Hydrochemical characteristics and irrigation suitability of surface water in the Syr Darya River, Kazakhstan

Assessment of water quality and source apportionment of pollution in a tropical river in eastern India: A study utilizing multivariate statistical tools and the APCS-MLR receptor model

The Mundeswari River, an ecologically distressed river in eastern India, has been subjected to water quality deterioration largely due to anthropogenic activities in its vicinity. This study aimed to comprehensively evaluate the current state of pollution in the river and assess the appropriateness of river water for irrigation, given its extensive use for agricultural purposes. Monthly water quality monitoring was undertaken at four distinct sampling sites (SP1-SP4) over a two-year period (2020-2022), considering seventeen water quality parameters. This research employed principal component analysis/factor analysis (PCA/FA) and absolute principal component score-multiple linear regression (APCS-MLR) receptor modelling. These methodologies were used to discern and quantify potential sources of pollution influencing the water quality of the Mundeswari River. The study revealed that the water quality of the Mundeswari River was most degraded during the pre-monsoon season. Among the four sampling sites, SP3 exhibited the highest level of pollution with mean biochemical oxygen demand (BOD) and chemical oxygen demand (COD) values of 5.36 mg/L and 44.72 mg/L, respectively. According to the one-way analysis of variance (ANOVA), there was considerable spatial and seasonal disparities (P < 0.05) in most water quality parameters. The PCA/FA extracted four latent pollution sources, accounting for 81.5% of the total variance. The primary factors influencing the quality of river water are natural weathering processes, discharge of domestic effluent and waste, and agricultural runoff. The APCS-MLR receptor model further revealed that agricultural drainage factors and the discharge of domestic effluent and waste had a greater impact on the Mundeswari River. The investigation concluded that the mean values of all indicators for irrigation suitability were below the defined threshold limits, indicating that the water of the studied river appears suitable for irrigation. The outcomes of this study may significantly contribute to the formulation of sustainable strategies for the ecological rejuvenation of the Mundeswari River.

Water quality and dissolved load in the Chirchik and Akhangaran river basins (Uzbekistan, Central Asia)

Uzbekistan (Central Asia) is experiencing serious water stress as a consequence of altered climate regime, past over-exploitation, and dependence from neighboring countries for water supply. The Chirchik-Akhangaran drainage basin, in the Tashkent province of Uzbekistan, includes watersheds from the Middle Tien Shan Mountains escarpments and the downstream floodplain of the Chirchik and Akhangaran rivers, major tributaries of the Syrdarya river. Water in the Chirchik-Akhangaran basin is facing potential anthropogenic pressure from different sources at the scale of river reaches, from both industrial and agricultural activities. In this study, the major and trace element chemistry of surface water and groundwater from the Chirchik-Akhangaran basin were investigated, with the aim of addressing the geogenic and anthropogenic contributions to the dissolved load. The results indicate that the geochemistry of water from the upstream catchments reflects the weathering of exposed lithologies. A significant increase in Na+, K+, SO42-, Cl-, and NO3- was observed downstream, indicating loadings from fertilizers used in croplands. However, quality parameters suggest that waters are generally suitable for irrigation purposes, even if the total dissolved solid indicates a possible salinity hazard. The concentration of trace elements (including potentially toxic elements) was lower than the thresholds set for water quality by different regulations. However, an exceedingly high concentration of Zn, Mo, Sb, Pb, Ni, U, As, and B compared with the average river water worldwide was observed. Water in a coal fly-ash large pond related to the Angren coal-fired power plants stands out for the high As, Al, B, Mo, and Sb concentration, having a groundwater contamination potential during infiltration. Spring waters used for drinking purposes meet the World Health Organization and the Republic of Uzbekistan quality standards. However, a surveillance of such drinking-water supplies is suggested. The obtained results are indicators for an improved water resource management.

