In recent decades, due to the importance of water quality issues and controlling the proposed environmental damages, the study of the pollutants behavior in water bodies has also became important. Sulfur compounds are contaminating factors in water bodies which should be considered in deep water bodies such as lakes and reservoirs of dams. The most common sulfur compounds in deep water bodies are sulfate and hydrogen sulfide. Accurate prediction of the interactions between these compounds can be helpful in designing hydraulic structures and water quality management. The present study examines this context and consider how they interact with each other. The international experiences in dealing with high concentrations of sulfur compounds in the reservoirs of dams and lakes are investigated in this study. This study also examines the relationship between the physical, chemical and biological reactions of the sulfur cycle in aquatic environments. The modeling will focus on two main sulfur compounds in the water, namely sulfate and hydrogen sulfide. To simulate the water quality in the reservoirs, the CE-QUAL-W2 model, which has recently been upgraded to the simulation of the sulfur cycle, has been employed. After model setup, its calibration is performed. Another point to be noted is that the spatial and temporal distribution of sulfur compounds is influenced by reaction factors and parameters affecting the temperature, hydrodynamics and the distribution of these types of pollutants. Setting the coefficients and parameters effective in the process of biological deterioration can be caused by the behavior of sulfur compounds. The access to the field data is a challenging task in this effort. In order to reduce the error of the concentration of sulfur compounds in this research, the choice of these coefficients is based on the quantities available in valid references. Modeling the concentration of sulfur compounds in the water due to the multiplicity of factors affecting the biological and chemical reactions of the sulfur cycle in aquatic environments is essentially a difficult and challenging issue. Therefore, studying this problem in water bodies seems to be necessary. On the other hand, no studies have been conducted to identify, investigate and use numerical models to simulate the sulfur compounds (sulfate and sulfide hydrogen) in water bodies in Iran. It seems that this research can be the first tackle to resolve the uncertainties and problems associated with the sulfur cycle in aquatic structures, and to examine the behavior of this cycle in the actual reservoir of the dam in Iran. In general, the objectives of this study are classified into two general sections. First, the study of the behavior of sulfur cycle in deep water bodies, such as lakes and reservoirs of dams, playing an important role in the behavior and performance of reservoirs of dams. Then, identification and prediction of the behavior and effects induced by the sulfur compounds in a case study using CE-QUAL-W2. In fact, the behavior identification and assessment of the contaminants effects are an essential step to ensure from the proper execution of a project and method for determining, predicting, controlling and changing their effects on the entire environment, public health, and the health of ecosystems that sustain life and survival of humans. In this study, the status of the sulfur compounds is simulated in various scenarios, along with the important quality factors such as thermal stratification and dissolved oxygen distribution in the platform of a real case study (Seymareh Dam reservoir). Additionally, based on the model results and analyzing these scenarios, analyzing the time trends and predicted depth profile for probable concentrations of the sulfur compounds (sulfate and sulfide hydrogen) and analyzing the behavior sensitivity of these compounds are examined in comparison with different parameters. The results of the present study revealed: (1) a significant relationship between the dissolved oxygen status and the distribution of the sulfur compounds along the reservoir depth exists, so that the hydrogen sulfide concentration is increased as the dissolved oxygen decreases; (2) the behavior of the sulfur cycle is significantly related to the interaction of main biological agents in the sediments of the reservoir bed; (3) by increasing the sulfate concentration in the reservoir, the amount of the sulfate reduction increases and it leads to an increase in hydrogen sulfide in the reservoir; (4) considering the limited capacity of dissolution of hydrogen sulfide in water, this substance is released as bubbles from the water so that the amount of hydrogen sulfide emissions increases rapidly with increasing sulfate content in water

Due to the advances made in remote sensing technology, collecting information on the quality of surface water resources by this technology, while reducing the cost and time of traditional sampling, can cover all surface water areas. To monitor. In this study, the capability of Sentinel-2 and Landsat-8 satellite images to estimate the concentration of water quality parameters including acidity, electrical conductivity, total soluble solids, alkalinity and surface water temperature were investigated. First, the Sentinel-2 and Landsat-8 satellite images were pre-processed and then the appropriate bands were determined to identify a significant relationship between the values of each water quality parameter and the images were determined using linear regression and their accuracy was calculated for the actual values. The results show the superiority of Sentinel-2 images with Pearson coefficient, standard error and RMSe for PH parameter equal to 0.58, 0.28 and 0.29, EC equal to 0.847, 78.7 and 77.22, TDS equal to 0.895, 45.8 and 44.37 and for the alkalinity parameter only through Landsat-8 images with Pearson coefficient, standard error and RMSe equal to 0.473, 22 and 21.8, respectively. Both satellite images can be used for the water surface temperature parameter due to the high Pearson coefficient. These values are 0.871, 2.9 and 2.85 for Landsat-8 and 0.752 for Sentinel-2, respectively. 0, 14.4 and 4.06.

