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This research aimed to investigate the effect of geological and geomorphological factors on the water quality of Gotvand Dam in Iran. Given the role of geomorphological parameters in water quality, the water quality indices were analyzed in the Excel and Chemistry applications. Water quality was evaluated by analyzing water samples obtained from the Statistical Data Center of Water and Power Organization of Khuzestan, and the total dissolved solids (TDS), electrical conductivity (EC), and pH of water were measured using the Mann-Kendall test. Then the effect of geomorphological factors on the physicochemical properties of the Karun River was assessed. The qualitative variables were pH, EC, and TDS in the statistical period of 2006–2021. The results of the Mann-Kendall test showed an insignificant decreasing trend in the TDS series in the Gotvand station. Meanwhile, August had a significant increasing trend in TDS, and considering the calculated Sen's slope, this parameter increased by 35% in the last 15 years (2006–2021). Like TDS, EC had both increasing and decreasing trends of changes. On the monthly scale, pH had a significant decreasing trend, meaning that the water is acidified, which severely affects the downstream fields and reservoirs. In the Gotvand station, the trend of changes in TDS and EC increased in 11 and 12 months of the year, respectively. [ABSTRACT FROM AUTHOR]

The impact of dams on fluvial hydro-morphology in arid and semi-arid regions, such as the Middle East, has received little attention, although such fluvial corridors represent major sources of livelihood for the local population. In this study, the influence of the Mollasadra Dam on the hydro-morphological conditions of the Iranian Kor River is numerically investigated using iRIC MFlow_02, by considering different flooding conditions. Simulating different scenarios with and without the dam, and looking at key parameters like flow rate and velocity, sediment transport rate, and bed topography, it is evident that the dam significantly reduces the water discharge and the relative flow velocities, while it has a relatively low impact on the bed morphology and sediment transport. This can be ascribed to the fact that the Kor River is a capacity-limited watercourse, characterized by rather coarse material and reduced sediment transport. [ABSTRACT FROM AUTHOR]

One of the geotechnical properties of rocks, which is particularly important in sensitive projects such as oil and gas extraction, nuclear waste disposal, and underground drilling, is their brittleness. Currently, there are no standards methods for direct measurement of rock brittleness. Different studies have used various indirect methods to predict rock brittleness index (BI). However, researchers have paid less attention to the prediction of BI using multivariate regression. Accordingly, this research has used the multivariate regression method to determine BI considering mechanical characteristics. Specifically, we used uniaxial compressive strength (UCS), modulus of elasticity (E), pressure wave velocity (Vp), and shear wave velocity (Vs), and physical characteristics, including porosity (n) and density (ρ) to determine the BI. Statistical indicators, R square, results of ANOVA (Analysis of Variance) test, coefficients, beta statistics, and VIF were used in the first step to evaluate the regression relationships. Then, residual analysis of each regression were performed. Finally, the correlation between the calculated and predicted BI values was investigated using each regression. The best results were obtained using UCS and E or UCS and Vs in the bivariate regression and UCS, E, and Vs in the three-variable regression. According to the results, increasing the number of variables in multivariate regressions leads to more accurate predictions of BI. [ABSTRACT FROM AUTHOR]

In the recent decades, dams have paradoxically been considered as a constraint and or a driving force of surface water conservation. On the other hand, dams have had a number of socio-economic and environmental impacts, the main reason for conducting the current case study on Shah-Qasem Dam in Yasouj, Iran, was to employ the survey field research through a questionnaire to assess the rural peoples’ viewpoint; this was done in four villages of the Southern Sar’roud County. Based on the (Cochran) formula, 192 individuals were relatively selected from each village. According to the findings, the most important impact of the dam was mainly economical (the average impact was between 2.37 and 3.7), whereas the least one was environmental (the average impact was between 1.81 and 3.54). Also, the results of the hypotheses’ analyses by means of x2 and Wilcoxon showed the following results: rise of the villages’ income, increase of the cultivated farms, increase in the employed individuals, enhancement of the cultivated crops, the regions production rising, improved tourism, lack of people’s participation in the decision making process, and reaming of the same plant varieties in the area, as compared with the pre-dam era. It is worth considering, however, that based on the statistical population used, this study was concerned mainly with the short benefits of the dam, rather than its long-term destructive ones. [ABSTRACT FROM AUTHOR]