Hydro-chemical characteristics of biring and Tangting Rivers (Nepal) and evaluation of water quality for drinking and irrigation purposes

Although river water is vital for drinking, irrigation and domestic needs, it faces threats from natural processes and human activities. Small and medium-sized rivers, especially in Nepal, remain understudied despite their vital importance in providing water to densely populated areas. This study evaluated the suitability for drinking and irrigation and the hydro-chemical characteristics of the Biring and Tangting rivers in Koshi province, Nepal. The results showed that turbidity, pH, EC, TDS, TH, NH4+, K+, Ca2+, Mg2+, Na+, Cl-, SO42-, HCO3- and NO3- values of all sampling sites in the Biring and Tangting rivers, except for the turbidity value of 10.39 NTU recorded in the PT9 site of the Tangting River, did not exceed maximum limit values set for drinking water. However, according to Water Quality Index results, the water of both rivers was in poor condition for drinking due to domestic wastewater discharges and cremation activities which caused high NH4+ levels. The major cations in both rivers were listed as Ca2⁺ > Na⁺ > K⁺ > Mg2⁺, while the major anions were listed as HCO₃⁻ > Cl⁻ > SO₄2⁻ > NO₃⁻. Gibbs and Piper diagrams showed that geogenic weathering of carbonate rocks prevailing in the region affected the hydrochemistry in both rivers. Evaluation based on seven different irrigation indices and US salinity laboratory diagram revealed that the water of both rivers was suitable for irrigation despite some magnesium-related limitations.

Toxicological risk assessment using spring water quality indices in plateaus of Giresun Province/Türkiye: a holistic hydrogeochemical data analysis

Water scarcity is a growing concern due to rapid urbanization and population growth. This study assesses spring water quality at 20 stations in Giresun province, Türkiye, focusing on potentially toxic elements and physicochemical parameters. The Water Quality Index rated most samples as "excellent" during the rainy season and "good" during the dry season, except at stations 4 (40° 35' 12″ North/38° 26' 34″ East) and 19 (40° 44' 28″ North/38° 06' 53″ West), indicating "poor" quality. Mean macro-element concentrations (mg/L) were: Ca (34.27), Na (10.36), Mg (8.26), and K (1.48). Mean trace element values (μg/L) were: Al (1093), Zn (110.54), Fe (67.45), Mn (23.03), Cu (9.79), As (3.75), Ni (3.00), Cr (2.84), Pb (2.70), Co (1.93), and Cd (0.76). Health risk assessments showed minimal non-carcinogenic risks, while carcinogenic risk from arsenic slightly exceeded safe limits (CR = 1.75E-04). Higher arsenic concentrations during the rainy season were due to increased recharge, arsenic-laden surface runoff, and human activities. Statistical analyses (PCA, PCC, HCA) suggested that metals and physico-chemical parameters originated from lithogenic, anthropogenic, or mixed sources. Regular monitoring of spring water is recommended to mitigate potential public health risks from waterborne contaminants.

Deployment of entropy information theory in the Indian Sundarban region using hydrogeochemical parameters and GIS for assessment of irrigation suitability

The evaluation of irrigation suitability plays a crucial role for the socio-economic development of the society, especially in the region of Sundarban. For sustainable agricultural practices, groundwater quality must be suitable for irrigation; otherwise, it can degrade soil and diminish crop yield. The entropy information theory, several irrigational indices, multivariate statistics, GIS, and geostatistics are used in this work to evaluate the geographical distribution and quality of groundwater in the Indian Sundarban region. In total, 33 groundwater samples were collected in 2018 (April and May), and they were evaluated for major cations, anions, as well as other parameters like electrical conductivity (EC), soluble sodium percentage (SSP), potential salinity (PS), total dissolved solids (TDS), Kelly ratio (KR), sodium absorption ratio (SAR), permeability index (PI), residual sodium carbonate (RSC), magnesium hazard (MH), and residual sodium bicarbonate (RSBC). The overall trend of the principal cations and anions is in the sequence of Na+  ≥ Mg2+  ≥ Ca2+  ≥ K2+ and HCO3-  ≥ Cl-  ≥ NO3-  ≥ SO42-  ≥ F-, respectively, whereas the spatial variation of %Na, SAR, RSBC, and MH demonstrate very poor irrigation water quality, and spatial variation of KR, RSC, SSP, PI, and PS signifies that the irrigation water quality is excellent to good. In order to identify the specific association and potential source of the dissolved chemical in the groundwater, statistical techniques like correlation and principal component analysis were also employed. The hydrochemical facies indicates that mixed type makes up the bulk (51.51%) of the water samples. Following the Wilcox plot, more than 75% of the water samples are good to doubtful; however, by the US salinity hazard map, roughly 60.60% of the samples had high salinity (C3-S1 zone). The EWQII reports that no samples fall into the very good (no restriction) category, whereas 30.30%, 30.30%, and 39.40% of the sample wells record good (low restriction), average (moderate restriction), and poor (severe restriction) irrigation water quality, respectively. Based on this study, the bulk of the groundwater samples taken from the study area are unsuitable for cultivation. The findings of this study will also help decision-makers develop adequate future plans for irrigation and groundwater resource management.

