applied to groundwater data collected from the municipality of Abomey-Calavi in Benin. The method is also compared to other methods used for saltwater intrusion including the Scholler-Berkaloff and Stiff diagrams and the Revelle Index. Comparatively to Scholler-Berkaloff and Stiff diagrams, the 1st method Parfait –Hounsinou, at spie chart level, the area of pie slices make it easier to compare the major cations between them and the majors anions between them and the Relative Content Index of the chloride ion allows further confirmation of the saltwater intrusion and its extent.•There are frequent saltwater intrusion into groundwater which are important freshwater reserves for our planet.•Governments around the world should delineate the levels of ocean intrusion into groundwater using scientific methods such as this method and seek to limit this saltwater intrusion.•In this article we have proposed a simple and reliable method based on a series of irrefutable proofs of saltwater intrusion into groundwater.

Mapping the spatiotemporal evolution of seawater intrusion in the Moroccan coastal aquifer of Ghiss-Nekor using GIS-based modeling

The impact of seawater intrusion on coastal aquifers is a major concern in managing groundwater resources. The unconfined coastal aquifer of Ghiss-Nekor, located in a semi-arid area, is particularly vulnerable to seawater intrusion (SWI) because of excessive groundwater pumping and climate change impacts. Therefore, the main goal of the present work is to track the spatiotemporal evolution of SWI in the Ghiss-Nekor aquifer by analyzing data from the years 2015 and 2022 using appropriate geochemical approaches. Accordingly, a range of geochemical techniques were employed, including the Piper diagram, Chadha's diagram, Gibbs diagram, Stiff diagram, major ions variation maps, Hydrochemical Facies Evolution Diagrams (HFE-D), and seawater fraction (fsea). As a result, Gibbs diagram clearly indicates the contribution of seawater to the salinization of the Ghiss-Nekor aquifer. Further information is provided by the Piper, Chadha, and Stiff diagrams, which reveal that 29%–38% of the wells studied display Na–Cl water type, a characteristic feature of seawater facies. Additionally, statistical analysis shows a significant increase in salinity levels between 2015 and 2022. Furthermore, the spatiotemporal analysis using the differential mapping technique (DMT) confirmed the increase of salinity, particularly near the shoreline. Additionally, the HFE-D showed that the region impacted by SWI increased from 14% to 20% between 2015 and 2022, and the maximum fsea value rose from 14.84% to 25.77% over the same time frame. Our findings reinforce the assumption that SWI is worsening over time in the Ghiss-Nekor aquifer. In summary, the techniques used in this study were effective in tracking the spatiotemporal evolution of SWI in the aquifer and in quantifying it. The results of this study can inform the development of effective strategies for managing SWI in coastal aquifers.

Groundwater Quality and Potential Pollution in the Southern Shimabara Peninsula, Japan

Nitrate pollution in groundwater is a severe problem in Shimabara Peninsula, Nagasaki Prefecture, Japan. Previous studies have investigated water quality characteristics in the northern part of the peninsula and shown serious effects of nitrate pollution in the groundwater. The present study aimed to investigate the groundwater quality in the southern areas of the peninsula for improved understanding of the water quality status for the entire peninsula. Groundwater samples were collected at 56 locations in Minami-Shimabara City from 28 July to 4 August 2021. The spatial distribution of water quality constituents was assessed by Piper-trilinear and Stiff diagrams for major ion concentrations. One agricultural area in the western parts exceeded Japanese recommended standards for water. According to the Piper-trilinear diagram, 44 sampling sites (78.6%) were classified as alkaline earth carbonate type, nine sites (16.1%) as alkaline earth non-carbonate type, and three sites (5.3%) as alkaline carbonate type. Stiff diagrams displayed Ca-HCO3 water type for most of the sites. Na-HCO3 and Mg-HCO3 types were found in coastal areas. Principal component analyses showed that the first component corresponded to dissolved constituents in groundwater and denitrification, the second effects of ion exchange and low nitrate pollution, and the third effects of severe nitrate pollution. Hierarchical cluster analysis was used to classify the groundwater into five groups. The first group included sites with relatively high nitrate concentration. The second group had relatively low ion concentration, distributed from center to eastern parts. The third group included intermediate ion concentration, distributed at lower altitudes along the coastal line. The fourth and fifth groups had a higher ion concentration, especially characterized by high sodium and bicarbonate concentration.

The State of Deformation and Stiffness Analysis of RC Beams Strengthened by Means of CFRP Strips at Different Load Levels

This work presented some selected results of laboratory tests and FEM analysis study of simple supported RC beams strengthened using carbon strips. The beams were examined to establish the effectiveness of this method of strengthening in terms of increasing their load-carrying capacity as well as flexural stiffness at different preloading states. A set of beams was divided into five groups, which differ in the level of the load applied before application of the composite strips on their bottom surfaces. Laboratory tests were supplemented with numerical analyses based on the finite-element method (FEM) using Abaqus software. The created numerical models were validated, and good agreement of the experimental results with the results obtained in the numerical analyses was observed. The deformation state existing in the main reinforcing bars, in concrete as well as in the strengthening composite strip, and its influence on the failure mechanism of the beams were analyzed. In the stiffness analysis, it was assumed that the stiffness of a beam strengthened with composite material after the elastic range (concrete and reinforcement steel) can be represented by the relation between the stiffness of the noncracked section B and beam curvature κ. The curvature–bending moment diagram as well as bending moment–stiffness diagram were prepared on the basis of laboratory and numerical results. Based on the results, it can be stated that the preload on the beam before strengthening affects the levels of deformation and the utilization rates of the composite material as well as reinforcing bars. The curvature and stiffness of the beams depend on the load level at which the CFRP strip strengthening is realized. The results of the analysis of preloaded beams before strengthening indicate that totally relieving them prior to strip application turns out to be the most beneficial solution.

