فهرست مطالب مجتبی قره محمودلو

In general, rivers have a hydraulic connection with aquifers and they affect each other quantitatively and qualitatively. River water percolates into the underground along its path and after passing through the subsurface layers, it feeds the aquifers. During the infiltration of water inside the layers, the concentration of contaminants in river water is reduced as a result of river bank filtration or because of some processes in the porous media. This makes the quality of the passing water inside the subsurface layers much better compared to the quality of the river water before infiltration and purification.In the east of Golestan Province and in the vicinity of the Doogh River, one of the main branches of the Gorganrud River, two Felmann wells have been drilled. The discharge of each Felmann Kalaleh wells is about 200 liters per second, which is equivalent to 5 deep wells drilled for drinking water in the Gorgan Plain. The water of these two Felmann wells is used to supply almost 20% of the water of the urban population of Gonbad Kavous. In addition, using the Felmann well method plays an important role in reducing water treatment costs (especially physical treatment). Therefore, the mentioned method can be of interest to water and sewage companies and water affairs located in the northern provinces of IranPrevious studies showed that Felmann Kalaleh wells have a good efficiency in improving the water quality of the Doogh River. However, the river discharge effect variations on the amount of water parameters extracted from Felmann Kalaleh wells is still unknown and needs to be investigated. Therefore, the investigation of the factors affecting the quality of the river water feeding the wells of Felmann Kalaleh, as well as its effect on the quality parameters of the wells, is important for the optimal and appropriate use of their water for drinking water. Hence, the current research is aimed to investigate the role of Doogh River discharge fluctuations and its effects on the water quality parameters of the river and Felmann well.

Doogh River is one of the important sub-basins of Gorganroud River and it drains parts of the three provinces of Semnan, North Khorasan, and Golestan. A part of the Doogh River catchment located in Golestan province has many differences with other parts of the basin in Semnan and North Khorasan provinces in terms of climatic conditions, vegetation, geology, physiography, and geomorphology. It plays a very important role in the agriculture of the region in addition to controlling the floods in the east of Golestan Province. Therefore, the quantitative and qualitative study of Doogh River water is very important in terms of agriculture and drinking.In general, there are two Felmann wells in Kalaleh City, which play an important role in supplying drinking water to Gonbad Kavous City. These two wells were drilled by the water and sewerage company of the province in 2013 in the vicinity of the Doogh River (one of the main tributaries of the Gorganrud River) and in the vicinity of the two villages of Ajen and Qarakhoja. The approximate depth of these two wells is about 20 meters, the diameter of their main opening is about 3 meters, at the end of which 12 radial galleries with an approximate length of 30 meters are drilled, which bring water into the water supply network of Gonbad Kavous City with a flow rate of about 200 liters per second.In this research, for the physicochemical and microbial analysis of well and river waters, samples were taken simultaneously from Doogh River and Felmann Kalaleh wells following the existing standard methods. For this purpose, 10 samples of river water and 10 samples of each of Felmann Kalaleh wells were collected at the same time in a period of approximately five months from October 2019 to February 2019. Also, the discharge values of Doogh River were collected from the hydrometric station in the vicinity of Felmann wells.Correlation test was used at the probability level of 0.05 to investigate the relationship between discharge fluctuations with the physicochemical characteristics of Felmann wells and also the relationship between river discharge fluctuations with the river's physicochemical characteristics. All statistical tests were performed in MINITAB 17 software.

Results revealed that most of the values related to chemical parameters such TDS, sodium, calcium, etc. are within the permissible limit for drinking water according to the 1053 standard of Iran and World Health Organization (WHO). However, the amount of turbidity and total coliform is higher than the permissible limit and needs to be purified for use in the drinking sector.Based on the p-value of the paired T-test for only 6 factors (including TDS, fluoride, sodium, chloride, nitrite, and manganese) out of 24 qualitative factors between the physicochemical characteristics of river water and Felmann 1 and 2 wells that were collected simultaneously and, no significant difference was observed. But this difference is evident in 18 parameters. This indicates that the riverbank filtration as a result of processes suchas surface absorption, aerobic, and anaerobic decomposition by microorganisms and filtration of sediments was not effective on the values of TDS, fluoride, sodium, chloride, nitrite, and manganese parameters.Based on the results of the removal efficiency by riverbank filtration, most of the removal rate due to riverbank filtration is related to turbidity, total coliform, and color, respectively, at the rate of 97.52, 96.91 and 79.17 for well number 1. However, similar numbers were obtained for well No.2. Also, the results revealed that during the riverbank filtration, the amount of some parameters such as calcium, total hardness, etc. increased in Felmann well due to the change in water chemistry and interactions taking place in the active zone created in the river bed.

Results:

 revealed that riverbank filtration played an important role in reducing some quality parameters, especially total coliform, turbidity, and color. But this amount has decreased significantly in nitrate. While some parameters such as bicarbonate and electricalconductivitynot only did not decrease much, but also slightly increased. This can be a result of change in water chemistry and the environment during the filtration process, as well as the change in pressure. Also, the mixing of water obtained from filtration with groundwater water can affect the concentration of these parameters.Investigation of the relationship between river water fluctuations and the physicochemical and microbial characteristics of river showed that 13 of 24 factors investigated include turbidity, color, TDC, total hardness, calcium hardness, chloride, bicarbonate, nitrate, calcium, magnesium, sodium, potassium, and total coliform. There is a significant relationship between the values of these 13 qualitative factors and the Felmann well, and for 11 qualitative factors, no significant relationship was observed between discharge fluctuations and the quality characteristics of river water.As expected, there is a direct, linear, and positive relationship between the changes in Doogh river discharge with turbidity, color, sodium, and electrical conductivity. This relationship indicates the existence of geological formations such as marl and clays containing evaporite minerals in a large area of sub-basins of this river in North Khorsan and Semnan Provinces, which the intensification of rainfall and the subsequent increase in the discharge of the Doogh River cause the dissolution of this formations in water, and consequently, increase in the amount of dissolved and suspended solids in Doogh River water.Contrary to the mentioned parameters, the changes between Doogh River discharge and total coliform of whole relationship are direct, linear but negative. So, with the increase in flow rate, the amount of total coliform of Doogh River decreases significantly.The results of the correlation test, to investigate the significant relationship between the river discharge and the physicochemical characteristics of Felmann well, revealed that the value of 12 factors out of 24 factors investigated in Felmann number 1 including turbidity, color, EC, TDC, total hardness, calcium hardness, ammonia, fluoride, calcium, magnesium, COD, and total coliform are dependent on river discharge fluctuations. For 12 other qualitative factors, including nitrate, nitrite, pH, sodium, potassium, etc., no significant relationship between discharge fluctuations and qualitative characteristics was observed for this well.The results of the above test for well number 2 showed that only in 8 of the 24 investigated factors, including turbidity, color, total hardness, calcium hardness, calcium, magnesium, COD, and total coliform, a significant relationship between these parameters and discharge fluctuations was observed. In Felmann number 2, for 16 other factors, no significant relationship between flow fluctuations and qualitative characteristics was observed.Based on Durov Diagram, there is no specific geochemical evolution direction for water resources, and the distribution of samples related to Doogh River and Felmann wells is at the same location. Water type of samples is bicarbonate type in the recharge areas (margins of the heights). Based on the rectangle related to pH, the value of this parameter in Doogh River (7.75-7.85) is slightly higher than in Felmann wells (>7.55). It seems that after the river bank filtration, the value of this parameter decreases due to the processes that occur in the active zone.

