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In this study, pollution level, distribution, toxicity, molecular composition, probable sources as well as health risks of polycyclic aromatic hydrocarbons (PAHs) in urban and industrial soils of Kerman metropolis were investigated. Kerman is a fast-growing city and a fine example of an arid city in a developing country. For this purpose, concentrations of 16 individual PAHs in 30 samples taken from the city soils and its industrial zones were determined by gas chromatography/mass spectrometry. The ∑PAHs concentration in urban soil samples varied from 26.1 to 902.8 μg/kg, with the mean and median of 302.6 and 148.4 µg/kg, respectively. In comparison, ∑PAHs in industrial soils ranged from 26.8to 251.9 μg/kg, with the mean and median values of 65.9 and 42.9 µg/kg, respectively. Four-ring PAHs comprise the dominant compounds in urban soils, whereas, two- and three-ring PAHs proved to be the most abundant compounds in industrial soils. Source apportionment was conducted using ring classification, diagnostic ratios, PCA, and multilinear regression (MLR). Also, human health risk assessment was undertaken through employing US EPA standard statistical models. This survey revealed that PAH pollution in urban soils originates mainly from fossil fuel combustion and in industrial soils from petrogenic sources. On the whole, in the Kerman environment, the shares of petroleum combustion, natural gas combustion, and petrogenic sources were 45.32%, 34%, and 20.68% respectively. Based on this study, the ecological risk of PAHs was low-to-moderate, and incremental lifetime cancer risk for children and adults were 1.35 × 10−4 and 1.04 × 10−4 respectively, indicating rather high risks.

There is an urgent need to increase knowledge on the distribution of microplastics (MPs) in wetlands because these are sites of special ecological value and the ever-growing use of plastic can threaten such fragile ecosystems. This research assesses, for the first time, the occurrence of MPs in surface sediment of the Freidounkenar International Wetland (Northern Iran), a valuable habitat for migratory birds. A total of 1368 MP/kg were identified in the surface sediments of the wetland. The distribution of MPs in sediments per area was Ezbaran (36.5%), Western Sorkhrood (32.0%), Freidounkenar (20.1%) and Eastern Sorkhrood Ab-bandans (11.4%). The most contaminated sites were located close to agricultural fields, Damgahs (agroecosystems for birds), fishing areas and roads. Fibers and white-transparent and black-grey MPs constituted the dominant MPs in the surface sediment. The most abundant MPs were250 μm and these were made of nylon, polypropylene-low density polyethylene copolymer, polystyrene, low density polyethylene and polypropylene. The identification of MPs was carried out visually and supported with Scanning Electron Microscopy (SEM)-Energy Dispersive X-Ray (EDX) and micro-Raman techniques. There were weathering signs in large proportion of the MPs, according to SEM analysis, which evidences their formation from the degradation of other plastics. This is a comprehensive study on MPs in surface sediment of this sensitive internationally recognized ecosystem with high ecological value.

Composition of groundwater in the mining areas can be affected by oxidation of sulfide minerals and related reactions. Given that in the Miduk copper mine area, groundwater is the only available water resource for drinking and agriculture purposes. In the study area, assessment and measurement of groundwater physicochemical properties such as pH, TDS, EC, major cations, and major anions were performed. Physicochemical studies showed that the calcium and sulfate are the main cations and anions (Ca-SO4 water type), respectively. Groundwater in the area is mainly fresh and with a source of meteoric water infiltration. Three pollution indices, HEI, HPI, and Cd, were selected to evaluate the concentration level of ten of heavy metal(loid)s (Al, As, Cd, Cu, Fe, Mn, Mo, Ni, Pb, and Zn). To investigate the source and relations between heavy metal(loid)s, multivariate statistical analysis was executed for eleven variables. The results of pollution indices showed that samples in group 1 (mine pit area) have the highest level of pollution and considering that the samples of this group are in the closest distance to the mine pit and group 3 (springs) around the study area had the least level of pollution. Multivariate statistical analysis showed a negative correlation between heavy metal(loid)s (with the exception of arsenic and molybdenum) with the distance from the mine pit. This suggested the origin of these elements can be considered as anthropogenic source due to mining activities. The geogenic source of arsenic, molybdenum, and lead can be cited based on Spearman's correlation coefficient supported by PCA analysis.

The groundwater vulnerability assessment is known as a useful tool for predicting and prevention of groundwater pollution. This study targets the DRASTIC, evidential belief function (EBF), and logistic regression (LR) models to assess vulnerability in Kabul aquifers, Afghanistan Country. The growth of urban sprawl, groundwater overexploitation, and lack of suitable municipal sewage systems as anthropogenic sources have been the main potential to increase groundwater contaminants such as nitrate in the study area. The vulnerability map has been developed based on various effective factors including altitude, slope (percentage rise), aspect, curvature, land-use type, drainage density, distance from river, annual mean precipitation, net recharge, geology/lithology units, the impact of the vadose zone, aquifer media, depth to water (unsaturated zone), saturated zone, drawdown, and hydraulic conductivity. To identify groundwater pollution, the spatial variation of nitrate concentration data in 2018 was considered indication of groundwater pollution. Based on descriptive statistics, the value of 2.65 mg/l (the median of the pixel values of nitrate map) was selected as a threshold to differentiate the occurrence and non-occurrence of pollution. The groundwater quality data were selected and randomly divided into two datasets for training and validation, including 70% and 30%, respectively. The success-rate and prediction-rate curves were computed based on the receiver operating characteristic (ROC) curve and the area under the curve (AUC) to estimate the efficiency of models. The ROC-AUC of success rates for EBF, LR, and DRASTIC models were estimated to be 67%, 66%, and 52%, respectively. Moreover, the ROC-AUC of the prediction rates of the EBF, LR, and DRASTIC models were obtained 61%, 63%, and 55%, respectively. Based on correlation between mean nitrate concentration and the mean vulnerability indexes in each model, the EBF model is the most compatible with the current developed vulnerability zones as the role of mankind in changing the environment in real conditions in comparison to LR and DRASTIC models.

