فهرست مطالب مهدی یاسی

Examining the changes in the water quality parameters of the Karun River using satellite data and determining the modified quality indicators can be used to assess the vulnerability of irrigation water. In this research, the data of seven qualitative parameters: Na+, SAR, pH, Cl-, HCO3-, EC and TDS were used in six water measuring stations of Abbaspur, Ahvaz, Farsiat, Gotvand, Molasani and Soosan of the Karun River (1392-1398) and NSFWQI general water quality index was calculated. Correlation relationship and estimation errors were determined for two principal component reduction (PCA) and multivariate linear correlation methods. The results showed that multivariate correlation method is more suitable. The coefficient of determination for the seven water quality parameters was calculated as 0.44, 0.43, 0.03, 0.43, 0.09, 0.45 and 0.46 respectively, and for the NSFWQI index it was calculated as 0.46. The statistical correlation for pH and HCO3- is at a very low level; but for the other five parameters and the NSFWQI index, it is in average state. The significance level of estimation for Na+, SAR, Cl-, HCO3-, EC and TDS parameters is acceptable (P<0.001), and for pH is unacceptable (P<0.122). In general, there is an acceptable correlation between the bands extracted through the Landsat 8 satellite and most of the quality parameters of the Karun River, but necessary actions are proposed to improve the correlation relationships. Also, the NSFWQI index shows that the quality of water in the Karun River along the Khuzestan plain is not good enough.

There is a number of evidence for the construction of weirs and diversion dams in river bends, and sometimes building water intakes on both sides of the river bend are needed. However, this encounters problems in terms of asymmetry of flow distribution into the intake structures. Most recent studies have been conducted for clear water flow conditions. The main purpose of this study was to investigate the uniformity of sediment transporting flows into bilateral intakes on both sides of a spillway in a channel bend. FLOW-3D numerical model was used to test the effects of intake angle, intake sill and sluice way on the uniformity of flow and sediment load entering the intakes and the distribution of sediment deposits in the intake area. The numerical model was calibrated and confirmed based on the information of the physical model for clear water flow conditions. Then, the numerical model for sediment transport flow was validated and adjusted, and it was implemented for seven scenarios of the arrangement of the weir and its related structures in the channel bend. The results showed that the most of the sediment deposition is towards the inner-bend intake. Without the intake sill and sluiceway, the ratio of outer to inner intake for five intake angles of zero, 30, 50, 60 and 90 degrees is about 2.1, 3.8, 5.0, 4.17 and 2.4, respectively. Using a 90-degree intake is more efficient due to less sediment entry and uniform inflow distribution to both bilateral intakes. Inclusion of sill and sluiceway in the intake system results in the reduction of the ratio of outer to inner intake to be reduced to 1.1 and 1.3 for the two intake angles of zero and 90 degrees, respectively. The results show that it is necessary to use the intake sill and the sluice way to control the sediments entering to the intakes, especially in inner intake.

Acoustic tomography technology is an advanced method of remote sensing, which has been used and verified by many researchers in recent years to measure flow velocity and temperature in different water environments. The purpose of this research is the feasibility of using this technology in reservoirs of dams to measure the flow velocity in different layers. The basis of this method is to calculate and record the travel time of acoustic rays in the water environment, including the reservoir of the dam. In the first step, the propagation of sound rays from the first station to the second station was simulated. Then, according to the propagated rays and the obtained travel times and solving the inverse problem with the regularization method, the average flow velocity, and layered flow velocity were calculated. In this research, two acoustic stations with mutual transmission with a frequency of 10 kHz were placed in the reservoir of Latian Dam on October 23, 2020. Five layers with a distance of ten meters in depth were selected. The results of solving the adjusted inverse problem showed that the maximum velocity of 0.0006m/s occurs in the first layer (0 to 10 m depth). For the flow velocity of layers, two to five, 0.0003, 0.0001, 0.0002, 0.0001 m/s were calculated respectively, which according to the close to zero flow velocity of the dam reservoir at the time of data collection, the velocity of the flow was obtained with a relatively good approximation. It is suggested that in future studies, data collection should be done when the water discharge valves are open so that the results can be compared with the results of this research.

A retaining wall is a structure that maintains the pressure due to the situation in the level difference caused by an embankment, excavation, or natural factors. Since comparing the performance of two different types of walls from retaining walls is the subject of this article, in this research, from rigid walls, weight retaining wall (concrete) and flexible walls, gabion retaining wall (in weight form) with almost the same conditions, It is evaluated in terms of stability and performance. The geometry of the concrete weight retaining wall is chosen so that the result of the forces acting on it (including weight and lateral forces) is in the core of the base or its horizontal sections. The expected results of this study include the study of retaining wall performance in terms of soil material change behind the wall, river water depth, and retaining wall slope, and finally, comparison and selection of suitable retaining wall to protect the river wall between two types of concrete and gabion walls.