Background and Groundwater serves as the primary drinking water source in Golestan Province. Therefore, this study aims to assess the non-cancerous health risks associated with nitrate and fluoride in the province's drinking water sources.  Physicochemical data from 139 drinking water wells were obtained from the Golestan Province Water and Wastewater Company during the spring and autumn. Significant ion variations were analyzed, and factors influencing the chemistry of drinking water sources in Golestan Province were investigated. Non-carcinogenic health risks posed by nitrate and fluoride were assessed using two indicators provided by the United States Environmental Protection Agency.  The maximum nitrate concentration in certain Golestan Province cities exceeds the Iranian drinking water standards (1053) and the World Health Organization's limits. However, fluoride levels in most cities fall below the range stipulated by domestic and international standards. The nitrate risk factor for children in select cities exceeds one, while it remains below one for other age groups. Notably, Khan Bebin City exhibits the lowest nitrate risk factor among the province's cities. Additionally, risk factor values show a slight increase during the autumn season. Non-cancerous health risk assessments for fluoride in drinking water sources across Golestan Province during spring and autumn indicate risk values below one for all age groups, including infants, children, teenagers, and adults.  The health risk assessments for nitrates and fluorides indicate that children in certain cities face a higher risk from nitrates than adults. Moreover, the low fluoride levels in the province's drinking water sources increase the likelihood of tooth decay.

Currently, soil erosion is considered one of the important environmental problems in Iran's watersheds. Accurate estimation of sedimentation and soil erodibility is very important for the protection and management of natural resources. Soil erodibility indicates the potential ability of soil to erode, and its increase is considered a serious threat to the stability and production capacity of agricultural lands. Measuring soil erodibility by direct method is expensive and time-consuming, and nowadays indirect methods are used to determine it. One of the most common indirect methods for estimating this parameter is the use of the Wischmeier and Smith nomograph, which was developed for non-calcareous soils. However, the majority of the soils in Iran is calcareous and the use of the nomograph method does not provide a correct estimate of the amount of erodibility. Loess is one of the most important Quaternary sedimentary formations in northeastern Iran, which consists of a relatively high percentage of lime. Therefore, the main goal of current research is to determine the most suitable indirect model to determine soil erodibility in Loess lands with the origin of calcareous sediments.

In the current study, Arab-Qara-Haji watershed with an area of 2596 hectares located in the east of Golestan province was selected as a typical loess area. The average annual precipitation of this watershed is 489 mm and it has a moderate semi-arid climate. This area is one of the sedimentary basins of Kopeh-Dagh zone related to the Jurassic period and consists of limestone and loess sediments. Based on the field studies, three main types of soil including hills (67.1%), loess plateaus (20.6%) and river terraces (12.3%) were identified in this watershed and the land unit was selected as working units. For this purpose, 48 surface samples (0-10 cm depth) were collected from each part of the land unit. In this research, two series of samples were taken from each section. The first series of samples was used to determine the soil physicochemical properties and the second series was sampled by a special cylinder to determine the soil saturated hydraulic conductivity using the falling head method. In the laboratory, soil texture was determined by hydrometric method (D<0.075), soil granularity by sieve analysis (D>0.075), soil organic matter by wet burning method and neutral lime percentage by Nelson method. The experience of the soil expert of this research was used to determine the soil structure in field. Then, soil erodibility was estimated using four indirect methods, including Weishmeier and Smith nomograph, Torri, Shirazi, and Vaezi. In this study, the soil actual erodibility was measured using rain simulator in the field (in plots of 1 m2). Then the validation of the models was performed using three standard indices MAD, RMSE and MAPE and the most appropriate model was selected.

Soil texture assessment in this watershed revealed that around 90 percent of soil samples have silt loam texture and the rest of samples has loam one. Also, the average lime in study area was estimated about 29%. The high percentage of lime (29%) and silt (60%) in this watershed has greatly increased the tunnel erosion probability. The validation results of the used models revealed that the use of the Vaezi method to estimate the soil erodibility factor in the loess lands of the study area has the highest accuracy (RMSE=0.00225). However, it is less estimated than the actual values. These results were confirmed in all 3 soil types of Arab-Qara-Haji watershed. After Vaezi model, Shirazi model (RMSE=0.03600) is more suitable than other models to estimate the soil erodibility factor in the loess lands of the area. This model has overestimated in all three types of soil including hill, loess plateau, and alluvial terrace, which is 11.2 times higher than the actual data from the rain simulator in the Arab-Qara-Haji watershed. After the Vaezi and Shirazi models, Wischmeier nomograph and Torri models, respectively, have a weaker performance in determining the soil erodibility factor in the limestone lands of the study area. Like the Shirazi method, Wischmeier nomograph and Tori methods have overestimated the soil erodibility factor. In the study area, this increase has been18.6 and 21.9 times higher than the actual data for Wischmeier nomograph and Torri models, respectively.

The present research results revealed that the use of Vaezi model to estimate soil erodibility in loamy lands with a high percentage of neutral lime is more appropriate compared to other used models. Based on the Vaezi and colleagues model, if the amount of neutral lime in the soil is less than 13%, it has a controlling role on the soil erodibility factor. While, this model is not able to estimate the soil erodibility in areas with neutral lime more than 30%. Therefore, for a number of soil samples in which the neutral lime was above 30%, the Vaezi model was not able to calculate the soil erodibility factor. It seems that currently, for the areas where the percentage of neutral lime in the surface soil is less than 30%, the use of the Vaezi model is more suitable than other models. It is suggested to recalibrate and update the Vaezi model for areas where the percentage of lime is more than 30%. The present research results revealed that the use of Vaezi model to estimate soil erodibility in loamy lands with a high percentage of neutral lime is more appropriate compared to other used models. Based on the Vaezi and colleagues model, if the amount of neutral lime in the soil is less than 13%, it has a controlling role on the soil erodibility factor. While, this model is not able to estimate the soil erodibility in areas with neutral lime more than 30%. Therefore, for a number of soil samples in which the neutral lime was above 30%, the Vaezi model was not able to calculate the soil erodibility factor. It seems that currently, for the areas where the percentage of neutral lime in the surface soil is less than 30%, the use of the Vaezi model is more suitable than other models. It is suggested to recalibrate and update the Vaezi model for areas where the percentage of lime is more than 30%.

