Hydrochemical Dataset Research Articles

Shallow and deep groundwater moderate methane dynamics in a high Arctic glacial catchment

Glacial groundwater can mobilize deep-seated methane from beneath glaciers and permafrost in the Arctic, leading to atmospheric emissions of this greenhouse gas. We present a temporal, hydro-chemical dataset of methane-rich groundwater collected during two melt seasons from a high Arctic glacial forefield to explore the seasonal dynamics of methane emissions. We use methane and ion concentrations and the isotopic composition of water and methane to investigate the sources of groundwater and the origin of the methane that the groundwater transports to the surface. Our results suggest two sources of groundwater, one shallow and one deep, which mix, and moderate methane dynamics. During summer, deep methane-rich groundwater is diluted by shallow oxygenated groundwater, leading to some microbial methane oxidation prior to its emergence at the surface. Characterization of the microbial compositions in the groundwater shows that microbial activity is an important seasonal methane sink along this flow-path. In the groundwater pool studied, we found that potential methane emissions were reduced by an average of 29% (±14%) throughout the summer due to microbial oxidation. During winter, deep groundwater remains active while many shallow systems shut down due to freezing, reducing subsurface methane oxidation, and potentially permitting larger methane emissions. Our results suggest that ratios of the different groundwater sources will change in the future as aquifer capacities and recharge volumes increase in a warming climate.

Shallow-groundwater-level time series and a groundwater chemistry survey from a boreal headwater catchment, Krycklan, Sweden

Abstract. Shallow groundwater can respond quickly to precipitation and is the main contributor to streamflow in most catchments in humid, temperate climates. Therefore, it is important to have high-spatiotemporal-resolution data on groundwater levels and groundwater chemistry to test spatially distributed hydrological models. However, currently, there are few datasets on groundwater levels with a high spatiotemporal resolution because of the large effort required to collect these data. To better understand shallow groundwater dynamics in a boreal headwater catchment, we installed a network of groundwater wells in two areas in the Krycklan catchment in northern Sweden for a small headwater catchment (3.5 ha; 54 wells) and a hillslope (1 ha; 21 wells). The average well depth was 274 cm (range of 70–581 cm). We recorded the groundwater-level variation at 10–30 min intervals between 18 July 2018–1 November 2020. Manual water-level measurements (0–26 per well) during the summers of 2018 and 2019 were used to confirm and re-calibrate the automatic water-level measurements. The groundwater-level data for each well was carefully processed using six data quality labels. The absolute and relative positions of the wells were measured with a high-precision GPS and terrestrial laser scanner to determine differences in absolute groundwater levels and calculate groundwater gradients. During the summer of 2019, all wells with sufficient water were sampled once and analyzed for electrical conductivity, pH, absorbance, and anion and cation concentrations, as well as the stable isotopes of hydrogen and oxygen. The data are available at https://doi.org/10.5880/fidgeo.2022.020 (Erdbrügger et al., 2022). This combined hydrometric and hydrochemical dataset can be useful for testing models that simulate groundwater dynamics and evaluating metrics that describe subsurface hydrological connectivity.

Protection of peri-urban groundwater catchments: a multi-tracer approach for the identification of urban pollution sources

Abstract. Groundwater catchment located in peri-urban areas may be impacted by many pollutants coming from different types of point or diffuse sources such as accidental spills, continuous hidden leaks in drainage networks, old landfills, treated/untreated wastewater and watercourses. In the scope of the CASPER project, a new methodological approach has been developed based on field survey and interpretation of the collected data in order to distinguish between the different sources of contamination and mixtures of pollutants. First, the groundwater catchment area corresponding to the land surface perimeter in which abstracted groundwater is recharged is determined and characterised in hydrogeological terms. The possible sources of pollution are identified. In a second step, a groundwater and surface water monitoring survey is established, and water samples are collected focusing on a combination of physicochemical parameters and set of various hydrochemical indicators. In particular, different stable isotopes are considered. The NO3- and Boron stable isotopes are used to distinguish between inputs linked to urban effluents, agricultural fertilisers and manure. Stable isotopes of SO42- are used to distinguish between sulphide minerals oxidation, sulphur-carbon compounds mineralisation, lixiviation and human pollution. Moreover, the occurrence of specific molecules like pharmaceutical and lifestyle products (carbamazepine, caffeine, etc.) are used as effective tracers of anthropogenic contamination. Microbiological analyses are also undertaken to identify microbial populations associated with specific sources of pollution or specific biochemical reactions occurring in soil and groundwater. The resulting hydrochemical dataset is then processed using multivariate and clustering analyses. In this context, the objective here is to describe the rigorous methodological approach to assess pollution sources and to illustrate the first steps of this process using a case study corresponding to a groundwater catchment is a chalk aquifer in Western Belgium.

