مجله هیدروژیولوژی
سال هفتم شماره 2 (زمستان 1401)

The leakage of natural gases mainly carbon dioxide into the Gariz aquifer has increased the concentration of dissolved gases and decreased groundwater quality. Therefore, the water supply of the residents of this region in various needs such as agriculture, drink, domestic, and industry, has faced some problems. Groundwater wells have been sampled to evaluate the hydrogeochemical processes of gaseous aquifers and determine the nature of dissolved gases during two-stage in July and September of 2019. Laboratory analysis includes the concentration of major anions and cations and, the dissolved gases in groundwater samples, and some physicochemical properties of water have been measured directly in the field. On the basis of the chemistry of major ions, most of the samples have classified as calcium-bicarbonate (Ca-HCO3), sodium-chloride (Na-Cl), and calcium-chloride (Ca-Cl) types, although other mixing types are also recognized. The most significant processes that affect the chemical composition of the groundwater of the Gariz aquifer are water-rock interaction, leakage of CO2-rich fluids, infiltration of saline water through faults and fractures, and silicate dissolution. Bicarbonate ion has increased in the groundwater samples due to the interaction of CO2-rich fluids with groundwater aquifer. The dissolved gases composition also indicates that CO2 is the dominant gas phase in most samples, with up to 2100 times higher than atmospheric values. High concentrations of dissolved CO2 of more than 730 cubic centimeters per liter indicate the infiltration of CO2-rich fluids with deep origin into the aquifer. The ratio of dissolved O2/N2 in the aquifer is lower than air-saturated water (ASW), therefore geochemical processes responsible for dissolved oxygen consumption during redox reactions.

Greenhouse crops production is one of the major strategies for managing optimum use of water resources due to creating desirable conditions for plant growth over the year, multiplying production and reducing water usage. In the present study, two scenarios were adopted according to the current policies for the development of greenhouse towns in Iran and an ideal scenario (third scenario) was also considered for the development of greenhouse towns. The soil and water assessment tool (SWAT) model was used to evaluate the impacts of the implementation of development scenarios of greenhouse towns. Statistical indicators showed very high accuracy in simulating hydrometric stations of study area, as for Akhola hydrometric station (basin outlet), the statistics of correlation factor, Nash-Sutcliffe efficiency (NSE), and root mean squared error (RMSE) in the calibration period were 0.77, 0.62, and 6.21 m3 s-1, respectively, and in the validation period were 0.83, 0.66, and 3.09 m3 s-1, respectively. The development of greenhouse towns with an area of ​​1875 ha in Ajichay basin for the first and second scenarios resulted in an average drop of 11.68 m and 4.41 m in the groundwater level of the aquifers in Ajichay basin compared to the initial conditions. Simulation of the third scenario increases the groundwater level of aquifers of Tabriz, Azarshahr, Damaneh Shomali Sahand, Bostanabad, Duzduzan, Mehraban, Bilverdi, Asbforoshan and Sarab by 4.12, 2.73, 1.45, 8.88, 10.93, 2.90, 4.79, 2.99, and 3.31 m, respectively, and also has compensated a large amount of their negative balance. The results revealed that the development of greenhouse towns using new water resources can increase agricultural crop production and also intensify the downward trend in groundwater levels.

Remote sensing technology, due to its valuable features such as taking multi-temporal and multi-spectral images, appropriate and varied temporal resolution and radiometric capability, wide and integrated view of the region, can be used in many agricultural tasks such as crop yield prediction, soil moisture measurement, information about the amount of drought and frost should be effective. In this study, to evaluate the networked meteorological datasets GLDAS-AgMERRA, GLDAS-CRU, GLDAS-AgCFSR in estimating the blue and green water footprints of wheat and blue water footprints of maize and comparing it with the estimated values of Qazvin plain during 1980-2010. Statistical evaluation was performed using R2, NRMSE and ME indices. The average total water footprint of wheat in study area was estimated at 869 (m3/ton) in which the share of green water footprint was 47% and the share of blue water footprint was 53%. Estimated data in scenarios 1 (Precipitation and evapotranspiration of GLDAS-Temperature of CRU) and 3 (Precipitation of GLDAS-Temperature and evapotranspiration of CRU) for green water footprint of wheat and for blue water footprint, scenario 5 (Precipitation and evapotranspiration of GLDAS-Temperature of AgCFSR) and Scenario 3 have the highest correlations for wheat and maize, respectively. The results show that these datasets are not suitable for estimating the water footprint of maize plants, but for estimating the green and blue water footprints of wheat plants, the information of networked meteorological datasets can be used with appropriate accuracy.

