IRANIAN WATER RESEARCH JOURNAL
Year:2015 | Volume:9 | Issue:3 (18)|Papers Count:24

Urban developments and increase in construction are associated with an increase in impermeable areas and, however, increasing impermeable areas may lead to an increase in surface runoff of these areas. Today, these increases in surface runoff and damages which are arising from extreme rainfalls have been emerged as big challenge urban areas. Urban surface water collection systems are a series of hydraulic structures which are being used as a mean for controlling and conveying storm waters in urban areas. Improving urban runoff quality is one of the important factors in proper performance of the urban runoff collection system. Sedimentation basins are one of the first components in urban drainage and are employed to improve runoff quality before reaching runoff to the storm water collection system by settling the coarse to medium-sized sediments. Design of these basins is usually based on uniform and non-turbulent flows without considering the presence of sediments and their effects. In reality, however, the incoming flow to an Urban Sedimentation Basin (USB) is syllabic that is naturally turbulent. Although, the removal of suspended solids in a USB will be performed by gravity, various inflow conditions, coarse solid particles and different geometry of the USB led to form a complicated hydrodynamic in the basin. The proper design of these structures by considering the real conditions may guarantees the other parts of the drainage network. Thus, understanding the hydrodynamics of a USB, in addition to determining the turbulent flow and concentration fields, the basin efficiency can be also calculated more accurately.In general, the flow in Sedimentation basins (SBs) is a two-phase turbulent flow. Many experimental and numerical studies have been carried out to understand the hydrodynamics of this turbulent flow in SBs. In previous years, most of the researches in the first place has been allocated to a better understanding of the hydrodynamics of flow and sediment particles by taking into account various parameters such as turbulence, the three-dimensionality of the flow and so on. In the second place, researchers have tried to improve the efficiency of SBs in various methods including changes in geometry and hydraulic conditions. In this paper, at the first stage, an accurate, complicated, Euler-Euler coupled two-phase model which uses similarity between solid particles with gas molecules were used to simulate the sedimentation process in a USB. In comparison with previously used methods, the advantage of this method is its more accuracy to calculate the properties of the solid phase. In other words, in this method for the solid phase, a separate momentum equation will be solved in which the characteristics of the solid phase, will be calculated using the kinetic theory. The model is able to simulate flows which contain a high proportion of sediment particles, with different flow pattern, through solving a separated momentum equation for solid phase. In this way, by using this model, first, the laboratory basin of Van Rijn (1986) was simulated, and the results were compared with their experimental data, and so, a well-accommodation was achieved. Then, however, the urban sedimentation basins (USBs) of Tehran, which have a relatively high sediment concentration and coarse solid particles, as a sample were studied. In the second section, parametric studies were performed on the basin. So, length, width and height of a USB with a constant volume were changed and their effects on the efficiency were investigated. Accordingly thirteen basins with different dimensions, by keeping the same volume, using the FLUENT model were simulated Results in the first part showed that one-hour average efficiency of the USB, is less than 30%. It has been resulted that the main factors in reducing the efficiency of the urban SBs are the two outlets at the bottom of the basin which are being used as drainage flow at low flow rates. In this part, the dynamic distribution of sediment in the basin is also obtained. In the second part, time variation of the basin efficiency diagram by different length, width and height was obtained. The efficiency calculations showed that, against other researcher’s studies that have considered length as the most effective parameter in the removal of the solid particles; width changes have the greatest impact on increasing the removal efficiency. The main reasons are related to coarse particles and the specific geometry of the USB.