Groundwater chemistry in Madeira Island (Portugal): main processes and contribution to the hydrogeological conceptual model

Groundwater resources are the main water supply source of Madeira Island, thus the characterization of the main hydrogeological mechanisms is vital for their sustainable management. Through the present study, a large hydrochemical dataset was analyzed by traditional and PCA analysis in light of the conceptual hydrogeological model of the island. Groundwater is mainly characterized by being low mineralized (mean EC = 128.6 µS/cm), cold (mean temperature = 13.4 °C) and slightly acidic (mean pH = 6.7). Springs draining local and small perched aquifer have low solute content and local flow path, while drilled wells, tapped in the basal aquifer near the coast, are more mineralized. Groundwaters are of the Na–HCO3, Mg–HCO3−, Ca–HCO3− and Na–Cl types. The latter is found in some springs and in a few drilled wells. The hydrogeochemical and principal component analysis identify silicate weathering process as the most important factor involved in groundwater mineralization, as also CO2 dissolution and seawater spraying. Based on the 3H levels, most groundwaters have a significant component of modern recharge. Springs correspond to young waters, whilst waters in tunnels/galleries and drilled wells are mixtures of modern and submodern waters. The lower 3H concentration in these waters indicates longer residence time in the aquifers than spring water with higher levels and recent recharge. In general, flow paths are local and shallow. The interpretation of the chemical data in conjunction with 3H and δ18O data is in line with the conceptual model of Madeira Island proposed by Prada et al. (Comun Inst Geol Min 90:125–142, 2003; J Hydrol 536:409–425, 2016).

Dataset on hydrogeochemical characteristics of groundwater and surface water in Kattumannarkoil Taluk, India.

Surfacewater overlay groundwater at the groundwater/surface water interface(GSI). Water and chemicals are continually exchanged via GSI. Surface water recharges the underlying aquifer and undergo significant changes in chemical composition before it discharges back into the stream or at the surface. Thus a sustainable management of water resource needs an insight in the water chemistry and seasonal variations. The hydrochemical dataset representing a total of 37 groundwater samples and 13 surface water samples has been collected from Kattumannarkoil taluk,India to identify the factors governing water chemistry of the region. Hence, the samples were collected during two different seasons summer (April 2015) and monsoon (September 2015) to broadly cover seasonal variation. The collected samples were analyzed for physical and chemical parameters. The physical parameters measured in the field are pH, electrical conductivity (EC), total dissolved solids (TDS). The chemical parameters analyzed in the laboratory are calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), chloride (Cl−), bicarbonate (HCO3−), nitrate (NO3−), phosphate (PO4), sulfate (SO42+) and silica (H4SiO4). Furthermore, the results were processed using AquaChem software, Geographical information system (GIS), multivariate statistical techniques and a computer program WATCLAST written in C++. This hydrochemical dataset ascertain the utility purpose of water. The dataset can serve as a guide for hydrogeochemistry of other predominantly agricultural area that share similar geological characteristics. The raw data of this research work is hosted in the mendeley repository [1]

Physical controls and ENSO event influence on weathering in the Panama Canal Watershed

