Hydrogeochemical Modeling Research Articles

Citizen Science as a Co-Creative Measure to Water Quality: Chemical Data and Local Participation in a Rural Territory

It is becoming increasingly clear that the threat to the use of natural landscapes and persistent droughts are affecting the water quality of rural communities. The socio-ecological fit emerges as an aid to advance in the search for solutions to environmental problems in rural communities. Consequently, between May 2016 and September 2021, an interdisciplinary study of community-based water quality monitoring (CWQM) was implemented at a coastal catchment in the Ñuble region, Central Chile. The objective of the study was to involve the participation of local communities in initiatives to control the water quality of various parameters [pH, total iron (FeT), alkalinity as CaCO3, hardness (Ca2+ and Mg2+), sodium (Na+) and potassium (K+), water temperature, sulfate (SO42−) chloride (Cl−), and nitrate (NO3-)] in groundwater, share local knowledge, and apply co-creative measures for improving water conservation. In situ chemical data were also analyzed in the laboratory to check data quality. The PHREEQC hydrogeochemical model is used to characterize hydrogeochemical parameters of groundwater and to know about hydrogeochemical processes related to water quality. High levels of NO3− and FeT are recorded in 75% of the groundwater samples, mainly when water scarcity is higher during the summer. According to Chilean standards, nitrate levels exceed the maximum permissible limits for drinking water. A type of mainly Ca (Mg)–HCO3− carbonated water was recorded with Ca2+, Na+, Mg2+, and HCO3− as dominant ions. This study demonstrated the opportunity of a rural community group to help fill spatial data gaps in water quality monitoring and reassess water quality protection, especially considering the decrease in water availability in the region. Therefore, the community together with researchers can respond with an early alert system to water quality to collaborate with the implementation of rural drinking established on a community-based water quality monitoring. Moreover, to prioritize the level of urgency of rural water, minimize water pollution and improve the perception of the water and the resilience of their social–ecological system.

Capability for Hydrogeochemical Modelling within Discrete Fracture Networks

A new method for simulating solute transport and geochemical interactions within fractured rock is presented. This will be an important capability for assessing the safety of radioactive waste disposal facilities that are located within fractured crystalline bedrock. Specifically, the discrete fracture network (DFN) module within the ConnectFlow groundwater flow and transport software has been updated to: (i) simulate the advection and diffusion of more than one solute species (with the flow and transport equations coupled by the evolving density and viscosity); (ii) model the diffusion of solutes into the rock matrix between fractures; and (iii) utilise the iPhreeqc library to model chemical reactions involving solutes, minerals on fracture/pore surfaces and rock minerals. The performance of ConnectFlow’s DFN module has also been significantly improved via parallelisation which allows more complex calculations to be attempted. These developments are significant because hydrogeochemistry within fractured rock is more accurately represented in an explicit DFN, rather than using more approximate equivalent continuous porous medium (ECPM) methods. Illustrative calculations have been completed for the disposal facility for spent nuclear fuel at Olkiluoto in Finland, and the former candidate site for spent fuel disposal, Laxemar, in Sweden. These calculations show that DFN simulations provide results that are qualitatively similar to results from ECPM calculations. However, because the ECPM is a less direct approach, notable differences exist when compared to the DFN approach.

Hydrogeochemical characteristics and processes of thermokarst lake and groundwater during the melting of the active layer in a permafrost region of the Qinghai–Tibet Plateau, China