This review focuses on investigations of groundwater flow and solute transport in karst aquifers through laboratory scale models (LSMs). In particular, LSMs have been used to generate new data under different hydraulic and contaminant transport conditions, testing of new approaches for site characterization, and providing new insights into flow and transport processes through complex karst aquifers. Due to the increasing need for LSMs to investigate a wide range of issues, associated with flow and solute migration karst aquifers this review attempts to classify, and introduce a framework for constructing a karst aquifer physical model that is more representative of field conditions. The LSMs are categorized into four groups: sand box, rock block, pipe/fracture network, and pipe-matrix coupling. These groups are compared and their advantages and disadvantages highlighted. The capabilities of such models have been extensively improved by new developments in experimental methods and measurement devices. Newer technologies such as 3D printing, computed tomography scanning, X-rays, nuclear magnetic resonance, novel geophysical techniques, and use of nanomaterials allow for greater flexibilities in conducting experiments. In order for LSMs to be representative of karst aquifers, a few requirements are introduced: (1) the ability to simulate heterogeneous distributions of karst hydraulic parameters, (2) establish Darcian and non-Darcian flow regimes and exchange between the matrix and conduits, (3) placement of adequate sampling points and intervals, and (4) achieving some degree of geometric, kinematic, and dynamic similitude to represent field conditions.

Groundwater depletion has appeared as a main socio-ecological challenge in the arid and semi-arid conditions such as Iran during the last decades. This study attempts to evaluate long-term spatiotemporal variations of water table in the Bieza alluvial aquifer in southern Iran (from 1973 to 2018). A hydrogeological conceptual model was developed to elucidate the spatiotemporal groundwater depletion, factors influencing the irregular decline of the water table and deterioration of groundwater quality in the study area. The conceptual model was developed based on the physical structures (e.g., well logs and geological evidence) as well as hydrological processes taken place during the studied period (e.g., spatiotemporal variation of water table). Although, the aquifer is known as an unconfined aquifer, the results revealed it partly functioned as a confined aquifer due to the complex and heterogeneous sequence of a wide range of sizes and types of deposits ranging from clay to boulder sizes. Four different hydrogeological units, HU, are introduced to explain the spatial heterogeneity of the aquifer (i.e., the particle size of the deposits is gradually increased for HU1–HU4). Comparing hydrogeological characteristics in the different geological cross sections elucidated that the recharge zone is mainly comprised with the HU3 and HU4, while, HU1 and HU2 are widely distributed in the intermediate and discharge zones of the aquifer. There were three wetlands in the area (e.g., Banish, Negarestan and Malusjan wetlands) that were active before 2006. Results revealed that in consequence of the complete drying of the three wetlands, groundwater flow direction has been reversed and the groundwater divide line has been relocated to adjust the new condition of the groundwater system which is affected by the considerable depletion of groundwater level. Spatial heterogeneity of the aquifer caused unequal groundwater level decline from a few to more than 40 m in the discharge and recharge zones, respectively. Multi-regression analysis elucidated that the groundwater level in the Bieza aquifer has been reduced in response to decreasing recharge rate due to the experienced drought periods as well as over-exploitation of the aquifer. As a consequence, the quality of groundwater is broadly lessened. Assuming the zero water-level change method, annual safe yield (value of 23.7 Mm3) is determined as a sustainable strategy for groundwater exploitation in the study area.

Karst aquifers are geologic media that consist of enlarged solution conduits. The geometry of such conduits is very difficult to delineate and its hydraulic parameters such as hydraulic conductivity (K) and specific storage (Ss) are difficult to estimate. Hydraulic Tomography (HT) shown to successfully map the hydraulic heterogeneity of porous and fractured rock aquifers may also be effective in karst aquifers. In this study, we utilize two synthetic karst aquifers with the Branchwork and Network Conduit Patterns (BCP and NCP) to explore the ability of HT to map conduit patterns and their hydraulic parameters. Prior to the HT analysis, forward models are built to study groundwater flow through synthetic karst aquifers to generate data and to gain insights into flow patterns. Forward modeling results reveal that: (1) flow rates at the outlet of the BCP model is higher than the NCP model even when the same water injection rates are applied at the wells; (2) the location of the injection well has a significant impact on the flow rate at the outlet; and (3) flow lines mainly follow the conduit pattern. These results suggest that the accurate mapping of karst networks is critical. Next, the HT analysis of these data is conducted using a set of six models (BCP and NCP) to map the heterogeneity of different conduit systems under steady state and transient flow conditions. Inverse modeling results reveal that the estimated K maps become more reliable as the number of injection tests and the corresponding monitoring data are increased in the HT analysis. Moreover, the results of the BCP model is closer to the original conduit pattern in comparison to the NCP model. A comparative study of three inverse models with different number of observation wells and assuming the availability of geological data has shown that a more reliable pattern of the conduits can be mapped by adding geological information even when a small number of observation wells are available. Overall, our results confirm the feasibility of HT in detecting major conduits as well as being able to differentiate between the BCP and NCP network types.