Recent empirical studies have documented the importance of tropical mountainous rivers on global silicate weathering and suspended sediment transport. Such field studies are typically based on limited temporal data, leaving uncertainty in the strength of observed relationships with controlling parameters over the long term. A deficiency of long-term data also prevents determination of the impact that multi-year or decadal climate patterns, such as the El Niño Southern Oscillation (ENSO), might have on weathering fluxes. Here we analyze an 18-year hydrochemical dataset for eight sub-basins of the Panama Canal Watershed of high-temporal frequency collected between 1998 and 2015 to address these knowledge gaps. We identified a strongly positive covariance of both cation (Ca2+, Mg2+, K+, Na+) and suspended sediment yields with precipitation and extent of forest cover, whereas we observed negative relationships with temperature and mosaic landcover. We also confirmed a statistical relationship between seasonality, ENSO, and river discharge, with significantly higher values occurring during La Niña events. These findings emphasize the importance that long-term datasets have on identifying short-term influences on chemical and physical weathering rates, especially, in ENSO-influenced regions.

Geohydrology of a Reference Mediterranean Catchment (Cilento UNESCO Geopark, Southern Italy)

In this paper, we studied the geo-hydrological structure and behavior of a reference catchment, located in the Cilento UNESCO Global Geopark, southern Italy, representative of the hilly, terrigenous and forested headwaters of the Mediterranean eco-region. Based on detailed hydrogeological and hydro-geomorphological surveys and geomorphometric analysis, starting in 2012, a hydro-chemical monitoring activity at the catchment and sub-catchment scale started, and a hydro-chemical dataset was progressively recorded at daily and sub-hourly time steps. Based on this dataset, the authors performed an original procedure to identify different runoff components, derived by applying cascade mass balance filtering. The integration of hydrological and geomorphological approaches allowed us to obtain an interesting conceptualization of the storm flow generation using hydro-chemical signatures related to different runoff components produced during the increasing–decreasing cycle of the flood event magnitude. The hydro-system activated progressively different runoff sources (i.e., groundwater, riparian corridor, hillslope and hollow) and involved various mechanisms (i.e., groundwater ridging, saturation-excess, infiltration-excess and soil pipe exfiltration). The geo-hydrological conceptualization was validated using a hysteresis Q-EC loop analysis performed on selected events that showed how hysteretic indices could be used to characterize the events in respect to their origins, mechanisms and pathways in similar catchments.

Role of Natural and Anthropogenic Influence on the Salinization of Groundwater from Basement Aquifers in the Middle Part of Mono River Basin, Togo

This study aimed to identify the role of natural and anthropogenic influence on geochemical processes controlling groundwater salinization in the middle portion of the Mono River basin, Togo. Multivariate statistical analysis, geochemical masse balance modeling, and conventional graphical methods were applied to the chemical dataset obtained from 110 groundwater samples collected during two campaigns (March-May 2011 and April 2014). The results showed that groundwater is predominantly fresh, acidic to circumneutral and mixed cations-HCO-3 water types. The proportion of ions (Na+, K+, Cl- and SO2-4) occurring ubiquitously in a saline environment increases substantially with TDS. Two factors, defined as natural and anthropogenic, account for 76.5% of the hydrochemical dataset variance. Based on the hierarchical cluster analysis, groundwater samples are classified into four clusters that corroborate the factor analysis results and illustrate different hydrochemical evolution stages along a topographically-driven groundwater flow path. The primary natural process contributing to cations and bicarbonate ions is the weathering of silicate minerals and possibly secondary carbonates by infiltrating water enriched with soil CO2 gas. Groundwater salinization indicators including Cl-, SO2-4 and NO-3, originate from potential sources such as human and animal wastes, agrochemicals, and deforestation. Thermodynamic equilibrium conditions ranged from saturation to oversaturation with respect to quartz, chalcedony, amorphous silica, calcite, dolomite, sepiolite, and talc. In conjunction with the lowering of CO2 partial pressure and evaporation, these conditions restrict acidic hydrolysis of primary silicates but magnify the groundwater salinization process in the lower elevation areas where soil crusts’ formation is favorable. This study showed the effective use of multivariate statistical analysis and complementary techniques in identifying the significant factors and processes controlling groundwater chemistry.