Construction of dams as an abnormal structure in the riverbed, although it is considered as a management and planning tool, but its lack of management and quantitative and qualitative monitoring can lead to environmental problems. Seymareh Dam in Karkheh catchment was flooded in 2011 with the aim of generating hydropower, increasing the regulation power of downstream dams and flood control. According to the water processes in the dam water resources network and quantitative and qualitative evaluation of the role of dewatering, quantitative and qualitative sampling was performed before and after the construction of the dam over a period of 10 years. The study of qualitative results showed that the role of geological formations, especially Gachsaran and Asmari formations is effective in increasing the concentration of solutes and dissolution and the left bank springs have more qualitative changes due to the greater thickness and volume of Gachsaran and Asmari formations. On the other hand, the correlation between reservoir water level during dewatering and quality parameters showed that dam reservoir dewatering had the greatest impact on the right bank springs and had more correlation in changes. The results of qualitative analysis in Seymareh river also showed that the anomaly in the quality parameters of R4 station due to two factors of rainfall in spring and the addition of water leaving the power plant has been effective in changing water quality.

One of the major issues in dam construction is water seepage، post impounding. Assessment and prediction of the amount of water leakage can be useful in preventing such events. The Seymareh dam has been constructed on the Seymareh River in Ilam province، Southwest of Iran. The dam controls the floods and generates hydroelectric power. It is already under impoundment and the seepage problem is being considered. Grout curtains have been employed in two directions at the right abutment of the dam to control the seepage. The normal reservoir level is 720 m and it has been impounded at the 660 m level up to the point. The purpose of this study is to predict the amount of water seepage through the right abutment of the dam by using numerical modeling. For this purpose، a new GW finite element code was used for a two-dimensional simulation of the water seepage. The Levels of the observations wells and the discharges of the downstream springs on the right river bank are used as the main data for this modeling and its verification. Assessments show that if the dam impoundment rises to the normal level، significant seepage may occur through the right abutment.

Large-scale landslides, especially those that block rivers, are among the most dangerous natural phenomena in mountainous regions all over the world. Occurrence of the world's biggest landslide in the Kabirkuh and on the way of Seymareh and Kashkan rivers blocked rivers and formed Seymareh and Jaydar dam lakes. The aim of this research which is an applied-developmental research and which is conducted using observational, historical and analytical methods is to reconstruct the dam lakes caused by Seymareh landslide occurrence and also to determine the age of them utilizing thermoluminescence techniques in order to determine the date of the occurrence of Seymareh landslide and formation of the lakes. Field studies using physical and conceptual tools together with laboratory methods have led to recognize four staged stalactites slips in the Kabirkuh and the subsequent formation of four lakes in the area of Seymareh valley and a single-stage lake within the Kashkan valley. The findings based on dating of eight samples from the surface and floor of Seymareh and Jaydar lakes using Thermoluminescence shows that the occurrence date of the Seymareh landslide and primary formation of of Seymareh lake is 85000 years ago.
The second Seymareh Lake formed 16500 years ago, the third one formed 10500 years ago and the fourth lake formed 10100 years ago. Therefore, Seymareh Valley has been exposed to consecutive landslides from 85000 to 10000 years ago. Jaydar lake sediments dating suggest that the formation of Jaydar Lake coincided with the occurrence of the main Seymareh landslide in about 85000 years ago and its evacuation in about 5000 years ago. Thus, Jaydar Lake has been lasted for about 80000 years.