Permafrost degradation and the development of thermokarst lakes are important factors driving the variability of regional hydrologic processes. Hydrogeochemical and isotopic analyses are important methods for investigating the hydrologic processes of thermokarst lakes. This study focused on comparing the chemical and hydrogeochemical characteristics between lake water and groundwater during the melting of the active layer in a typical thermokarst lake region on the Qinghai–Tibet Plateau (QTP). Ninety-five samples were collected during different periods of active layer melting and analyzed using statistical, isotope, hydrogeochemical, and modeling methods. Statistical results showed that the average concentrations of almost all ions were lower in lake water than in groundwater, with wider spatial variability in groundwater. The lake water is of the ClNa and HCO3-Ca type with low TDS (total dissolved solids), whereas groundwater is of the HCO3-Ca and mixed type (or transition type) with high TDS. The chemical types of the lake water and groundwater are mainly driven by rock weathering. In terms of the saturation index (SI), halite and gypsum are unsaturated dissolved, whereas dolomite and calcite are generally saturated. Evaporation significantly affects the chemical composition of groundwater, while the hydrochemical compositions of lake water are relatively stable under the joint control of evaporation, precipitation, surface runoff, and groundwater. The isotopic analysis results showed that the contribution of permafrost meltwater and precipitation to groundwater and lake water varied during different stages of active layer melting. According to hydrogeochemical modeling, the main chemical reactions in groundwater are the precipitation of calcite and the dissolution of halite, dolomite, and gypsum. The intensity of groundwater flow determines the degree of chemical reactions along the flow path at different stages of active layer melting. The findings can provide deeper insight into hydrogeochemical processes in thermokarst lake regions under the background of permafrost degradation.

The risk of scaling in Danish geothermal plants and its effect on the reservoir properties predicted by hydrogeochemical modelling

Injectivity problems have been observed in two of three Danish geothermal plants. The utilized geothermal reservoirs comprise sandstones of Lower Triassic and Upper Triassic – Lower Jurassic. The great variations in the formation mineralogy and the chemical composition of their brines allow for a thorough analysis of the differences in the potential risks of scaling. The key scaling processes upon injection of the cooled brines into the reservoirs were identified and changes in the reservoir porosity assessed by hydrogeochemical modelling. Scaling was predicted to be of importance only in one of the geothermal reservoirs, where barite precipitation in the near field of the injection well was identified as a potential risk and could potentially alter the reservoir porosity. Scaling induced by barite nucleation in the injection well, and precipitation and dissolution of carbonates, silicates and clays in the geothermal reservoirs are all of minor importance.

Assessment of chemo-mechanical impacts of CO2 sequestration on the caprock formation in Farnsworth oil field, Texas

This study evaluates the chemo-mechanical influence of injected CO2 on the Morrow B sandstone reservoir and the upper Morrow shale caprock utilizing data from the inverted 5-spot pattern centered on Well 13-10A within the Farnsworth unit (FWU). This study also seeks to evaluate the integrity of the caprock and the long-term CO2 storage capability of the FWU. The inverted 5-spot pattern was extracted from the field-scale model and tuned with the available field observed data before the modeling work. Two coupled numerical simulation models were utilized to continue the study. First, a coupled hydro-geochemical model was constructed to simulate the dissolution and precipitation of formation minerals by modeling three intra-aqueous and six mineral reactions. In addition, a coupled hydro-geomechanical model was constructed and employed to study the effects of stress changes on the caprock’s porosity, permeability, and ground displacement. The Mohr–Coulomb circle and failure envelope were used to determine caprock failure. In this work, the CO2-WAG injection is followed by the historical field-observed strategy. During the forecasting period, a Water Alternating Gas (WAG) injection ratio of 1:3 was utilized with a baseline bottom-hole pressure constraint of 5500 psi for 20 years. A post-injection period of 1000 years was simulated to monitor the CO2 plume and its effects on the CO2 storage reservoir and caprock integrity. The simulation results indicated that the impacts of the geochemical reactions on the porosity of the caprock were insignificant as it experienced a decrease of about 0.0003% at the end of the 1000-year post-injection monitoring. On the other hand, the maximum stress-induced porosity change was about a 1.4% increase, resulting in about 4% in permeability change. It was estimated that about 3.3% of the sequestered CO2 in the formation interacted with the caprock. Despite these petrophysical property alterations and CO2 interactions in the caprock, the caprock still maintained its elastic properties and was determined to be far from its failure.