Software SLOPE/W is the most advanced slope stability software for soil and rock slopes from the GEO-STUDIO 2012 software suite. SLOPE/W effectively analyzes various types of slip surface shapes and determines factors of safety, pore water pressure conditions, soil properties, and loading conditions. In this study, the Morgenstern-Price method has been used. In this method, the balance of forces and anchors for sliding sections is determined, and by Entry and Exit method, the factor of safety is determined.In this study, different factors such as type of wall and river bed materials, water depth in the river, type of retaining wall materials, the slope of retaining wall, and soil adhesion were investigated. Based on the critical conditions in the evaluation of the stability of retaining walls, the saturation state (the most critical state possible) was considered for the wall and river bed materials. To apply the soil properties behind the retaining wall in modeling, a homogeneous porous medium and isotropy (Kx/Ky = 1) were considered, and for the slip criterion of the Mohr-Coulomb resistance model, which is the most common method for expressing shear strength in geotechnical materials, used. To compare the results, the retaining wall was designed and modeled in mirror conditions, i.e. the vertical part of the wall on the riverside and the stair part of the wall under the soil.

Since the permeability and hydraulic conductivity of medium gravel are higher than that of average sand, it has a greater capacity to drain excess water. It was observed that the active force and torque of the average gravel are 7% and 11% lower than the average sand, respectively. This is also true for the gabion retaining wall as well as the state of the river with a water depth of 2 meters and 4 meters. In a river, without water, the amount of active force and torque is about 20% more than in a river with a water depth of 2 meters and about 40% more than in a river with a water depth of 4 meters. In the retaining wall in the mirror state, in the river without water, the active force and torque have both increased by about 16%, and in the river water depth of 2 meters, it has increased by about 17% and in the depth of 4 meters, it has increased by 23%. The results of stability and factor of safety for two wall slopes in the conditions of water level drop showed that the factor of safety at a depth of 2 meters decreases by about 20% compared to a depth of 4 meters and Also, the factor of safety of the river without water is reduced by about 30% compared to a depth of 4 meters. The results showed that the retaining wall in mirror conditions has a better performance than other models in terms of factor of safety. Also, the index wall in the vertical position, at a depth of 4 meters, which is the same depth equal to the total height of the wall from the riverbed, has the lowest factor of safety.

In this research, the stability and performance of two types of concrete and gabion retaining walls were examined with SLOPE/W software under similar river conditions. A total of 24 models were designed using two types of bank material (gravel and sand), two slopes of the retaining walls, and three river water depths. Also, 6 models of vertical walls were considered for comparison. The results indicated that the coarser-grained bank material produces a lower level of pore pressure, which in turn results in lower values of active force and torque by 11% and 7%, respectively, compared with the sand material. The results of this applied research can be used as a guideline for selection between two types of retaining walls (i.e. Concrete or masonry walls, and gabion walls) in different river conditions.

Floodplain vegetation can alter the flow characteristics of a river through the application of redundant drag forces. In this study, turbulence characteristics and flow structure were investigated under the influence of partially double-layered vegetation in a compound channel. To investigate the phenomenon, a three-dimensional numerical model was used to solve the Navier-Stokes equations and track the evolution of the free surface. To ensure the performance of the model, the numerical results were validated using data from previous experimental studies. The validation results showed that this model captured the flow dynamics with high accuracy. In the next step, the model was used to predict the free surface fluctuations and velocity field of the steady flow in the layered vegetated floodplains. The modeling results showed that the formation of a velocity gradient at the interface between the main channel and the floodplain can lead to the development of secondary flows and the mass and momentum exchange at this interface. In addition, turbulent kinetic energy and turbulent dissipation of the flow through vegetation in floodplains was observed in the numerical results. It was concluded that the layered vegetation can increase the flow turbulence and the dissipation rate of the flow energy. The maximum values of turbulence kinetic energy and turbulence intensity were observed at the interface between the floodplain and the main channel. Therefore, the flow disturbance at the interface between the floodplain and the main channel may increase the mass and momentum exchange in this region.

