نشریه تحقیقات مهندسی سازه های آبیاری و زهکشی
سال بیست و سوم شماره 86 (بهار 1401)

The growing need for food and the increase in agricultural production, and consequently the increasing demand for water on the one hand, and the harmful environmental effects of agricultural drainage water on natural ecosystems and receptive water resources on the other, have led the world to look for methods and techniques that, along with reducing the harmful and adverse consequences of drainage water, make it possible to reuse them to meet part of human needs. In many areas facing water shortages for irrigation, drainage water is used to meet the crop's water requirement. Due to high volume and special quality, agricultural drainage water have a high potential for pollution in the environment, especially water resources. According to water shortage in Iran and population growth and increasing water needs in various uses, planning for the protection and quality management of water resources and optimal use of unconventional water, especially agricultural drainage water as alternative water resources has become more necessary.

For this purpose, the present study investigated the efficiency of a natural reed bed on a real scale in qualitative treatment of incoming drainage water of Khuzestan sugarcane during a period of one year (2010-2011). According to the trend of qualitative changes and wastewater treatment stages at the reed bed level, the length of the reed bed was divided into three parts, namely three stations ST1, ST2, and ST3 with a length and width of 3.5*1.2 hectares, respectively. The efficiency of the natural reed bed was evaluated by measuring parameters such as BOD, COD, PO4, and TP.

The results of the T-Test showed that there are significant differences in terms of BOD values between ST0-ST1, ST0-ST2, ST0-ST3, ST1-ST2, ST1-ST3, and ST2-ST3 study stations. The highest difference in BOD was observed between ST0 and ST3 stations equal to 6.96 mg/l. In addition, the lowest difference in BOD was detected between ST0 and ST1 equal to 1.73 mg/l. At the ST3 station, which is the farthest from the entry point, the highest percentage of BOD removal was obtained. There was a significant difference of 1% for COD between study stations. The largest difference in COD was observed between ST0 and ST3 stations equal to 9.62 mg/L followed by ST1-ST3 stations equal to 7.12 mg/L. There was also a significant difference of 1% levels in PO4 and TP of study stations and the highest difference in PO4 and TP with 0.2724 and 0.3790 mg/l, respectively, between stations. ST0-ST3 was observed. The results showed that the performance of the reed in eliminating the studied parameters was very good and acceptable. The removal efficiency of BOD, COD, PO4, and TP to the last station was noticeable and acceptable in all four seasons. Under different retention times (1.26, 1.10, 1.30, and 1.60 days), the removal percentage of BOD, COD, PO4, and TP was significant in ST1, ST2, and ST3 stations and with increasing the distance from the entry point, of the drain, the reed efficiency increased. Considering the different performances of the three stations in improving the quality of drainage and considering the efficiency target above 50% of all organic matter and phosphorus compounds, the ST2 station can be assumed as the optimal limit in terms of efficiency and cost.

In general, this system can be used as an efficient system in reducing common drainage water pollutants to the level of drainage water treatment standards and acceptable reduction of BOD, COD, PO4, and TP parameters of agricultural drainage water and improving the quality of this drainage water for discharge to surface and groundwater and also reuse for irrigation in agricultural fields.

The dissolved oxygen concentration in water is one of the most important parameters of water quality and plays an important role in improving the environmental conditions of rivers as well as the processes of removing iron and manganese from drinking water in water treatment plant. One of method to increase level of the dissolved oxygen in water is installation of structures that by increasing turbulence of water lead to entrainment of small bubbles of air into water body. Block ramps are one of the gravity-falling structures that in addition to the optimal performance in the stability of riverbeds, due to the structure of over passing flow and the possibility of applying various roughness’s in size and arrangement, can also act as an aerator structure.

Experimental Setup and procedure

In this study, the effect of different arrangements of intermediate-scale roughness on increasing the performance of dissolved oxygen in water in the downstream of the block ramp with slopes of 1:3, 1:5 and 1:7 was investigated experimentally.Experimental measurements were conducted in the hydraulics modeling laboratory of the University of Guilan, Iran, in a flume with a rectangular cross-section with, 0.88 m width, 1 m depth and 8.6 m length. A centrifugal pump controlled with an adjustable frequency AC motor supplied a range of discharges in semi-uniform regimes. It should be noted that the flow rate was adjusted using an ultrasonic flow meter with an accuracy of ±0.1 l/s.The DO measurements were conducted with two calibrated portable HQ30D Model DO meters 0.7 m upstream and 2.5 m downstream from the toe of the weirs where air bubbles completely disappeared from view. . During this process, the DO meters continuously recorded the DO measurements.To investigate the performance the block ramp with different slope and arrangements of roughness particles with intermediate scale (2.5<yc/ks<6.5), flow discharges (3.7<H/yc<6.9), and free and submerged hydraulic jump, 248 tests were carried out.