Hydrochemical variations and driving mechanisms in a large linked river-irrigation-lake system

A linked river-irrigation-lake system exhibits intricate and dynamic hydrochemical variations, closely related to changes in natural conditions and anthropogenic activities. However, little is known about the sources, migration and transformation of hydrochemical composition, and the driving mechanisms, in such systems. In this study, the hydrochemical characteristics and processes in the linked Yellow River-Hetao Irrigation District-Lake Ulansuhai system were studied, based on a comprehensive hydrochemical and stable isotope analysis of water samples collected during spring, summer, and autumn. The results showed that the water bodies in the system were weakly alkaline with a pH range of 8.05-8.49. The concentrations of hydrochemical ions showed an increasing trend in the water flow direction. Total dissolved solids (TDS) were less than 1000 mg/L (freshwater) in the Yellow River and the irrigation canals, and increased to more than 1800 mg/L (saltwater) in the drainage ditches and Lake Ulansuhai. The dominant hydrochemical types varied from SO₄•Cl-Ca•Mg and HCO₃-Ca•Mg types in the Yellow River and the irrigation canals to Cl-Na type in the drainage ditches and Lake Ulansuhai. The ion concentrations in the Yellow River, the irrigation canals, and the drainage ditches were highest during summer, while ion concentrations in Lake Ulansuhai were highest during spring. The hydrochemistry of the Yellow River and the irrigation canals was mainly affected by rock weathering, while evaporation was the principal controlling factor in the drainage ditches and Lake Ulansuhai. Water-rock interactions including the dissolution of evaporites and silicates, the precipitation of carbonates, and cation exchange were the main sources of hydrochemical compositions in this system. Anthropogenic inputs had a low impact on the hydrochemistry. Therefore, greater attention should be paid in future to hydrochemical variations, especially salt ions, in the management of linked river-irrigation-lake system water resources.

Spatial heterogeneity of chemistry of the Small Aral Sea and the Syr Darya River and its impact on plankton communities

The shrinking of the Aral Sea represents one of the greatest ecological disasters of modern time. The data on the surviving northern part (Small Aral) is scarce and requires an update. This study aimed to analyze the chemistry, phyto- and zooplankton composition, and their relation in the waters of the Small Aral and its tributary, Syr Darya River. The chemistry of both ecosystems was significantly different. Small Aral was characterized by higher ionic concentrations, salinity, and electric conductivity and more significant spatial variation of chemical properties. The area near the river mouth was more pristine, while the ions concentration and salinity in the distant bays were much higher (>10‰). The highest concentrations of nitrates and total phosphorus in the Syr Darya were observed near Kyzylorda, indicating urban pollution. Overall, 109 phytoplankton taxa were identified in both ecosystems, with diatoms, green algae, and cyanobacteria being most abundantly represented. Oligohalobes dominated, but no polyhalobes and euhalobes algal species were identified. In total, 27 taxa of zooplankton were identified in both studied ecosystems, with the domination of rotifers over microcrustaceans. An exceptionally high level of dominance (65-91%) of rotifer Keratella cochlearis in the Syr Darya was found. The phyto- and zooplankton species richness was higher in the Syr Darya. Plankton communities of the Small Aral reflected horizontal variability of chemical properties. The total phosphorus promoted the prevalence of diatoms, rotifers, and crustaceans. Increased nitrogen concentration promoted cyanobacteria, chlorophytes, cryptophytes and chrysophytes, and rotifers Keratella cochlearis and K. quadrata. The abundance of dinophytes, diatoms Navicula cryptotenella and Cocconeis placentula, green algae Mychonastes jurisii and rotifer Keratella tecta was driven by the higher alkalinity and conductivity/salinity levels. The results represent a reference point for future monitoring of the area and add to understanding the complexity of biological transformations in the Aral Sea and its tributary.

