مجله هیدروژیولوژی
سال چهارم شماره 2 (زمستان 1398)

Natural CO2 leakage through water wells into four alluvial aquifers Hamadan, Razan, Komijan and Chardoli in Hamadan province, in addition to decreasing by about one unit of pH and significantly altering physicochemical parameters and soluble constituents in groundwater has led to trace metals enrichment in groundwater. To investigate the effect of CO2 leakage on mobility of trace elements, one hydrothermal spring and 19 water wells were sampled in September 2018. Trace elements, which have increased in gas-rich groundwaters, are classified into two groups based on correlation with Cl. The first group including As, Li, B, Sr, V, Rb and Cs, which are related to mixing of CO2-rich saline hydrothermal water with fresh groundwater. While origin of Al, Ba, Zn, Cr, Ni and Cu is in-situ weathering of aquifer materials. Se, Hg and Sn show no correlation with Cl and their concentration have been decreased in the gas recharged groundwaters. Carbon dioxide gas leakage into the groundwater of the study area does not appear to affect the mobility of these rare elements. The most important factors influencing on the impact of CO2 leakage on the aquifer quality that can attenuate the effects of CO2 leakage on trace elements mobility are high pH buffering capacity of the aquifer materials and CO2 degassing from the CO2-rich groundwaters near the ground surface and consequent precipitation of secondary minerals. Despite all these processes, the groundwater of the study area contains concentrations of several elements (Hg, As, B, Fe and Mn) above the WHO and national thresholds.

Water extraction from groundwater resources has been increasing in recent decades. Qaleh Tol plain is one of the critical plains in Iran, located in Khuzestan province, that is necessary to determine the groundwater potential in the plain to meet the water needs of the region. Also, in spite of the regional decline in groundwater level in the plain in recent years, the drop of water level in some observation wells in special areas, is lower than other plain areas. Accordingly, it was necessary to carry out deep geoelectrical exploration in Qaleh Tol plain for the purpose of detection of buried formations under the alluvium and determining the hydrogeological heterogeneities of the plain. Therefore, a combination of hydrogeological and geoelectrical studies in Qaleh Tol plain was carried out. Vertical Electrical Sounding (VES) using Schlumberger array was carried out at 86 VES stations in six profiles. 1-D interpretation have been performed using IPI2WIN to determine the types and depths of subsurface layers and geoelectrical tomography of subsurface was done by RES2DINV. In order to provide an appropriate image of underground the electrical resistivity tomography maps (ERT) were prepared. In the tomography sections, the investigation depth over than 450 meters has been able to accurately determine the bedrock of Qaleh Tol plain. The results showed that the bedrock of Qaleh Tol plain are composed of limestone of Asmari Formation, conglomerate of Bakhtiari formation and shale of Pabdeh formation. The Asmari limestone strip shaped bedrock in deeper parts of the aquifer with high groundwater potential along the plain is the cause of hydrogeological heterogeneities in the Qaleh Tol plain, which has led to very different hydrogeological behaviors in neighborhood water wells.

Qanats are the most important device for the exploitation of groundwater in arid and semi-arid regions. The hydrogeology of Gonabad Plain Qanats was studied in this research. For this purpose, catchment area of Gonabad Plain Qanats was determined primarily. Water budget calculation in the catchment area shows that 3.7 MCM of groundwater more than catchment recharge and from aquifer storage was extracted annually which led to 0.06 meter per year groundwater level drawdown in catchment aquifer and decrease in qanats water bearing zone. To identify the effect of precipitation decrease on qanats discharge, Variations in catchment precipitation during 1997-2017 along changes in mean precipitation in four periods (five years period) were perused. Six major qanats of Gonabad Plain namely, Qasabeh, Bahabad, Baidokht, Rahn, Dizagh and Khesuie were selected, hydrographs of them during 1997-2017 were drawn and changes in hydrograph slopes in two specific periods were considered.The hydrograph slope of Qasabeh and Bahabad qanats become five and two times steeper during 2006-2017 compare to same in 1997-2006 periods respectively. Lack of dredging, dam construction and drilling of deep well in the catchment of these qanats has reduced the discharge of them. The hydrograph slope of Dizagh Qanat from the beginning has been constant almost 0.3 meter per year and this qanat has the lowest discharge decrease. High specific yield of aquifer in the qanat water bearing zone, absence of well in the qanat catchment and qanat recharge through groundwater infiltration in tunnels of upstream qanats have caused this qanat not to have high discharge decrease. The discharge of Gonabad Plain qanats has dropped from 6 to 20 liters per second during 1997-2017.