Experimental observations and analysis of the results showed that by creating intermediate-scale roughness on block ramps, the flow overpasses in different directions on the rough elements at lower approaching flow depth. Therefore, diffusion of flow along the structure intensifies and performance of increase of dissolved oxygen increases. Experimental observation showed that for smooth block ramp and high level of overpassing flow over roughed surface of block ramp, flow regime is skimming and there is no aeration occurred along structures. Comparison of results showed that for upstream dissolved oxygen of 2 to 5 mg/l at both free and submerged hydraulic jump, performance of the blokramps to increase of Ef increase by increase of flow discharges and corresponding H/yc. However, more increase of flow discharge caused to slightly decrease of Ef.Comparison of results indicated that at Cu = 2mg/l and submerged hydraulic jump, by increasing the slope of smooth block ramps from 1:3 to 1:5 and 1:7, Ef changed from 0.99 to 1.1 and 1.36, respectively. Furthermore, for free hydraulic jump, reduction of slope of smooth blockramp from 1:3 to 1:5 and 1:7, Ef changed from 1.35 to 1.53 and 1.44, respectively.By installing intermediate-scale roughness with various arrangement, on average by increasing the slope of block ramps from 1:3 to 1:5 and 1:7, Ef changed from 1.1 to 1.2 and 1.47, respectively. Furthermore, for free hydraulic jump, reduction of slope of smooth block ramp from 1:3 to 1:5 and 1:7, Ef changed from 1.43 to 1.34 and 1.61, respectively.Comparison of results showed that by installing intermediate-scale roughness with various arrangement Ef increases 7 percent on average for submerged hydraulic jump.

Comparison of performance of tested structures in all upstream dissolved oxygen concentrations shows that for block ramp with a slope of 1:3, installation of intermediate-scale roughness with different arrangements, performance of dissolved oxygen concentration (Ef) compared to no roughness conditions in ramp hydraulic jump conditions, it has improved by 8%, however, by changing the hydraulic jump to free, the performance of these structures decreased by 3%. Comparison of the results shows that by changing the slope of the structure to 1:5, create intermediate-scale roughness with different arrangements in ramp hydraulic jump conditions a 6% increase in performance of dissolved oxygen concentration was observed compared to no roughness conditions, however, by changing the hydraulic jump to free, the performance of these structures decreased by 14%. By changing the slope of the block ramp to 1:7 and create intermediate-scale roughness with different arrangements like other slopes studied, the performance of dissolved oxygen concentration for ramp and free hydraulic jump conditions, improved by 7 and 3%, respectively, compared to no roughness conditions.

It's important to live in a river. Structures in the present age Cross structures in the river can have negative effects on the environment, thus preserving the environment and preserving the aquatic ecosystem, which cross-section prevents the migration of fish upstream. Side effects of this problem include lack of spawning, reduced reproduction, and extinction of a species of fish. The fish route is a structure that allows fish to cross river barriers and provide fish access to their habitats. The hydraulic design of the fishway structure must be consistent with the characteristics of the fish's swimming behaviors in order to improve fish crossing efficiency (Castro et al., 2009; Kim et al., 2016). On the other hand, turbulent kinetic energy (TKE), its distribution, and volume are the most important reasons for the low efficiency of fish (Puzdrowska & Heese, 2019). Therefore, it is necessary to study this variable along the flow path to determine the behavior of fish. Also, due to the fact that fish structure structures act as rough by colliding with the flow, it seemed that the study of hydrodynamic parameters such as TKE as well as knowledge of the performance of the fish structure as roughness under the new w-w structure is less studied. has taken. Therefore, in the present study, the strength of structures and turbulent kinetic energy (TKE) in the W-W path have been investigated and evaluated.