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.jhydrol.2018.10.050 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/

Pollution of the potentially toxic elements (PTEs) is a major concern in the metal ore-mining environment. Active polymetallic industries and mines cause great continuous devastation of both terrestrial and aquatic environments on a local and regional scale. This study investigated the pollution of surface water and groundwater in the area containing six large-scale iron ore mines, which have been in operation for more than a few decades. In order to assess the PTEs pollution, the spatial and temporal distributions of 13 different PTEs (Al, As, Co, Li, Mn, Mo, Ni, Pb, Rb, Se, Si, Sr, and Zn) were measured in 42 water samples collected from the multi-aquifer system including three distinct aquifers (upper alluvial aquifer (UAA), lower alluvial aquifer (LAA), and hard-rock aquifer (HRA)) of the Gohar-Zamin mining area in Iran. The highest concentrations of total dissolved solids (TDS = 164,000 mg/l) and PTEs were measured in HRA. Three trends were identified between the PTE concentration and increasing of TDS based on Spearman correlation analysis: (1) an increasing trend for Al, Co, Li, Mn, Rb, Se, Sr, and Ni; there were strong positive correlations in HRA between TDS and Mn (0.83), Al (0.65), Co (0.74), Li (0.90), Ni (0.83), Rb (0.91), Se (0.82), and Sr (0.84), suggesting a common origin for these elements; (2) no obvious trend for As and Mo, no correlation was founded between As and Mo with other PTEs and TDS, indicating a natural geogenic origin and mutual dependencies of these elements; and (3) a decreasing trend for Si, Zn, and Pb; TDS had a significantly negative correlation with the PTEs and attributing to different chemical properties of infiltrated groundwater. In the principal component analysis (PCA), the first PC that covers 85.09% of the total observed variance is mainly attributed the groundwater salinization. This component is composed of Al, Co, Li, Mn, Rb, Se, Sr, and Ni. The second PC contains elements As and Mo. This PC explain 14.4% of total variance and may be referred to natural origin of PTEs. Si, Zn, and Pb are in the third principal component and cover 9.64% of the variance of the data. Third PC have been attributed to lithogenic and/or primary water chemistry factors. The PTE pollution were evaluated based on heavy metal evaluation index (HEI), heavy metal pollution index (HPI), and degree of contamination (Cd). The results indicated that all of the groundwater samples collected from HRA had HEI, HPI, and Cd values greater than 21, 264, and 14 (highly pollution limits of indices), respectively, and were classified as highly polluted groundwater. HPI values within the UAA, LAA, and salt playa (SP) were lower than the critical level of 100, suggesting a threshold for the drinking water pollution. Moreover, HEI and Cd with values of less than 10 and 7 suggested low-level pollution in UAA, LAA, and SP. However, the contaminated level of PTEs exceeded the WHO standard for drinking water in HRA only. Since groundwater in HRA is a brine with the high values of PTEs, pumping of this water out to the surrounding natural environment may cause harmful impacts on the environment and perhaps living species in Bahram-e-Goor protected area.

Since traditional graphical methods are weak to provide a reliable result for assessing the hydrothermal circulation depth and mixing processes, principal component analysis (PCA) and inverse geochemical modeling are used to evaluate the relation between the chemical and physical parameters affecting the spatiotemporal composition of Semnan thermal springs. These waters belong to the Na-Cl water type, with the total dissolved solids of about 9847-mg/L and mean temperature of 31.5 °C. PCA extracted three components that explain 87.89% of the sample variances from a matrix of 35 monthly samples, taken from five thermal springs and analyzed for ten variables. Based on the results of the PCA, the water-rock interactions including evaporate dissolution, cation exchange, and dedolomitization control the chemical composition of thermal waters, and dilution by aquifer recharge creates the seasonal variation in water quality. Geochemical mass-balance modeling simulates the microbial SO4 reduction and silicate weathering and allows quantification of the evolution of the hydrothermal system. Based on the isotopic data, the meteoric water is the major origin of thermal waters without oxygen-18 shift. In addition, Chenaran anticline is the most probable catchment area of thermal springs based on the water balance calculation and geological setting. These results are quite convenient with the previous hydrological conceptual model obtained from the geochemical data. The present study highlights the importance of applying both PCA and inverse modeling simultaneously with conventional methods for assessing the origin of thermal water and deep understanding of predominant processes controlling the hydrogeochemical evolution in a carbonate aquifer includes low enthalpy thermal waters. This methodology has the potential for application in other regions with similar condition.

In order to determine the characteristics of the flow system in a karstic aquifer, an extensive hydrogeological study includes dye tracing test was conducted. The aquifer suited left abutment of Seymareh Dam, in Ravandi Anticline and discharges by more than 50 springs in the southern flank. Flow system in the aquifer is mainly controlled by the reservoir of Seymareh Dam. Time variations of the spring discharge and water table in the observation wells were highly correlated with the reservoir water level. The average groundwater velocity ranges from 0.2 to more than 14 m/h based on the dye tracing test. The probable flow paths were differentiated in two groups including the flow paths in the northern and southern flanks of Ravandi Anticline. Types of groundwater flow in the proposed flow paths are determined as diffuse or conduit flow type considering groundwater velocity and shape of the breakthrough curves . An index is proposed for differentiation of diffuse and conduit flow system based on relationship of groundwater velocity and hydraulic gradient. Dominant geometry of the flow routs (e.g., conduit diameter and fracture aperture) is estimated for the groundwater flow paths toward the springs. Based on velocity variations and variance coefficient of the water table and discharge of springs on map view a major karst conduit was probably developed in the aquifer. This research emphasizes applying of an extensive hydrogeological study for characterization of flow system in the karst aquifer .