A study is undertaken to exploit the contrast between disjunctive use and conjunctive use of multiple resources comprising: surface water, groundwater and wastewater. The primary aim is the increase in system reliability but decrease in water deficits and operational costs. Groundwater budget is studied by two alternatives models of (GMS) and conjunctive use of water resources (PSO) are considered for Hashtgerd basin in Iran. In both models, the objective function is minimization of mean groundwater drawdown. The first step in this approach is estimation of the hydrodynamic parameters and groundwater budget in steady and unsteady conditions using a simulation by GMS model. The next step involves incorporating these amount of groundwater budget into the optimization model. The results of the simulation model indicate that groundwater budget of Hashtgerd plain is negative, which reservoir storage loss is almost 17 MCM per year (2011-12). The results of the optimization model indicate that the most increases of the aquifer storge are in November, April and Februry, respectively, and the discharg of groundwaters in all zones of basin is located at the borderline for sixty percent of months. According to conditions in the plain and the results of the optimization model, the groundwater shoudn,t been withdrawal more than presented values when the reservoir storge changes is zero, then the maximum use of surface water and wastewater Could avoid more groundwater declination. Eventually the best solution to mange water resources to avoid over abstraction is the hybrid use of all water resources within each zone.

Assessing the efficiency of water quality monitoring networks and improving various components of these systems, such as optimal location of monitoring stations, is of particular importance in water resource management systems. The main reason for this is the significant cost of setuping, maintenance and operation of these monitoring networks. So reducing the amount of surplus information can have a significant impact on reducing system costs, without reducing the value and accuracy of the information. In this study, the efficiency of monitoring network of the quality of groundwater resources in the Sefiddasht, Chaharmahal and Bakhtiari province was evaluated using the discrete entropy theory. For this purpose, the entropy indices, including ITI(i), R(i), S(i) and N(i) were calculated in three different classes of 6, 9 and 12 for 9 stations distributed across Sefiddasht plain. The results showed that the optimum station for groundwater quality in this plain is Safarpour well and the Tahmasebi well and Shadikhar Qanat, while gaining low rank in the network, have a critical situation and their continuation requires a general revision.

The study of temporal and spatial variations and the estimation of groundwater fluctuations in researching and planning water resources management are important for continuation or development of exploitation.So far, various models have been used to estimate the groundwater level parameter. Stochastic models have been used more than the other models for hydrological studies. The most common stochastic model is autoregressive integrated moving average model (ARIMA). This model is based on the Markov chain theory.In previous studies, one or a few wells have been studied using stochastic models but in this research, 46 selected stations with the monthly data of the Tabriz catchment were used to analyze temporal and spatial variations of groundwater level.In this case study, there was a good correlation between the values of the groundwater level of wells near each other than the other wells, thus to avoid the effects of closed wells fluctuations, at first the whole stations are divided into seven sections using the clustering process, thenspatial studies done just for selected station in every section. The results indicate that the first, third and seventh clusters didn't have acceptable accuracy in simulation due to the throw data and four other clusters had good accuracy. Also, the second and first clusters had the best and worst modeling with maximum R-Square and minimum RMSE, respectively.The use of the Arima model on various stations in the Tabriz catchment area revealed that the accuracy of the model is reduced when the time series have more fluctuations with trends in the mean and variance that lead to unsteady series.

Hydrodynamic parameters of the aquifer are of particular importance in most hydrogeological studies. There are various methods for estimating and determining these parameters, the most accurate of which is the use of pumping test data. The pumping test method is very costly and the range of hydrodynamic parameters is limited to the well influence radius. In the present study, first the study area was divided into 13 polygons based on 13 existing piezometers; Using three methods of vertical electrical sounding (VES), numerical modeling in the GMS software and envelope straight-line method (ESL), the specific yield rate was determined for each polygon. Finally, the specific yield obtained from the above-mentioned methods was verified using a pumping test of two exploratory wells in the two polygons. Results showed that all the three methods for calculating the specific yield are closely related to the pumping test method; Moreover, among the three methods, the accuracy of the geoelectric method is slightly higher than other methods. The highest specific yield value is about 0.09 in the west and northwest of the study area; Also the lowest value is estimated from about 0.007 to 0.016 in the east and northeastern of the study area and its average value is estimated about 0.04. Approximate volume of water in aquifer using the aquifer thickness, aquifer area that is about 86 km2 and the average porosity of the aquifer is obtained 1.7 billion cubic meters, that all is not accessible. By multiplying the specific yield coefficient in the approximate aquifer water volume, the extracted water is obtained which is about 74 million cubic meters.