Development and Application of a Hydrogeochemical Model for the Groundwater Treatment Process in Waterworks

Drinking water quality is one of the most important factors affecting human health. The task of the waterworks is to purify raw water into drinking water. The quality of drinking water depends on two major factors: the raw water quality, and the treatment measures that are applied in the waterworks. Since the raw water quality develops over time, it must be determined whether the treatment measures currently used are also suitable when the raw water quality changes. For this reason, a hydrogeochemical model relevant to the drinking water quality during the treatment process was developed. By comparing the modeled results with the measured values, with the exception of chloride and sodium, all other relevant water quality parameters were consistent with one another. Therefore, the model proved to be plausible. This was also supported by the results of mass balance. The model can be used to forecast the development of drinking water quality, and can be applied as a tool to optimize the treatment measures if the raw water conditions change in the future.

Hydrogeochemical vertical zonation and evolution model of the Kongjiagou coalmine in Sichuan, China

Abstract With mine drainage and activities, the hydrogeochemical environments has greatly changed in Kongjiagou coalmine, Sichuan Province, southwest China. This study aimed to summarize an ideal model of coalmine hydrogeochemical zonation and evolution. In total, 24 groundwater samples from different depth were collected to analyze their components, with the combination of methods such as ion sources, normalization index, ions ratios, cation exchange and inverse modeling. The hydrogeochemical formation main factor was water–rock reactions and more weathering by sulfuric acid. Dissolution and pyrite oxidation were the main sources of , whereas carbonate weathering was the dominant source of . The vertical extent could be distinguished to three zones by mean and standard deviation of burial depth. The normalization index, ions ratios, cation exchange and water types exhibited clear vertical zonation. In shallow groundwater, dissolution led to a Ca- type water and overall stable concentrations of ions. Redox reactions in the middle region have caused significant increases in the total dissolved solids (TDS) and and a considerable reduction in pH; hence, Ca + Mg-SO4 + HCO3 became the dominant type. Re-dissolution and cation exchange played important roles at depth and caused the pH and TDS to increase slowly. The , Ca2+, and Mg2+ concentrations increased rapidly, whereas the concentration remained basically unchanged, and the water type was either Ca + Mg-HCO3 + SO4 or Na-HCO3 + SO4. This study will be of great significance to coalmine safety production and water environments protection.

Hydrogeochemical evaluation and geospatial distribution modeling of the major ion chemistry of groundwater and their suitability for drinking and irrigation in Lagelu, Southwestern Nigeria

Shallow groundwater is an essential resource for domestic, agricultural, and small-scale industrial uses in Lagelu in Oyo State, Southwestern Nigeria. A total of 20 representative groundwater samples were collected from different hand-dug wells and analyzed for the major cations, anions, and heavy metals to establish their suitability for drinking and irrigation. Geospatial variation maps of the major cations and anions were produced using the inverse distance weighted algorithm. The results of the respective concentrations of pH, TDS, EC, HCO3−, NO3−, SO42−, Cl−, PO42−, Ca2+, Mg2+, Na+, K+, Zn2+, Cu+, Pb2+, and As+ except Fe2+ are within the recommended range set by the World Health Organization (WHO) and Nigerian Industrial Standards for Drinking Water Quality (NSDWQ). Based on the hydrogeochemical facies, the groundwater belongs to Na+–K+–Cl−–SO42−, and Ca2+–Mg2+–Cl−–SO42− water types. Gibb’s diagram shows that the interaction of rocks and water dominate the processes that control the ionic compositions of the groundwater due to rock weathering and dissolution. The correlation matrix that specifies the ion concentration relationship showed that TDS, K+, and Fe2+ strongly correlate positively with EC, Na+, and Ca2+, respectively. CO32−, Na+, and Cu moderately correlate positively with Cl−, Mg2+, and pH, respectively. The indices used to determine groundwater suitability for irrigation classified over 90% of the samples as suitable for irrigation.