Dam removal is one of the methods of restoring the river ecosystem. The decision to remove a dam is based on the multidisciplinary indicators and the type of dam body and its location, as well as the downstream conditions and the type of dam removal method. In the present study, the removal of the Voshmgir Dam on the Gorganrud River, Iran, was considered, because of the high volume of sediment deposition in the reservoir and the loss of its useful life. Three scenarios were selected for the removal of the dam: 1- complete removal; 2- stepped removal of the spillway; and 3- removal with stable sediments. In the first step, numerical modeling for river morphological changes was performed using the HEC-RAS model for unsteady flows with sediment transport. The erosion and sedimentation processes were simulated in six reaches (from the Voshmgir Dam to the Caspian Sea), with total length of 128 km. The results indicated that the second scenario (stepped removal of the spillway) is the best alternative due to the gradual processes of river-bed changes. In the present research, the two-dimensional hydrodynamic and water quality model CE-QUAL-W2 is used for qualitative modeling of Gorganrud River in three scenarios of dam removal, within 128 km downstream of Vashmgir dam to the Caspian Sea Estuary. Qualitative modeling was performed for the existing conditions of Gorganrud (without removing the Vashmgir dam) at two hydrometric stations of Aqqala (68 km downstream of the Vashmgir dam) and and Basirabad (112 km downstream of Vashmgir Dam), where a set of water level and water-quality data was available for model calibration. Model results are presented in the period of rapid river changes after dam removal up to 60 days. Based on the results of qualitative modeling, the amount of dissolved oxygen (DO) has increased in three scenarios of dam removal in two sections of the river (Aqqala and Basirabad). The amount of biochemical oxygen demand (BOD) in the first scenario (complete removal) and the second (stepping removal) has increased slightly (less than 10% of the river conditions before removal). In the third scenario (removal with stable deposition), no significant change in BOD occurred. In three scenarios and in both study periods, the pH changed very little in the two periods, before and after the removal of the dam. The total amount of soluble solids (TDS) in the early days of the simulation is equal to or greater than that before removal. The TDS rate is to be decreased by time. The overall results indicated that the second scenario of the dam removal (i.e. stepped removal of the spillway) is the best alternative due to the less impacts on the river-bed changes, and the gradual processes of river-ecosystem rehabilitation.

The study of surface water quality has special importance. Unfortunately, sometimes sewage and industrial effluents are discharged into the river. If the mechanism of transport and diffiusion of pollution in rivers with different geometry is known, it can be planned to reduce the effects of pollution on the general health of human society by raising the issue of water mixing and strengthening the self-purification of rivers. The governing equation over the pollution transport phenomenon in rivers is advection-dispersion equation. This equation is classic and does not have the necessary accuracy in predicting the amount of pollutant concentration in the river; Therefore, this equation must be changed in such a way to have the least error in the simulation. The fractional calculus method is used to accurately investigate the transport of pollutants in the stream. To model the pollutant transport in the river, differential equation must be solved. Meshless method is one of the newest numerical methods in recent years that was able to correct some of the disadvantages of mesh-based methods. Studies show that the most studies have focused on solute transport in steady-state flow regimes and regular cross-sections. This study seeks to provide a comprehensive model for simulating the phenomenon of pollutant transport in rivers with steady and non-uniform flow to eliminate the shortcomings of common models. In this study, the parameters of dispersion coefficients, fractional order derivatives and skewness coefficients were optimized in the longitudinal and transverse directions. The values of dispersion coefficient in the longitudinal and transverse directions were 68 and 2.5 m2/s, respectively. The output of the proposed model was compared with the observational data of the Athabasca River and the Mike21 model for three cross sections. The results showed that the amount of R2 in the Meshless Local Petrovo-Galerkin method increased by an average of 11% compared to the Mike model.

Urban development and land use change have seriously damaged the quality and conditions of geomorphological equilibrium, drainage capacity and river ecosystem services. On the other hand, these changes and human interventions have affected the environmental sustainability of the area. To manage and prevent the loss of natural and geomorphological functions of rivers, it is necessary to assess the morphological quality of the river. In the Karaj River, due to the expansion of urbanization, encroachment on the riverbed, channeling, sand extraction, etc., serious damage has been inflicted on the river ecosystem. In the present study, the hydro-geomorphological quality of the Karaj River in the urban area of Karaj of Iran (from Beylqan Bridge to the railway bridge) was evaluated. Using IHG hydro-geomorphological index along the main river, the basin was divided into seven sections and the value of this index was determined for each section. The IHG index evaluates 9 parameters in three groups (Functional Quality, Channel Quality, Riparian Quality). The value of each parameter calculated between 1 and 10 depending on the physical state and performance of the river basin. Based on the results of this study, sections of 1, 2, 3, 4, 6 and 7 have poor hydro-morphological quality; and section 5 due to human activity (including changes in morphological pattern, construction of engineering structures, disconnection of the main waterway and floodplain) have very poor quality. Also, the hydro-geomorphological quality of the urban area of Karaj River has the most negative effects due to the expansion of city and residential space, urban facilities and uncontrolled extraction of sand. The results show that the IHG index is a good indicator and sensor for assessing the hydro-geomorphological quality of rivers.

Mountain streams are characterized by coarse-bed materials, steep slopes, and low flow depth. In these type of streams, direct measurement of discharges and/or flow velocities is often difficult, particulaly in high flows. Therefore, the use of flow resistance relationships will be inevitable. The present research aims to develop dimensionless relationships of hydraulic geometry in estimating the discharge without measuring the water depth. In this study, flow resistance in three mountain streams, including Ansarood, SaeedAbad and Lighvan with various bed-forms was investigated based on measured data, and a new equation was proposed. The present study results revealed that in the case of mountain rivers, the inclusion of the geometric standard deviation of bed materials in the non-dimensional hydraulic geometry relationships increases the correlation coefficient and the accuracy of the predictive equations.