Considering the importance of groundwater resources in the country, the study of hydrogeological droughts and effective factors on groundwater drawdown is essential to provide management solutions of these vital resources. Therefore, the purpose of this study is to analyze the trend of groundwater variations and assessment of groundwater drought in the Zohreh- Jarrahi watershed using SDI and GRI drought indices in a ten-year statistical period (2006-2016). The results show that in most study areas, there is a correlation between GRI and SDI indices. However, in some cases, the effect of hydrological drought on groundwater was shown with the delay of 6 months to one year. In general, the GRI drought index is more prominent during the ten-year statistical period in the center and around the west of the Zohreh- Jarrahi watershed and in particular the Imamzadeh Jafar study area. Moreover, in the final years of statistical period, the study areas in the southeastern part of the region have also been affected by droughts which are also correlated with SDI values. In the year 2015- 2016, the groundwater of the Leishter study area, according to the GRI index, has a severe drought with a value of 1.60, and according to this indicator, the average drought in the same year with a value of 1.42 in the Fahlian study area occurred. Although, in most cases, the occurrence of climate drought and consequently hydrological droughts caused a groundwater drawdown in the watershed area, but the results of the comparison between the two types of drought indicate that other factors such as excessive groundwater withdrawal are also effective.

Abstract Abstract All of the engineering structures construct on the ground, thus it is necessary to investigate and evaluate the geological engineering characteristics and probable geo hazard like karstifiaction potential of the construction sites. Hydraulic structures are from this structures that because of their immediately relation to the ground, the importance of this investigation is more noticeable. The constructed hydro structure on the carbonate rocks maybe confront to damage because of solution, enlarging and spreading of joints. This phenomenon may led to karstification and large seepage amount of water from foundation and inefficiency of dam. This article discusses about the rate of extension of the joints in different velocity and temperature regard to their original opening. The evaluation is obtained by experimental tests on rock cores of Khersan1 dam site. The results show that there are many factors that affect joint behavior against water flow; these factors are primary opening of joints, flow velocity, temperature, acidity and etc. In this research behavior of the joints with different opening in different temperature has been evaluated. The results show direct relation between extension of the joints and decreasing of the temperature and indirect relation between joint extension and their primary opening. Also the results show that filling and washing out of the joints in identical condition is controlled by flow velocity and their primary opening as the joint with opening of 0.3 mm shows washing out and filling against high and low velocity respectively. 

Karst regions have been considered unsuitable for dam construction because of complex hydrogeological characteristics. The most frequent problem at the karst dam sites is water leakage from the reservoirs. The Shah Ghasem Dam with a reservoir capacity of 9 million cubic meters, was constructed at the south of Yasouj City to regulate water flow of Shah Ghasem Spring. The dam is located on the northern limb of Shah Ghasem Anticline, a fold which is mainly composed of the marlstone layers of the Pabdeh-Gurpi Formation, alternative marlstone and limestone layers of Transition Zone and karst limestone belonging to the Asmari-Jahrom Formation. The reservoir water is in direct contact with the impermeable Pabdeh-Gurpi Formation, karstic Asmari Formations and their transition zone. By starting of dam operation in 1996, leakage occurred from the reservoir through the limestone layers of the Asmari Formation and Transition Zone. To reduce leakage, ten boreholes were drilled and grouted, but no effect on leakage amount was observed. The main object of this study is to determine leakage paths at the Shah Ghasem Dam reservoir, by considering the geological and hydrogeological settings, water pressure tests, cement consumption, and time series of water table in the reservoir and downstream boreholes. Results indicated that an extensive treatment work was needed to reduce the water leakage amount, but performing a benefit cost analysis was required to make a proper decision. Moreover, the karst aquifer at the northern limb of the anticline was recharging by the reservoir leakage water, supplying downstream drinking water.