Reservoirs are artificial lakes that have been created by humans for specific purposes. Water reservoirs has different uses which the most important are: municipal water supply, agricultural irrigation, aquaculture, power generation and etc. According to increasing of water demand the accurate study of water resources, determination of their pollutants, prevention, pollution control and optimal use of available water resources are required. Saymareh Dam is located about 40 km northwest of DARREH SHAHR in ILAM province. This dam was constructed with the aim of producing electric power, controlling and regulating of river floods. The aim of this study was to survey on the bacterial contamination of Seymareh Reservoir and its relationship to some water physical and chemical factors. According to the geographical and hydrological status of the reservoir, five stations (one station near the water entrance to the lake, 3 stations at the beginning of the lake, middle and near the crown, and one station after the reservoir) were sampled 8 months in 3 seasons of year for bacteriological, physical and chemical evaluation. Water quality standards for microbiological sampling were used. Then microbial tests including total bacterial count, total coliform count, fecal coliform and fecal streptococcus count were performed. In each station simultaneous measurements of some physical and chemical parameters of water (temperature, dissolved oxygen and pH) were also evaluated. The results showed that the highest total bacteria counted during sampling at station 5 (after reservoir) and the lowest rate at station 4 (before the reservoir's crown). Also the average of total and fecal coliform was the highest at station 5 in all sampling seasons and the lowest in station 2. The stations grouping in this three indices showed that the entrance and outlet stations of the reservoir (1 and 5) are in the same group and the stations located on the reservoir (2, 3 and 4) are in the other group that showed a significant difference (p<0.05).In the Pearson test, correlation between water temperature and pH changes with the number of total bacteria and fecal coliform was positive and with the total coliform was negative, while dissolved oxygen showed a negative correlation with three bacterial indexes. In comparison to the bacterial parameters with available aquaculture standards, the water of this reservoir is suitable for fish production in all seasons.

Since Maurice Lugeon (1933) invented the water pressure test (Lugeon), it has been recognized as the best method to evaluate hydraulic conductivity (permeability) of rock masses. One of the main advantages of this test is its simplicity, easy measurement of required parameters and simplicity of interpretation.  In this research water pressure test (WPT) has been used to evaluate of seepage from grout curtain at Seymareh dam. The dam is constructed on Seymareh River at Ilam Province. Dam site is located 40 km northwest of DarehShahr and 95 km southeast of Ilam. The geographical coordinates of the Seymareh dam are located at 47° 12' 7" East and latitude 33° 17' 32" North. The Seymareh dam Power Plant site is located 1.5 km from the Dam site (Fig 1). The study area is geologically located in the southwestern part of the Zagros fold and consists of relatively high mountains with a general northwest – southeast trend. The low-lying straits that the Seymareh River created during its erosion are one of the morphological features of these areas. The rock masses of the dam and power plant and all structures associated with the Seymareh Dam belong to the Asmari Formation. Three units of this Formation can be identified as follows: Upper Asmari: This unit is outcropped in the upper parts of the Ravandi anticline and inlet of the valley. The thickness of this unit is 50 to 55 meters. Middle Asmari; In general, the middle Asmari unit is about 220 meters thick, with small karstic effects evident. Lower Asmari: This unit has a slight outcrop downstream of the diversion tunnel outlet and near the Ravandi anticline. This unit is about 12 meters thick from the riverbed (Fig.2).     Fig.1: Location of Study Area in Ilam Province   Fig.2: Geological map of Seymareh Dam site Above the Asmari Formation, the Gachsaran Formation (Miocene-Pliocene) is exposed. These sediments are composed of siltstone and red and green marl between thin gypsum layers and fossilized limestones.Gypsum was replaced by anhydrite at certain times and thick salt layers were sometimes found. The recent or quaternary sediments in the study area include coarse-grained alluvial sediments, fine-grained lake sediments, debris sediments, and old alluvial sediments of the Seymareh River that formed in varying thicknesses along several river paths (Fig. 2).

Over the past few decades, there has been a great deal of effort to develop methods of calculating seepage in rock masses, most of which are based on calculating water flows at fully open joints using hydraulic laws and then comparing them with performance measurements in mathematical models. From the point of view of rock mechanics, the seepage in the rock can be estimated based on calculations of theoretical methods whose accuracy is confirmed in model experiments. By definition, one Lugeon is equivalent to one liter of water per minute for one minute at one meter of borehole under 10 atmospheres pressure. The definition of Lugeon is shown in the following formula (Eq. 1):(1) By converting units and simplifying the face and denominator we will deduct (Eq.2):(2) If the right-hand side of Equation 2 is multiplied by the fluid dynamic viscosity, then the intrinsic permeability of the environment is obtained for the numerical value of one Lugeon value (Eq. 3) (water dynamic viscosity of approximately 0.01 (dyne.s. cm2-1) , N is Lugeon value). (3) There is a relationship between hydraulic conductivity (k) and intrinsic permeability ( ) (Eq. 4):  (4) Therefore, the hydraulic conductivity for one Lugeon value will be as follows (Eq. 5, Eq. 6): (5) (6) In order to estimate the hydraulic conductivity of the Seymareh Dam, the WPT results were analyzed in 244 boreholes at 4331 stages. Of these, 123 boreholes and 2254 stages were related to control boreholes (after the execution of the grout curtain). Also, before the execution of the grout curtain, 1277 stages boreholes were calculated in 121 boreholes and the hydraulic behavior of each stage was determined. The Lugeon value of each stages converted to hydraulic conductivity using Equation 6. Using equations 7 and 8, the horizontal (kx) and vertical (kz) hydraulic conductivity values ​​are calculated in each borehole: (7) (8) In equations 7 and 8, k1 represents the hydraulic conductivity of the first stage and z1 represents the length of the same stage and z represents the total borehole length.