Oxygen consumption in seasonally stratified lakes decreases only below a marginal phosphorus threshold

Areal oxygen (O2) consumption in deeper layers of stratified lakes and reservoirs depends on the amount of settling organic matter. As phosphorus (P) limits primary production in most lakes, protective and remediation efforts often seek to reduce P input. However, lower P concentrations do not always lead to lower O2 consumption rates. This study used a large hydrochemical dataset to show that hypolimnetic O2 consumption rates in seasonally stratified European lakes remain consistently elevated within a narrow range (1.06 ± 0.08 g O2 m−2 d−1) as long as areal P supply (APS) exceeded 0.54 ± 0.06 g P m−2 during the productive season. APS consists of the sum of total P present in the productive top 15 m of the water column after winter mixing plus the load of total dissolved P imported during the stratified season, normalized to the lake area. Only when APS sank below this threshold, the areal hypolimnetic mineralization rate (AHM) decreased in proportion to APS. Sediment trap material showed increasing carbon:phosphorus (C:P) ratios in settling particulate matter when APS declined. This suggests that a decreasing P load results in lower P concentration but not necessarily in lower AHM rates because the phytoplankton community is able to maintain maximum biomass production by counteracting the decreasing P supply by a more efficient P utilization. In other words, in-lake organic matter production depends only on APS if the latter falls below the threshold of 0.54 g P m−2 and correspondingly, the atomic C:P ratio of the settling material exceeds ~155.

Identification of the components of a complex groundwater flow system subjected to intensive exploitation

The Mexico City region, like many other densely populated regions in the world, has problems in guaranteeing the supply of drinking water to its inhabitants. Its groundwater flow system is subject to intensive exploitation. To ensure proper water management, it is important to understand the behavior of groundwater flow system components under conditions of intensive exploitation. In this study, we analyzed 169 samples from drinking water supply wells, according to their chemistry. The principal components of the flow system were inferred using exploratory statistical analysis and analysis of the mixture of the end-members of the hydrochemical dataset. Four components were identified: (1) waters of recent infiltration and local circulation, (2) waters with evidence of intermediate chemical evolution, (3) waters that are chemically more evolved and of large flow trajectories, (4) waters that are chemically more evolved and of deep circulation. A relationship between the components, the structural geology, and the recharge zones was established. The mixing proportion of the four components in each water sample extracted from drinking water wells was identified. It was observed that the faults and the design of screened section of the well tubes influenced the mixtures captured by the wells. The impact generated by the intensive exploitation with respect to the distribution of the components within the flow system was evaluated.

Conceptual hydrogeological and numerical groundwater flow modelling around the Moab Khutsong deep gold mine, South Africa.

Prediction of response to fissure water pumping from a shaft on the surrounding areas is conducted with a numerical model, which was refined using environmental stable isotope (ESI), Tritium and hydrochemical datasets. The numerical model domain covers the local carbonate rock units mainly because it is known to be the main source of groundwater.Based on the hydrochemical dataset of the fissure water pumped at the shaft, strong signature of Na–Cl type water originating from the seepage of a waste rock dump as well as polluted water from mine offices, loading/unloading and parking lot areas, is evident. The environmental isotope data demonstrated that fissure water intercepted at the shaft has strong footprint of surface water and polluted groundwater from nearby areas. The 30-year numerical model prediction indicates that pumping at a rate of 2500 m3/day or more would cause the radius of influence to expand to areas where the central tailings storage facility is located and could possibly draw highly acidic water. Interception of acid rock drainage could cause sever corrosion of pump infrastructure, enhance dolomite dissolution and local ground subsidence as well as possibly compromise the structural integrity of the central tailings dam.It is recommended that the current groundwater monitoring network be revised for taking proactive action. The study highlights the relevance of integrating various sets of data to improve understanding of the conceptual flow before any numerical modelling is attempted.