Tracer breakthrough curves provide valuable information about the traced media, especially in inherently heterogeneous karst aquifers. In order to study the effect of variations in hydraulic gradient and conduit systems on breakthrough curves, a bench scale karst model was constructed. The bench scale karst model contains both matrix and a conduit. Eight tracing tests were conducted under a wide range of hydraulic gradients from 1 to greater than 5 for branchwork and network-conduit systems. Sampling points at varying distances from the injection point were utilized. Results demonstrate that mean tracer velocities, tracer mass recovery and linear rising slope of the breakthrough curves were directly controlled by hydraulic gradient. As hydraulic gradient increased, both one half the time for peak concentration and one fifth the time for peak concentration decreased. The results demonstrate the variations in one half the time for peak concentration and one fifth the time for peak concentration of the descending limb for different sampling points under differing hydraulic gradients are mainly controlled by the interactions of advection with dispersion. The results are discussed from three perspectives: different conduit systems, different hydraulic-gradient conditions, and different sampling points. The research confirmed the undeniable role of hydrogeological setting (i.e., hydraulic gradient and conduit system) on the shape of the breakthrough curve. The extracted parameters (mobile-fluid velocity, tracer-mass recovery, linear rising limb, one half the time for peak concentration, and one fifth the time for peak concentration) allow for differentiating hydrogeological settings and enhance interpretations the tracing tests in karst aquifers.

Breakthrough curves (BTCs) are known as adequate evidence to characterize karst aquifers which mainly specified by dual flow systems (matrix and conduit) as well as some degree of connection between dual media. Conduit Flow Process version 2 (CFPv2) is a discrete conduit continuum model applying which it is possible to simulate such characteristics. In this research, first CFPv2 was employed to evaluate the effect of several factors including hydraulic conductivity, exchange flow, tracing distance, hydraulic gradient, and conduit diameter and roughness on BTCs in a synthetic karst aquifer. Then, 253 BTCs from 24 dye tracing tests, conducted in karstic aquifers of Iran, were analyzed to evaluate the effect of hydraulic gradient and tracing distance on the BTCs with taking into account the effect of medium type (matrix or conduit) and karst development. These tests were conducted under either natural or elevated man-made hydraulic gradient conditions. The results revealed that peak concentration decreased with enlarging conduit diameter because of considerable flow rate. Likewise, it decreases over longer distances specifically in the elevated man-made hydraulic conditions. However, with increasing hydraulic gradient, peak concentration and its timing have upward and downward trends, respectively. When BTCs start to demonstrate tailing and become flattened, it could be an indication of low matrix hydraulic conductivity or lower hydraulic gradient in conduit as a result of less exchange flow from the matrix into conduits. Based on this study a new intermixture of flow and solute transport parameters was engineered to classify karst development. High peak concentration, short peak time, high velocity particularly over long distances and under the natural hydraulic gradient conditions and feasible conduit flow regime whether laminar or turbulent suggested as indication of well-developed karstic system.

The safe groundwater yield plays a major role in the appropriate management of groundwater systems, particularly in (semi-)arid areas like Iran. This study incorporates both the water balance equation and the water table fluctuation to estimate the annual safe yield of the unconfined aquifer in the eastern part of the Kaftar Lake, an Iranian semiarid region. Firstly, the water balance year 2002–03, owing same water table elevation at the beginning and year-end, was chosen from the monthly representative groundwater hydrograph of the aquifer to be taken into account as a basic water year for determining the safe yield. Then the ratio of the total groundwater pumping to the annual groundwater recharge in the selected water balance year together with the quantity of total recharge occurred in the wet period (October to May) of the year of interest were applied to evaluate the annual safe yield at the initiation of the dry period (June to September) of the year of interest. Knowing the annual safe groundwater withdrawal rate at the initiation of each dry period could be helpful to decision makers in managing groundwater resources conservation. Analysis results indicate that to develop a safe management strategy in the aquifer; the ratio of the annual groundwater withdrawal to the annually recharged volume should not exceed 0.69. In the water year 2003–04 where the ratio is equal to 0.52, the water table raised up (about 0.48 m) while the groundwater level significantly declined (about 1.54 m) over the water year 2007–08 where the ratio of the annual groundwater withdrawal to the annually recharged volume (i.e., 2.76) is larger than 0.69.

Pumping test is a well-known method for determining hydraulic characteristics of an aquifer. Diagnostic plot technique is applied to facilitate the identification of an appropriate groundwater flow conceptual model, and for interpretation of the pumping test data. The diagnostic plots of six observation wells around a pumping well at the Salman Farsi Dam Site showed simultaneous presence of integer and non-integer flow dimensions of pumping test around the pumping well. Type of flow pattern on two observation wells shows two-dimensional flow and that on four observation wells follows one-and-a-half-dimensional flow. The results revealed that flow pattern around the pumping well in the karst study area changes from two-dimensional within a distance of less than about 100 m from the pumping well to one-and-a-half dimensional at a distance from the pumping well larger than about 100 m. The change of flow dimensions with increasing distance from the pumping well is due to radial flow around the observation wells within a distance of less than about 100 m from the pumping well, and bilinear flow around the observation wells with a distance of more than about 100 m from the pumping well. Radial and bilinear flows are related to cone of depression and preferential flow paths, respectively.