In recent decades, the growing population, limited water resources, and overexploitation of aquifers have caused irreparable damage to the quantity and quality of the country's aquifers. In the current study, geographical information system (GIS) models and machine learning (ML) techniques using available groundwater quality variables were applied for the prediction and zoning of salinity and SAR of groundwater in the Zahedan plain and then the accuracy of these methods was compared.The input data were based on water quality sampling in 2018 from 59 observation wells. The study of parameters showed that in Zahedan plain, EC, SAR, and TDS parameters had high variability (CV>41%) and acidity showed low variability (CV = 4.16%). The results of the geostatistical analysis showed that the IDW model represented better results with the power value of 2 for TDS and EC parameters while for pH and SAR parameters, the ordinary Kriging method revealed the best result with minimum RMSE in the test stage. Performance evaluation of ML models showed that all three models RF, ANN, and SVM showed acceptable results with R2 above 90% and NRMSE values below 15% for all parameters (except acidity). However, better estimations were observed in the training step than in the test step. A comparison of different GIS models and ML also revealed the notable superiority of ML models in estimating these parameters. Finally, it can be concluded that under a shortage of field facilities for the assessment of groundwater quality, data-driven methods can be a reliable alternative to water quality monitoring.

The extensive knowledge of groundwater resources' status has double importance for the planning of the sustainable future in the arid regions. Strictly, without an efficient model with accurate simulation, it is impossible to have a good understanding of groundwater behavior. Since groundwater modeling in real problems comprises irregular boundaries, heterogeneity, anisotropy, and conceptualization, there exist many challenges in the simulation process. Due to proper acceptable performance, this study aims to present a proper framework to simulate groundwater flow based on Finite Difference (FD), Finite Element (FE), and Meshfree (Mfree) methods. The governing equation of groundwater flow was discretized through FD, FE, and Mfree approximations, and their performance was examined in two case studies: hypothetical case and field study. The findings of this study revealed that the Mfree has more applicability than others because some noticeable challenges were found in the simulation process of the FD and FE. Comparison of analytical solutions and simulated values in the hypothetical aquifer indicated that all methods are compliant. In terms of the RMSE criterion, the Mfree, FE, and FD were evaluated respectively, 0.005, 0.016, and 0.018 m. However, the numerical methods' act, especially the mesh-based methods (FD and FE) in the field study, becomes less accurate. Performance assessment of the FD indicated that this method has good ability in a simple test case with regular geometry, while in an aquifer with irregular geometry associated with isotropy and heterogeneity, its accuracy is greatly diminished. So that, the RMSE for FD methods in field study was evaluated 1.77 m. The same results may be obtained from the FE method, such that its RMSE was obtained 0.36 m. Investigations of this study showed that the FE needs time-consuming preprocessing practices to implement in the different aquifer. The results of the Mfree application indicated that this method is more efficient than others due to its very high flexibility in irregular geometry with isotropy and heterogeneity issues. The RMSE for the Mfree in the field study obtained 0.26 m.

Spring distribution and flow rate are influenced by a variety of factors such as tectonics, climate, geology, distance from the drainage network, geomorphology, etc. The current study aims to determine the effect of structural parameters, lithology, and drainage network on two indicators related to springs, notably number and annual water flow in Kamyaran, Kurdistan province. Correlation relationships have also been investigated between springs in watersheds and hydrometric stations downstream of them. A correlation coefficient of 0.947exists. The correlation between the number of springs and the distance from the river is significant and is around 0.76. But there is no significant relationship between these two parameters with the amount of spring water. The discharge variable has a significant relationship with the formation type, with the sand limestone formation having the most annual drainage and the andesite, micro granite, and silty shales having the least. The results of the correlation between springs and hydrometric stations revealed that there are significant relationships between temperature parameters and annual discharge, but no significant relationships between pH and EC indicators.