The optimal operation of dam reservoirs can be programmed and managed by predicting the inflow to these structures more accurately. To this end, there are various linear and nonlinear models. However, some hydrological problems like inflow with extreme seasonal variation are not purely linear or nonlinear. To improve the forecasting accuracy of this phenomenon, a linear Seasonal Auto Regressive Integrated Moving Average (SARIMA) model is combined with a nonlinear Artificial Neural Network (ANN) model. This new model is used to predict the monthly inflow to the Jamishan dam reservoir in West Iran. A comparison of the SARIMA and ANN models with the proposed hybrid model's results is provided accordingly. More specifically, the models' performance in forecasting base and flood flows is evaluated. The effect of changing the forecasting period length on the models' accuracy is studied. The results of increasing the number of SARIMA model parameters up to five are investigated to achieve more accurate forecasting. The hybrid model predicts peak flood flows much better than the individual models, but SARIMA outperforms the other models in predicting base flow. The obtained results indicate that the hybrid model reduces the overall forecast error more than the ANN and SARIMA models. The coefficient of determination of the hybrid, ANN and SARIMA models were 0.72, 0.64 and 0.58, and the root mean squared error values were 1.02, 1.16 and 1.27 respectively, during the forecast period. Changing the forecasting length also indicated that these models can be used in the long term without increasing the forecast error. [ABSTRACT FROM AUTHOR]

Introduction: Heavy metals are regarded as toxic stable elements in the environment that with the entry into water sources, finally it enters into the biological cycle of life and develops some adverse effects. Therefore, the present study aimed to determine the concentration of chromium and arsenic heavy metals in the river basins of Baft and Ravar dams. Methods: This descriptive cross-sectional study was conducted from August 2013 to June 2014. During the field surveys of the river basins, 4 sampling stations of river basins of Baft and Rabor dams were selected. One combined sample was taken on 15th of each month from the mentioned river basins as well as Baft and Rabor dams. The chromium and arsenic concentrations were measured for 12 months in river basins of Baft and Rabar dams by Furnace Atomic Absorption device, and the study data were analyzed applying SPSS software. Results:. The mean concentration of chromium was reported 5.01 and 5.19 in the river basins of Baft dam and 5.44, 5.5, 5.42 and 5.45 ppb in river basins of Rabor dam. The mean concentration of arsenic in the river basins was demonstrated to be 16.52 and 11.71 ppb in Baft dam, and 12.28, 13.6, 7.13 and 8.78 ppb in Rabor dam. In addition, the mean concentration of chromium was reported 5.02 and 5.38, and arsenic concentration was obtained 23.53 and 9.12 ppb, respectively in Baft and Rabar dams. Conclusion: Based on the study results, the chromium concentration in the studied stations was demonstrated to be significantly less than guidelines of WHO, EPA and Institute of Standards and Industrial Research of Iran, whereas arsenic concentration was demonstrated to be significantly higher compared to these guidelines(p<0.0001). As a result, this difference needs to be diminished via implementing the required plans. [ABSTRACT FROM AUTHOR]