In Iran, the climatic conditions are such that even in the rainiest areas of the country, there is a need for groundwater resources, and this demand is increasing every year. Since, groundwater is one of the most valuable water resources in Iran, it is very necessary to predict its changes in order to use it optimally with the aim of sustainable development. One of the most complex hydrological processes in nature is the rainfall-groundwater level process, which is affected by various physical and hydrological parameters. Although, various models have been presented to predict the changes in the groundwater level using the rainfall patterns, but less attention has been paid to the transfer function model. Hence, the main objective of this research is to introduce and use the transfer function (TF) model to predict the monthly groundwater level using rainfall data and to compare its results with ANFIS and Artificial Neural Network (ANN) models.In the present study, 30-year data (1992-2021) of meteorological stations and observation wells in 3 watersheds of Galikesh, Ramian and Mohamadabad were used to model the rainfall and groundwater level. of the Gorganroud river basin.Then, considering that the years closer to the present time have more accurate information about the situation of this time, the years were considered as a forward process in artificial neural networks. The model fitting and prediction of the groundwater level values using rainfall data for the next 12 months was performed with applying three models: Artificial Neural Network (ANN), Adaptive neuro fuzzy inference system (ANFIS), and transfer function (TF). For this purpose, MINITAB SAS, SPSS, and R software were used. Next step, the validation of the values predicted by the models was evaluated using three indices Mean Absolute Distance (MAD), Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE).The results of the autocorrelation plots of the groundwater level of the wells revealed that all time series have a seasonal trend with a period of 12 months. Based on the cross-correlation plots, it was also found that rainfall has direct effect on the groundwater level in the two watersheds of Galikesh and Mohamadabad with lag time of three months and in the Ramian watershed with a delay of one month. The validation results of the models using three indexes MAD, RMSE and MAPE revealed that the artificial neural network model for predicting the groundwater level using monthly rainfall data in all three investigated watersheds had the most appropriate performance (RMSE=0.0778, 0.0243, 0.0532m) and the ANFIS model is ranked second (RMSE=0.1841, 0.0832, 0.1012m). Although the transfer function model was less accurate than the other two methods (RMSE=0.5711, 0.5023, 0.3234m), but this model has performed well in fitting the monthly groundwater level values. This model is very effective in identifying the delay in the impact between the input and output variables, as well as expressing the model based on which the impact of rainfall can be expressed as a model.The results of this research show that all three models of artificial neural network, ANFIS and transfer function can be used to predict the groundwater level using monthly rainfall values. Consecutive overestimation and underestimation, which increases the error and decreases the performance of the models, was not observed for the three used models. Also, all three models perform well in detecting trends and data changes. However, the artificial neural network model is more accurate than the other models. In addition, when forward process is used in artificial neural network modeling, compared to the case where the complete series of data is used, the efficiency of the model is significantly improved.

Groundwater is one of the most important water resources that is always used by humans in different sectors. The composition and chemical quality of groundwater sources are always threatened by natural factors such as climate, soil type, geology, topography, precipitation and evaporation, as well as human factors such as population growth, extensive agricultural activities, and industrial development. Hence, hydrogeochemical researches can provide very detailed information about the effect of the aquifer materials of the study area, the route of recharge and discharge, the areas of evaporation from the groundwater, the effect of surface water on the groundwater of the region, as well as its quality in various uses for decision makers. This research  was conducted to 1) compare and determine the significant difference (using the paired samples t-test) between physicochemical parameters in the statistical period under review (between wells and springs), 2) use geochemical ion ratios in order to discover the origin of ions and influencing processes that are responsible to alter the concentration of ions in the studied water resources, 3) investigate and identify the ion exchange process (normal and reverse) using chloro-alkaline indices and some hydrogeochemical graphs, and 4) identify saline water intrusion from subsurface layers or human pollution into the groundwater sources.

 In this study, 14 piezometric wells in the eastern part of Gorgan plain and 8 springs located in the heights between the cities of Ramyan, Minoodasht, Kalaleh and Gonbad were selected for hydrogeochemical study for which hydrogeochemical processes and qualitative changes of physicochemical parameters results (including Ca, Mg, Na, K, HCO3, Cl, SO4, TDS, pH and EC) were used over a period of 10 years. To compare and determine significant differences between physicochemical parameters in the statistical period under study between wells and springs, paired samples t-test and analysis of variance were performed in Minitab software. Before performing the paired sample t-test, normality of the data was checked using the Anderson-Darling test. In  paired samples t-test, if the p-value estimated by the software is greater than or equal to 0.05, with a probability of 95%, the hypothesis H0, which means that there is no significant difference between the average of the investigated treatments, is accepted and the hypothesis H1 is rejected. However, if the calculated p-value is less than 0.05, the hypothesis H0 is rejected with a probability of 95% and the hypothesis H1, which means that there is a significant difference between the averages of the investigated treatments, is accepted. Next, the maps related to the spatial changes of the groundwater parameters were plotted in the GIS environment and by using the IDW method, and then the trend of their changes in the studied area was interpreted. Aq.QA software was also used to better analyze the hydrogeochemical data and to draw the stiff and piper diagrams. Finally, to identify the factors governing changes in groundwater quality and also to investigate the relationships between variables, Gibbs diagram, ion ratios, and compositional diagrams have been used. All the mentioned graphs were prepared using Excel software.

   The spatial distribution of hydrochemical parameters showed that the concentration of most physicochemical parameters due to groundwater flow (from west to northwest) is increasing. The results of the investigation of the water type in the springs showed that magnesium bicarbonate (Mg-HCO3) is the dominant type of water in the studied springs. Unlike springs, a wide range of water type is observed in piezometric wells (Mg-HCO3, Mg-Cl, Na-Cl and Na-HCO3). Also, Ca-Mg-CO3-HCO3 bicarbonate facies and then mixed Ca-Mg-Cl-SO4 facies are the most abundant in water resources. Based on the distribution of water source samples in the Gibbs diagram, the chemical composition of all the samples, except for one sample related to the well, is controlled by the reservoir rock of springs or piezometric wells in the plain. Since the main ions show a linear relationship with TDI, it can be concluded that there is a possibility of intrusion of saline water containing sodium and chlorine ions or dissolution of halite minerals in the groundwater of the plain. The results of ion ratios showed that groundwater is recharged by dolomite, dolomite-limestone, and lime-dolomite formations associated to different geological periods is the main factor controlling hydrogeochemical parameters in the springs. But in the observation wells of the plain, in addition to the above cases, the weathering of silicates and the small intrusion of saline water into the ground water table have caused changes in hydrogeochemical parameters. The results of ion exchanges showed that the normal ion exchange process has a more effective role than the reverse ion exchange process in final concentration of main elements in the groundwater of studied water sources.

The changes in the concentration of ions in the springs are much less than the observed wells in the plain. Bicarbonate is the dominant anion in both well and spring water sources. Nevertheless, in the two wells no. 3 and 10 chloride ions prevail, which can be caused by the intrusion of saline water from the lower layers into the groundwater. Based on the spatial distribution of the physicochemical parameters, the concentration of most of the parameters in the direction of the groundwater flow is increasing due to the presence of layers with poor quality, the infiltration of urban sewage and agricultural effluents, as well as the intrusion of saline water from the subsurface layers. The investigation of the water type of the springs shows that magnesium bicarbonate is the predominant water type. Therefore, it can be concluded that the reservoir rock that recharges the springs is more than dolomite limestone. Similar to the springs, all the wells drilled on the edge of the highlands have the dominant type of magnesium bicarbonate. But by moving away from the mountain front and changing the concentration of some ions due to environmental and human factors, the type of groundwater becomes more diverse. Based on the composition graphs, it can be concluded that there is a possibility of intrusion of saline water containing sodium, magnesium, sulfate and chloride ions or the dissolution of some minerals such as halite and gypsum sulfate, especially in the groundwater of the plain. The results the ionic ratios related to the intrusion of salt water in water resources show the good quality of the groundwater and the recharge of the aquifer by limestone formations. Considering that the springs are located in the groundwater recharge area (fresh water), they are less affected by human pollution and, as a result, they have better chemical quality. On the other hand, the wells situated in the plain, due to human activities such as the excessive use of nitrogen fertilizers for agricultural products and the infiltration of urban or domestic sewage into the aquifer along with the intrusion of saline water into the groundwater in some areas of the plain show a greater tendency to become salty.