A unified multivariate statistical approach for the assessment of deep groundwater quality of rapidly growing city of Maharashtra Province, India, with potential health risk

The main aim of this research is to assess the consequences of natural and anthropogenic processes on the groundwater quality of 65 deep aquifers of Nagpur city, Maharashtra Province, India, using a unified multivariate statistical approach. The dominant groundwater type recognized is Ca-HCO₃ (recharge waters) in 43.1 and 38.5% of groundwater samples of pre- and post-monsoon seasons, followed by mixed water types. The seasonal distribution of physicochemical parameters shows increase in the concentration of EC, TDS, TH, Mg²⁺, SO₄^2-, and NO₃^- signifying the high mineralization and anthropogenic loading from pre- and post-monsoon season respectively. The entropy-weight water quality index categorizes the 84.6% and 75.4% of total samples from pre- and post-monsoon seasons into moderate quality. The multiple linear regression and PCA analysis reveal the masking of rock weathering mechanism by anthropogenic activities. The % of PCA Variance varies from 79 to 83.7% from pre- to post-monsoon season. The high contributions of EC (0.76, 0.72), TDS (0.79, 0.73), TH (0.97, 0.962), Ca²⁺ (0.84, 0.78), Mg²⁺ (0.79, 0.83), Cl^- (0.73, 0.75), and NO₃^- (0.78, 0.68) in PC1 components expose high salinity and hardness in urban groundwater that signifies the consequences of urbanization on the groundwater regime. About 55.4 and 70.8% of children population as compared to the adult female (53.8%, 69.2%) and male (32.3%, 46.1%) population in PRM and POM respectively were at high non-carcinogenic health threat of NO₃^--enriched groundwater. The study is beneficial for understanding the variation in groundwater composition due to unplanned urbanization and is very useful for protecting groundwater resources in urban areas.

Assessment of Ismailia Canal for irrigation purposes by water quality indices

Ismailia Canal is one of the significant streams of the Nile River in Egypt. The study aimed to determine the water quality of Ismailia Canal based on the regional and seasonal variability of physicochemical parameters, irrigation criteria, and the irrigation water quality index (IWQI). It was observed that the physicochemical parameters were within the acceptable FAO irrigation limits. All cations and anions values were within the acceptable FAO limits for irrigation, except the potassium (K⁺) concentrations were over the permissible irrigation limits. The one-way analysis of variance (ANOVA) suggested a significant seasonal variation in the canal's water quality concerning all parameters (p value ˂ 0.05). However, the regional variation among various sites was statistically insignificant (p value > 0.05). Statistical analysis was used to calculate the correlation coefficient between different parameters, and the study showed highly significant correlation coefficients between different pairs of water quality parameters. The correlation matrix showed that the pH significantly affected IWQI (r = 0.661). The irrigation criterion values for Ismailia Canal were good, and the WQI levels for irrigation utilization at all studied sites were satisfactory. Deterioration of water quality may occur due to industrial, municipal, and agricultural activities. Drainage water should be treated before being mixed with irrigation water to improve its suitability for irrigation.

Combining hydrochemistry and hydrogen and oxygen stable isotopes to reveal the influence of human activities on surface water quality in Chaohu Lake Basin

The input of pollutants caused by human activities induces the deterioration of surface water quality. To reveal the characteristics of surface water quality in Chaohu Lake Basin and the influence of human activities, the hydrochemistry and stable isotope composition of hydrogen and oxygen in lake water and inflow river water were analyzed. The results show that the hydrochemical type of lake water is the Na-Cl type,while river water is the Na-Cl, Ca-Cl and mixed types. The ion proportional coefficient method and principal component analysis show that surface water is controlled by weathering of evaporated salt rocks and silicate rocks, in which Cl^- and SO₄^2- are affected by fertilizers and sewage to some extent. There is a strong correlation between conventional ions and nutrient indexes, which indicates that dissolved ions are affected not only by rock weathering but also by human activities (such as the discharge of domestic sewage or nitrogen-containing wastewater and the use of fertilizers). The stable isotope values of hydrogen and oxygen in surface water are distributed at the lower right portion of the local precipitation line and are close to it, indicating that surface water mainly originates from precipitation. The high value of d-excess values in surface water indicates that evaporation is weak. As pollution indicators, EC, Cl^- and NO₃^- indicates that the Nanfei River, Dianbu River, Shiwuli River and Pai River flow in northwestern of Chaohu Lake Basin through Hefei urban city are severely polluted, NO₃^- originates from manure and sewage. Rivers flowing through farmland areas are less polluted, and the use of agricultural fertilizer contributes greatly to NO₃^-.