Modeling the process of water flow, heat transfer and transmission of soil contamination requires hydraulic parameters, thermal conductivity and dispersion coefficient in soil. The purpose of this study is to evaluate the characteristic parameters of these properties from an infiltration test of flow and transfer of heat and soluble materials. Data collection were done during the two infiltration experiments, one was recorded for 24 hours in a sand column and another for 36 hours in a silt soil column. To monitor the temperature of the soil at depths of 4, 8 and 12 cm in each column, thermal sensors were installed and the temperature of the infiltrated water was regulated at 40 ° C and the steady infiltration of a source was monitored by the peristaltic pump. A solution of one molar of KCl in a steady state condition was injected on each column of sand and silt soils and the Cl concentration and temperature was recorded during the sampling of water and sensor readings at depths of 4, 8 and 12 cm. The hydraulic parameters of the soil (shape parameters in the van Genuchten equation  and n), the transport parameter (longitudinal dispersion coefficient), and the soil thermal conductivity parameters (coefficients b1, b2 and b3 in the Chang and Horton soil heat transfer function) was estimated using inverse modeling techniques. Validation of the results was performed by comparing the measured and simulated Cl concentration and the heat data by the model using the calculated root mean square error RMSE and R2 coefficient. The most valuable result of this research is the use of the cheapest tracer, ie, temperature, along with the concentration data, to obtain unique solutions to the estimation of the hydraulic functions of sand and silty soils by inverse solution.

Nowadays, the issue of freshwater supply is the main concern of researchers in the arid and semi-arid countries like Iran. Available water resources are necessary to be protected against pollution due to arid climate and frequent droughts and lack of water resources. One of the ways to protect groundwater against pollutants is to identify the areas with high potential of pollution. The quality of groundwater and surface water resources of Varzeqan plain can also be affected by the wastewater from the Sungun Copper Mine, which is impounding in tailing dam the north of Varzeqan plain. The groundwater flow direction is from west to east which thought to coincide with the surface water flow direction. The theory of groundwater vulnerability was first introduced in the 1960s in France to create an alertness of groundwater contamination. Several studies were carried out in different parts of the world to assess the pollution and vulnerability of groundwater. Many approaches have been developed to evaluate aquifer vulnerability. They include process-based methods, statistical methods, and overlay and index methods. One of the most common frameworks for assessing the vulnerability is the DRASTIC and SINTACS. The DRASTIC framework was developed by the National Groundwater Association (NGWA) in collaboration with the United States Environmental Protection Agency (USEPA). The SINTACS method used in this study was developed to evaluate relative groundwater pollution vulnerability using seven hydrogeologic parameters. In this paper, to assessment aquifer intrinsic vulnerability, a point count system framework called SINTACS and DRASTIC was selected, Also, in this study, the Corrected SINTACS framework has been introduced for the first time in assessing the vulnerability of confined aquifer.

Hydrogeological, geological characteristics of the study area The results of geophysical study and exploratory wells, piezometer and observation logs prepare evidence to identify two types of aquifers: alluvium aquifer including unconfined (with approx. 150 km2) and confined (with approx. 57 km2) aquifers. Confined aquifers surrounding by the unconfined aquifer and hence multiple aquifers and just alluvium aquifer located in the plain. The aquifers within the study area are a complex system and comprise two confined aquifers, surrounded by one unconfined aquifer. Varzeqan alluvium aquifers classified into three main hydraulic conductivity sections (i) High hydraulic conductivity (about 90 m/d) area in the eastern part of the plain composed of coarse-grain size sedimentary; and (ii) Moderate hydraulic conductivity (about 25 m/d) area in the central part of the plain composed of sand, gravel, and silt grains; and (iii) Low hydraulic conductivity (about 8 m/d) area in the western part of the plain composed of silt, clay and slightly sand. DRASTIC framework DRASTIC is an acronym of seven hydrogeological parameters comprises depth of groundwater (D), net recharge (R), aquifer media (A), soil media (S), topography (T), impact of vadose zone (I) and hydraulic conductivity (C). Each of these parameters is assigned a rate and a weight according to their relative importance. To prepare a vulnerability map, the required data of various parameters are given to ArcGIS software package in order to perform GIS processing, then, the vulnerability map is prepared. The overall DRASTIC vulnerability index (DVI) is calculated using Eq. 1. As follows, DVI = DwDr + RwRr+ AwAr + SwSr + TwTr + IwIr + CwCr (1) Where D, R, A, S, T, I, and C represent the DRASTIC parameters, and the r and w subscripts correspond to the rates and weights respectively. SINTACS framework SINTACS is an updated model of DRASTIC frameworks and includes seven parameters such as water table depth (S), net recharge (I), unsaturated zone (vadose zone) (N), soil media (T), aquifer media (A), hydraulic conductivity (C) and topographic slope (S).The SINTACS is similar in type and number of parameters to the DRASTIC model, but the rates and weights of this framework are different from the DRASTIC. Vulnerability index is calculated using Eq. 2. ISINTACS= ∑7 i=1 Pi*Wi (2) Where ISINTACS is the SINTACS vulnerability index, Pi is the rating of each parameter and Wi is the relative weight of SINTACS parameters. Corrected SINTACS framework In this study, Corrected SINTACS framework is presented for the first time to assess the vulnerability of confined aquifer that mechanism of this framework is derived from DRASTIC in the evaluation of confined aquifer and how to rate and assign the weight of the proposed framework, such as SINTACS in unconfined aquifer. DRASTIC and SINTACS differ from Corrected SINTACS for confined aquifer in the process of preparing the layers and the difference in rating for this framework.