The present study was conducted in order to evaluate and compare the quality of underground water resources (springs and wells) in the eastern part of Gorgan Plain in terms of potability and irrigation in a 10-year period. In this research, the results of chemical analysis of 14 wells and 8 springs were used. Water quality index (WQI), Schuler's diagram and some criteria and standards were used to evaluate the quality of drinking water sources. Electrical conductivity, corrosion ratio, magnesium ratio, sodium absorption ratio, soluble sodium percentage, permeability ratio and overall ratio were used in the irrigation section. Then, the zoning of some effective parameters and indicators in each section was done in the GIS environment using the IDW method. Based on the WQI index, the quality of all springs and wells on the edge of the highlands is in the excellent category, but as you move away from the plain, the quality of some wells varies from good to poor. Based on the concentration of some hydrochemical parameters, standards and Schuler's diagram, except for one remaining well, the studied water sources are of suitable quality for drinking. In the irrigation sector, based on the Wilcox diagram, sodium absorption ratio, salinity risk, residual sodium carbonate index and overall ratio, water from wells in the west of the region should be used with caution. In general, the quality of spring water in both drinking and irrigation sectors is much better than well water.

Fluoride is one of the important ions in drinking water, which in low or high concentrations causes some problems related to human health, such as tooth decay, dental fluorosis, or skeletal fluorosis. Present study was carried out to investigate the fluoride concentration as well as the effective factors in the fluoride distribution in drinking water supply sources of Golestan province.

For this purpose, Golestan province was divided into four regions according to the distribution of loess. Next, groundwater samples from these areas were collected and chemical parameters of TDS, HCO3-, Cl-, SO42-, NO3-, NO2-, F-, PO42-, Ca2+, Mg2+, Na+, K+ and Fe2+analyzed. After hydrogeochemical and statistical assessment, the relationship between fluoride and loess deposits and some physicochemical parameters were investigated.

Results of four regions showed that the fluoride amount is directly related to the loess deposits spread, so that in region 1 including Maraveh Tappeh, Kalaleh, and Gonbad there is the most spread of loess deposits, the fluoride amount is more than other areas. Results revealed that high correlation of fluoride with some ions such as calcium, bicarbonate, iron, sodium, and phosphate. Also, there is a high correlation between electrical conductivity as a salinity parameter and fluoride concentration in groundwater. So, an increase in salinity, the fluoride amount in the province's water resources has increased significantly. Water-rock reaction is the main factor controlling the groundwater chemistry and as a result, most possible factor for the fluoride leaching into groundwater.

Chemical cement of loess along with some clay minerals is the main source of fluoride in groundwater sources in region 1 with the most spread of loess deposits. Saline water of the lower layers and their intrusion into the fresh water aquifer can be considered as the fluoride second source in Gorgan Plain.

It is important to find a simple connection between physic-chemical parameters and indices due to complexity and difficulties of using some indices. This research was performed to determine the relationship between physicochemical parameters and water quality indices

In this research, dominant water type of Gamasyab and GharehSou rivers was first determined using radial diagram. Then, to classify the water quality of two rivers, 14 quality water indices together with national standards for drinking water 1053 and WHO were used. Linear regression was used to determine the relationships between quality indices and physicochemical parameters. Finally, for the accuracy of the results of linear regression, the obtained relationships were tested for two other water sources (river and Gorgan Bay).

Based on hydrochemical results, the predominant type of water in both rivers is Ca-HCO3. Based on diagrams and criteria related to drinking and agriculture, the water quality of both rivers is in the desired range. The results of Langelier, Ryznar, Larsson-Skold and Puckorius indices showed that water quality for the industrial sector was relatively corrosive. Also, the water quality at the study stations is suitable for livestock drinking. The results of linear regression between quality indices with physicochemical parameters of water and some ion ratios showed that the resulting relationships for calculating quality indices can be used for different water types from fresh to saline. Also, comparing the results of linear regression simulations with water quality indicators, indicates the high accuracy of the relationships in water classification for different uses.

The present study was conducted to investigate the effect of increasing uncontrolled drilling of water wells and subsequent extraction of renewable capacity of Gorgan plain aquifer on the decrease in groundwater level and some water quality parameters in a specific period of 30 years. For this purpose, the trend of rainfall changes, drilling wells, groundwater level fluctuations, as well as some physicochemical parameters were investigated in the studied period. Data analysis of variance was used to investigate the statistical differences between quantitative and qualitative parameters. The annual changes in drilling of authorized and illegal wells in the province shows an increasing trend in the number of wells drilled in the Gorgan plain, followed by an increase in the volume of water extracted since the early 1980s. The results of statistical studies, histograms of annual changes in groundwater level of deep and semi-deep wells as well as hydrographs of deep and semi-deep aquifers studied show a reduction in groundwater level in both semi-deep and deep aquifers in the study period. Since the average annual rainfall in the study period is almost constant, the drilling of shallow and deep wells followed by uncontrolled abstraction of deep and semi-deep aquifers is the most likely major factor in the decline of groundwater levels in the study plain. Based on the statistical results, a significant difference was observed between most of the physicochemical parameters of semi-deep and deep wells in the old and new periods. However, these changes are greater in semi-deep wells than the deep ones. Also, the two parameters Cl and Na, which are the main factors of water salinity, show the greatest changes. Hydrogeochemical diagrams of plain aquifers show an increase in soluble solids as well as changes in the type and hydrochemical facies of groundwater in the new period. However, the trend of changes in the shallow aquifer is more intense.

Groundwater is one of the most valuable water resource in Iran, which is mainly influenced by rainfall patterns in a region. In the present study, 30-years rainfall and groundwater level data were used in the three watersheds of Galikesh, Ramian and Mohammadabad to model the rainfall and groundwater level. The prediction of the groundwater level using the rainfall data for the next 12 months was done using the Transfer Function (TF) and using SAS and MINITAB software. Validation of predicted values was done using MAD, RMSE and MAPE indices. The results showed that according to the autocorrelation diagrams, all time series have seasonal trend with a period of 12 months. The results of the autocorrelation diagrams showed that in Galikesh and Mohammadabad watersheds, rainfall has a direct effect on the groundwater level with a delay of three months, but in the Ramian watershed, this delay was one month. It was also found that the transfer function model had a good performance in fitting the monthly groundwater level in all 3 studied watersheds.

To investigate the flood effect on changing the Zarrin-Gol water quality parameters, water was sampled from five stations on the river in three periods before, during, and after a flood and then some physicochemical parameters were determined. F-test was used to compare and determine the statistical difference between the qualitative parameters. Then, the hydrogeochemical changes of the river, effective factors in controlling the chemical composition as well as the dominant processes of the river water were determined. Finally, saturation indices were used to predict the possibility of precipitation/dissolution of some carbonate and evaporative minerals in all three periods. Results revealed that during the flood, chloride, and sodium ions were predominant ions in water and the most changes at different times were related to these two ions. The predominant water type in the periods before and after the flood was Mg-HCO3. Based on the Piper and Durov diagrams, most pre- and post-flood samples have facies of recharge areas. While, during the flood, with the abundance of chloride and sulfate ions in the water, composite facies prevail, and TDS at this time is almost three times before it occurs. Based on the accumulation, distribution, and orientation of the samples on the Gibbs diagram, the main factor controlling the water chemistry of the Zarringol river in all three periods is the chemical weathering of the minerals that form the basin rocks. Also, based on the results of ionic ratios, some evaporative minerals dissolution such as gypsum simultaneously with the phenomenon of cation exchange is one of the dominant hydrogeochemical processes during floods. While in most samples before and after the flood, the reverse ion exchange process is predominant. According to the results of bivariate diagrams, the main source of salinity of the Zarringol river is the dissolution of evaporative minerals (such as halite) belonging to the Mubarak Formation.