Information on soil erosion and sediment production, meteorological features, hydrological features of rivers such as discharge, as well as human factors, are often very complex, indefinite, and nonlinear. Therefore, the use of machine intelligence algorithms (such as machine learning algorithms) is a good option in simulating and predicting river water quality variables such as suspended load. The aim of the present study is to present a proposed method based on Multilayer Perceptron Artificial Neural Network (MLP-ANN) and Non-Dominant Sorting Genetic Algorithm (NSGA) for predicting suspended river load. In the proposed method, the NSGA was used to train the MLP using the error propagation method and determining the optimal weight for the neurons. In this study, the suspended load of Tilabad station located in Gorganrood river during the 1982-2015 years was used as a case study. The results showed that the proposed method has a higher correlation coefficient compared to MLP and the value of R2 was 0.6728 and 0.4372, respectively. The value of Root-Mean-Square Error (RMSE) in the proposed method and MLP based on back-propagation (BP) algorithm is 4.7225 and 8.548, respectively. Therefore, in the proposed method, the NSGA has caused a good improvement of the MLP. The NSE value in the proposed method and MLP based on BP algorithm is 0.4321 and 0.2941, respectively. The results showed that the proposed method had good accuracy in predicting the suspended load. The proposed method with BP training algorithm has a better performance compared to the descending and Bayesian gradient training algorithm.

Vegetation plays an essential role in modifying the flow characteristics of natural channels, such as rivers. Efficient hydraulic modeling of flow in compound channels with vegetated floodplains is necessary to understand and identify natural flow processes. In both natural and artificial channels, there are various types of vegetation with differing densities and heights. The main goal of this study is to investigate the effect of double-layered vegetation on flow characteristics in compound channels using the FLOW-3D model. The results of the numerical model have been calibrated and validated with the results of the physical model of the research of Takuya et al., 2014. Experiments were conducted in 2014 in the hydraulic laboratory of the Akashi National University of Technology in Japan, and in a straight trapezoidal channel with a length and width of 4.8 and 0.8 m respectively. During calibration, the model's estimation error for the depth-averaged velocity was within 4 to 6%, which was reduced to approximately 1.5% during validation. The average error in water depth estimation was around 3%. The numerical and physical models showed good agreement in simulating the flow pattern. The numerical model showed that, for larger floods when vegetation is submerged, the vertical profile of velocity in the floodplain is S-shaped. However, during smaller floods or when short and tall vegetation is emergent, the vertical velocity profile is relatively uniform or logarithmic. The resistance caused by the presence of vegetation in the floodplains leads to a decrease in the flow velocity in the floodplain area of the river and an increase in the capacity of flow transfer in the main channel.

Sustainable river management requires the construction and operation of dams that provide environmental flows to support downstream rivers ecosystem. Dam construction in Iran has significantly altered natural flow regimes and caused various environmental issues. The main aim of the present study was to evaluate the hydrologic and environmental alteration of the flow regime in the Jajrud River downstream of the Latian Dam. In this study, a set of long-term flow data (1947-2017) was analyze using the IHA and RVA models. The results show that the degree of alterations for the 24 flow variables is in the range of high to medium, denoting the high hydrological alterations of the Jajrud River. The values of mean, maximum and minimum monthly flows have decreased by 57, 94 and 21 percent, respectively. The overall change is 51%. Magnitude and duration of annual extreme flows have decreased, and in particular, the minimum flows and the base-flow indices have changed the most. The large flood events has been eliminated and small and frequent floods has been damped in the downstream river system. The results indicate that the goals of RVA have not been achieved in the post-construction period of the Latian Dam, and the environmental conditions of the river have been severely damaged. With reference to the eco-hydrological indices, the rehabilitation of the environment status of the Jajrud River requires the dam releases of minimum monthly flows in order of 2.3 to 33.8 m3/s, with an average annual discharge of 6.5 m3/s.

Local scour downstream of the hydraulic structures is of great importance. In wide channels, a set of multi gates instead of a single gate may be responsible for transferring water and adjusting upstream water level due to difficulty in gate maneuvering, economic considerations, and ease of movement. Operating parallel sluice gates can create different scenarios owing to clogging or failure in some gates. This study was aimed to assess the effect of different cases of parallel sluice gates operational management, gate opening to channel width ratio, and length of the separator walls on local scour development downstream of parallel sluice gates in different operations. Five operational scenarios were investigated on three parallel sluice gates. The results of the present study showed that the dimensions of the scour hole are a function of the symmetrical and asymmetrical operation of the gates. By reducing the gate opening to channel width ratio, the dimensions of the scour hole increased compared to the classical hydraulic jump mode. Maximum scour depth in the symmetric operational management scenario (B) and the asymmetric scenario (A), increased by 120% and 43%, respectively, compared to the ABC scenario. Increasing the length of the separating walls can be a suitable option to control the dimensions of the scour hole in different operations. Owing to a 20% increase in the length of the separator walls, the maximum scour depth decreased by 68% in the maximum Froude number (8.6) and 122% in the minimum Froude number (4.5) in scenario B. These percentages for scenario A are equal to 17 and 58, respectively. In addition, relations were presented to estimate the dimensions of scour hole in the symmetrical and asymmetrical operation of the parallel gates.

