دکتر جواد فرهودی

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.

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.

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.

Innovative and sustainable agricultural water management is critical in adaptation programs to climate variability and change, and emerging, eco-friendly irrigation technologies are expected to play a key role in the world's future water and food security. The current study was carried out with the aim of discussing pros and cons of new irrigation and agricultural water technologies in the world, and the possibility of application of these technologies in Iran. These techniques are classified into seven categories: smart technology, nanotechnology, greenhouse technology, superabsorbent technology, cloud seeding technology, deep water technology, and seawater desalination technology. These technologies are analyzed in terms of economics, water and energy usage, and certain environmental factors (such as toxicity and greenhouse gas emissions). The state-of-the-art of modern irrigation and agricultural water technologies in Iran is examined, and the issue of their domestic application is matched with the country’s potentials. According to documentary studies, our country is at the beginning of the road in terms of intelligent technologies for agricultural water management and nanotechnology, and further study is required to employ these technologies. However, intelligent irrigation management utilizing crop growth and yield models, mobile phone applications, and micro-irrigation implementation was proposed as a feasible solution. The use of silver nanoparticles was suggested for the disinfection of water in remote areas, and the use of titanium dioxide for areas that do not have power supply problems. Employing the vertical farming is not recommended in the country due to the problems of electrical power supply and air pollution and presence of unlimited arable land. The technology of artificial light and solar panels has been adopted in Iran and more research is needed to justify their applications in greenhouses. Cloud seeding, deep water, and seawater desalination technologies have become indigenous to Iran. Cloud seeding is ineffective to alleviating droughts and strengthening aquifers. Because of the environmental consequences, the employment of deep-water technologies is not recommended. Employing of seawater desalination technologies for drinking and industrial (not agricultural) uses is cost effective.

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

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.

In practical applications, for instance, at the downstream of hydraulic structures, in some cases the width of the basin may be larger than the upstream supercritical flow (sudden expansion in flow section). In such cases, an expanding hydraulic jump with symmetrical or asymmetrical shape will be developed at the downstream. Under the design of three parallel gates, the operation of the side or middle gate can be lead to the asymmetrical or symmetrical hydraulic jump, respectively. According to the position of jump toe, expanding hydraulic jump can be classified into four types. The present study focuses on a T-shaped hydraulic jump which the toe is established at the beginning of the divergence section.Most of the previous studies are related to the symmetrical expanding hydraulic jump. In this case, the downstream diverging channel is symmetric on the central axis of the channel. However, a systematic study investigating the effect of symmetry and asymmetry on the expanding hydraulic jump was not found in the literature. In this study, using the momentum principle, some theoretical equations were derived to determine the sequent depths ratio of symmetrical and asymmetrical expanding hydraulic jump. Also, some regression relations were proposed to estimate the length of expanding hydraulic jump. The new proposed equations were also extended for the presence of a sill. The equations were calibrated using available experimental data from this study and the literature. This research also considered the characteristics of expanding hydraulic jump under the symmetrical and asymmetrical operation of parallel gates.

To calibrate the new proposed relations and investigate the effects of different parameters on the expanding hydraulic jump characteristics, two experimental data sets were used. In addition to the data set from Bremen (1990), the experimental data from the present study were used. The data were collected from a hydraulic model of three parallel radial gates for operating the side or middle gate which corresponds with the asymmetrical or symmetrical expanding hydraulic jump, respectively. The experiments provided a wide range of different parameters as the approaching Froude number, hydraulic jump length, sequent depths ratio, divergence ratio, sill height and relative length of gate separator wall.

Equation (4) was developed to determine the ratio of the sequent depths of expanding hydraulic jump based on the Momentum equation. For the presence of a sill, a combination of Equations (4), (7) and (8) can be used to calculate the ratio of sequent depths under the asymmetric and symmetric developments, respectively.Determining the ratio of the sequent depths requires the calculation of the adjacent water depths of the closed gates. For this purpose, in addition to developing the regression equation (Equation 13), Equation (12) was proposed which based on the calculation of the hydraulic jump profile. It was observed that under the calibration range, the regression equation is more accurate. However, Equation (12) is recommended for the range outside of the experimental observations. The results showed that:As the divergence ratio increases, the ratio of sequent depths approaches to the classic hydraulic jump.By decreasing the relative length of the gate separator wall and decreasing the width of the gate on the downstream channel width, the relative depth at the side gate and consequently the ratio of the sequent depths will decrease.For the lower length of separator wall and under operation of the middle gate, more lengths are needed to develop the jump than the side gate. However, as the length of the separator wall increases, the length and sequent depth of hydraulic jump due to the side gate increases on the middle gate.In the presence of a sill, the relative length of hydraulic jump decreases and the ratio of secondary depths increases.It was observed that the hydraulic jump due to the operation of the middle gate leans toward the left or right side of the channel due to oscillatory behavior.Under operating the middle gate and in the absence of a sill, an asymmetric hydraulic jump is formed in the channel face when the length of the separator wall is less than 38% of the classical hydraulic jump length. For the presence of a sill, the minimum length of the separator wall decreases to about 26%.By decreasing the initial depth of the hydraulic jump on the width of the gate and converting the output jet into a linear jet, the relative development length will increase.
As the sill height increases, the difference in the depths attached to the side gates will decrease and the hydraulic jump will develop more symmetrically.As the relative height of the sill decreases, the minimum length of the separator wall to form a symmetrical hydraulic jump in the flanks, increases.