Nitrate contamination and subsequent hydrogeochemical processes of shallow groundwater in agro-livestock farming districts in South Korea

In last several decades, the nitrogen cycle has been significantly perturbed, largely due to intensification of agricultural activities throughout the world. In this study, we examined the impact of agricultural N inputs on the quality and chemistry of shallow groundwater, based on a large hydrochemical dataset (n ≈ 4000) collected from 100 agro-livestock farming districts in South Korea. The South Korean groundwater, studied mostly in silicate aquifers, shows very high nitrate concentrations (median NO3− = 22.2 mg/L) and acidification (median pH = 5.6). The groundwater nitrate levels tend to increase with the estimated N loadings, and the groundwater pH generally decreases with increasing nitrate levels. The relationship between the concentrations of Ca2+ + Mg2+ and HCO3- has a moderate adjusted R2 value (0.4), and the molar (Ca2+ + Mg2+) / HCO3- ratios (r) tend to increase with nitrate concentrations. This implies that the chemical composition of the groundwater is controlled by multiple hydrogeochemical processes, which include weathering of silicates and carbonates induced by carbonic acid (r = 0.5), nitrification (r ≥ 1) and denitrification (mostly, r < 0.5 in this study). In particular, undrinkable (NO3− > 44.3 mg/L) groundwater (n = 988) shows an average molar ratio of 1.04, indicating that such highly contaminated groundwater experiences the enhanced geochemical weathering of aquifer materials by an anthropogenic process (e.g., addition of N fertilizers). The results of principal component (PC) analysis also support our explanation: the first PC shows significant negative correlations with major components including NO3− while there is a weak positive correlation with pH, indicating anthropogenically enhanced weathering that includes the buffering process by agricultural liming materials, while the second PC shows negative correlations with Eh, DO and NO3− but positive correlations with pH and HCO3−, suggesting the denitrification process. A few groundwater samples (about 4%) experienced heterotrophic denitrification, and they have molar ratios (r) of less than 0.5. The results of this study indicate that 1) geochemical weathering of aquifer materials in shallow groundwater systems is enhanced by nitrate contamination caused by high N loadings in agro-livestock farming districts, causing increased salinity, and 2) in silicate aquifers, the prevailing hydrochemical process can be interpreted by the molar (Ca2+ + Mg2+) / HCO3- ratios of groundwater.

Regression Approaches for Hydrograph Separation: Implications for the Use of Discontinuous Electrical Conductivity Data

Understanding of runoff generation mechanisms affects the ability to manage streamflow quantity and quality issues. Concerning the baseflow in particular, measurements are almost never available and hydrograph separation is generally applied to characterize its relevant patterns. As an alternative to well-known recursive digital filters and mass balance filtering methods, this paper deals with the use of regression approaches, based on electrical conductivity measurements, as a proxy for total dissolved solids, to separate baseflow from total flow. Particular focus is placed on their flexibility and ability to adapt to discontinuous electrical conductivity data measurements. To illustrate this, we analyze a hydrochemical dataset collected from the Ciciriello experimental catchment (Southern Italy). The main findings are as follows: A comparative analysis suggests that the performance of regressive approaches in the case of daily electrical conductivity measurements is better than that of calibrated recursive digital filters. Weekly monitored electrical conductivity data led to performances comparable to the daily scale monitoring, and even monthly observation leads to a nonsignificant reduction in regression hydrograph filter performance; this shows how spot geochemical data monitoring may present valid and operational alternatives for characterization of baseflow in poorly gauged catchments.

Investigating Hydrochemical Groundwater Processes in an Inland Agricultural Area with Limited Data: A Clustering Approach

Groundwater chemistry data are normally scarce in remote inland areas. Effective statistical approaches are highly desired to extract important information about hydrochemical processes from the limited data. This study applied a clustering approach based on the Gaussian Mixture Model (GMM) to a hydrochemical dataset of groundwater collected in the middle Heihe River Basin (HRB) of northwestern China. Independent hydrological data were introduced to examine whether the clustering results led to an appropriate interpretation on the hydrochemical processes. The main findings include the following. First, in the middle HRB, although groundwater chemistry reflects primarily a natural salinization process, there are evidence for significant anthropogenic influence such as irrigation and fertilization. Second, the regional hydrological cycle, particularly surface water-groundwater interaction, has a profound and spatially variable impact on groundwater chemistry. Third, the interaction between the regional agricultural development and the groundwater quality is complicated. Overall, this study demonstrates that the GMM clustering can effectively analyze hydrochemical datasets and that these clustering results can provide insights into hydrochemical processes, even with a limited number of observations. The clustering approach introduced in this study represents a cost-effective way to investigate groundwater chemistry in remote inland areas where groundwater monitoring is difficult and costly.