The present study was performed in the hydraulic laboratory of the Faculty of Water and Environmental Engineering, Shahid Chamran University, Ahvaz, in a 10 m long, 50 cm high, and 25 cm wide flume. The slopes tested in the present study were 4, 7, and 10%, the tested discharges were considered 0.025, 0.025, 0.029, 0.034, 0.043 liters per second, and the angle of the structure was 20. W-shaped overflow barriers were placed about 5 meters from the flume, and in order to reduce the effects of the initial turbulence caused by the inlet flow to them, the first overflow was placed at a distance of about 3.5 meters from the beginning of the flume. W-shaped overflows were placed as barriers at D / L = 3, D / L = 6 and D / L = 9 distances .

With increasing dimensionless flow, the drop coefficients decrease; Because increasing the flow rate and consequently the flow depth, reduces the effect of the presence of obstacles as bed roughness on the flow conditions. On the other hand, with increasing slope, the flow depth is greatly reduced and this increases the effect of obstacles as roughness in the flow path. The inverse effect of the Froude number is on the drop coefficients and thus reduces the resistance of the structures, which are roughness to flow.. It was observed that by increasing the relative distance between obstacles, the current resistance decreases. The reason for this is that as the distance between the obstacles increases, the density of the obstacles along the flow path and the effect of roughness actually decrease At a constant slope, as the relative distance increases, the effect of relative depth changes on the flow resistance decreases. Increasing the depth of flow through the overflow of obstacles reduces the effect of the presence of obstacles as the roughness of the duct bed and reduces the flow resistance by about 53%. In contrast, increasing the slope and decreasing the flow depth increases the flow resistance. After being aware of the roughness changes, in this section, when the flow rate is 0.029, the kinetic energy changes of the turbulence will be investigated. Longitudinal changes of TKE on the center line from the structure i to i + 1 relative to the relative longitudinal distance D / L = 3 It is clear that by increasing the relative longitudinal distance from the upstream structure by 50% near the center between two consecutive structures almost maximum TKE occurs.

The inverse effect of flow and slope on the reduction of drop coefficients and the ineffectiveness of the presence of obstacles as roughness.The inverse effect of the landing number on the drop coefficients and thus reduces the resistance of structures that are as roughness to flow.By increasing the relative distance between obstacles, the resistance to current decreases. Increasing the relative distance, the effect of relative depth changes on the flow resistance decreases. The formation position of the maximum TKE is independent of the slope of the path.The maximum amount of turbulent energy occurs near the water surface.The best distance for fish is D / L = 9.

Pistachio cultivation is important because of its considerable area under cultivation in Damghan region and its share in the economy of the region and the province. Due to the amount of irrigation water required and limited access to water in the region and the unusual conditions of water and soil in the region, it is necessary to manage water consumption and optimize it. Improving irrigation systems in pistachio orchards, while reducing demand and saving water consumption, allows for better distribution of available water. If the current conditions continue and with an increase in groundwater levels, an increase in the negative balance of the aquifer and a decrease in water quality will cause many problems. This study was conducted to determine pistachio water consumption, status of water productivity index and also to compare irrigation systems in Damghan pistachio orchards.

For sampling, 148 samples were randomly selected from among the orchards of farmers in different areas of Damghan region, some of which lacked technical conditions and reliable data. Therefore, research data was collected by random sampling method and also through questionnaire data and interviews with operators or farm managers of 112 pistachio orchards. In this study, 112 gardens in Damghan region were selected and studied in terms of water use and water productivity. The amount of water consumption, yield and water productivity of selected pistachio orchards in Damghan region were determined. Damghan Pistachio Research Station is located at 54o20′8″ east longitude and 36o9′48″ north latitude and the altitude is 1130 meters above sea level. In agriculture, the physical productivity of water is generally used. The physical productivity index of irrigation water was obtained from the ratio of crop yield under each of the treatments to irrigation water. Three systems of surface irrigation, surface drip irrigation and subsurface drip irrigation were evaluated in 7 selected gardens.

The average yield of trees over 20 years of selected orchards was 4950 kg.ha-1 and the average yield of trees over 10 years of selected orchards was 3088 kg.ha-1. The average water consumption in surface irrigation method in the gardens of exploiters was estimated to be more than 8380 m3.ha-1, which is less than the water requirement documents. The amount of water used in drip irrigation is 8000-5000 m3.ha-1 and in subsurface drip irrigation is 4927 m3.ha-1, which is less than the national document. The water productivity index in each of these systems (surface irrigation, surface drip irrigation and subsurface drip irrigation) were 0.6-0.5, 1.5-2.5 and 0.406 kg.m-3, respectively. Water productivity index in trees over 20 years of selected orchards was equal to 0.54 kg.m-3 and in trees over 10 years old was equal to 0.349 kg.m-3. 53% of orchards have water productivity of less than 0.20 kg.m-3. Water productivity in surface irrigation, drip irrigation and subsurface drip irrigation systems were 0.5-0.6, 0.25-0.15 and 0.406 kg.m-3, respectively. Obviously, the relative advantage of irrigation methods for pistachio orchards depends on water quality and soil characteristics, water availability, tree age and garden management.