In this study, an explicit equation is presented for estimating the height of the end sill in the trapezoidal stilling basin based on the energy equation. In addition to the experimental results were compared with energy and momentum methods which have been solved by numerical methods. Evaluation results indicate proper coordination between experimental and computational data and confirmed that the presented explicit equation can compute end sill height with suitable accuracy. In recent decades, several studies aimed at understanding the function of hydraulic jumps in trapezoidal sections have been made Forrester and Skrinde (1950) to find an analytical equation based on the Froude number, initial depth, sequent depth and sill height for controlling jump in rectangular sections which used rectangular broad-crested weir equation for determining discharge which was created by Barker and Doeringsfeld (1941). Achour and Debabeche (2003) investigated the effects of broad-crested end sill on the U-shaped sections as well as the effect of the sharp-crested end sill on the triangular sections with the apex angle of 90o, by comparing the theoretical and experimental equations in U-shaped sections. They also found that the required sharp-crested end sill for controlling the hydraulic jump with the same conditions should be slightly taller than broad-crested end sill in U-shaped cross sections. Achour and Debabeche (2003) presented an explicit relationship in rectangular sections to find the minimum broad-crested end sill height necessary to control the hydraulic jump which indicated good agreement with the results of Forrester and Skrinde (1950). If a broad-crested end sill placed on the supercritical flow path in the stilling basin, hydraulic jump is formed. The minimum height necessary for the sill according to the specific energy concept can be calculated. In this case, due to the existence of critical depth on the sill, this section will act as a control section. To evaluate the results of the proposed explicit equation to determine the end sill height, a number of tests were carried out. Experiments were done in a horizontal channel with symmetrical trapezoidal cross-section, and with side slopes z=0.5, 1, 1.5, Length of 3 m and a width of 5.0 meters to measure the characteristics of flow jumps in the discharges range of 19.3 To slow down and measure the input flow in laboratory model, upstream primary reservoir, with dimensions of 1.25 m wide, 1 m long and 1 m high were designed and built. Inlet water flow to model supply through the circulated flow system with the closed circuit pipes in the laboratory, and through the branch of pipe near the model was connected to the first tank. To calm the approaching flow to the weir, a mesh with 1.25 m width and 1 meter height was used. Discharges measured with a calibrated weir in upstream tank. With the crossing of water over the weir, the flow was entered to supply-height reservoir. The purpose of constructing this reservoir was providing the required energy for the formation of the hydraulic jump with desired Froude number.Initial and sequent depth was measured with an accuracy of 1.0 mm by a point gage. In order to create jump without the end sills, flow was controlled by a terminal movable valve as a tailgate. For each of the experimental data obtained from the Fr1, in the range of 3 given that the critical depth was created on the broad-creased sill, by writing momentum equation at the section of the sequent depth and sections with critical depth on the sill, the sill height can be calculated. As well as the sill height can be calculated by Bernoulli equation without taking into account the energy loss. Using any of these two methods is needed to solve nonlinear equations implicitly. With the proposed explicit equation, estimation of height end sills is provided easily in terms of the flow characteristics and canal cross sections with high accuracy. The values obtained from the proposed explicit equation for the height of broad-creased end sills with predicted values of energy and momentum equations are approximately the same, and all three methods have little difference with the experimental results. Also, it can be said that this equation can be predicted experimental data with high accuracy and indicates good performance as terms of practicality.In this study, the control of hydraulic jump with broad-creased end sills in trapezoidal sections with three side slope of 1: 0.5, 1: 1 and 1: 1.5 was investigated. Flow analysis over the broad-creased sill allowed that the minimum sill height necessary for controlling the hydraulic jumps to be estimated.The results of the comparison of the proposed equation with momentum and energy equations and experimental results showed good accuracy in estimating the required broad-creased sill height to control the jumps in trapezoidal sections. Because there are no more experimental results, presented equation can be used as a guide in designing of energy dissipators to determine the broad-creased sill in trapezoidal sections with the explicit equation. It is noteworthy that the broad-crested sill is superior in comparison with other dissipators hydraulic jump structures, due to its structural stability and lower costs.

Worldwide, over 45, 000 large dams have been built, and nearly half the world's rivers are obstructed by a large dam. The belief that large dams, by increasing irrigation and hydroelectricity production, can cause development and reduce poverty has led developing countries and international agencies such as the World Bank to undertake major investments in dam construction. By the year 2000, dams generated 19 percent of the world's electricity supply and irrigated over 30 percent of the 271 million hectares irrigated worldwide. However, these dams also displaced over 40 million people, altered cropping patterns, and significantly increased waterlogging of arable land. Dams are artificial barrier usually constructed across a stream channel to store water in a reservoir which is then used for a variety of applications such as irrigation and municipal water supplies. Dams must have spillway systems to convey normal stream and flood flows over, around, or through the dam. Spillways are commonly constructed of non-erosive materials such as concrete. Dams should also have a drain or other water withdrawal facility to control the water level and to lower or drain the lake for normal maintenance and emergency purposes. Dams are constructed especially for water supply, flood control, irrigation, energy production, recreation, and fishing. Dams are mainly divided into four parts on the basis of the type and materials of construction as gravity dams, buttress dams, arch dams, and embankment dams. These dams are divided into two types: homogeneous and non-homogeneous earth dams. Non- homogeneous dams are made of different parts that each part has much influence separately on the dam body’s performance, stability, and other design components. In designing of an earth or the rock fill dam, the foundation, abutments, and embankment should be considered as a unit. The entire assemblage must retain the reservoir safely without excessive leakage. Provisions for seepage control have two independent functions. The first is the reduction of water losses to an amount compatible with the project purpose. Another independent function is that, eliminating the possibility of structural failure by piping. It may also be concerned with the stability of construction slopes and slopes around the reservoir after impoundment. One of the most important components in dam designing is the dam core. The dam core is a significant factor in caulking and controlling dam body seepage.One of the key aims of this study is to develop the numerical model for measuring seepage through a dam, stability factor and hydraulic gradient based on materials and geometry specification of earth dams. The methodology includes parts such as: Simulated annealing algorithm, modeling and optimization part that included seepage model, slope stability model and hydraulic gradient model.In this study, a new model is proposed to predict the seepage rate, slope stability, hydraulic gradient in a non-homogeneous earth dams using Geo-Studio software. Thorough this model, seepage, slope stability, and hydraulic gradient are formulated by different factors which are related to material properties and geometric dimensions of the dam. It should be noted that permeability in shell for the non-homogeneous earth dams are more than core. Hence, the seepage rate for the shell can be ignored because existing remarkable difference between shell and core dam. Therefore, the core can be considered as a homogeneous dam. In this research, 150 assumed sections with different materials and dimensions are designed.In this paper, new regression models including leaking from the dam body model, hydraulic gradient model, and stability safety factor model were developed to calculate the designing variables. The results indicated the high performance of new regression models for determining the coefficient of stability, leakage from the body, and hydraulic gradient. For developing the necessary model, hydraulic gradient and stability safety factor were considered as constraints. Also, the multi objective function was expressed as reduction of seepage through the dam body, and the volume of core material is minimized. This problem was optimized using the Shuffled complex evolution (SCE). The SCE method combines the strengths of the simplex procedure with the concept of controlled random search, competitive evolution and the newly developed concept of complex shuffling. As the search progresses, the entire population tends to converge toward the neighborhood of the global optimum. The results of modeling were compared by the actual geometry of Birjand Hesar Sangi earth dam. A result indicates the 24 percent reduction of material type in dam core and 8.5 percent reduction in dam shells. The high performances of the integrated developed model demonstrate the capability of this model in optimal design of earth dam on stable condition.