Groundwater resources are valuable resources to supply water for various uses in all areas, especially arid and semi-arid areas. Due to the limited resources and increasing population and the growth of agriculture and industry, the optimal use of groundwater needs more attention. In this research, the temporal and spatial variation of groundwater quality of Sefiddasht plain located in Chaharmahal and Bakhtiari province and its capability for agricultural purposes have been investigated. For this purpose, the time series of qualitative variables collected in 9 sampling stations (including 6 wells, 2 qanats and a spring) in the Plain during a 29-year period (1991-2018) was used. The trend of changes in groundwater quality variables of this plain was investigated using the modified Mann-Kendall test (after complete elimination of the autocorrelation effect). The trend line slope was also calculated for each time series using the Sen slope estimator. The results showed that groundwater quality has decreased in recent years in some places, especially in the southern parts of Sefiddasht. In order to draw zoning maps of qualitative variables at the beginning and end of the studied period, the accuracy of various geostatistical methods, including inverse distance weighting (IDW), Kriging, Co-Kriging, etc. for Sefiddasht plain was evaluated and the IDW method was selected for this plain. Comparison of zoning maps of qualitative variables at the beginning and end of the studied period showed that the groundwater quality of this plain has decreased during the considered 29 years. Finally, the usability of groundwater in Sefiddasht plain for agricultural use was evaluated using the USSL diagram for the beginning and end of the studied period. The results indicated a decrease in the quality of groundwater for agricultural use in this plain during the studied period.

Today, due to widespread land use changes, including increasing urban population and drinking needs, industrial and agricultural growth of communities on the one hand and further reduction of surface water resources on the other hand has increased the use of groundwater resources. Therefore, it is necessary to evaluate the effect of land use change on aquifer vulnerability. Since the potential for pollution in different parts of an aquifer is different in terms of contaminants reaching the groundwater, predicting the extent of vulnerability changes in aquifers by predicting future land uses. In this study, for the first time, the effect of the future land use changes on the vulnerability of Hashtgerd aquifer for the periods of 2025, 2035 and 2045 has been investigated and compared with the current situation in 2018. In this regard, first, using the Markov chain method in TerrSet software, land use changes for the three periods of 2025, 2035 and 2045 were extracted. Land use mapping was performed using Landsat satellite images for 1998, 2008 and 2018 in ENVI 5.3 software. The generated maps were added as a parameter to the DRASTIC vulnerability method and finally DRASTIC-Lu was predicted for three periods. This study shows that the vulnerability in high and very high class in 2045 will increase by 34% and 83%, respectively. Furthermore, the increasing trend of vulnerability in the classroom is very high for three incremental periods and will increase from 14% in 2025 to 20% and 83% in 2035 and 2045. This study shows that in the coming years, in order to preserve groundwater resources, it is necessary to consider special monitoring measures in the northern and northeastern regions of the aquifer.

Proper water resources management relies on recognizing and evaluating the factors affecting the quantity and quality of the water resources. In the present study, the hydraulic relationship between the karstic structures of the Izeh territory located has been assessed using hydrogeochemical and isotopic information of water resources. To investigate the number of 31 water samples (17 wells, 8 springs and 6 rain samples) in the areas of Kamarderaz, Mongasht, Shavish-Tanosh, Anticlines and the Naal-e-Asbi (Horseshoe) Syncline were taken on June 1398 and June 1400, and hydrogeochemical as well as isotopes δ18O and δ2H were examined until to the hydrogeological and hydraulic behavior of this complex karstic system. The results of hydrogeochemical analysis of the specimens showed that the concentration of ions is influenced by the dissolution of calcareous rocks. The isotopic content of groundwater samples is from 5.62 to 3.49- ‰ and from 20.97 to 12.29- ‰ for δ18O and δ2H. Investigating the isotopic content of water wells and springs of the region indicates three groups of water. The first group of indentation springs is fed from altitudes and snow from altitudes. Fast water in the canal system caused a low latency in these springs. The second group is enriched more than the first group, and in addition to precipitation, the mixing of underground water is also effective in providing their water. The third group has longer than other samples due to evaporation and distances longer than the feeding site and the enrichment system. The decrease in Sr+2 and incremental Ba+2 of dolomitic limestone samples (Shavish-Tanosh and Mongasht) to water samples of chemistry and hinges, as well as structural and isotopic data indicate the probability of nutrition. The karstic aquifers of the region are from the anticline, as well as the hydraulic relationship between these structures.