Groundwater Suitability for Drinking and Irrigation Using Water Quality Indices and Multivariate Modeling in Makkah Al-Mukarramah Province, Saudi Arabia

Water shortage and quality are major issues in many places, particularly arid and semi-arid regions such as Makkah Al-Mukarramah province, Saudi Arabia. The current work was conducted to examine the geochemical mechanisms influencing the chemistry of groundwater and assess groundwater resources through several water quality indices (WQIs), GIS methods, and the partial least squares regression model (PLSR). For that, 59 groundwater wells were tested for different physical and chemical parameters using conventional analytical procedures. The results showed that the average content of ions was as follows: Na+ > Ca2+ > Mg 2+ > K+ and Cl− > SO42− > HCO32− > NO3− > CO3−. Under the stress of evaporation and saltwater intrusion associated with the reverse ion exchange process, the predominant hydrochemical facies were Ca-HCO3, Na-Cl, mixed Ca-Mg-Cl-SO4, and Na-Ca-HCO3. The drinking water quality index (DWQI) has indicated that only 5% of the wells were categorized under good to excellent for drinking while the majority (95%) were poor to unsuitable for drinking, and required appropriate treatment. Furthermore, the irrigation water quality index (IWQI) has indicated that 45.5% of the wells were classified under high to severe restriction for agriculture, and can be utilized only for high salt tolerant plants. The majority (54.5%) were deemed moderate to no restriction for irrigation, with no toxicity concern for most plants. Agriculture indicators such as total dissolved solids (TDS), potential salinity (PS), sodium absorption ratio (SAR), and residual sodium carbonate (RSC) had mean values of 2572.30, 33.32, 4.84, and −21.14, respectively. However, the quality of the groundwater in the study area improves with increased rainfall and thus recharging the Quaternary aquifer. The PLSR models, which are based on physicochemical characteristics, have been shown to be the most efficient as alternative techniques for determining the six WQIs. For instance, the PLSR models of all IWQs had determination coefficients values of R2 ranging between 0.848 and 0.999 in the Cal., and between 0.848 and 0.999 in the Val. datasets, and had model accuracy varying from 0.824 to 0.999 in the Cal., and from 0.817 to 0.989 in the Val. datasets. In conclusion, the combination of physicochemical parameters, WQIs, and multivariate modeling with statistical analysis and GIS tools is a successful and adaptable methodology that provides a comprehensive picture of groundwater quality and governing mechanisms.

Distribution of dissolved and suspended forms of heavy metals in the water of the Syr Darya, South Kazakhstan

The water of the Syr Darya is the main source of fresh water in South Kazakhstan and heavily used for agriculture. The use water from the Syr Darya for irrigation of agricultural fields affects its chemical composition and is reflected in the water quality class provided in the bulletins of the Ministry of Ecology, Geology and Natural Resources of the Republic of Kazakhstan. In the present work, the distribution of suspended and dissolved forms of heavy metals in the water of the Syr Darya has been studied in two areas – the upper reaches of the river from the Shardara reservoir to the «Koksaray» bridge and the lower reaches of the river from Turkestan to Terenozek. Concentrations of heavy metals and metalloids were determined by inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7500A, United States) and compared to these recommended levels. Total concentrations of several metals (V, Cu, Mn, Fe, Sr) exceed the Maximum Permissible Concentrations established for waters of fishery reservoirs. The role of the suspended form in the geochemical migration of a number of metals in the water of the Syr Darya River is estimated and it was shown that this form is a significant fraction of the total metal concentration. The distribution of suspended forms of metals correlates to the turbidity of the water of the Syr Darya.