The main purpose of this study was to investigate the uniformity of sediment transporting flows into bilateral intakes on both sides of a spillway and compare it with a single intake either in outer or inner bend. The results indicated that most of the sediment deposition is towards the inner-bend intake. In the case of a single intake structure, the comparative results with the bilateral intakes indicated that both the water inflow rate and sediment entrainment increase in the case of a single intake located on the outer bend. In the case of a single intake on the inner bend, the water inflow rate decreases, but the inward-sediment load increases. It is necessary to use both the intake sill and sluice way to control the sediments entering the intakes, especially for the inner-bend intake.

The main aim of the present study was to simulate flow pattern upstream of sharp- and broad-crested weirs across a 90- degree laboratory channel bend, using the FLOW-3D model. The results indicated that Modeling results were not sensitive to the turbulent mixing length and roughness heights of the channel. Moreover, horizontal crested weirs are sufficient outside the bend. Sloping crest weirs provide better convergence of the unit flow rates across the bend in sections between 30 and 60 degrees. It was proved that the slope of the weir crest is to be in the range of 2º to 5º toward the outer bank of the bend. The broad-crested weirs are superior within the channel bend. Simulation results from the two FLOW-3D and FLUENT models are almost identical for flow patterns around the weirs.

The construction of water structures such as spillways in the longitudinal curvature of rivers is not appropriate (Ayaseh, 2011), and causes the asymmetric distribution of water and sediment flow throughout the river and along the tributary, uneven water load along the river, unbalanced operation of sluices, differences on the left and right banks capacity of the river and problems in the operation stages.There is a long history of flow studies in waterway turns (Chanel and Doering, 2008; Abad and García, 2014). The secondary current in the curvature causes a causal slope in the water surface from the outer arch to the inner arch and lateral pressure across the width, interacts with the non-uniform longitudinal velocity profile, and creates a helical flow in the output area of ​​the bend (Yasi and Valimohammadi Moghim, 2016; Hoseini Mobara and Yasi, 2017).One of the hypotheses to establish a more uniform distribution of flow across the river bend is to change the transverse floor profile to sloping (Abdolahpour, 2010).FLOW-3D has a good capability for modeling complex systems (Chanel and Doering, 2008; Developer of software for computational fluid dynamics (Flow Science Inc.), 2008). Thus, in the present study, it is applied to simulate overflows in a waterway turn and to detect the effects of the inclined crest on the flow pattern.

The FLOW-3D model is capable of simulating the flow of the overflows at the turn of a waterway. This model simultaneously solves the three-dimensional equations of continuity and Navier-Stokes,  Eqns 1-2, (11). The model applies the FAVOR leveling method to take into account solid boundary geometry (Fig. 1), and the VOF fluid volume method to simulate the flow with a free surface.Input boundary experiences fixed yield, constant pressure governs output boundary condition, and for the rest of the boundaries, the condition of symmetry was considered. The FLOW-3D model is calibrated and adjusted for three-flow, low-medium, and high-flow conditions based on the results of experimental flow tests in the flume screw interval. The simulation process in the FLOW-3D model is shown in the display process in Fig. 2.In this study, the flow pattern at six cross-sections (upstream, inlet or zero degrees, 30, 60, 90 degrees, and downstream of the turn) were derived, for three states 1) there was a sharp-crest overflow, 2) there was a wide-crest weir, and 3) there was no overflow. The experiments were performed under low (26 liters per second), medium (45 liters per second), and high (58 liters per second) flow.

Ensuring the calibration and validation process of the FLOW-3D model, the results were compared with similar experimental results for 16 sharp-crest weir tests and 16 wide-crest weir tests, also compared with results from the FLUENT simulator model.The results were presented for each of the weir installation sections (in the interval of twice the width of the flume from the upstream of the overflow to twice the width of the flume from downstream of the weir), and for the weir with horizontal and inclined crest. The results show that canal discharge for the state of the installed (sharp or wide-crest) weir is more than for the state where a weir was not installed, Fig. 3. Moreover, it shows that inclined-crest overflows cause discharge distribution per unit width (q) to be more non-uniform across the upstream section control of the weir. Therefore, horizontal-crest overflows (sharp or wide-crest) are more suitable for the upstream section of the curvatures.Fig. 4 indicates that both horizontal-sharp-crest and wide-crest overlays produce a more uniform flow (q) in the initial section (zero degrees). However, the wide-crest overflow performs better, and the sharp-crest overflow increases the discharge intensity toward the outer wall.According to Fig. 5, for the cross-section located at 30°, when there is no overflow the maximum velocity occurs at the inner walls of the bend. Although the flow shows similar behavior where a wide or sharp crest weir was installed, installing a weir decreased the measure of speed changes.Investigation of the effect of overflow on flow pattern at 60° showed that a horizontal-sharp-crest overflow causes to deviate the maximum velocity and consequently discharge to the middle of the weir crest, while the horizontal wide-crest overflow causes the maximum velocity to deviate towards the outer wall, Fig. 6.The flow pattern at 90° (Fig. 7) shows that a horizontal sharp-crest overflow causes to deviate the maximum velocity towards the inner wall, while the horizontal wide-crest overflow deviates it to the middle of the weir crest.