Karst systems show high spatial variability of hydraulic parameters over small distances and this makes their modeling a difficult task with several uncertainties. Interconnections of fractures have a major role on the transport of groundwater, but many of the stochastic methods in use do not have the capability to reproduce these complex structures. A methodology is presented for the quantification of tortuosity using the single normal equation simulation (SNESIM) algorithm and a groundwater flow model. A training image was produced based on the statistical parameters of fractures and then used in the simulation process. The SNESIM algorithm was used to generate 75 realizations of the four classes of fractures in a karst aquifer in Iran. The results from six dye tracing tests were used to assign hydraulic conductivity values to each class of fractures. In the next step, the MODFLOW-CFP and MODPATH codes were consecutively implemented to compute the groundwater flow paths. The 9,000 flow paths obtained from the MODPATH code were further analyzed to calculate the tortuosity factor. Finally, the hydraulic conductivity values calculated from the dye tracing experiments were refined using the actual flow paths of groundwater. The key outcomes of this research are: (1) a methodology for the quantification of tortuosity; (2) hydraulic conductivities, that are incorrectly estimated (biased low) with empirical equations that assume Darcian (laminar) flow with parallel rather than tortuous streamlines; and (3) an understanding of the scale-dependence and non-normal distributions of tortuosity.

Groundwater seepage into open pit mines must be controlled carefully. Slope instability, dewatering of blast holes, and mining operations below the groundwater table are important issues caused by groundwater seepage into the Gol-Gohar open pit mine, Iran. There are several methods to overcome these problems, such as construction of cut-off walls, ditches and sumps, horizontal drains, and pumping wells. Drilling of a new pumping well has several difficulties in which the determination of its location is a major issue. In this study, a stochastic simulation approach called simulated annealing was used to determine the best possible locations for new pumping wells. Three major groundwater variables, including the groundwater level, electrical conductivity, and transmissivity were selected for the geostatistical study. The results of simulations showed reliable correlation (Pearson) between the variables. Comparison of the variograms at different depths of the Gol-Gohar pit mine revealed that the effect of faults intensified with increasing depth. The best potential locations for drilling of new pumping wells were identified by the use of multi-criteria decision analysis performed on the simulation results. This method can be used in other regions with similar hydrogeological settings.

Dasht-e-Arjan Lake is located in the southern Zagros mountain ranges of Iran. It is a tectonic karst polje, fed by a single spring plus local surface runoff, and drained by a single ponor. The fate of sinking water from the ponor had not been determined before this study. Previous investigations suggested two alternatives: (1) underground flow ~ 24 km southwest to Parishan Lake and/or springs in the Kazeron area, and (2) underground flow ~ 20 km southeast to springs at Domeasb Gorge. To clarify this question, an integrated hydrogeological study including a dye tracer test was undertaken. Comparison of the discharge into the Arjan ponor and the discharge of the Domeasb springs shows a reliable correlation. Further, annual water balance analysis reveals that the discharge at the Domeasb springs is too great for its topographic catchment, requiring a major additional source. The dye tracer test, using 5 kg of uranine, was detected only at the Domeasb springs. Flow through time after the dye injection was 210 h. The tracer breakthrough curves are very simple and sharp, with a clear peak concentration of 7 ppb. The total tracer mass recovery and groundwater flow velocity were estimated to be 58% and 105 m h−1, respectively. The results indicate a simple and direct limestone karst hydraulic connection along the geologic strike between Dasht-e-Arjan Lake and the Domeasb springs. The results clearly suggest the possibility of designing a dam around the ponor to protect drying up the lake during drought periods.

Pumping and tracer tests are commonly used to measure aquifer parameters such as hydraulic conductivity. Hydraulic conductivity is, however, difficult to characterize; especially in heterogeneous karst terrain. In this research, results of pumping and tracer tests are combined to determine hydraulic conductivities of the karst terrain at the Salman Farsi Dam Site. Pumping test data were analyzed by dual-porosity analytical models. The tracer tests were used to determine seepage velocities based on the assump- tion of Darcy's law, with calculated Reynolds numbers consistent with laminar flow. Geometric means of the hydraulic conductivities calculated from tracer tests were consistently higher than results derived from pumping tests. Movement of injected dye in a natural groundwater flow system is strongly controlled by preferential flow paths; therefore the estimated hydraulic conductivity is mainly affected by major dissolution openings. However, estimated hydraulic conductivity based on the pumping-test data is representative of the average hydraulic conductivity. In addition, Lugeon (or packer) tests were used to delineate the distribution of hydraulic conductivity within three boreholes.

The hydraulic properties of hard rock and karst formations are typically highly heterogeneous. Quantification of the groundwater flow in these media is a complicated process with numerous uncertainties. There are several approaches to overcome this problem. Stochastic simulation is one of the promising approaches for quantification of the intrinsic uncertainty in karst formations. In the present research, the sequential indicator simulation was used as a tool for the simulation of the hydrogeological and geotechnical properties of a karstic formation at the Karun IV dam site, Iran. In this regard, two variables of interest, RQD and Lugeon, were considered as criteria for the development of karst. One hundred realizations of these variables were produced and then combined to obtain an expected value and the probability of exceeding a threshold value for each cell. The results showed a weak negative correlation between the expected values of RQD and Lugeon. Also, it was determined that the geologic structures (i.e., faults) and lithology play an important role in the development of karst in the study area. A decrease in the simulated values of Lugeon was observed with increasing depth of karstic layers and the distance from faults. The results of this study helped to overcome the intrinsic uncertainty in karst media and to present a conceptual model of karst development. This approach can be applied in other dams for the evaluation of risk and uncertainty of hydrogeological parameters.