The main purpose of this study was to evaluate and compare the grout curtain leakage rate with the calculation method of hydraulic conductivity obtained from the WPT (Lugeon test) and the direct measurement of discharge at drainage galleries. Accordingly, the grout curtain is divided into different zones and after obtaining the average depth of the grout curtain and calculating the hydraulic conductivity of exploratory and control boreholes in each zone, the amount of leakage before and after the grout curtain execution is calculated. . The total leakage from different parts of the galleries indicates the total leakage from the grout curtain executed at the dam site. Determining the average hydraulic conductivity (k) and the average depth of the boreholes (b) in each zone, the transmissibility (T) for each zone is calculated and with determining the gallery length in each zone, the total amount of leakage (Q) for each zone is estimated. According to the calculation, the leakage rate of the Seymareh dam grout curtain is based on tests performed before and after the grout curtain execution for a reservoir with a water level of 720 m.a.s.l equals 560 and 212 liter per Second. Therefore, it was found that the execution of the grout curtain reduced the amount of leakage in the Seymareh Dam by 62%. The behavior of fractures and joints in a borehole can be interpreted by a WPT in which a series of effective pressures are applied to the borehole sections. The Lugeon values obtained for the pressure steps of a stage test can, in sum, indicate the relative number and size of joints and fractures, the suitability of the maximum design pressure, and the tendency of the joints to be leached by flow pressure. Since the injection operation changes the hydraulic behavior of the rock, the hydraulic behavior of all sections was investigated before and after the grout curtain execution. The results show that 8% of stages have wash out behavior before grout curtain execution and 10% of stages show wash out behaviors after grout curtain execution. Also, 4% of the sections had void filling behavior prior to grout curtain execution, and 5% of the stages showed void filling behavior after the grout curtain execution. In dam construction projects, the actual discharge from the dam curtain is measured based on the drainage holes discharge. For the validation of the calculated real leakage number, drainage borehole discharge data have been estimated. The total discharge of drainage in full open valve was 211 liters per second. Since at the time of drainage discharge measurement in fully open valve, the reservoir water was at level 698, for verification, the leakage calculation based on level 720m.a.s.l was calculated again based on level 698m.a.s.l. According to the calculation, the leakage rate of the Seymareh dam grout curtain is based on tests performed before and after the grout curtain execution for a reservoir with a water level of 698 m.a.s.l equals 441 and 193 liters per Second. Drainage discharges are usually influenced by two basic factors: 1 - The amount of water that passes through the grout curtain. 2 - The amount of water that moves down behind the grout curtain and leaks under the grout curtain. In the case of seepage under the dam, only the vertical hydraulic conductivity (kz) of the lower dam galleries is effective. Whatever the vertical hydraulic conductivity of the upper levels, the seepage under the grout curtain is proportional to the potential for vertical overburden. Based on the leakage calculations of the exploratory boreholes (before the grout curtain execution), the total vertical leakage of the galleries is 8 liters per second. As mentioned, based on the analysis of the Lugeon test results after the grout curtain execution, ten percent of the wash out  behavior sections show that they will theoretically increase the leakage by 10 percent over time (+ 10%). Also, five percent of void filling behaviors indicate that they will theoretically decrease leakage by 5 percent over time (-5%). The difference between the two can be seen as an increase of five percent over time. Also, based on the analysis of the Lugeon test before the grout curtain execution, eight percent of the sections show wash out behavior that theoretically will increase the leakage by 8 percent over time. Also, four percent of the stages show void filling behavior, which theoretically will reduce the leakage by four percent over time. Comparing the two can predict a four percent increase in leakage over time. The amount of drainage discharge at the Seymareh Dam when the reservoir level is 698 m is calculated as follows: Drainage discharge = (grout curtain leakage+ 5% leakage) + (seepage under grout curtain + 4% leakage) Drainage discharge (reservoir level 698) = (193×1.05) + (8×1.04) = 202.65 + 8.32 = 210.97 = 211 Ls-1 The calculated number corresponds to the measured real number, which indicates very high accuracy of the model. This is for two reasons: 1- The boundary conditions in the model are well considered and 2- The equation presented in this study for converting the Lugeon value to hydraulic conductivity is highly accurate.