The Kowsar Damis constructed on the Kheyrabad River at the northern limb of the Duck Anticline, close to itsNW plunge, SW Iran. The dam is built on the karstic Asmari Formation, and the reservoir is in direct contact with this formation from the dambody to the upstream impermeable Gachsaran Formation. After reservoir impounding, several new springs emerged from the Asmari Formation, adjacent to the old small springs at the southern limb of the Duck Anticline. The discharge of these downstream springs was not reduced despite grout curtain treatment works. The main water leakage route is not below or through the grout curtain, as shown by considering rock permeability in pilot and check holes, cement consumption in grouting boreholes, boreholewater levels, spring locations, and discharge of the dam galleries. The Duck Anticline is hydrogeologically connected to the adjacent Dill and Pahn Anticlines, comprising the Asmari Karst Aquifer, which is divided into three karst sub-aquifers. The general flow direction of karst water in each sub-aquifer was determined using hydrogeological analysis and water balance calculations. Two alternative models are proposed for water flow at the northern limb of the Duck Anticline. The main leakage route toward the downstream springs is most probably through a relict karst conduit system, developed along bedding planes of the Asmari Formation at theNWplunge of the anticline, according to the first proposed model. In this case, the water leakage can be significantly reduced by extension of the grout curtain further into the upstream impermeable Gachsaran Formation. [ABSTRACT FROM AUTHOR]

Latian dam is located in the North East of Tehran in Elburz Mountain. It falls in the category of large dams according to the International Committee on Large Dams (ICOLD). It was constructed in 1967 for agricultural purposes, drinking water, and power generation. Producing triggered earthquakes may be a consequent result of dam construction. In this paper, the complete seismic statistics of the region from 1996 onwards has been studied to understand the seismic condition of Latain region. For this purpose, frequency of earthquakes within a radius of 30/60 km around the dam is studied considering its relationship with the reservoir volume variation. Using Gutenberg-Richter rule, parameter b of the region was determined within the same region. The results of this study show the existence of triggered seismicity around the reservoir of Latian dam. Considering the tectonic-geological condition of the region, the existence of triggered earthquakes may create landslides in the reservoir and around it. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) in freshwater environments have been recognized as one of the important sources of plastic contamination in marine ecosystems. Reducing the amount and spatial distribution of MPs reaching the sea through accumulation behind dams remains unclear. In this study we analyzed the spatial distribution of sediment and surface water MPs in the Aras Dam and from nineteen upstream and downstream locations of the Dam in the Aras River. The MPs abundance ranged from 32 to 528 items/kg dry weight (mean 217.8 ± 132.6) and 1 to 43 items/m 3 (mean 12.8 ± 10.5) in the sediment and surface water stations, respectively. MPs abundance in surface waters collected within the Dam reservoir was significantly higher than those found either upstream or downstream (P < 0.05). For sediments, reservoir MPs concentration was generally higher than upstream and downstream, although their differences were not significant. High MPs concentration was observed in the vicinity of urban areas. Moreover, MPs abundance was positively correlated with total organic carbon (TOC) and clay content (P < 0.01). GAM analysis revealed that clay is the most important variable with lowest Akaike information criterion (AIC) and explained 61.3 % of deviance (R-sq.(adj) = 0.344) in MPs abundance. MP particles ranged from 0.1 to 5 mm in size and were dominated by fibers (53.5 %), black color (24 %) and PE polymer (36.6 %). Our results highlight the high MPs distribution in the Aras River and demonstrate that they accumulate in the surface waters behind the Dam. Consequently, the fate and effects of MPs in international rivers is one of the most politicized issues between countries with a common boundary and therefore needs joint management policies that help mitigate this insidious problem., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Chamshir Dam site is located in southwest of Iran, on Zuhreh River, 20 km southeast of Gachsaran city. The study area mainly covered by evaporite formations of Fars Group especially Gachsaran Formation. Dam axis is located on limestone beds of Mishan Formation but nearly two-thirds of the dam reservoir is in contact with the Gachsaran Formation. The reservoir and dam site have been brecciated by several faults such as Dezh Soleyman thrust and Chamshir fault zone that lead to development of karst in this region. The region has a wide variety of developed karstic features such as karrens, dissolution dolines, karstic springs and cavities. These karst features can compromise on the ability of Chamshir Dam to hold water in the reservoir, and can even cause collapse of the dam. Gypsum karst in the Chamshir Dam reservoir may develop the solution channels and cavities which cause water to flow toward downstream of the dam reservoir. Therefore, to eliminate these problems, construction of cutoff wall or clay blanket is proposed. [ABSTRACT FROM AUTHOR]