Nowadays, demand for water is increasing especially in arid and semi-arid regions (e.g., Iran) due to population growth, economic development, higher standard of living, and changes in consumption patterns. Hence, optimal management of water resources in these areas is essential. Furthermore, climate change and increasingly extreme weather events have caused a surge in natural disasters (e.g., floods) over the past 50 years in arid and semi-arid regions. Thus, forecasting and modeling of runoff data is extremely necessary for planning and managing of water resources. Water flow forecasting plays a key role in flood reduction, reservoir optimization, and reservoir management. These models are mostly developed and applied for simulation and prediction. Therefore, different types of forecasting methods have been proposed over the decades including: Box and Jenkins (SARIMA), Artificial Neural Network (ANN), Adaptive Neuro-Fuzzy Inference Systems (ANFIS), and Genetic Algorithm (GA) models. Forecasting hydrological reactions invariably involves uncertainty. So far, numerous studies have been performed to improve the reliability and accuracy of hydrological forecasts, resulting in reduced risk error. Therefore, the main objective of current research was to use artificial intelligence methods consisting of ANN, ANFIS, GA, and SARIMA models to predict monthly runoff data and also select the best model for the efficient management of water resources in the Gharasou River basin.

Gharasou river basin with an area of 1624 square kilometers is located in the west of Golestan province and has an important role in providing water resources required in this province. In this research, to model and forecast the runoff process, the monthly runoff time series of 4 hydrometric stations of Pol-Tuskestan, Naharkhoran, Ghazmahale, and Siah-ab over Gharasou River basin were used for a period of 36 years (1982-2018). The time series homogeneity was examined using the Chow`s method. Runoff data are time dependent, so initially these data were arranged in time series. After sorting the data, four models consisting of Box and Jenkins (SARIMA), Artificial Neural Network (ANN), Adaptive Neuro-Fuzzy Inference Systems (ANFIS), and Genetic Algorithm (GA) models were used to forecast monthly runoff. To increase the prediction accuracy of other methods, the far time series of monthly runoff were first ignored based on to neural network method and then the number of effective years for modeling was determined. Later, the monthly runoff was forecasted for the next 12 months using four models consisting of SARIMA, ANN, ANFIS, and GA. Lastly, based on the forecasted values and using MAD, RMSE and MAPE indices, the accuracy and precision of SARIMA, ANN, ANFIS and GA models were compared. Modeling and forecasting were done using Minitab, R and SPSS software packages.

Based on the type of distribution of monthly runoff and the presence of zero data, log(1+Yt) conversion was used in the models to stabilize the variance. The results according to the autocorrelation diagrams revealed that the time series in all stations have seasonal trend with a period of 12 months. Then, the monthly runoff of the next 12 months was forecasted using four models including SARIMA, ANN, ANFIS and GA. Model validation results using three indicators of MAD, RMSE and MAPE revealed that the ANN model in the three hydrometric stations of Naharkhoran, Pol-Tuskestan and Siah-ab had the best performance. In these three hydrometric stations, after ANN model, the ANFIS model has been selected as the most suitable model. However, the performance of these two models has been very similar. In the Ghazmahaleh hydrometric station, two models of ANFIS and ANN had the best performance, respectively. In this study, it was also found that in four selected hydrometric stations, the GA model had a good performance after the two models of ANN and ANFIS. Although SARIMA model performed very well in identifying the trend of monthly runoff changes, it had the weakest performance among the methods. The forecast data using SARIMA model were overestimated compared to the actual data for March and April, but in other months, the forecast data using this model were relatively appropriate.

In this research, to model and predict the monthly runoff process, four models including SARIMA, ANN, ANFIS, and GA models were used for four selected hydrometric stations in Gharasou River basin. The results of model validation using three indicators of MAD, RMSE and MAPE showed that the ANN and ANFIS models had the best performance among the four models used. It was also found that time series of runoff data in hydrometric stations have undergone structural changes due to the physical and climatic alterations in the upstream of rivers. Therefore, the distant past of time series may cause deviations in modeling and forecasting results. To overcome this problem, making use of an algorithm to select the number of effective years in modeling and forecasting can be useful. Artificial neural network provides a suitable criterion for selecting the number of effective years due to its high accuracy in modeling and forecasting. Based on the effective years identified by this model, other models can be modified and provide more appropriate input data for forecasting from other models.

Soil hydraulic conductivity is one of the important parameters to estimate soil erodibility, soil water flow, estimate runoff, and design drainage systems. This study was carried out to determine the hydraulic saturation (Ks) of surface and subsurface loess soils of Aghemam watershed (2) that located in the northeast of Golestan province. For this purpose, three types of soils in this area including hill, loess plateau and alluvial terrace in two surface and subsurface layers were sampled. In this study, in addition to determining Ks using the falling head method, some physicochemical properties of soil samples such as salinity, neutral lime, organic matter and soil texture were measured in the laboratory and their relationship with Ks was investigated. Then, the spatial variations of surface and subsurface saturation hydraulic conductivity in the study area were plotted using GIS software and IDW method. The spatial variations of Ks in both layers indicated its direct relationship between the two layers. However, the value of this parameter in the surface layer is more than for the subsurface layer. Also, the amount of Ks is relatively high in the two types of loess plateau and hill (3.9 cm/h), except in the alluvial terrace type, which is generally low (0.9 cm/h). The statistical results of linear multiple regression and stepwise methods showed that among the variables studied, the organic matter and neutral lime parameters, respectively, have the most impact on determining the amount of surface Ks (R2 = 0.9556) and subsurface (R2=0.8607) in the study area.

In this study, the ability of three rangeland species Atriplex halimus, A. canescens and A. lentiformis to remove nitrate from soil in vitro (greenhouse) in a completely randomized design was investigated. For this purpose, potassium nitrate salt (KNO3) was used in four treatments control, 6.3 ppm, 9.5 ppm and 14.5 ppm in three repetitions. Plant species used in this study with an approximate age of 6 months were prepared from the village of Chaparquimeh, Gonbad Kavous city in Golestan province. Selected species were cultivated in nitrate-contaminated soils with the concentrations mentioned and after a period of three and six months, the amount of dry weight and nitrogen of aerial and underground organs of the species and the amount of nitrate in the soil were measured. With increasing salt concentration from 6.3 ppm to 14.5 ppm, the amount of dry weight of aerial parts in A. canescens  has decreased from 28.31 ppm to 14.05 ppm, in A. halimus from 28.83 ppm to 11.75 ppm and in A. lentiformis from 39.17 ppm to 16.05 ppm . A downward trend was observed in the amount of dry weight of underground organs in the studied species, so that by increasing the salt concentration from 6.3 ppm to 14.5 ppm, the amount of underground dry weight in A. canescens  from 8.31 ppm to 5.05 ppm, in A. halimus from 6.83 ppm to 4.75 ppm and in A. lentiformis decreased from 10.17 ppm to 6.47 ppm. The results of study showed that the level of soil nitrate removal at different concentrations decreased in all three species. The percentage of soil nitrate removal efficiency by A. canescens at concentrations of 6.3 ppm, 9.5 ppm and 14.5 ppm is 71%, 52% and 37%, respectively, by A. halimus are reported to be 62%, 45% and 38%, respectively. However, A. lentiformis removed nitrate at a higher level than the other two species with 80%, 64% and 47%, respectively. The results showed that with increasing the concentration of this contamination in the soil, the phytoremediation capacity of the studied species decreased and A. lentiformis with high nitrogen storage in its tissues has an effective role in clearing nitrate-contaminated soils.