Data on hydrogeological and lithological characteristics of geological formations are obtainable at every dam site. In practice, it is essential to examine the data using an engineering-based approach such as geostatistical methods. Specifically, it is important to recognize the principal factors that significantly control hydrogeological characteristics, such as Rock Quality Designation (RQD) and average hydraulic conductivity of the rock mass (Lugeon value). In this study, the statistical properties of these parameters are examined as functions of depth, lithology and the spatial distribution of the data points. The results of this study show that the spatial distribution and lithology are the main controls. Using this approach one can determine the most permeable rock formations, potential karst locations and the areas that may warrant more extensive study. The results of stochastic simulation could be extensively enhanced by considering the spatial distribution of hydrogeological characteristics.

Semnan thermal springs with high TDS and moderate temperature are located northwest of Semnan, the northern part of Iran. The spatial and temporal variations of physicochemical characteristics of the thermal and cold springs were investigated for the recognition of origin and dominant hydrogeochemical processes. Results show that the thermal springs have the same origin, but due to different ascending flow paths and different conductive cooling mechanism, their temperatures vary. The chemical composition of thermal waters is controlled by dolomite, halite and sulfate minerals dissolution and calcite precipitation and bacterial sulfate reduction. The concentration of major and trace elements in the thermal springs does not change in wet and dry seasons notably because they are derived from old groundwater with deep circulation and high temperature. Seasonal change in the concentration of some trace elements is due to the seasonal variation of pH, Eh, temperature and dilution by shallow waters. Decreasing SO4 and carbonate saturation index and increasing Na/Cl ratios and Ca content in the dry season show dilution effect caused by the previous heavy rainfall events. The temperature of the heating reservoir based on K–Mg, chalcedony, quartz and chemical equilibrium approach was approximately estimated in the range of 60–80 °C. Hydrogeologically, a conceptual model was suggested for the thermal springs. The general groundwater flow direction is probably from the dolomite Lar Formation in Chenaran anticline toward the adjacent syncline in a confined condition, and then a thrust fault acts as a conduit and redirects the thermal water to the emerging springs at the surface.

Estimation of the groundwater recharge is extremely important for the groundwater management in semiarid regions. A simple water balance equation is used for quantifying the total annual groundwater recharge during 8 water years (from 2002 to 2010) in the Burazjan aquifer, south Iran. Total annual groundwater recharge was estimated using two approaches: (1) sum of the known inflow components to the aquifer system, and (2) sum of outflow components from the aquifer and annual change in the aquifer storage. Comparison of the results from two approaches shows a considerable difference with an average of 91.30 million m 3 /year for the annual recharge. This difference could be caused by (i) error in quantifying the inflow components and/or (ii) missing an unknown inflow component. Sensitivity analysis reveals that the difference in the estimated annual recharge is more than the estimated 20% error in quantifying the components of the water balance equation. However, considering the geological setting and previous investigations, a missed inflow component related to Burazjan Fault is proposed. Contribution of this inflow component in annual groundwater recharge ranged from 33.25 to 132.90 with an average of 91.30 million m 3 /year.

Earth science phenomena are primarily spatially dependent with variations occurring on varying scales. Geostatistics is a well-known approach for the assessment of spatial models of regionalized variables, such as porosity. In this study, we used the results of 953 Lugeon tests (402 tests in exploratory wells and 550 tests in grouting wells) to assess effective porosity and karst development at the Tangab Dam site, Iran. Lugeon values were first normalized, following which the variogram method (i.e., range, sill, and nugget effect) was used to identify the spatial variability of Lugeon values. A high correlation range of 200 m was obtained along the grout curtain galleries, while the range was about 40 m in the vertical direction. The simple kriging method with Gaussian variograms was determined to be the best method for estimating the Lugeon values in the study area using cross validation-criteria (e.g., RMSE = 0.835 and ρ = 0.914). Spatial variation of Lugeon values was mapped using a simulated annealing approach. The analysis revealed: (1) a higher potential for karst development on the left abutment of the Tangab Dam site, (2) the average of simulated Lugeon values decreased from values of about 180 close to the ground surface at 1,440 m a.s.l. to lower values of about 50 at 1,260 m a.s.l., and (3) high Lugeon values in the abutments of the dam site approximately followed the 15° bedrock dip, which confirms the potential development of karst features in the Asmari limestone. A schematic model for development of karst at the Tangab Dam site is proposed based on hydrogeological data and results of simulated Lugeon values around the dam site.

This study presents the effect of annual precipitation amount (P) on the characteristics of spring hydrograph such as recession coefficient (α), volume of dynamic flow (V d), base flow (V b), and quick flow (V q) in two karst springs, Pireghar and Dime from the Zagros Region, Iran. Length of the studied period in Pireghar and Dime Springs is 10 and 11 water years, respectively. Hydrograph characteristics such as α’s, V d, V b, and V q were computed according to the annual spring hydrograph for each water year. The results reveal negative correlation between P and α 1 and positive correlation between P and V d and V q in Pireghar Spring. There is no increasing trend between P and V d in Dime Spring. Results show that analysis of several annual hydrograph provides detailed knowledge about development of karst. The behavior of the karst system in Pireghar Spring reflects higher degree of karst development in comparison to Dime Spring based on the values of quick flow, infiltration rate, and time variation of the spring discharge. A schematic conceptual model was proposed for the studied springs responsible to water storage and movement. As a result, the hydrodynamic characteristics of spring hydrograph are controlled by type of recharge, type of storage, and mechanism of water movement in the karst aquifer.