Assessment of groundwater in Sana’a Basin aquifers, Yemen, using hydrogeochemical modeling and multivariate statistical analysis

Assessment of groundwater in Sana’a Basin aquifers, Yemen, using hydrogeochemical modeling and multivariate statistical analysis

Aqueous Arsenic Speciation with Hydrogeochemical Modeling and Correlation with Fluorine in Groundwater in a Semiarid Region of Mexico

In arid and semiarid regions, groundwater becomes the main source to meet the drinking water needs of large cities, food production, and industrial activities. For this reason, necessary studies must be carried out to estimate its quantity and quality, always seeking sustainable management, thus avoiding social conflicts or a decrease in the productive activities of humanity. This research explains the behavior of groundwater quality concerning arsenic speciation and its relationship with fluoride. The average total arsenic concentration of 19.95 µg/L and 20.29 µg/L is reported for the study period from 2015 to 2020, respectively, according to the Mexican standard. If the population drinks water directly, it is exposed to possible damage to health. The predominant arsenic species is As (V), with 95% and As (III) with 5%, this finding will allow us to define in greater detail the type of remediation that is required to reduce the content of this element in the water. Regarding the relationship between arsenic and fluorine, very small Pearson correlation coefficients of the order of 0.3241 and 0.3186 were found. The estimation of the space–time variation made it possible to identify the areas with the highest concentration of arsenic and fluorine, allowing the definition of the operating policies of these wells, thereby protecting the health of the inhabitants who consume this water.

Hydrogeochemical characteristics and processes of groundwater in an over 2260 year irrigation district: A comparison between irrigated and nonirrigated areas

A comprehensive understanding of groundwater chemistry and its evolution in irrigation districts is essential for irrigation management. In this study, with emphasis on a comparison between irrigated and nonirrigated areas, the groundwater chemistry and hydrogeochemical processes of a typical irrigation district with an irrigation history of over 2260 years were studied to clarify the effects of long-term irrigation on groundwater quality. Based on 107 water samples collected from across the study area, a comprehensive analysis was conducted using multivariate statistics, stable isotope analysis, and hydrogeochemical modeling. The results showed that the variation range and average concentrations of almost all the ions in the irrigation district are much greater than those in the nonirrigated areas. The groundwater in the nonirrigated areas could be characterized by low TDS and HCO3 or HCO3·SO4 types, whereas the groundwater in the irrigation district could be characterized by complex water types and high TDS. Stable isotopes of hydrogen and oxygen indicated that the groundwater in the irrigation district experienced strong evaporation. The calculated groundwater residence time showed that it takes approximately 2180 years for the groundwater to flow through the irrigation district. Some old irrigation water was present, and it influenced the current groundwater chemistry in the study area. The processes forming the current groundwater chemistry in the irrigation district can be formulated as: mixing → evaporation → water–rock interaction. For mixing, the proportions of rainfall, irrigation water from the Jing River, and lateral recharge from the nonirrigated areas were found to be approximately 30%, 49%, and 21%, respectively. For evaporation, the ratio based on the TDS was 3.83 when comparing the groundwater in the irrigation district with the mixed water after evaporation. Hydrogeochemical modeling showed that the irrigation area is a potential carbon source. The dissolution of halite and gypsum, the precipitation of calcite and dolomite, CO2 degassing and Na-Ca exchange are the main chemical reactions in the geochemical evolution of groundwater. The lesson learned from this irrigation district is that long-term irrigation will lead to salinization and complexity of the groundwater. Hence, in the water resource management of irrigation districts, attention should not only be paid to the balance of water quantity, but also to the balance of salts and the hydrochemical evolution of groundwater.