groundwater. In the present study, the 3-year drought and wet periods were determined using 23-year rainfall data of four meteorological stations and the SIAP index. To investigate the physicochemical properties of groundwater, after considering the data of observation wells in the Eastern part of Gorgan plain, 14 deep and semi-deep wells were selected. Then, three criteria of EC, SAR, and Na were used to assess the water in the agricultural sector and the Schoeller diagram was used to assess the water in the drinking sector. To estimate the significant differences between the physicochemical properties of groundwater in the three periods of the wet period, drought, and long-term, an F-test at the probability level of 0.05 was used. The results revealed that the water quality of semi-deep wells is better than for deep wells in agriculture and drinking water sections. Based on the Piper diagram, the chemical facies of semi-deep wells are less diverse than deep wells. The results of both deep and semi-deep wells showed that chemical facies in the dry season show a greater tendency to achieve seawater composition. The results of the F test showed that there is a significant difference with 95% probability between groundwater quality parameters in semi-deep aquifers in wet and dry periods. In contrast, the occurrence of wet and dry periods in the study area had little effect on the physicochemical properties of deep aquifers.

Doogh river is one of the main tributaries of Gorganroud in the east of Golestan province, which has an important role in supplying drinking water to Gonbad Kavous. Furthermore, it is one of the water supply sources of Golestan dam with agriculture use. Therefore, the study of hydrochemical and water quality of this river for drinking, agricultural, and industrial uses is of great importance. In this study, Stiff, Piper and Gibbs diagrams were used to investigate river hydrochemistry. Wilcox, sodium soluble percentage, magnesium ratio, and permeability index was evaluated to classify water for irrigation purpose. To investigate Doogh river water for drinking purpose, NSFWQI index, Schoeller diagram, and water quality standards were used. Eventually, water quality for industry was assessed using corrosivity ratio, Langelier Ryznar indices. Results showed Ca-Mg-HCO3 is dominant hydrochemical facies and rock-water interaction is the main controlling factor in river water chemistry. Based on NSFWQI index and Schoeller diagram, water quality was in acceptable class for drinking purpose. However, turbidity and fecal coliforms values based on water quality standards were higher than drinking limit and needs to be purified. Based on the results of sodium percentage, magnesium ratio, and permeability index, water quality is well evaluated for agriculture purpose. Industrial indices indicate that the relatively corrosive property. Water quality for irrigation purpose is well evaluated and there is no need for soil regeneration after use. Although Doogh river water is relatively corrosive, but it is save to use all metallic equipment to transfer and extract water

Nowadays, forecasting and modeling the rainfall-runoff process is essential for planning and managing water resources. Rainfall-Runoff hydrologic models provide simplified characterizations of the real-world system. A wide range of rainfall-runoff models is currently used by researchers and experts. These models are mainly developed and applied for simulation and prediction. They allow decision-makers to make the most effective decision for planning and operation. Rainfall-runoff modeling is essential in flood routing, flood prediction, flood frequency estimation, real-time flood forecasting, warning climate changes, and other cases. Time series analysis includes methods for analyzing and modeling time-series data to extract forecasts and other characteristics of the time-series data. Time series forecasting is using a model to predict future values based on previously observed values. The transfer function is an advanced and multivariate time series model that enables us to utilize other time series to produce response time-series forecasts. Although the rainfall-runoff process has been modeled by various methods so far, less attention has been paid to the transfer function model. The primary purpose of this study is to introduce the transfer function to model the rainfall-runoff process and compare its results to the common time series model (SAIRMA) in Ramian and Galikesh watersheds.

In this research, to model the rainfall-runoff process, the monthly averages of rainfall and discharge time series of Ramian and Galikesh watersheds were used for a period of 36 years (1981-2017). These two watersheds are branches of the Gorganroud River which has an essential role in providing water resources required in Golestan province. The time series homogeneity was examined using Chow`s method. The existence of trends in time series was investigated based on the moving average time series plot, and the existence of seasonal trends was explored using autocorrelation charts. The cross-correlation diagram was used to investigate the relationship between rainfall and runoff time series. The SARIMA and transfer function models were used to predict monthly runoff. Without considering the rainfall time series, the runoff time series was modeled by a SARIMA model. Also, considering the precipitation time series as an input time series, a transfer function is used to model runoff time series as a response time series. The transfer function modeling was performed in three steps, pre-whitening, selecting the appropriate parameters of the transfer function model, and finally fitting a SARIMA model to the residual values. For the SARIMA model, the goodness of fit test was evaluated based on the Box Pierce statistic. For the transfer function model, two indices were computed. The first index investigated the relationship between runoff and rainfall, and the second index performed the goodness of fit test for residual time series. Then, based on the forecasted and fitted values and using MAD, RMSE, MAPE, and E indices, the accuracy, and precision of SARIMA and transfer function models were compared.

 Results :

According to the autocorrelation diagrams, the results showed that the all-time series has a seasonal trend over 12 months. Also, according to the moving average time series, there was no significant shift in rainfall time series, but there was a decreasing trend in the runoff time series. The transformation log(1+Yt)   was used to the monthly average discharges time series. Then, the transfer function and SARIMA models were used to forecast the monthly average discharges for the next 12 months by using Minitab and SAS software. In the next step, the validation of the predicted data and the fitted data of monthly average discharges of two models were evaluated using MAD, RMSE, MAPE, and E indices. The results showed that the transfer function model in both Galikesh and Ramian watersheds has higher precision from the two perspectives of forecasting and model fitting than the Box and Jenkins (SARIMA) model.

Discussion & Conclusions :

In this research, to model the rainfall-runoff process, the monthly average of rainfall and runoff were used in Ramian and Galikesh watersheds. Then SARIMA and transfer function models were used to predict monthly runoff. The results showed that the transfer function model in both Galikesh and Ramian watersheds has higher precision than the SARIMA model from the two forecasting and model fitting perspectives. Changes in rainfall, directly and indirectly, cause changes in runoff, and this effect might be happened either at the same time or with a time lag. The transfer function model can consider the time lags of both time series in forecasting runoff time series. The SARIMA models lack the information of other environmental parameters and apply just the runoff in the present and past times to predict future values. Since the pattern of these parameters changes annually, not considering these changes leads to unreliable forecasts from SARIMA models. However, in transfer function models, it is possible to investigate the effect of more than one environmental parameter on the runoff changes, increasing the accuracy of model fitting and forecasting.

Corrosion and precipitationare physicochemical processes that reduce the amount of water flow in water transfer pipes and the effective life of water supply facilities, increase the energy consumption for water transfer, and cause some diseases among consumers. The present study was conducted to investigate the corrosion tendency and precipitationalong the Gorganroud River from highlands to the Gorgan Gulf.