A hydrochemical approach to quantify the role of return flow in a surface flow‐dominated catchment

AbstractStormflow generation in headwater catchments dominated by subsurface flow has been studied extensively, yet catchments dominated by surface flow have received less attention.We addressed this by testing whether stormflow chemistry is controlled by either (a) the event‐water signature of overland flow, or (b) the pre‐event water signature of return flow. We used a high‐resolution hydrochemical data set of stormflow and end‐members of multiple storms in an end‐member mixing analysis to determine the number of end‐members needed to explain stormflow, characterize and identify potential end‐members, calculate their contributions to stormflow, and develop a conceptual model of stormflow. The arrangement and relative positioning of end‐members in stormflow mixing space suggest that saturation excess overland flow (26–48%) and return flow from two different subsurface storage pools (17–53%) are both similarly important for stormflow. These results suggest that pipes and fractures are important flow paths to rapidly release stored water and highlight the value of within‐event resolution hydrochemical data to assess the full range and dynamics of flow paths.

Temporal and spatial variability of chemical and isotopic composition of soil solutions from cambisols - field study and experiments

The chemical and isotopic composition of soil solutions is highly relevant for environmental and forensic tasks. We investigated interstitial solutions from soil horizons of three cambisols in Styria (Austria). The soils consisted mainly of quartz, feldspar and clay minerals with a vertical variability. Two soil solution fractions from meso-, macro- and micropores (m) and micropores only (μ) were extracted at two subsequent hydraulic pressure steps corresponding to matrix potentials of up to pF 5.43 and from 5.43 to 5.73, respectively. While solute concentrations indicated diverse distribution in soil solution fractions m and μ, heavy stable hydrogen and oxygen isotopes of H2O (−92.5‰<δ2H<−34.4‰; −11.9‰<δ18O<−4.0‰, VSMOW) are clearly enriched in the μ versus m fractions. Principal component analysis on the hydrochemical data set indicates that the intensity of the overall silicate weathering is higher in autumn versus spring, whereas the anthropogenic impact on weathering behaves inversely. The anthropogenic impact is related to seasonal variability of nitrification of N-fertilizers. In consequence of evaluated signals for overall silicate weathering about three-fourths of the soil solutions sampled in autumn indicated elevated total dissolved solid concentration vs. those in spring accompanied with washing out solutes from the soil cover following precipitation events in autumn before sampling. Isotopic shift of soil solutions from the local meteoric water line in spring obviously followed an evaporation trend because of less precipitation and high evaporation before sampling. Experimentally simulated evaporation of soil samples confirmed the observed isotopic evaporation trend. Wetting experiments indicated the infiltration of water within minutes into the micropores of the soils. Exchange of water molecules between micro-, meso- and macropores is an almost instantaneous process and soil solutions in micropores are not as isolated from the soil water system as it was formerly suggested, e.g. for plant uptake. Highly dynamic and complex mechanisms in the gas-water-solid system of soils have to be considered for the application of elemental and isotope proxies related to environmental, forensic and agricultural tasks.

Temporal distribution of water characteristics in the Miri estuary, east Malaysia

AbstractThis baseline study was carried out to investigate the physicochemical factors such as pH, salinity, temperature, turbidity, total dissolved solids (TDS), total suspended solids and dissolved oxygen (DO), as well as nutrient (nitrate, phosphate, ammonium) concentrations and the level of heavy metals (Fe, Zn, Cu, Mn) in the surface water of the Miri estuary at four sampling times based on the four seasons of Malaysia. Results indicated marked temporal differences in each of the water characteristics measured (except ammonium), where DO level (mean: 3.6 mg/L) was found in a concern level. The principle component analysis (PCA) was applied to the hydrological and hydrochemical data set of the Miri estuary; results indicated that principle component 1 and principle component 2 explained 61.78 and 18.69%, respectively, of the total variance in the data set. Besides, results of PCA also indicated that the factors for water characteristics variations were mainly related to TDS, salinity, and Fe. The data...