This research developed a set of theoretical and regression relationships for estimating the length and sequent depth ratio of expanding hydraulic jump. Moreover, the effects of sill height, divergence ratio and the length of the gate separator wall, were investigated. This study compares the effects of side and middle gate operations based on the variation of jump length and sequent depth ratio. The results can be used as a guide for the hydraulic structures operators to reduce the asymmetric severity of the expanding hydraulic jump and achieve the complete development under the minimum length.

Most of the previous studies related to radial gates are focused on the estimation of discharge from the gates as a flow measurement structure. However, determination of the gate opening for passing a certain value of the discharge is rarely considered in previous studies as a regulator structure. The present work presents some theoretical equations for explicit estimation of the outflow from the gate (first problem), and gate opening (second problem) for free and submerged flow conditions by combination of Energy and Momentum principles. For any problems, it was developed some criteria to identify flow conditions These equations were calibrated and validated by means of 2657 experimental records retrieved from research conducted on three types of radial gates. The paper would present an analytical approach to illustrate the reliability of proposed equations for estimation of discharge and the opening of the gate by taking benefits from the mean absolute relative errors which observed to be 1.94% and 2.67, respectively. It was noted that the used criteria conform with 99.6% and 98.8% of all observations at first and second problems, respectively. The results show that the tailwater depth under distinguishing limiting decreases by increasing in the gate lip angle and the ratio of turnnion pin height to the gate arm radius. Also, the hard rubber bar gate tends to operate under free flow condition in a wider range in comparison with two other gates.

Scouring is one of the issues that is important in the design of various types of hydraulic structures. One of these structures is a stepped spillway. The aim of this study is to evaluate the similarity between the profiles of scour holes downstream of the stepped spillway. To do so، results of 67 experiments in two different experimental models were used; these results were in a wide range of particle Froude number، the stilling basin length، downstream depth، sediment particle size distribution and two different slopes of stepped spillway. In this study، 5 different lengths of stilling basin، from 37 cm to 120 cm، were used. Also، the range of utilized discharge was from 8. 43 lit/s to 88. 95 lit/s. Duration of the tests were selected to be 6-hours، 8 hours، 12 hours and 24 hours and، in total، 834 scour profiles and approximately 85000 points to were used derive required relations and to performother analyzes. Based on the experiments results، the similarity between scour-holes located in downstream of stepped spillway was analyzed. In this process، two methods were used to make the profiles dimensionless. Based on statistical parameters، best method was selected and similarity of downstream profiles were shown. Relations that predict maximum scour depth، the distance from maximum depth to the end of the stilling basin and volume of transported sediments are developed based on the dimensionless parameters in different time periods. Furthermore، impact of different parameters on the geometry of scour holes were studied. When the Froude number increases، while all other parameters are constant، the dimensions of the scour-hole increases. When the stepped spillway slope increases، the dimensions of the scour-hole decreases and، moreover، when the tail water depth increases، while all other parameters are constant، a deeper hole with longer longitudinal distance forms. Overall، 8 cross section profiles under different conditions were taken. These profiles indicate transverse development of the scour-hole، in addition to longitudinal development.

This research is focused on local scour downstream of adverse stilling basins where the flow jet was issuing from a submerged sluice gate. Totally, 233 tests were performed and 3262 scour profiles were recorded in a wide range of Froude numbers, sediment grain sizes, tail-water depths, stilling basin lengths and bed slopes. The results showed that the scour holes are self-similar at any slopes. A polynomial equation was derived to define the non-dimensional scour profiles at different slopes. In a certain condition of sediment grain Froude number, tail-water depth and length of basin, a change in the slope of basin from 0 to 15.6%, caused a decrease of 15% in maximum depth of scour hole. A theoretical approach was also derived to evaluate the bed shear stress, weight shear stress and shear stress at threshold state along the scour hole. It was found that the weight and bed shear stresses along the scour hole follow a time-dependent similar trend of variation. Finally, the geometry of basin was investigated to examine its effects on the weight and bed shear stresses.

The hydrodynamic behavior of approaching flow and the amount of sediment entry into right-angled lateral intakes in diversion dams were investigated using a laboratory channel by experimental measurement and observation. The velocity field upstream of the intake in the main channel and before it at the sluice gate was measured at different elevations of flow at different discharge rates of the river, intake and sluice gate. Velocity profiles were also measured from upstream to downstream for the intake and the amount of sediment entry into it. Analysis of the velocity data showed that discharge at the sluice gate strongly affected velocity profiles and the mechanism of sediment entry. All velocity profiles where the sluice was closed had an inflection point, where the flow direction changed, leading to a return velocity near the bed. The elevation of this point was a function of the intake discharge and approximately equal to the height of the entrance sill. Observation showed that sediment entered the intake in whirlpool vortices. The strength and frequency of the vortices depended on the intake and sluice gate discharges. Analysis of sedimentary data showed that the amount of sediment entering the intake increases with an increase in intake discharge. In addition, for any given intake discharge rate, an increase in the sluice gate discharge caused an increase in sediment entry into the intake.