In this study, the results of the analysis of 11 physicochemical parameters (Calcium, Magnesium, Sodium, Potassium, Bicarbonate, Sulfate, Chloride, total dissolved solids, electrical conductivity, temperature, and pH) of the Gorganroud River during a period of 10 years were used (2004-2014).First, the annual mean changes in the qualitative parameters of water samples during the statistical period of the studied stations were investigated. Then, triangular diagrams were used to assess the Gorganroud River hydrochemical at the studied stations. Next, changes in water hardness as an important qualitative parameter in the industrial, agricultural, and drinking sectors were investigated along the Gorganroud River. Saturation indices were used to predict and the probability of precipitation or dissolution of some carbonate minerals (such as calcite, dolomite) and evaporites (such as anhydrite, gypsum, and halite) along the Gorganrood River. Then, the trend of changes in Langelier, Ryznar, Puckorius, Larson-Skold corrosion indices, corrosion ratio, and the calcium carbonate precipitation potential of Gorganroud River at four stations was investigated. Next, a one-way ANOVA test was used to investigate the significance level of indices in the studied stations. Finally, the relationship between mineral saturation indices and corrosion indices was investigated.  

Based on the accumulation and distribution pattern of the samples in the triangular diagram, the dominant water type in the Gorganroud River is bicarbonate on the margin of heights, and as it enters the plain and the chloride ion concentration increases, it tends to reach full maturity, the sodium chloride type. Hardness increased along the water movement path. The results of saturation indices showed that the river’s water is supersaturated with carbonate minerals and undersaturated with evaporite minerals. Based on Ryznar, Puckorius and Larson-Skold indices, Gorganroud River water tends to cause corrosion. However, the precipitation rate increased from the margin of highlands to Gorgan Gulf. The results of the calcium carbonate precipitation potential and Langelier Index indicated that Gorganroud River tends to precipitation over the study area. Investigation of the relationship between saturation indices with corrosion indices and calcium carbonate precipitation potential showed linear relationships between qualitative indices and saturation indices. The results of the statistical test showed a significant difference between the calculated indices in the studied stations.  

Although based on the hydrochemical results the main factor controlling water chemistry of the Gorganroud River was the water-rock reaction, factors such as saline water intrusion of Gorgan Gulf in the lower part of the river and inflow of untreated effluents into the river caused rapid hydrochemical evolution of the river and reached the sodium chloride type. Increasing the number of physicochemical parameters along the river path in addition to increasing the water hardness, has reduced corrosion and increased precipitation rate. Statistical results showed a clear linear relationship between saturation indices and corrosion and sequestration indices in water.

In order to investigate the effect of flood in March 2019 on quantitative and qualitative changes of groundwater, the floodplain at the end of Gorganroud river basin, which was naturally exposed to floods, was selected. To investigate changes in groundwater quantity and quality, 17 and 11 observation wells with suitable distribution in the study area were selected, respectively. Then, quantitative (groundwater level) and qualitative data (11 physicochemical parameters) of wells were collected in two periods before and after the floods. First, groundwater level changes in two periods were evaluated by paired T-test and average groundwater level of the plain. Then, physicochemical characteristics changes in two periods were evaluated using paired T-test. Finally, hydrogeochemical changes were assessed using Gibbs, Durov and Piper diagrams, and the water quality for agricultural and drinking purposes were investigated using Wilcox and Schoeller diagrams. Paired T-test results showed that the groundwater level in 88.2% of the observation wells after the flood had a significant increase. This has increased the groundwater level as well as the unit hydrograph of the plain (about 2 meters) after the flood. The results of changes in groundwater quality parameters showed that the amount of EC, anions and cations (except NO3) were decreased in most of the observed wells after the flood. This has reduced the hardness of groundwater but has not had a significant effect on the type and hydrogeochemical facies of floodplain groundwater. The reason can be the hydrochemical similarity of infiltrated water and groundwater of the plain aquifer.

One of the important parameters for identifying the erosion-sensitive points is the use of soil erodibility factor, which is determined by two methods; direct and indirect methods. The direct method for calculating soil erodibility has good accuracy. However, it is economically expensive. Therefore, this method is not considered by experts. The indirect and conventional method for calculating the soil erodibility is the Wischmeier nomograph method, which was presented for non-calcareous and semi-wet soils of the United States. Since the majority of the soils in Iran are calcareous, hence in this research, the Vaezi method, which is designed for this type of soil, was used. Loess is one of the most important Quaternary sedimentary formations in northeastern Iran, which has variable sedimentation and erosion potential due to its physicochemical properties. This study was conducted to evaluate and compare the estimated values of soil erodibility (K) from two methods of Wischmeier nomograph and Vaezi method in calcareous-loess soils of Arab-Qareh-Haji watershed in the east of Golestan province.

The study watershed with an area of 2595 hectares is located in the northeast of Golestan province. To perform this research, after the initial studies, the components of the land unit in the study area (including river terrace, loess plateau, and hill) were selected as the working unit. For this purpose, 42 surface samples (0-10 cm depth) were collected from each part of the land unit. In this study, the standard laboratory methods were used to determine the soil physicochemical parameters. Soil physicochemical properties, including soil texture, neutral lime, organic matter, coarse sand, very fine sand+silt, and soil structure, were measured in the laboratory. The saturation hydraulic conductivity of soil in the laboratory was estimated using the falling head method. In this research, the actual soil erodibility was measured using a rain simulator in the field (in plots of 1 m2). Then, spatial changes of soil erodibility in the study area were plotted using GIS software and inverse distance weighting (IDW) method. F-test and Games-Howell at the probability level of 0.05 were used to compare and determine the statistical difference between the estimated erodibility values (the Wischmeier nomograph and Vaezi methods) with actual data. To estimate the most effective parameter in the soil erodibility using the Vaezi method, multiple linear regression and stepwise methods were used. Statistical tests were performed using Minitab software.

The average silt particles in the soil were measured about 60% in the Arab-Qareh-Haji watershed, which plays an important role in the soil erodibility. In this watershed, the ratio of fine sand to coarse sand was calculated about 18, and this can be one of the main causes of runoff in this area. Soil texture assessment in this watershed revealed that around 90 percent of soil samples have silt loam texture, and the rest of the samples has loam one. Also, the average lime in study area was estimated at about 29%. This amount is higher than the standard lime (15%) in the soil to create stable aggregates in the wet state. Then, soil erodibility values were determined by three methods Wischmeier nomograph, Vaezi method, and rain simulator (actual data). The results showed that the value of soil erodibility using Wischmeier nomograph was estimated at about 30.4 and 18.8 times higher than for the Vaezi method and actual data, respectively. The results of F-test and Games-Howell test with 95% probability showed that there was no significant difference between the soil erodibility from the Vaezi method and the actual data, while there was a significant difference between the Wischmeier method and the actual data. Results of multiple linear regression and stepwise methods showed that the most important variables in estimating the soil erodibility are silt, organic matter, neutral lime factors, and coarse sand, respectively (R2 = 0.9648, R2-adj = 0.9539). In this study, it was not possible to estimate the soil erodibility factor by Vaezi method due to the high percentage of neutral lime for a number of samples.

In this study, the average lime was estimated at about 29%. This amount is higher than the standard lime (15%) in the soil to create stable aggregates in the wet state. Therefore, it seems that excess lime in the wet soil can reduce the stability of aggregates. In this watershed, a large number of tunnels and gully were observed, which indicates that this soil is erodible. The statistical analysis results showed that the soil erodibility values from the Vaezi method in this watershed were relatively close to the actual data but were less estimates, while the Wischmeier nomograph method was significantly different from the actual data and was overestimated. However, for areas where the amount of neutral lime was over 30%, the Vaezi method was not able to calculate the soil erodibility factor. Hence, for the areas where the percentage of neutral lime is lower than 30%, the use of the Vaezi method is more suitable than the Wischmeier nomograph method, and for areas where the percentage of neutral lime is higher than 30%, the model needs to be calibrated and updated.