Health risk assessment and hydrogeochemical modelling of groundwater due to heavy metals contaminants at Basundhara coal mining region, India

ABSTRACT The enrichment of heavy metals and mixing with groundwater resources, which makes a serious threat to human health and the environment. The present study was conducted to determine the enrichment of heavy metals in groundwater, geochemical modelling, and to estimate the probable health risks (non-carcinogenic and carcinogenic) of a coal mining region, in eastern India. The relative abundance of mean heavy metal concentration was in the order of Fe > Zn > Al > Ba > Mn > Sr > Ni > Ag > Cu > Pb > V > Cr > Co > Cd, and are within the WHO standards limits for drinking water values. Groundwater shows pH values as generally acidic to alkaline in nature, while Eh values indicate an oxidising environment. Principal component analysis indicates, metal concentration in the groundwater to be mainly derived from the geogenic sources and in-situ leaching of mine overburden materials. Hydrogeochemical modelling indicates heavy metals are in supersaturation to near neutral state in the groundwater with oxide and carbonate mineral phases. Based on (HPI), and (HEI) values, the majority of groundwater samples are low to moderately contaminated. The health risk assessment model based on hazard quotient (HQ) and hazard index (HI) values show few groundwater samples as crossing the reference limit and have non-carcinogenic health risks for both children and adults. The study identifies the chemical characterisation and potential health risks due to the presence of heavy metals in the groundwater of the coal mining region.

Investigation into the Durability Degradation and Fracture of Cable Bolts Based on the Laboratorial Tests and Hydrogeochemical Modelling Under Underground Conditions

Investigation into the Durability Degradation and Fracture of Cable Bolts Based on the Laboratorial Tests and Hydrogeochemical Modelling Under Underground Conditions

Hydrogeochemical modeling of mineral alterations following CO2 injection

Alterations of the mineral phase of deep reservoirs are desired as a process for carbon capture and storage, driven by changes in fluid composition due to CO2 injection. Underlying concepts for hydrogeochemical modeling are implemented in the codes PHREEQC and MIN3P, adapted to cope with pressures and temperatures in deep reservoirs with up to 300 °C and 1000 atm. Simulations were performed using field data from the Heletz, pilot CO2 injection site (Israel), located at the edge of a decommissioned oil field in a sandstone formation, showing a shift of saturation index (SI) and dissolution/precipitation reactions of silicates and carbonates subsequent to injection of CO2. Alterations of the mineral phase with time were largest in the sequence Ankerite > Dolomite > Calcite > Magnesite, and for the mineral Dawsonite during early stages when only Na+ is present in high ionic concentrations. The uncertainty of mineral saturation, a consequence of the variability of water chemical composition and the database records, was investigated by principal component analysis and sensitivity coefficients. A large variability in the occurrence of Dolomite can be explained by salinity variations and the inverse dependency of total amount of carbon mineralization between Pitzer and Debye-Hückel/Davies (D-H/D) based activity computation.

Integration of self-organizing maps, statistical analysis, and hydrogeochemical modeling methods to identify spatio-seasonal variations in mine water quality

Monitoring the quality of mine drainage is an important task in the Ruhr coalfield in western Germany, especially after decommissioning all mining activities in 2018. In this study, seasonal and spatial variations in mine water quality of abandoned coal mines around the lower Ruhr river area were investigated. Statistical analysis, self-organizing maps (SOMs), and hydrogeochemical modeling were used to reveal changes in the water quality of 103 water samples collected between January 2018 and November 2019. An analysis of physical and chemical properties using SOM subdivided mine water samples into five groups: freshwater (groups 1, 2, 3, and 4) and brackish water (group 5) with different physical and chemical characteristics. Freshwater samples were mostly distributed in the southern and central parts, whereas brackish water samples were mostly distributed in the northeastern part of the study area. Approximately 18% of the sampling locations experienced significant seasonal changes during the study period, while 82% of the remaining locations showed only slight variations. Across all groups, seasonal variations in the water quality were less pronounced than differences between southern and northeastern sampling locations. A significant increase was observed in major ion concentrations, TDS, and EC values from southern to northern and northeastern sampling points during the monitoring period. A general trend of approaching saturation state from studied mineral phases was detected with increasing TDS concentrations from groups 1, 2, 3, and 4 to group 5. Trace element concentrations were relatively low, except for several streams with higher Fe and Mn concentrations, and varied between seasons. The SOM approach helped to identify the seasonal changes in mine water properties in the area. The evaluation of changes in mine water quality is useful for the management and protection of water resources, especially drinking water resources, in the densely populated Ruhr area.