The Doosti Dam, with a reservoir capacity of 1,250 million cubic meters, was constructed on the Harirood River at the border of Turkmenistan and Iran. The reservoir is in direct contact with permeable formations on the right abutment of the dam including the Neyzar Sandstone, the Kalat Limestone and the Pesteleigh alternative layers of marlstone and sandstone. After the reservoir impoundment, several new springs and seepages emerged from these formations and the alluvium. The amount of leakage increased with the rise in reservoir water level. Fifteen kilograms of sodium fluorescein were injected into a 113-m deep borehole intersecting three permeable sandstone layers of the Pesteleigh formation. Dye was detected downstream of the grout curtain in boreholes and springs that were in direct contact with parts of the Pesteleigh formation having the same sandstone layers as the injection borehole. The dye velocity was in the range of diffuse flow, confirming the good performance of the grout curtain in the Pesteleigh formation. No dye was detected in the other formations because the injection borehole was not in direct contact with these formations. The hydraulic relation of the other formations with the reservoir was determined by considering direct contact of the formations with the reservoir, emergence of new springs and seepages after reservoir impoundment, correlation of time variations of the springs discharge and the borehole's water level with the reservoir water level, and in some cases the hydrochemistry of the water. The results show that the Kalat and Neyzar formations are hydraulically connected to the reservoir, but the small amounts of leakage from these formations at a hydraulic gradient of 24% indicates good performance of the built grout curtain. The total reservoir leakage at maximum reservoir water level was 100 l/s which is insignificant compared with the 15 m/s average annual release of the reservoir. [ABSTRACT FROM AUTHOR]

This paper discusses the results of the engineering geological and geotechnical investigations that have been carried out at the Daroongar dam site. According to the geomorphology and geological conditions and economic reason, the dam has been designed as an earth dam with a clay core. The dam foundation is composed of a sequence of sandy limestone and limy marl of the Upper Cretaceous period. This study is based on field and laboratory investigations, surface discontinuity surveying, drilled borehole data and permeability of dam foundation. The present studies include the evaluation of the dam foundation by water pressure tests. The water pressure tests indicate the necessity to provide a grout curtain below the dam foundation.The geology of the Daroongar dam foundation has a significant influence on the permeability and groutability characteristics. The permeability of jointed rock masses is strongly depended on joint characteristics; degree of jointing, opening, continuity and presence of filling materials. The laboratory tests included tests for unit weight, porosity, uniaxial, triaxial, tensile strength and deformation parameters. The strength and modulus of elasticity of rock masses were determined using the Hoek-Brown empirical strength criterion. The rock mass qualities and classifications of the dam site is assigned using the rock mass rating (RMR), the rock quality (Q) and the geological strength index (GSI) classification systems. [ABSTRACT FROM AUTHOR]

Water tightness of the reservoir is considered not only a common problem; but also it is time-consuming and expensive when constructing a dam. The water seepage of Karun IV was observed at the initial impounding stage. The dam site consists of highly heterogeneous karst terrain. 2D dual-porosity numerical model with the geometry-based finite element is used to investigate the performance of the grout curtain, drainage tunnels, as well as proposed curtain length for seepage control. The model is calibrated before and after impounding for the dam site aquifer, to achieve the best possible fit between the calculated and observed groundwater heads, and variations of the reservoir water level. The obtained hydraulic conductivity of the site has indicated the existence of very high heterogeneity and few conduits coinciding with the faults. The water seepage mainly occurs in the left abutment; the faults which have been centered near the river in the right abutment play a significant role in the water seepage rate as well. The swing of the curtain is crucial to the impervious layers in both horizontal and vertical directions to reduce the seepage. The results have indicated that there may be a conduit(s) which does not coincide with the position of the fault, or reported the opening of core logs, or the water seepage may be due to the improper sealing of the site. [ABSTRACT FROM AUTHOR]