Systematic discrimination of irrigation and upheaval associated salinity using multitemporal SAR data

The increasing salinization in the soil profile by irrigation water and groundwater upheaval is a widespread issue and considered as a major threat to agricultural production in arid and semi-arid regions. The present study aimed to propose a systematic SAR simulation involving the imaginary part of dielectric constant measurements of two consecutive seasons (dry and wet) to quantify and discriminate the irrigation-induced and upheaval-associated salinity from total salinity levels and investigate its impact on crop growth. The Sentinel-1 data of C-band frequency (5.36 GHz) acquired for both the dry and wet spells from 2015 to 2019 was instrumental in the present study. The total soil EC (Electrical Conductivity) was quantified from the imaginary part of dielectric constant (ε″) using semi-empirical microwave simulation "DSDM-SS". Irrigation-induced salinity (ε_Irrigation″) and upheaval-associated salinity (ε_Upheaval″) were extracted from ε″ by proposing a site-, and climatic-specific novel model. The ε_Upheaval″ and ε_Irrigation″ have shown promising statistical significance with the in-situ soil EC (R² = 0.89, p = <0.001, rMSE = 1.08, Bias = 0.584) and groundwater EC measurements (R² = 0.85, p = <0.001, rMSE = 1.28, Bias = 1.16). The study found that the rate of salinity increase over time due to irrigation (77%) was considerably higher than the upheaval (42%) process. This demonstrated that the intensive use of groundwater for irrigation has a higher impact on vegetation vigor (θ = -0.87) than the upheaval process. The study revealed that crop failure in the dry season was provoked by osmotic stress and waterlogging conditions.

Hydrochemical Assessment of the Irrigation Water Quality of the El-Salam Canal, Egypt

The El-Salam canal in Egypt is considered an important stream of fresh water for the agricultural sector that extends from the Nile River to Sinai, while it is subjected to several anthropogenic stresses. In this study, five-georeferenced stations (named from S1 to S5) were monitored along the El-Salam Canal before El-Sahara of the Suez Canal, via the estimation of the WQ index based on major cations and anions analysis including salinity hazard, permeability index, residual sodium carbonate, magnesium hazard, sodium percentage, sodium adsorption ratio, Kelley index, potential salinity, total hardness, and irrigation water quality index (IWQI). The sequence of average concentration of cations in water were Na+ > Ca2+ > Mg2+ > K+. The major cations constitute around 60% of the total dissolved salts. While the sequence of major anions in water were SO42− > HCO3− > Cl− > CO32−. These cations and anions showed an increasing trend from S1 (intake of the canal) to S5 (before El-Sahara) of the El-Salam Canal. Moreover, the order of heavy metals was Zn < Cd < Cr < Ni < Fe < Mn < Co < Cu < Pb. According to the US EPA (1999) guidelines, the levels of Fe and Zn in the El-Salam Canal are within the permissible limits for drinking and irrigation purposes, while Mn, Pb, Cu, Co, Ni, Cr, and Cd were detected at higher concentrations than those recommended. The value of IWQI in water samples varied from 40.26 to 114.82. The samples of S1 showed good water, the samples of region S2 (after mixing with Faraskour drainage) showed poor water quality, samples of regions S3 (after mixing with the El-Serw drain waters) and S5 (before El-Sahara) fell under the very poor water category and samples of region S4 (after mixing with the Hadous drainage) showed unsuitable water. Croplands irrigated with such water will not be exposed to any alkaline risks but will be exposed to the risk of salinity, which is more severe after mixing at the S3 and S4 sites. It is recommended to treat the drainage water before mixing with the irrigation water of El-Salam Canal to raise the suitability of irrigation water for crops, particularly for the Hadous drain.

Assessment of surface and groundwater quality for irrigation purposes in the Danube-Tisa-Danube hydrosystem area (Serbia)

The study evaluates irrigation water quality in the Danube-Tisa-Danube hydrosystem area (Vojvodina, northern Serbia). The area is dominantly a plain with about 75% arable land, suitable for agricultural production and irrigation. Use of water of inadequate quality can have long-term effects on irrigated land and affect the yield of cultivated crops. The analyses included data from 40 surface water and 23 groundwater quality monitoring locations, observed during the period 2013-2018. The average annual values of the concentrations of major cations and anions and of electrical conductivity in surface and groundwater were comparatively analyzed. These values were statistically significantly higher (by p < 0.05) in groundwater bodies with most of the analyzed parameters. Hydrochemical classification of water types shows that 95% of surface and 87% of groundwater locations belong to the Ca·Mg-HCO₃ water type. Water suitability for irrigation was assessed using specific parameters and indices (sodium adsorption ratio, Na%, residual sodium carbonate, magnesium hazard, permeability index, and Kelly's index). The results showed that surface and groundwater resources are generally of good quality and suitable for irrigation, with sporadic deviations at several locations. The principal component analysis (PCA) was used to identify the most important variables affecting the chemical composition of the analyzed waters and group the monitoring locations by their chemical characteristics. The spatial variation of the analyzed water quality indices was shown on thematic maps.