An integrated modeling approach for mineral and metal transport in acidic rivers at high mountainous porphyry Cu systems

The natural occurrence of acid waters in mountainous porphyry Cu systems poses challenges for water management considering the increasing water demand and global environmental change. Unraveling the transport and fate of minerals and metals in these types of acidic river systems is crucial for environmental management. To this purpose, we develop a transport and a hydrogeochemical model by coupling five components: (i) hydrology; (ii) hydrodynamics; (iii) sediment transport; (iv) solute transport; and (v) hydrogeochemistry. Our study domain is the Yerba Loca creek, a high-altitude acid rock drainage (ARD) basin located in the central Andes, Chile. Water in the upper basin shows a low pH (around 3) and high aluminum, copper, iron, manganese, and sulfate concentrations. Our model reproduced the observed mineralogical and chemical processes by inducing the expected pH dependence on mineral precipitation along the river. Results showed good agreement between modeled and field data, highlighting the main processes that control the transport and fate of minerals and metals in mountainous river systems.

Response of a hydrothermal system to escalating phreatic unrest: the case of Turrialba and Iraz\xfa in Costa Rica (2007\u20132012)

This study presents the first hydrogeochemical model of the hydrothermal systems of Turrialba and Irazú volcanoes in central Costa Rica, manifested as thermal springs, summit crater lakes, and fumarolic degassing at both volcanoes. Our period of observations (2007–2012) coincides with the pre- and early syn-phreatic eruption stages of Turrialba volcano that resumed volcanic unrest since 2004, after almost 140 years of quiescence. Peculiarly, the generally stable Irazú crater lake dropped its level during this reawakening of Turrialba. The isotopic composition of all the discharged fluids reveals their Caribbean meteoric origin. Four groups of thermal springs drain the northern flanks of Turrialba and Irazú volcanoes into two main rivers. Río Sucio (i.e. “dirty river”) is a major rock remover on the North flank of Irazú, mainly fed by the San Cayetano spring group. Instead, one group of thermal springs discharges towards the south of Irazú. All thermal spring waters are of SO4-type (i.e. steam-heated waters), none of the springs has, however, a common hydrothermal end-member. A water mass budget for thermal springs results in an estimated total output flux of 187 ± 37 L/s, with 100 ± 20 L/s accounted for by the San Cayetano springs. Thermal energy release is estimated at 110 ± 22 MW (83.9 ± 16.8 MW by San Cayetano), whereas the total rock mass removal rate by chemical leaching is ~ 3000 m3/year (~ 2400 m3/year by San Cayetano-Río Sucio). Despite Irazú being the currently less active volcano, it is a highly efficient rock remover, which, on the long term can have effects on the stability of the volcanic edifice with potentially hazardous consequences (e.g. flank collapse, landslides, phreatic eruptions). Moreover, the vapor output flux from the Turrialba fumaroles after the onset of phreatic eruptions on 5 January 2010 showed an increase of at least ~ 260 L/s above pre-eruptive background fumarolic vapor fluxes. This extra vapor loss implies that the drying of the summit hydrothermal system of Turrialba could tap deeper than previously thought, and could explain the coincidental disappearance of Irazú’s crater lake in April 2010.