Jowshan geothermal system comprises 6 thermal springs with outlet temperatures ranging from 39.3 to 46.6°C. The thermal water of these springs is presently used for swimming and as a treatment for rheumatism, sinusitis and skin diseases. The pH value of these springs is slightly acidic to neutral and the electrical conductivities about 1500 μS/Cm. The presence of many faults in the area, the alignment of all springs along the Sirch Fault and the similar chemical and isotopic composition of all springs in combination with the hydrogeological setting and geochemistry of water samples indicate that these springs are associated with deep circulation of meteoric water. According to this heating mechanism, meteoric waters infiltrate through fault openings to depth and after heating by geothermal gradient rise to the ground surface due to the hydraulic and buoyancy forces, a mechanism which is common in the southern parts of Iran. The use of various chemical geothermometers and mineral equilibrium states suggests a range of temperature about 50–90°C for the reservoir of Jowshan geothermal system.

The geochemical processes controlling chemical composition of groundwater are studied using hydrochemical and isotopic data in Abdan-Dayer coastal plain, south of Iran. The salinity of groundwater in the coastal plain ranges from 1,000, a fresh end-member, to more than 50,000 μS cm−1, a saline end-member. Groundwater salinity increases from the recharge area toward areas with a shallow water table close to the Persian Gulf coast due to direct evaporation and sea water intrusion as confirmed by mixing binary diagrams, stable isotope content, and Br−/Cl− ratio. Groundwater flow pattern in the study area has been modified due to over-pumping of groundwater in recent years which resulted in further saline water migration toward fresh water and their mixing. The maximum mixing ratio is estimated about 15% in different parts of the study area according to chloride concentration.

This study addresses the hydrogeochemistry of thermal springs that emerge from the Asmari limestone in a gorge at Changal Anticline in the vicinity of the Salman-Farsi dam. The Changal thermal springs vary in temperature between 28 and 40 °C. Chemical and isotopic compositions of the thermal waters suggest two distinct hydrogeological systems: a deep, moderate-temperature (∼40 °C) geothermal system recharged by deeply circulating meteoric waters, and a shallow cold aquifer system related to local groundwater. The source geothermal fluid temperature was calculated using different geothermometers and mineral saturation indexes. Based on chemical and isotopic data, it is hypothesized that: (1) mixing occurs between the ascending geothermal water and shallow cold water; (2) the resulting thermal waters reaching surface are a mixture of 80% local, shallow meteoric water and 20% geothermal water; and (3) the circulation depth of the meteoric water is about 1500 m. The thermal reservoir temperature is estimated to be between 70 and 80 °C according to calculations using different geothermometers and computation of saturation indices for different solid phases.

This paper describes the use of multivariate statistical analysis to trace hydrochemical evolution in a limestone terrain at Zagros region, Iran. The study area includes a deep confined aquifer, overlaid by an unconfined aquifer. The method involves the use of principal component analysis (PCA) to assess and evaluate the hydrochemical evolution based on chemical and isotope variables of 12 piezometers drilled in both the unconfined and confined aquifers. First PCA on all variables shows that water–rock interaction under different conditions with respect to the atmospheric CO2 is the main process responsible for chemical constituents. As a result, combinations of several ratios such as Ca/TDS, SO4/TDS and Mg/TDS with physico-chemical and isotope variables reveal different hydrochemical evolution trend in the aquifers. Second PCA on the selective samples and variables reveals that displacement of the unconfined samples from dry to wet season follows a refreshing trend towards river samples that is characterized by reducing electrical conductivity and increasing sulphate and tritium contents. However, the refreshing trend cannot be traced in the confined aquifer samples suggesting no recharge from river to the confined aquifer. Third PCA reveals that, chemical composition of water samples in the unconfined aquifer tends to have considerable difference from each other in the end of recharge period. In contrast, the confined aquifer samples have a tendency to show similar chemical composition during recharge period in comparison to end of dry period. This difference is caused by different mechanism of recharge in the unconfined aquifer (through the whole aquifer surface) and the confined aquifer (through the limited recharge area).

A geostatistical approach was used to study temporal structures in a time series of discharge and electrical conductivity (EC) in 15 karst springs from the Zagros mountain range, Iran. Two types of temporal behaviors, a periodic structure and nugget effect, plus one or two temporal structures, were identified and interpreted. These correspond to characteristics of karst systems, such as the catchment area, percent of conduit flow, and general degree of karst development. Springs were grouped into three categories based on their ranges (e.g., residence time) obtained by variogram analysis. The first group of springs include those that present the same temporal behaviour in variograms of discharge and EC. These springs are characterized by generally constant EC with increasing discharge suggesting the existence of a large underground reservoir. The second group of springs are those with varying temporal periodic behavior in variograms of discharge and EC. Positive correlation between discharge and EC values is the main characteristic of these springs and is interpreted to result from a piston-flow system in poorly developed karst aquifers. The third group of springs includes those that exhibit different temporal behaviors when compared with the periodic and non-periodic variograms. This group exhibits a negative correlation in scatterplots of discharge versus EC values suggesting a well-developed solution-conduit system that facilitates rapid response of the karst system to precipitation events. This study's results document the role of variogram analysis in delineating temporal structures of spring behaviors by means of time series of discharge and EC. Variogram analysis can be considered as a valuable tool for hydrogeological investigations in karstic terranes. DOI: 10.4311/jcks2009es0079

The Asmari limestone formation is the major aquifer system at the Khersan 3 Dam site, Zagros, Iran. Characterization of the aquifer system and study of karst development are essential for forecasting leakage potential and to plan remediation works. The aquifer functioning and karst structure were evaluated by geology, well hydrodynamics and natural tracing studies, showing one unconfined and three artesian sub-aquifers, the last being characterized by rapid flow, with contributing old recharge water, and a recharge at higher elevation than the unconfined sub-aquifer. The anticline structure outcrops the artesian sub-aquifers downstream of the site. The confining layers disappear and the aquifer system discharges as a mix of all groundwater. Artesian groundwater is estimated to contribute about 80% (dry season) and 50% (wet season) of flow in the mixing zone. Very few karst features are observed in cores and galleries at the site, despite some karst landforms in the reservoir area. However the aqu...