Zagros Mountain, southwest Iran, includes karst springs with high discharge, so that the large springs in Iran are discharged from the limestone (Sarvak and Asmari formations) of this mountain. The hydrochemistry and hydrogeology of eight large springs located in the northeast of Khuzestan province, with an average discharge more than 1.5 m3/s  have been investigated from April 2018 to November 2019. Initially, the location of large karst springs in Iran has been determined based on the available data. The location of these springs in relation to distribution of karstic formations and digital elevation model (DEM) as well as the relationship between the average discharge, altitude and electrical conductivity have been investigated. Piper diagram has been used to determine the type of the spring water. The ion ratios and saturation indices were used to identify the dissolution intensity of carbonate rocks as well as water residence time in the karst system. The results show the relationship between the springs altitude and the electrical conductivity with the discharge is inverse. The predominant type of the spring’s water is HCO3-Ca and in some springs discharge frome Asmari  limestone is Ca-SO4 and Na-Cl due to recharge via Gachsaran Formation.The lack of significant change in the Mg2+/Ca2+ concentration in Sarvak springs indicates a long residence time in the karst system. The large springs of Sarvak and Asmari with high discharge (including Brahim Mardun, Chalshah Sarbazar, Sabzab, and Bibi Tarkhun) have large catchment area, the base flow is more than quick flow in most of the springs. The Keynow anticline is the richest aquifer with high dynamic reservoir in Zagros Mountain.

Groundwater quality is an important subject in hydrologic studies and the study of its qualitative parameters variations is very crucial for determining its suitability for drinking, agricultural or industrial consumptions. Information on spatial variations of groundwater quality is a way for tracing the effect of forcing elements alike contaminants. In the present study, geo-statistics methods were applied for studying groundwater qualitative parameters (e.g. Chlorine, Sulfate, Total Hardness, Total Dissolved solid, Electric conductivity, Sodium Adsorption Ratio, Magnesium, Sodium, Calcium, pH) in Tabriz plain during a 15-years period. The employed techniques included Inverse Distance Weighing, Radial Basis Functions and Kriging. The obtained results showed that the concentration of these parameters has been increased in Northwestern, west and southwestern parts of the plain, revealing the degradation of water quality in those regions. Also, the accuracy of the two methods of Radial Basis Functions and kriging, depending on the type of parameter studied, was found to be suitable for modeling. In general, comparing the maps prepared for the parameters, it is observed that the zones specified for these parameters follow almost a specific pattern and the minimum and maximum of all parameters are located in common areas of the plain.

One of the main challenges facing water resources management is groundwater conservation and its sustainable use. Building an underground dam can be one way to solve this problem if it is possible to do. Hassanabad watershed lies between the Shiyan and Mahidasht plains in Kermanshah province. However, despite the same rainfall in the region, this basin has more unfavourable conditions in terms of water resources, vegetation and type of agriculture than the two adjacent plains. The purpose of this study is to identify suitable areas for the construction of an underground dam in the Hassanabad basin. To achieve this goal, after preparing different layers of information in Arc GIS, areas with potential were investigated using the Boolean method based on slope, material and land structure criteria, hydrological conditions and land use. Consequently, 7 axes were selected as potentially suitable locations for underground dam construction on the southern margin of the Hassanabad Plain. In the next step, these axes were prioritized by the analytical hierarchy process method based on general socio-economic criteria, dam reservoir, dam location and water characteristics, and axes 6, 7 and 1 took the first to third orders, respectively. According to aerial photography maps, field visits, structural geology analysis, and groundwater flow direction, axis 6 is identified as the most optimal axis for the construction of the dam.