This research simulates an overflow (sharp or wide-crest) in different sections of a 90° bend with FLOW-3D to derive the flow pattern. The results showed that in all cross-sections, the wide-crest weirs have a better performance than the sharp-crest weirs. The horizontal-crest overflow is more effective than an overflow with an inclined crest in the upstream, beginning, end, and downstream cross-sections, although, inclined-canopy overflows distribute the flow more uniformly. Moreover, the flow patterns obtained by both FLOW-3D and FLUENT numerical models are the same and satisfactory, however, the FLUENT model products better the flow velocities in the boundary layer (near walls).

Most rivers are naturally meandering and are constantly eroding on the outer bank and sedimentation on the inner bank. As a result, cognition of the flow pattern in river bends is critical. Today, one of the constructions employed in river bends is the diversion dam. When the position of the bend changes, the diversion dam alters and its position shifts. Moreover, the adjacent agricultural lands' water requirements necessitate the intake construction on both sides. Hence, it is significant to study broad-crested weirs as one of the structures for maintaining uniformity of flow in river bends and during dewatering. In general, the presence of in-stream structures such as sediment control structures or out-of-river structures such as intakes at the bend of rivers require further investigations on sedimentation problems and flow patterns. One way to maintain a uniform flow in river bends is to create a secondary flow by broad crested weirs. Accordingly, the primary purpose of this study is to investigate the flow pattern and evaluate the uniformity of the distribution of unit flow discharge distribution at the intakes located on both sides of the broad crested weir in a 90-degree bend using a laboratory model.

The experiments were carried out in a rectangular flume trough 0.92 width, 0.6 depth, and 90-degrees bend. Indeed, the radius of relative curvature of the bend is 2.05, which falls into the category of sharp bends. The weir model is of the broad crested weir type, and the intakes were placed on both sides of the weir in the direction of flow and with an angle of zero. The weir was installed at an angle of 60 degrees from the bend inlet, and velocity and depth were measured in various transverse and longitudinal sections. All experiments were run at three flow rates of 37, 50, and 60 liters per second.

In general, the results show that bends and secondary flows affected the water level and caused a difference in water depth in the inner and outer banks in the case of without weir. This difference is indeed due to the effects of the bend. In this event, the side slope of the water surface deviates from the horizontal position and falls towards the inner bank of the bend, and rises towards the outer bank of the bend. One of the motives for the problems associated with sedimentation in river bend dewatering is related to this issue and the flow pattern in river bends. With the installation of a horizontal crest weir in the bend, the uniformity of the distribution of unit flow discharge has increased.However, in the case of the inclined sloped weir, the difference in unit flow discharge of the inner and outer bank is the largest compared to the other two cases. Therefore, the performance of the sloped crest weir was not acceptable in the sharp bend and upstream control section. The results of the discharge distribution in the intakes on both sides of the bend confirms the effectiveness of the hypothesis that the slope of the weir crest directs flow to the catchments on both sides of the bend. With the weir installation, more water flows into the intakes than without a weir.

 Regardless of the effect of the weir slope, the distribution of flow in the intakes on either side of the weir is more uniform than without the weir due to weir construction in the bend. The sloped crest weir has contributed to the distribution of intakes discharge. The highest uniformity of dewatering on either side of the weir was at an inlet in maximum flow discharge. The discharge ratio of the outer bank intake to the inner bank in the horizontal crest weir and sloped crest weir was 1.04 and 1.06, respectively. A sloped crest weir crown has the most significant influence on the uniformity water flow on both sides of the weir in all cases of the upstream inlet flows. An average, the discharge ratio of intakes in the outer bank to the inner bank in sloped crest increased by 11%, compared to the case of horizontal crest weir.