The paper discusses the investigations into the Khersan 3 Dam site in the Zagros Zone, southern Iran, where the Rig, Shorom and Laki Anticlines meet. The Asmari Limestone is the main aquifer system in the area of the dam site and its reservoir. Marly bands within the Lower Asmari Unit create three confined sub-aquifers under artesian pressure overlain by one unconfined sub-aquifer. The impounded water will be in direct contact with the Asmari Limestone hence leakage may occur through existing karst features. As the recharge zone of the artesian sub-aquifers is higher than the normal water level in the reservoir, no direct leakage through the artesian sub-aquifers is anticipated. However, when the water head in the unconfined sub-aquifer rises with the construction of the dam, leakage may occur and further karstification develop.

The excellent topographic condition of the limestone canyons for dam construction may be rejected if they are karstified. Karst features cause the reservoir not to be impermeable enough to permit the water to fill it and leakage occurs and often increases with time. Moreover, karst features may involve the stability of the dam itself. A few operated dam sites at the Zagros Zone encountered a leakage problem. Furthermore, more than 30 dams are presently under study for construction in the Zagros Zone. Karst conditions and leakage potential were investigated at an under-study site (Khersan 3 Dam) for assessing the general methodology for the study of leakage potentials. Conventional methods for studying karst features, geological mapping, geomorphology and extensive borings were applied before the dam was constructed. These methods are not efficient enough to precisely reveal the karst structure, especially hidden and paleokarst, nor the hydrological behaviour of the karst structure in different settings of groundwater flow. Based on the present case study and previous applied approaches by other authors, this paper introduces a methodology by means of karst structure and functioning approaches at local and regional scales that cover the conventional methods and overcome their shortages. The proposed methodology should be applied before construction of a dam and should include three steps (a) recognition of geological and hydrogeological settings, (b) delineation and functioning of the karst system related to the future reservoir, and (c) assessment of the leakage potentials. Following this methodology, the most probable leakage zone(s) and path(s) at the dam site can be highlighted.

A dye-tracing test is employed to study the karst development and flow regime at an artesian limestone sub-aquifer, the Khersan3 Dam site, Zagros Zone, Iran. Tracer breakthrough curves showed an early dominant peak followed by a pronounced tailing effect. The peak concentration was a response to induced pressure during dye injection. The results suggest that the dye was pushed into the small pores and fissures around the injection point during dye injection. Hence, the dye moved out as a result of matrix and fissure diffusive processes and created a long pronounced tailing. The maximum flow velocity in the upper artesian sub-aquifer ranged from 0.97 to 2.9 m/h. However, the mean tracer velocity ranged from 0.19 to 0.51 m/h based on the mean residence tracer time; consequently, the flow regime in the artesian sub-aquifer was determined to be mainly diffusive. The results reveal (1) a low hydraulic gradient from upstream of the dam axis to downstream; consequently, there is no considerable flow; (2) poor karst development and diffuse flow at the tracing test area; (3) a discharge zone at a location downstream of the dam axis which is the main terminal of general flow direction at the dam site.

Chemical analyses of water samples from 19 hot and cold springs are used to characterize Takab geothermal field, west of Iran. The springs are divided into two main groups based on temperature, host rock, total dissolved solids (TDS), and major and minor elements. TDS, electrical conductivity (EC), Cl−, and SO4 2− concentrations of hot springs are all higher than in cold springs. Higher TDS in hot springs probably reflect longer circulation and residence time. The high Si, B, and Sr contents in thermal waters are probably the result of extended water–rock interaction and reflect flow paths and residence time. Binary, ternary, and Giggenbach diagrams were used to understand the deeper mixing conditions and locations of springs in the model system. It is believed that the springs are heated either by mixing of deep geothermal fluid with cold groundwater or low conductive heat flow. Mixing ratios are evaluated using Cl, Na, and B concentrations and a mass balance approach. Calculated quartz and chalcedony geothermometer give lower reservoir temperatures than cation geothermometers. The silica-enthalpy mixing model predicts a subsurface reservoir temperature between 62 and 90 °C. The δ18O and δD (δ2H) are used to trace and determine the origin and movement of water. Both hot and cold waters plot close to the local meteoric line, indicating local meteoric origin.

In this paper a geostatistical approach based on the variogram concept is used for decisions about the size of a grid network applicable to a groundwater model. One of the important properties of the variogram function is the range of influence, which is interpreted as a measure of similarity and correlation distance between spatial phenomena. Taking the concept of range into account, several available spatial variables of the under study aquifer were used to plot the variogram in different directions. The study area is an unconfined aquifer (Boushkan Plain in southwest Iran) with an average thickness of 50 m and area of 100 km2. The variables used for computing the variogram include aquifer thickness (D), groundwater pumping rate (Q) and electrical resistivity (R) of the aquifer material. The range of influence was estimated to be 2,000, 2,500, and 2,000 m for D, Q and R, respectively. Comparisons of statistical parameters of spatial variables over a grid size ranging from 1,000 to 5,000 m were done to confirm the proposed grid size according to variogram plots. The bounded area of each cell could be considered as homogenous media according to the spatial variation of the variables used. The optimum size of the grid network was selected according to the minimum of the variance and coefficient of variation over each cell size. Results suggest a 2,500 × 2,500 m grid size for the modeling process in the studied aquifer. The results emphasize the role of variogram function in selection of grid size for the groundwater model.