The following results have been obtained WPT in the rock formations of the Seymareh Dam site: 1-   By performing the Lugeon test, the intrinsic permeability of the environment can be directly measured. 2-   Comparison of the results obtained from the calculation of leakage from this relationship with the measured leakage from drainage galleries indicates the appropriate accuracy of the obtained relationship in this study. 3-   The results of direct measurements of the leakage from downstream galleries show that the grout curtain executed in the Seymareh Dam is of good quality and has been effective in reducing leakage (about 62%). 4-   In analyzing the leakage at the dam site, one should also consider the hydraulic behavior of the rock and pay particular attention to the behavior of wash out and void filling because wash out and void filling behavior are both dependent on the passage of time. In areas with wash out behavior and void filling, the amount of water passing through these sections increases and decreases with time. Since increasing the number of WPT plays an important role to more accurate estimation of hydraulic properties and better evaluation of rock mass behavior against water flow, it is recommended some Lugeon test perform in the exploratory boreholes and check holes in each grout gallery.

Seymareh Dam site is located in 40 km northwest of Darreh Shahr City and in Ilam Province. In this study, the origin of the downstream brines of Seymareh Dam with the results of chemical and using two computational methods of Schoeller's Index Base Exchange and weight ratio (Na/Cl)-Cl and two graphical methods of Hounslow and Sulin graph were studied. The results of these methods show a lot of conformity. In this study, part of the aquifer has been contaminated with oil brines, and the polluted water is drained through springs into the Seymareh River, which has reduced the quality of the river's water for agricultural purposes. Based on the equivalence maps of the Index Basic Exchange and the water type, a hydraulic connection has been established between the oil brines and the aquifer through the observation wells. Based on the interpretation of the results, the study area has been affected by the oil spills in the Seymareh Dam area, and the Gachsaran Formation in the area has also increased the salinity of water resources, including sulfate. Based on this, until 1396, the area of polluted aquifer was 1.8 km2. Examining the quality of irrigation water of Seymareh River in the period of 2011 to 2017 shows that since 2013, the quality of river water based on Wilcox classification is not suitable for irrigation. Based on the regression of SAR and EC diagrams with respect to time, it is predicted that in 1401 the quality of river water will reach C4-S4.

In this study, the quantitative effects of the construction of Seymareh Dam in the Karst site of this structure on the fluctuations of groundwater level and discharge of springs have been investigated. According to 10-year measurements, it was found that there is a direct hydraulic relationship between the water surface of the dam reservoir and the water level of observation wells. The results revealed that a significant difference in the amount of water level of the North Edge wells compared to the South Edge wells, especially in the right abutment and the right abutment wells compared to the left abutment can be clearly seen, respectively, the evidence and confirmation of an Asmari core with Low permeability is along the axis of the anticline and also more efficiency of the sealing curtain on the right side is another reason for this difference. Changes in the total discharge of the total springs measured on both banks (right and left) have a similar trend to the changes in the discharge of the left bank springs, which is due to the more discharge of the left abutment springs. The results showed that with increasing the water level of the reservoir to 660 meters, the amount of discharge of springs in the region reached 1400 liters per second and with decreasing the level of reservoir water in the next year this amount decreased and again with increasing level to 704 meters, the amount of discharge to 1800 Liters per second has increased.

Landslide-dammed lakes are a geological phenomenon that, despite of its beauty can be studied as a geologic hazard. Seymareh rock avalanche has created at least three dams and lake landslides in southwest Iran. Jaydar dam is a horseshoe-shaped landslide dam is composed from large rocky blocks. The length of the dam is more than 11,000 m and average height is 140 m from its bedrock. This dam is formed on the permanent Kashkan River in south ofPoldokhtar city and between the Sarab Jahangir and Baghe Jaydar villages. Due to the geometry dimensions and stability of the dam until now, it could be the oldest and largest rocky landslide dam in Iran. Jaydar Lake is the 2nd landslide lake in region, has a length of 36,000 m and an area of 65 Km2. The Jaydar Lake has expanded from the south of Poldokhtar city to Jolgeh Khalaj village on the Poldokhtar- Khorramabad road. The Present Research shows, that the formation and death of Jaydar Lake are in 4 stages. 1. Seymareh rock avalanche and formation the Jaydar landslide dam. 2. The closure of Kashkan River route 3. Formation of the landslide lake behind of dam and filling up to 740 meters above sea level (m.a.s.l). 4. Lake drainage through a valley (spillway) on bedrock in the northwest of the lake.4. Discharge of lake water by a solution channel (spillway) in the Gachsaran Formation (bedrock of The Jaydar Lake). ...