Dam removal is one of the methods of restoring the river ecosystem. In the present study, the removal of the Voshmgir Dam on the Gorganrud River, Iran, was considered, because of the high volume of sediment deposition in the reservoir and the loss of its useful life. Three scenarios were selected for the removal of the dam: 1- complete removal; 2- stepped removal of the spillway; and 3- removal with stable sediments. Numerical modeling for river morphological changes was performed using HEC-RAS model for unsteady flows with sediment transport. The erosion and sedimentation processes were simulated in six reaches (from the Voshmgir Dam to the Caspian Sea), with total length of 128 km. The results indicated that the first scenario causes the highest rate of both erosion and sedimentation in the river reaches. In the second scenario, the intensity of river-bed changes is considerably reduced, and the highest deposition and erosion occurs in the first and the fifth reaches, respectively. The simulation results from the third scenario were uncertain. The second scenario (stepped removal of the spillway) is recommended due to the less impacts on the river-bed changes, and gradual processes of river-ecosystem rehabilitation

Culvert is one of the main structures in drainage systems at crossing with railways and roads. Flood flows, along with the transport of sediments and floating debris, can cause blockages and backwater, thereby reducing flood flow capacity. The main purpose of this study was to physically model and numerically simulate the effects of different percentages of blockages on culvert hydraulic characteristics. Blockage effects investigated in 21 laboratory experiments. Complementary tests were carried out with the use of OpenFOAM numerical tool box. Three blockage scenarios have been numerically simulated with 20, 40 and 60 percent coverage of inlet area. The numerical model was calibrated using the experimental data. The simulation results of OpenFOAM in different culvert inlet blockages indicated that the LES turbulent model is more adaptive than RAS models. The main flow characteristics were compared with the corresponding simulation results from the trademark FLOW-3D model, and showed good agreement for verification purpose. Results for different flows (i.e. 40, 60 and 100 percent of the design discharge) showed that the increasing rate of upstream water level is not identical, and is higher for the lower discharges. Blockage also intensifies turbulence and shear stress levels in the outlet section. For design discharge, the 40 percent blockage resulted in the increase of shear stresses up to 10 times, which cause severe scour in downstream channel.

There are evidences of the construction of weirs and diversion dams in river bends, and the necessities for building water intakes on both sides of the river bend. The construction of weirs in rivers reaches encounters problems in terms of asymmetry of flow distribution into the intake structures on both sides of the river. The purpose of this study is to investigate the effect of relative curvature on the ratio of the inlet discharge of bilateral water intakes from a weir in a channel bend. The experiments were carried out in three laboratory channels with different relative curvatures (i.e. 3.3, 2.55 and 0.84), which falls into the category of mild, moderate and sharp bends. A broad-crested weir with two types of horizontal and sloping crests was installed at an angle of 60 degrees from the bend inlet. Two intakes were located next to the inner and outer banks. The results indicated that the weir installation in the mild bend performed better uniformity of intake discharges on both channel sides. The performance of sloping crest weir was superior compare with the horizontal crest weir. With the sloping crest weir, average inlet discharge into the inner and outer intakes increased by 8%, 4% and 8%, in three bends of  relative curvatures 3.3, 2.55 and 0.84, respectively, compared to the horizontal crest weir. Considering the sloping crest weir, the discharge ratio of the outer to inner intakes in the three mild, moderate and sharp bends was 1.00, 1.10 and 1.12, respectively. Increasing the channel discharges would result in more uniformity of inflows in the inner and outer banks in the three bends with different relative curvatures.

Transport of pollutants in rivers is one of the most important issues in the environment. Many researchers have solved the advection-dispersion equation by various numerical methods, including finite difference and finite element methods. Despite their advantages, these methods also have disadvantages that are often related to netting of the problem domain. Therefore application of mesh-free methods which do not require solution domain network seems necessary. In the present study, the one-dimensional advection-dispersion equation has been solved using the Mesh-free Local Petrov-Galerkin method in the unsteady state. The Murray Burn River data were used to evaluate the performance of the model. The used approximation and weight function were the moving least squares function and the cubic spline function, respectively. In this study, 9 experiments were used to calibrate the model and 2 experiments were used to validate it. For calibration, the discharge coefficient and velocity plotted against the flow rate, and the power regression equation was extracted which had correlation coefficients of 0.925 and 0.988, respectively. In the validation mode, the dispersion coefficient and velocity were optimized by minimizing the mean squared error between computational and observational concentration for each model. The dispersion coefficient in this study was in the range of 0.13-1.1 m2/s for the flow rate of 13-437 L/s. The results indicated the acceptable performance and accuracy of mesh-free method.

Balancing aquifers located in agricultural areas requires improving the performance of the surface water transmission, distribution and delivery system. This study investigates the effectiveness of improving the performance of the water distribution system (main irrigation canal) in balancing the aquifer. In the first step, the numerical model of Qazvin aquifer, with MODFLOW code in GMS software, was developed to show the effect of operation methods in the main irrigation canal. Next, the hydraulic flow simulator model of the water distribution system in the main irrigation canal was developed, calibrated and validated with MATLAB software. Finally, it was linked to the predictive automatic control system. Finally, the effect of predictive automatic control system on aquifer balance was investigated. The results showed that by improving the performance of the water distribution system in the main irrigation canal, the adequacy index improved by upgrading the existing operation method to a centralized automatic control system (MPC). It is about 30% in the end areas of the irrigation district. Accordingly, the rate of reduction of abstraction from the aquifer by using the automatic predictive control system is about 401.86 million cubic meters per year. The results of numerical modeling of the aquifer showed that in the present method, the operation of the groundwater level continues to maintain an increasing trend of decline. As the results show the amount of annual drop of about 150 cm in the usual operation method. The use of predictive centralized automatic control system has increased the adequacy of water delivery to reservoirs and this has led to an increase in water levels in observation wells located in agricultural areas.