Calculation of targeted eco-environmental water requirements in a dry inland river: a case study of the Yarkand River Basin, Xinjiang, China

Analysis of eco-environmental water requirements along a dry inland river under extreme drought conditions can provide a theoretical basis for the sustained utilization and management of water resources in arid regions. This paper uses the Yarkand River Basin in Xinjiang, China, as a case study to determine and assess a method to calculate targeted eco-environmental water requirements (TEEWR) for different ranges of ecological protection of inland riparian forests. The proposed method is intended to comprehensively analyze the water resources along arid inland rivers. Specifically, the ranges of ecological protection were gradually expanded at intervals of 1 km (or multiples of the smallest distance) away from the river course while the TEEWR was determined as a function of the ecological water demand of riparian forest vegetation (Yec) and its corresponding river loss (Xloss). The developed method was shown to be feasible for analyzing TEEWR in the Yarkand River Basin and thus provides a novel and effective approach for the rational utilization and management of water resources in inland river basins in arid regions.

Article Highlights

Hydrochemistry of sediment pore water in the Bratsk reservoir (Baikal region, Russia)

This study aimed to identify the factors responsible for the major ion composition of pore water from the bottom sediments of the Bratsk water reservoir, which is part of the largest freshwater Baikal-Angara water system. In the Bratsk reservoir, the overlying water was characterized as HCO₃–Ca–Mg type with the mineralization ranging between 101.2 and 127.7 mg L⁻¹ and pore water was characterized as HCO₃–SO₄–Ca, SO₄–Cl–Ca–Mg and mixed water types, which had mineralization varying from 165.9 to 4608.1 mg L⁻¹. The ionic composition of pore waters varied both along the sediment depth profile and across the water area. In pore water, the difference between the highest and lowest values was remarkably large: 5.1 times for K⁺, 13 times for Mg²⁺, 16 times for HCO₃⁻, 20 times for Ca²⁺, 23 times for Na⁺, 80 times for SO₄²⁻, 105 times for Cl⁻. Such variability at different sites of the reservoir was due to the interrelation between major ion concentrations in the pore water and environmental parameters. The major factor responsible for pore water chemistry was the dissolution of sediment-forming material coming from various geochemical provinces. In the south part of the reservoir, Cl⁻, Na⁺ and SO₄²⁻ concentrations may significantly increase in pore water due to the effect of subaqueous flow of highly mineralized groundwater.

Hydrogeochemical evaluation, suitability, and health risk assessment of groundwater in the watershed of Godavari basin, Maharashtra, Central India

In this investigation, the geochemical progression of a total of 31 groundwater samples of pre-monsoon season was assessed with categorization based on entropy weight water quality index and risk assessment on public health in the semi-arid area of Godavari basin, Maharashtra, Central India. Graphically, the major groundwater types identified were Ca-HCO₃, mixed Ca-Mg-Cl, and mixed Ca-Na-HCO₃. Based on [Mg²⁺/Na⁺] with [Ca²⁺/Na⁺] and [HCO₃^-/Na⁺] with [Ca²⁺/Na⁺] plots, carbonate and silicate weathering were identified as a major geochemical process governing groundwater chemistry. The presence of reverse ion exchange process was authenticated by (Ca²⁺ + Mg²⁺) vs. (HCO₃^- + SO₄^2-) and Na⁺ + K⁺-Cl^- vs. (Ca²⁺ + Mg²⁺)-(HCO₃^- + SO₄^2-) plots. The saturation index values for calcite and dolomite showed that these minerals were in dissolution state. The dissolution of gypsum, dolomite, and anhydrite increased Ca²⁺ load in groundwater which accelerated the precipitation of calcite. The high toxic level of NO₃^- (> 45 mg/L) was identified in 64.5% of the 31 groundwater samples, whereas F^- concentration exceeded the threshold value in 12.9% of samples. Based on the entropy weight water quality index values, 70% of the samples were found to have moderate quality for drinking. In addition, health risk evaluation showed that the total hazard, due to fluoride and nitrate through oral pathways, was much higher than that through the dermal pathway. Children were found to be at high risk due to the consumption of NO₃^- and F^- contaminated water. The calculated irrigation water quality index (IWQI) diverge from 7.4-89.2, expressing excellent to good quality for irrigation. Based on the irrigation water quality index, 90.3% of samples were found excellent for irrigation and 6.4% of good quality for irrigation. Authors recommend that continuous water quality monitoring programs along with effective management practices should be developed to avoid excessive extraction of groundwater.