The use of packaged drinking water is on the rise nowadays in most countries, including Iran. Currently, more than 100 different brands of packaged drinking water are produced and distributed in Iran. This study was done to evaluate the quality of Iranian, foreign packaged drinking waters and municipal drinking water in Golestan Province, north of Iran.

This descriptive-analytical study was done on 56 packaged drinking waters of different Iranian and foreign brands, eight brands produced in Golestan province and a number of municipal drinking water samples were collected from Gorgan and Gonbad Kavous cities in northern Iran. To assess the quality of packaged drinking water and drinking water, their physicochemical parameters were compared with National Iranian Standards 1053 and WHO. Stiff and Piper diagrams were plotted to determine the type and hydrochemical facies of water samples. Gibbs and Schoeller diagrams were used to determine the water chemistry controlling factors of water samples and their water quality for drinking, respectively.

The concentrations of physicochemical parameters (except bicarbonate) were within the range of national drinking water standards 1053 and WHO. The average nitrate concentration in all packaged drinking and drinking water was within the standard range. The fluoride concentration of all packaged drinking waters and drinking water was within the range of WHO standard. However, only 14 samples of all packaged drinking and drinking water samples are within the range of 1053 National Iranian Water Standard. The total concentration of soluble solids and the total hardness of packaged drinking water were within the range of 1053 NW. There was also a significant difference (P<0.05) between the chemical parameters of magnesium, sodium, chloride and nitrate in packaged drinking water produced in Golestan province with the municipal drinking water samples.

The amount of fluoride in drinking water in this study was less than desirable and required fluorination. The quality of packaged drinking water in Golestan province is better than the municipal drinking water.

Soil compaction reduces pore space in the soil and subsequently diminishes the diameter of capillary tubes in the soil. This limits the plantchr('39')s access to minerals and pore water. Hence, it is necessary to evaluate soil compaction in order to improve rangeland’s management as well as agricultural lands. In this study, soil compaction effect on root growth of five rangeland plant species, Ferula gummosa, Agropyrin elangatum, Medicago minima, Atriplex canescens and Atriplex lentiformis, at laboratory scale was investigated. First, three soil compaction levels (0.36, 0.47 and 0.56 persentage of porosity) for a loam-clay soil were provided using hammer dropping method within plastic pots. In the next step, three seeds from each species were cultivated in each plastic pot with three replications. After a period of 60 days, the length of main and subsidiary roots were measured. One way ANOVA test method was used for statistical analysis of data. Results shows a linear relationship between soil compaction and growth of main and subsidiary root for cultivated species. So, with decreasing in soil compaction degree, the growth of main and subsidiary root was significantly increased. Comparison of main and subsidiary root growth of the studied plant species showed that the growth of main root of Atriplex canescens was higher than other species in all soil compaction levels. Moreover, Atriplex canescens was only species in which its subsidiary roots length was not significantly different in all soil compaction levels. Also, in two plant species of Medicago minima and Atriplex lentiformis, there is not significantly different between the growth of their main roots in all soil compaction levels. Results showed that subsidiary root number increased with reducing soil compaction. The highest percentage of measured frequency in all plants is related to the subsidiary roots of 0-100 cm in porosity of 56%. Therefore, by increasing the amount of porosity and consequently increasing soil porosity, the conditions for longitudinal growth of the roots of rangeland plants are provided. However, the rate of root growth changes in the subsidiary roots is far greater than the main root.

In this study, the hydrochemical evolution and qualitative deterioration of Gorganrud River water were investigated in a distance of approximately 100 km from the northern margin of the Alborz highlands to Gorgan Gulf. For this purpose, the analyses results of elven physicochemical parameters related to four hydrometric stations over a ten-year statistical period were used. Gibbs, Stiff, Piper, Durov diagrams as well as five saturation indices for carbonate, sulfate and chloride minerals were used to study the hydrochemical evolution of the river. Water quality changes from drinking (using Schoeller Diagram), agricultural (using Wilcox Diagram), industrial and (using corrosion indices) along the Gorganrud River were also investigated. In this study, F test and hierarchical cluster analysis were used to analyze the variance of data and the number of factors affecting water hydrochemistry, respectively. The results showed that rock-water reaction, evaporation, and Gorgan Gulf saline water intrusion are the most important factors controlling the river water chemistry. Also, the dominant water type of Gorganrud River at the highlands margin is bicarbonate and as it enters the plain, it tends to reach full maturity (i.e. the type of sodium chloride). At all stations, river water is supersaturated with respect to calcite and dolomite but it is under saturated with respect to anhydrite, gypsum and halite. However, evaporite minerals saturation increases in the flow direction. The quality of water for drinking and agriculture is suitable at the margins of highlands and it decreases sharply as enters the plain and pathes into the Gorgan Gulf. According to the statistical analysis results, most of the changes are observed between the Lazoure Station at the highlands margin and the Qazaghli Station in the middle parts of the plain and after that no significant changes is observed between the quality parameters as far as Gorganroud outlet.

In this study, a part of the Gorganroud basin was selected to evaluate of the drought effect on 13 water physicochemical parameters. After collecting meteorological and hydrometric stations data in a period of 43-year (1350-1393), a 5-year drought index was determined using the standard precipitation index and moving average method. Then, the water quality parameters were obtained for a long-term and a drought period using the available hydrometric stations data. The average concentration of most of anions and cations, electrical conductivity, and sodium adsorption ratio have increased from upstream to downstream, so that, this increase in the downstream station is about seven times higher than its upstream station in the drought period. The average of anions, cations, electrical conductivity, and sodium absorption ratios were increase during the drought period compared to the long-term period. Using the Wilcox diagram, agricultural water quality is decreases in the direction of river flow, so that the water category changes from C2S1 (suitable for agriculture) in the upstream to C4S3 (harmful to agriculture) in the downstream. Therefore, it can be concluded that the occurrence of drought periods has a significant effect on the water quality factors in comparison with the long-term period, so that, the agricultural water quality drastically has reduced by a decrease in rainfall and subsequently decrease in river discharge within the drought period.

Rivers water quality study can be a great help to water-resource management and planning. This study was conducted to investigate the water quality of Chehelchay River using the IRWQISC.

In this study, water samples were collected from seven different stations along Chehelchay River during a period of 6 months. In order to use IRWQISC, the physicochemical and biological some parameters were measured. After calculating the IRWQISC values for each station, the changes in the IRWQISC values were investigated along river. Then, the results of IRWQISC were compared drinking water and agriculture water standards.

The results of this study showed that Chehelchay River water was situated in a relatively good quality category based on the IRWQISC. IRWQISC diminished in the flow direction from the upstream sampling point to the outlet of basin resulting in a reduction in water quality of river. Results also showed that there is a direct relationship between IRWQISC and the rate of discharge so that the value of IRWQISC increases with increasing the rate of discharge.

The results of this study showed that the average IRWQISC index was better than summer season in spring. Flow changes and IRWQISC index indicate a direct relationship between them, with a slight increase in the rate of fluctuation. Comparison of parameters used in IRWQISC with drinking water and agriculture water standards showed the Chehelchay River water is suitable only for agriculture uses and it cannot be used for drinking purposes. Results showed that water purification must be performed to remove fecal coliform and reduce turbidity of water before using as a drinking water source.