Groundwater Classification by Using Fourier Analysis

The article illustrates a statistical technique for the visual representation of geochemical data. Quaternary and Pre-Quaternary groundwater samples from Northern Sinai Peninsula, Egypt, were interpreted statistically using Andrews plots, which use Fourier analysis to transform and represent a set of multivariate data by a waveform pattern. The resulting waveform patterns were classified into low, middle, and high amplitudes, following up the increase in the total dissolved solids of the samples. Comparison with the traditional hydrochemical polygonal Stiff diagrams resulted in a complete matching. The proposed mixing between the Quaternary and Pre-Quaternary aquifers has been proved via the similarity of waveform patterns of the mixed water. The application of Andrews plots is investigated by comparison with the Stiff conventional diagrams. The correlation between different amplitudes and the TDS value of every sample indicates that the amplitude increases with the increase in the salinity.

Hydrogeochemistry of Shallow Groundwater and Suitability to Irrigation: The Case of the Karfiguéla Paddy Field in Burkina Faso

Shallow groundwater is often exposed to multiple sources of pollution that can make it unsuitable for certain uses. Complete hydrogeochemical studies are necessary for the better management of these resources. Well water samples were collected on the extent of Karfiguéla paddy field for physico-chemical parameters, such as pH, EC, TDS, Na+, Ca2+, Mg2+, K+, NH4+, NO3−, NO2−, SO42−, CO32−, Cl−, and HCO3−, and metallic trace elements analyses as a case study. Due to the alluvial nature of aquifer deposits and the short residence time of groundwater, physical parameters and ion concentrations are low and within the recommended guideline values for irrigation water of the Food and Agriculture Organization (FAO) of the United Nations. However, Cd presents concentrations above 10 µg/L, the limit recommended by the FAO, while NO3− presents a slight to moderate risk. Piper and Stiff diagrams showed two types of water, Ca·Mg·HCO3 and Ca·Mg·SO4·Cl. Saturation indices revealed the under mineralization of natural minerals. Gibbs and bivariate diagrams, correlations and factorial analyses indicated that groundwater mineralization is mainly controlled by anthropogenic agricultural activities (60.05%), calcite and magnesite alteration (15.01%) and CO2 dissolution process (9.05%). Irrigation water suitability parameters, such as sodium adsorption ratio (SAR), sodium percentage (%Na), potential salinity (PS), the Kelly ratio (KR), residual sodium carbonate (RSC) and irrigation coefficient (Ka), confirmed that the shallow groundwater is 100% good for irrigation, while NO3− and permeability index (PI) indicated that it is permissible. However, according to magnesium hazard (MH), the groundwater is 100% unsuitable for irrigation and could lead to soil alkalinity.

Influence of coastal alluvial aquifer on groundwater chemistry in Wates, Yogyakarta, Indonesia

Saline groundwater is found far from the coastline, whereas closer groundwater has low salinity in the Wates area, Indonesia. This situation which has led to problems linked to the coastal aquifer, shows different groundwater chemistries. This connection needs to highlight the geochemical evolution of aquifers. This research aims to evaluate the hydrochemical characteristics in Wates Sub-District, Kulon Progo District, Indonesia. The study area is located in the southern part of the Kulon Progo with an aquifer of marine and fluvial deposits. The boundary of the south is the Indian Ocean. The approach is based on analyzing the major ions of 27 groundwater samples, and the XRD results include the Stiff diagram and the Stuyfzand classification. The Stiff diagram showed in agreement with that of the Stuyfzand classification. Results showed that the F2-(CaHCO3)2Ø and F1-(NaMix)Ø types reflect the recharge process and dominate the dissolution of silicate minerals. Halite dissolution originates in topographically flat areas of the Bs1-NaCl (-) water. Total hardness is softer than others as a result of cation exchange. The groundwater chemistry’s geochemical processes are the dissolution of silicate and halite minerals, ion exchange, and fresh and seawater mixing. This research indicates to focus on pumping problems in the aquifer.

Self-organizing map improves understanding on the hydrochemical processes in aquifer systems

The holistic understanding of hydrochemical features is a crucial task for management and protection of water resources. However, it is challenging for a complex region, where multiple factors can cause hydrochemical changes in studied catchment. We collected 208 groundwater samples from such region in Kumamoto, southern Japan to explicitly characterize these processes by applying machine learning technique. The analyzed groundwater chemistry data like major cations and anions were fed to the self-organizing map (SOM) and the results were compared with classical classification approaches like Stiff diagram, standalone cluster analysis and score plots of principal component analysis (PCA). The SOM with integrated application of clustering divided the data into 11 clusters in this complex region. We confirmed that the results provide much greater details for the associated hydrochemical and contamination processes than the traditional approaches, which show quite good correspondence with the recent high resolution hydrological simulation model and aspects from geochemical modeling. However, the careful application of the SOM is necessary for obtaining accurate results. This study tested different normalization approaches for selecting the best SOM map and found that the topographic error (TE) was more important over the quantization error (QE). For instance, the lower QE obtained from min-max and log normalizations showed problems after clustering the SOM map, since the QE did not confirm the topological preservation. In contrast, the lowest TE obtained from Z-transformation data showed better spatial matching of the clusters with relevant hydrochemical characteristics. The results from this study clearly demonstrated that the SOM is a helpful approach for explicit understanding of the hydrochemical processes on reginal scale that may capably facilitate better groundwater resource management.