3D dynamic model empowering the knowledge of the decontamination mechanisms and controlling the complex remediation strategy of a contaminated industrial site

Knowledge of the geology and hydrogeology of the polluted site emblematize a key requirement for environmental remediation, through assembling and synthesizing findings from various sources of physical evidence. In an increasingly virtual era, digital and geo-referenced metadata may serve as tools for collecting, merging, matching, and understanding multi-source information. The main goal of this paper is to emphasize the significance of a 3D hydrogeochemical model to the portrayal and the understanding of contamination dynamics and decontamination mechanisms at a highly contaminated industrial site. Some remediation measures are active on-site, due to the evidence-based presence of chlorinated solvents in groundwater. These are attributable to a slow-release source of pollutants in the saturated zone associated with very low permeability sediments. Therefore, in this research, a new technique for the remediation of secondary sources of dense non-aqueous phase liquid (DNAPL) contamination was investigated for the first time on a full-scale application. The combination of groundwater circulation wells (IEG-GCW®) and a continuous electron donor production device was set up to boost in situ bioremediation (ISB). A multi-phase approach was followed handling and releasing data during various remediation stages, from site characterization via pilot testing to full-scale remediation, thus allowing users to monitor, analyze, and manipulate information in 3D space-time. Multi-source and multi-temporal scenarios reveal the impact of ongoing hydraulic dynamics and depict the decontamination mechanisms in response to the interventions implemented over time, by quantifying the overall performance of the adopted strategies in terms of removal of secondary sources of pollution still active at the site.

First conceptual hydrogeological model of two intermountain Andean basins based on isotopes and hydrochemistry

ABSTRACT Mountains arid environments are vulnerable under climate change scenarios. Variations in the recharge sources and the rising temperature can affect the water availability, threaten the socio-productive systems on local and regional scales. In this sense, two hydrological systems were studied in the Andes Range, Argentina, by hydrochemical and isotope techniques, with the purpose to understand the origin of water, the groundwater recharge, and to conceptualize the groundwater flow system. In the two sampling periods (winter and summer seasons) most of the waters were characterized by low mineralization and a HCO3-Ca type. The isotopic composition showed wide ranges of variation consistent with the altitudinal differences existing in the study systems. However, no significant isotope changes were observed between the samples collected in winter and summer periods. Therefore, little influence of liquid precipitation is inferred in the recharge source of both hydrological systems. This means that the western sector of the valley, where the ice bodies and permafrost are located, is the main recharge area for groundwater of both basins. This confirms the former hypothesis used for the hydrogeochemical conceptual model proposed, and highlights the importance of protecting these environments to ensure the provision of water in arid lands.

Hydrogeochemical and Hydrodynamic Assessment of Tirnavos Basin, Central Greece

A combined hydrogeochemical and hydrodynamic characterization for the assessment of key aspects related to groundwater resources management was performed in a highly productive agricultural basin of the Thessaly region in central Greece. A complementary suite of tools and methods—including graphical processing, hydrogeochemical modeling, multivariate statistics and environmental isotopes—have been applied to a comprehensive dataset of physicochemical analyses and water level measurements. Results revealed that the initial hydrogeochemistry of groundwater was progressively impacted by secondary phenomena (e.g., ion exchange and redox reactions) which were clearly delineated into distinct zones according to data processing. The progressive evolution of groundwater was further verified by the variation of the saturation indices of critical minerals. In addition, the combined use of water level measurements delineated the major pathways of groundwater flow. Interestingly, the additional joint assessment of environmental isotopes revealed a new pathway from E–NE (which had never before been validated), thus highlighting the importance of the joint tools/methods application in complex scientific tasks. The application of multivariate statistics identified the dominant processes that control hydrogeochemistry and fit well with identified hydrodynamic mechanisms. These included (as dominant factor) the salinization impact due to the combined use of irrigation water return and evaporitic mineral leaching, as well as the impact of the geogenic calcareous substrate (mainly karstic calcareous formations and dolostones). Secondary factors, acting as processes (e.g., redox and ion exchange), were identified and found to be in line with initial assessment, thus validating the overall characterization. Finally, the outcomes may prove to be valuable in the progression toward sustainable groundwater resources management. The results have provided spatial and temporal information for significant parameters, sources, and processes—which, as a methodological approach, could be adopted in similar cases of other catchments.