Results of DRASTIC, SINTACS and Corrected SINTACS frameworks The objectives formed for the present study involve carrying out intrinsic vulnerability assessment using DRASTIC and SINTACS frameworks to priorities area according to their vulnerability to contamination. After preparing the raster layers of the frameworks, these layers were combined using the Raster Calculator command in the ArcGIS software and final vulnerability map was obtained. The vulnerability index based on DRASTIC in unconfined aquifer, varied in the range of 91 to 160 and for confined aquifer of 48 to 93, That's unconfined aquifer 33, 59, 8% of the study area is located in areas with low, medium and high vulnerability, respectively and for confined aquifer, 26%, 53%, 21%, respectively, are located in areas with low, medium and high vulnerability. The results of the evaluation with SINTACS framework for unconfined aquifer showed a number between 123-188, based on this, 12, 53 and 35% of the plain are located in areas with low, medium and high vulnerability, respectively. In assessing the confined aquifer using corrected SINTACS, the vulnerability index range was between 80-133. Validation In order to find out more accurately and compare the frameworks in this study, the correlation coefficient between vulnerability maps and nitrate data was calculated. Nitrate concentration data were used to validate the frameworks used in the study area separately for both types of aquifers, that is for unconfined aquifer, the results show a relative correlation with the value of R2 equal to 0.59 and 0.24 for DRASTIC and SINTACS, respectively. The value of the correlation coefficient in confined aquifer, for Corrected SINTACS and DRASTIC is 0.55 and 0.3, respectively. The CI between vulnerability maps and nitrate concentration were used for validation of the frameworks. The results show that DRASTIC and Corrected SINTACS have higher CI for the unconfined and confined aquifer, respectively. To more accurately assess and select the best vulnerability assessment framework for both types of aquifer, the (CI) method was used.

The purpose of this study was to determine the intrinsic vulnerability in multiple aquifer of Varzeqan plain using DRASTIC and SINTACS frameworks and finally, to compare the efficiency between them. In this study, simultaneous assessment of the intrinsic vulnerability of two aquifers confined and unconfined of Varzeqan plain and the determination of areas with contamination potential based on the hydrogeological conditions of the study area has been investigated. In this study, Corrected SINTACS has been proposed to assess the vulnerability of confined aquifer. Varzeqan multiple aquifer vulnerability index indicates that this aquifer is classified the capability of the contamination potential is in the medium to high range that in the unconfined aquifer due to the low water table depth, lower thickness of the unsaturated region and high hydraulic conductivity and for the confined aquifer due to the thickness of the impermeable layer. To assess the ability of frameworks in both aquifer, in fact, (R2) and (CI) were used to validate the frameworks. The results showed that DRASTIC with higher correlation coefficient (R2) and correlation index (CI) values than SINTACS values is the better framework to vulnerability assessment of unconfined aquifer in Varzeqan plain. However, Corrected SINTACS have higher performance than DRASTIC for confined aquifer. In determining the vulnerable points of the confined aquifer, the most important factor is the thickness of the impermeable layer (clay and silt), whatever this layer is thicker, the possibility of contaminant transfer is less and as a result, the vulnerability index values will decrease.