Application of Irrigation Water Quality Indices and Multivariate Statistical Techniques for Surface Water Quality Assessments in the Northern Nile Delta, Egypt

Under sustainable development conditions, the water quality of irrigation systems is a complex issue which involves the combined effects of several surface water management parameters. Therefore, this work aims to enhance the surface water quality assessment and geochemical controlling mechanisms and to assess the validation of surface water networks for irrigation using six Water Quality Indices (WQIs) supported by multivariate modelling techniques, such as Principal Component Regression (PCR), Support Vector Machine Regression (SVMR) and Stepwise Multiple Linear Regression (SMLR). A total of 110 surface water samples from a network of surface water cannels during the summers of 2018 and 2019 were collected for this research and standard analytical techniques were used to measure 21 physical and chemical parameters. The physicochemical properties revealed that the major ions concentrations were reported in the following order: Ca2+ > Na+ > Mg2+ > K+ and alkalinity > SO42− > Cl− > NO3− > F−. The trace elements concentrations were reported in the following order: Fe > Mn > B > Cr > Pb > Ni > Cu > Zn > Cd. The surface water belongs to the Ca2+-Mg2+-HCO3− and Ca2+-Mg2+-Cl−-SO42− water types, under a stress of silicate weathering and reverse ion exchange process. The computation of WQI values across two years revealed that 82% of samples represent a high class and the remaining 18% constitute a medium class of water quality for irrigation use with respect to the Irrigation Water Quality (IWQ) value, while the Sodium Percentage (Na%) values across two years indicated that 96% of samples fell into in a healthy class and 4% fell into in a permissible class for irrigation. In addition, the Sodium Absorption Ratio (SAR), Permeability Index (PI), Kelley Index (KI) and Residual Sodium Carbonate (RSC) values revealed that all surface water samples were appropriate for irrigation use. The PCR and SVMR indicated accurate and robust models that predict the six WQIs in both datasets of the calibration (Cal.) and validation (Val.), with R2 values varying from 0.48 to 0.99. The SMLR presented estimated the six WQIs well, with an R2 value that ranged from 0.66 to 0.99. In conclusion, WQIs and multivariate statistical analyses are effective and applicable for assessing the surface water quality. The PCR, SVMR and SMLR models provided robust and reliable estimates of the different indices and showed the highest R2 and the highest slopes values close to 1.00, as well as minimum values of RMSE in all models.

Combining Water Quality Indices and Multivariate Modeling to Assess Surface Water Quality in the Northern Nile Delta, Egypt

Assessing surface water quality for drinking use in developing countries is important since water quality is a fundamental aspect of surface water management. This study aims to improve surface water quality assessments and their controlling mechanisms using the drinking water quality index (DWQI) and four pollution indices (PIs), which are supported by multivariate statistical analyses, such as principal component analysis, partial least squares regression (PLSR), and stepwise multiple linear regression (SMLR). Twenty-two physicochemical parameters were analyzed using standard analytical methods for 55 surface water sites in the northern Nile Delta, Egypt. The DWQI results indicated that 33% of the tested samples represented good water, and 67% of samples indicated poor to unsuitable water for drinking use. The PI results revealed that surface water samples were strongly affected by Pb and Mn and were slightly affected by Fe and Cr. The SMLR models of the DWQI and PIs, which were based on all major ions and heavy metals, provided the best estimations with R2 = 1 for the DWQI and PIs. In conclusion, integration between the DWQI and PIs is a valuable and applicable approach for the assessment of surface water quality, and the PLSR and SMLR models can be used through applications of chemometric techniques to evaluate the DWQI and PIs.