A New Approach to Identify Recharge Areas in the Lower Virgin River Basin and Surrounding Basins by Multivariate Statistics

Many studies group hydrochemical datasets into hydrochemical facies using graphical and multivariate statistical methods. Compared to graphical methods, cluster analysis and principal component analysis (PCA) can handle large datasets and great number of parameters, so are widely used by researchers. However, cluster analysis and PCA can be subjective, raising questions about the significance and confidence of the groupings. In this study, cluster analysis is combined with multiple discriminant function analysis and measures of association (Cohen’s Kappa and Cramer’s V) to objectively find the optimum clustering technique, number of clusters for a hydrochemical dataset, and stable clusters, and to assess the effect of hydrochemical data transformation, analytical errors, and outliers on a clustering outcome. The proposed combined statistical and mathematical analysis is a robust approach for classifying hydrochemical dataset into optimum hydrochemical facies. The approach is used to demonstrate that the best clustering method for the hydrochemical data from the Lower Virgin River Basin, utilized in this study, is the “within-groups linkage with squared Euclidean distance” clustering method, yielding six optimum hydrochemical facies. The six optimum hydrochemical facies solution is independently supported by test statistical analyses that are used for deciding the number of plausible clusters. Also the application shows that choosing an appropriate data transformation is a key step in delineating optimum hydrochemical facies. Further, it is demonstrated that the effect of outliers and analytical errors on clustering is insignificant when the dataset contains outliers \(\le \)7 % or analytical error \(\le \)19 %. Interpretations of the spatial and graphical analysis of the hydrochemical facies reveal that principal recharge in the study area occurs in the Clover and Bull Mountains and Valleys as well as areas further north. Also the analysis indicates that Virgin River and Beaver Dam Wash water possibly recharges their adjacent floodplains. In an agreement with previous studies in hydrogeology of the study area, the new approach demonstrably is consistent, reproducible, and validated for identification of recharge distribution over large basin areas.

Prediction of water pollution sources using artificial neural networks in the study areas of Sivas, Karabük and Bartın (Turkey)

The determination of the rock types from which the water is recharged/discharged is an essential component of hydrochemical, hydrogeological and water pollution studies. Especially, detection of sources of groundwater contamination is very important in terms of human health and other living organism. This study aims at prediction of water pollution sources using artificial neural networks (ANNs) in Sivas, Karabuk and Bartin areas of Turkey, which have different types of rocks, agricultural activity and mining activity. In this study, a model based on ANNs was developed for forecast to the water discharging from different types of rocks and the water pollution sources in the study areas. Back propagation and Bee Algorithm (BA) were used in ANN training. For achieving the aim of the study, 14 hydrochemical data set were used. The best ANN classification of water discharging from different type of rocks was accomplished with 80 % accuracy using BA. These results indicate that the researches that are similar to this study can provide quite convenience for the assessment of groundwater pollution sources when applied on a large and regional scale.

Geochemical processes controlling water salinization in an irrigated basin in Spain: Identification of natural and anthropogenic influence

Salinization of water bodies represents a significant risk in water systems. The salinization of waters in a small irrigated hydrological basin is studied herein through an integrated hydrogeochemical study including multivariate statistical analyses and geochemical modeling. The study zone has two well differentiated geologic materials: (i) Quaternary sediments of low salinity and high permeability and (ii) Tertiary sediments of high salinity and very low permeability. In this work, soil samples were collected and leaching experiments conducted on them in the laboratory. In addition, water samples were collected from precipitation, irrigation, groundwater, spring and surface waters. The waters show an increase in salinity from precipitation and irrigation water to ground- and, finally, surface water. The enrichment in salinity is related to the dissolution of soluble mineral present mainly in the Tertiary materials. Cation exchange, precipitation of calcite and, probably, incongruent dissolution of dolomite, have been inferred from the hydrochemical data set. Multivariate statistical analysis provided information about the structure of the data, differentiating the group of surface waters from the groundwaters and the salinization from the nitrate pollution processes. The available information was included in geochemical models in which hypothesis of consistency and thermodynamic feasibility were checked. The assessment of the collected information pointed to a natural control on salinization processes in the Lerma Basin with minimal influence of anthropogenic factors.