In analyzing the productivity index and yield of pistachio orchards, in addition to garden management, other factors such as tree age, cultivar type, water and soil quality, soil characteristics, alignment of climatic data and plant nutrition, process and ease of nutrient uptake and ..... also be noted. But this does not mean the advantage of drip or subsurface irrigation over surface irrigation. The range of water – yield relationship and analysis of the water productivity index indicate the existence of a yield and water productivity gaps in Damghan pistachio orchards. By choosing the best models and providing additional technical recommendations in the form of promotional training, he solved the existing gaps. Acknowledgement The valuable assistance of Agricultural Engineering Research Institute, Semnan Agricultural Jihad Organization, Damghan Agricultural Jihad Management and colleagues of Damghan Pistachio Research Station in carrying out related research are gratefully acknowledged.

Ski jump as one of the energy dissipater systems at the end of weir has been considered by hydraulic engineers due to its cost-effectiveness. Despite the dissipation of a significant portion of the flow energy, the bed is subject to scouring and can pose hazards to the structure. In recent decades, equations have been proposed to estimate the scour rate of this structure, each of which has a specific problem. For example, in some of these relationships, there are some factors that affect scouring, such as the bucket radius or the lip angle of bucket. The equation of Azmatullah et al. Is one of the most complete relationships mentioned in most sources. In this equation, the depth of scour increases with increasing mean sediment size of bed materials, which contradicts previous research. In the present study, the neural network was trained to estimate the depth of scour and the transmission functions, number of layers and type of network training were optimally selected. Using neural network and sensitivity analysis, the effect of different variables on the scour depth was determined. A high-precision relationship was presented to predict the scour depth using explicit genetic programming

In order to investigate the scour depth in flip-bucket, a laboratory model with a width of 0.5 m, height of 45 cm, length of 59 cm, bucket radius of 15 cm and lip angle of bucket of 45 degrees was constructed. The flow rate through the laboratory model is 7 to 21.2 lit/s, head between upper reservoir water level and tail water level is 0.3 to 0.38 m, the tail water depth is 0.028 to 0.1 m and the D50 bed materials is 4.3 mm. In the present study, in addition to the measured laboratory data, used data related to the research of Azmatullah et al. In this study, neural network has been used to predict the depth of scour hole. The optimal structure of the neural network is affected by variables such as the number of neurons in the latent layer, the stimulus functions between the neurons, and the number of latent layers. In the present study, the optimal structure of the neural network was determined by trial and error. It should be noted that in this study, NeuroSolutions software was used for the architecture of the multilayer neural network of perceptron.

Stimulus functions, number of hidden layers and type of training are factors that affect the accuracy of the model. In this study, the optimal structure of the neural network was determined by considering the variables affecting network accuracy and using various laboratory data. The results show that if the number of hidden layers of a number is a function of hyperbolic tangent transfer and network training type, Levenberg-Marquardt, the accuracy of the neural network in estimating the maximum scour depth is better. Also in this study, the scour depth sensitivity index to discharge per unit width flow, upstream head, lip angle of bucket, bucket radius, tail water depth and mean sediment size were calculated. The sensitivity index of scour depth to discharge per unit of flow width, fall height and lip angle of bucket is more than zero and this shows that with the increase of these variables, the depth of the scour hole increases. In order to reduce the amount of scour holes, the depth of the tail water can be increased or a riprap can be used. According to the calculated sensitivity indices, if the depth of tail water or particle diameter increases by 10%, the maximum depth of the scour hole decreases by about 3.9 and 1.3, respectively. Depending on the economic considerations and the feasibility of each case, the appropriate option can be selected. In this study, using the data of Azmatullah et al. And using GEP software, a relationship was presented to estimate the maximum scour rate in the flip bucket, with an average error rate of 9.8% which shows the model's ability to estimate scour.