One of the structures for controlling and measuring flow in open channels are the sluice gates. In this study, to estimate the outflow from the sluice gates, the existing relationships for orifices evaluated theoretically and experimentally. A new method was established for estimating the contraction coefficient and energy loss coefficient under free-flow condition. Some equations proposed to estimate the outflow from sluice gates under submerged flow conditions using the energy-moment principles and relationships for orifices. In order to evaluate the accuracy of recommended relationships, the outflow from the sluice gates was experimentally tested in a channel of 18 meters long and one meter wide. Comparison of the results showed that all the presented orifice relationships have similarly good capabilities to estimate the outflow from the sluice gates under free-flow conditions. It was concluded that the applying of Henry relationship would be the simplest one in determining the contraction coefficient. Under submerged flow conditions, all the orifice relationships have competent accuracy in estimating the flow rate, with an order of errors less than 10 percent. Under full ranges of free to submerged flow conditions, the discharge coefficient can be determined by the relationship of Rajaratnam and Subramanya as a function of the head loss coefficient, the contraction coefficient and the opening-to-depth ratio.

Optimization of operational performance in irrigation networks is essential for increasing water consumption efficiency in Urmia Lake Basin and its restoration. Various optimization algorithms have been developed. In this research, PSO algorithm with the ability of swarm intelligence and convergence speed was used to optimize the water delivery schedule of Zarinehroud left bank Irrigation Network in two reduced water allocation scenarios. The first scenario follows the Urmia Lake Restoration Plan (ULRP) based on the reduction of agricultural water consumption by 40%; and the second scenario focuses on the delivery of 70% to 90% of network water demand. Suitable values of model parameters have been determined by sensitivity analysis, and used in the modeling of two scenarios. Results of the first scenario indicated that, with supplement of 66% of water demand, the feasibility of 9% increase in water efficiency, 30% and 38% increase in the stability and adequacy indices can be achieved, respectively. In the second scenario, with 82% supply of water demand; the efficiency, stability and adequacy indices could be increased by 25%, 32% and 42%, respectively. The second scenario is recommended due to the gradually reduction of water allocation and greater values of the performance indices, while preserving the dependability and trust of water-users in the Zarinehroud irrigation network.

Submerged weirs are short-height structures that are completely beneath the water surface and are constructed to improve shipping conditions, create aquatic habitats, control the movement of bends, etc. The purpose of this study was to evaluate the patterns of erosion and sedimentation at a 90o sharp bend. To achieve this goal, a series of weirs with the relative heights of 30% and 70% and crest slopes of 0 and 7% were constructed on the outer wall of the bend. The angle, length, and distance between weirs were kept constant. The results showed that bendway weirs with a relative height of 70% and a flat crest slope had the best performance in protecting the bed near the outer bend wall. With the construction of these structures in the bend, 7% of sedimentation was done near the outer wall at a cross-section corresponding to the maximum scour location in the unstructured state. Changes in the height and crest slope of the bendway weir did not have a significant effect on reducing the maximum relative height of point-bar, and only at Froude number of 0.43 the average maximum relative point-bar height decreased by 10%. Moreover, with increasing the height and crest slope of the weirs, the maximum relative scours depth at the nose of the third weir increased by 11% and decreased by 6%, respectively.

Identification and evaluation of effective parameters in Inter-Basin Water Transfer (IBWT) projects are essential for the calculation of financial and economic indicators. Due to many qualitative parameters in these projects and inability to quantify most of them, an integrated economic valuation model is presented in this study.

In this model, the effective criteria and indicators are first prioritized using Analytic Network Process (ANP) as a Multi Criteria Decision Making (MCDM) method. Then, these criteria and indicators are quantified by two direct and relative valuation methods. Finally, two financial indicators: Benefit-Cost Ratio (BCR) and Net-Present Value (NPV) are modified and evaluated.

The results indicated that the political and security criterion is in the first place with significant difference with the others. Also, applying model for economic reassessment of the Chalus Water Transfer Scheme in Iran showed the value of BCR at discount rates of 6% and 8% are to be 0.2 and 0.14, respectively; and NPV is negative. Therefore, this project is not considered to be economically beneficial at its present feature.

It seems that political and security issue is very considerable in Inter-Basin Water Transfer (IBWT) projects. On the other hand, quantifying and valuating effective parameters can help more accurate economic analysis for new and ongoing projects