In this study a neural network model was given to estimate the depth of the scour hole in the flip bucket. The results show that if the number of hidden layers of a number is a function of hyperbolic tangent transfer and the type of network training is Levenberg-Marquardt, the neural network accuracy in estimating the maximum scour depth is better. Also in this study, the sensitivity index of scour depth to input variables was calculated. The greatest effect on the scour depth is related to the water discharge per unit width rate, if the flow rate increases by 10%, the maximum depth of the scour hole will increase by 8.5%. In this study, a relation was presented to estimate the depth of the erosion hole, the accuracy of which is evaluated very well according to the criteria. کلیدواژه‌ها [English]

Seepage through the soil is one of the most important issues of Fluid-Structure Interaction (FSI) that can lead to liquefaction, boiling of sand in downstream, settlement of hydraulic structures, instability and failure of embankments and earth dams. Accurate calculation of the amount of leakage passing through the earthen dam is an important factor in ensuring its safety and stability. On the other hand, the results of seepage analysis in calculating the dimensions of drainage and filters of the dam deformation is very important (Kalateh and Afshari, 2018; Jafarzadeh and Asadnia, 2005).

To deterministic solving of the Laplace equation in soil medium is performed by Smith and Griffiths (2004), FORTRAN programming code is written that calculates the flow rate and piezometric head in the body of a homogeneous and non-homogeneous earth dam. The FORTRAN code for solving seepage equations is similar to the code for solid mechanics equations. In this code, inspired by solving the equations of static and dynamic equilibrium in solid mechanics and using the finite element method, the differential equation of seepage is solved with the difference that instead of displacement and force components in mechanical problems of seepage and pizometric head is used. In the present paper, a program based on the finite element method in FORTRAN programming language has been developed by the author that solves the Laplace equations to determine the leakage discharge of an earth dam assuming the uncertainty of the components involved. In fact, in the previous code related to seepage, soil permeability has been considered definitively, which in this study is probabilistically investigated. First, the FORTRAN code is assumed that the permeability values of the materials are constant, and the results are expressed as two leakage currents, input and output, in which case these two values are equivalent. The results show that in the isotropic state where the permeability is equal in the vertical and horizontal directions, the slope of the line is greater than the two non-isotropic states. As mentioned for deterministic modeling, the permeability of dam materials is constant in this case and is solved analytically by the Seep_4 subroutine, but in the probabilistic model and the Monte Carlo method, instead of the stability of the conductivity coefficient, the mean and standard deviation are entered in the calculations.

Figure 1 shows the relationship between the average seepage resulting from Monte Carlo Simulation for downstream reservoir ratios of 0.087, 0.136 and 0.19, which shows a graph in the range of 0.71<Kx/Ky<1 inequality slope. It has an ascending interval of 1<Kx/Ky<1.41 To be more precise, the slope of the descending section in the definite position for downstream ratios to the reservoir is 0.087, 0.136 and 0.19, respectively, equal to 0.96, 0.96 and 0.48 in the descending position and 0.73. 0, 0.88 and 1.032 are in the ascending state, with no significant difference. But in probabilistic mode for downstream ratios to reservoir 0.087, 0.136 and 0.19 with 0.41, 0.48 and 0.069 in descending mode and 0.78, 0.91 and 1.032 respectively is in the ascending state, in which the slope of the ascending part is at least one and a half times greater in all three states. It is worth mentioning that in all three cases and in both intervals, the coefficient of explanation of the linear relationship is above 0.98, which was calculated by SPSS software and linear regression method. Fig 1-a- Average seepage flow of earthen dam for changes in horizontal to vertical permeability ratio (Kx/Ky) in deterministic analysis. 1-b- The amount of flow through the Earth dam in change for changes in the ratio of horizontal to vertical permeability (Kx/Ky) in probabilistic analysis.

In the deterministic analysis, the effect of horizontal permeability on the seepage flow rate not show a significant difference compared to the effect of vertical permeability, but in probabilistic analysis, the effect of horizontal permeability on average of seepage flow rate is at least 89% higher than vertical permeability. • The results of probabilistic leakage study show that with increasing the ratio of downstream to upstream, the range of discharge in the frequency distribution function (PDF) and the average leakage discharge decreases. • With decreasing the width of the earthen dam crown, the average seepage flow decreases and with the upward movement of the dam crown, this amount increases. • In all cases, the average seepage flow calculated in different cases of Monte Carlo Simulation (MCS) models is 16 to 270% less than the seepage flow in the definite case.