Flow Duration Curve (FDC) shows the percentage of time that the daily or monthly river flow in a basin in the course of time exceeds from a certain amount. The flow duration curve is widely used by hydrologists around the world in diverse applications associated with water, such as hydropower projects, irrigation system design and management of river pollution, erosion, reservoir sedimentation and erosion. The curve is widely used in water resources engineering, but the number of studies related to this issue is low compared to its importance. The flow duration curve in these studies has focused on water resources engineering, while some others cover regional FDCs. Because some water resources projects are in basins with no data but require flow duration curve, information can be used from adjacent basins to design hydrological projects in ungauged basins. Then regional flow duration curve is useful for analyzing the hydrologic behavior in order to consider the consequences of project designs.The present study assesses regression relations as a parametric approach in order to draw flow duration curves for ungauged sub-basins. For this purpose, 18 hydrometric stations having adequate data in the Salt Lake basin with an area of 92670 square kilometers located central Iran were selected. The lowest and highest elevations of the basin are 795 m and 4315 m above sea level, respectively, while the annual average precipitation is 250 mm. The vegetation cover distribution in this part shows a diverse pattern.The quality of data was checked and incomplete data were reconstructed based on the established regression equations. Then, index discharges of flow duration curve thresholds (Q10, Q20, Q95) were extracted. In the next step, the regression relations were established based on the stepwise method, between the index discharge values of flow duration curves and the selected variables including physiographic factors (e.g. basin area, length of main stream channel, basin average slope, minimum, average and maximum elevation of the basin, drainage density, elevation difference), precipitation as a climatic factor and land use including the area of rain-fed and irrigated lands, rocks and rangelands. Then the statistics of regression model including the prediction error sum of squares (PRESS) and mean square error (MSE) as well as Nash-Sutcliff coefficient was evaluated. The results showed that among the studied variables, main river length, watershed area, average annual rainfall and the basin slope had the largest role in river flow. Therefore, based on the significance of relations at the 95% threshold level and having the values of these variables, the obtained relations could be used as a regional index in drawing and establishing flow duration curves for ungauged basins.The study classified FDC into five different conditions, including flooding, wet, average, dry and low flow status. The discharge with and exceedence level of 10% was considered for flooding threshold while 40% and 90% were classified as average and low flow levels. The values indicate the time in which flooding, wet, average, drought and low flow condition are prevailing status of the basin. The results of discharge occurrence percentage briefly show that flooding condition is mostly seen in the basin for discharge with the exceedence percentage of 0-10 and then to 10-40 percentage which shows the wet condition.It was tried in this study to consider the most influential variables in the regression equations included in this respect, land use and geological maps were prepared. But the maps were without significant information that could determine the role of these factors in river discharge. Although the regression equation was significant, the role of the geologic formation permeability and Curve Number (CN) in different discharges cannot be ignored. According to the prevailing conditions in arid areas, permeability can be effective in flow characteristics. If the data are collected and used in future studies, it can be expected to achieve better results than current study. Also, evaluation of different approaches (parametric, non-parametric and statistical) can be useful to calculate the index discharges of ungauged basins to select the appropriate approach. Multiple linear regression approach was used to establish regression equations have been widely used in other research and not only the basin area but also other as independent variables used to model the flow duration curve. As a final conclusion, the area of the basin is highly correlated with the main stream, but it stated only the size of the catchment area. While the combined area of the watershed with the main stream length, shape and size of the river basin better shows the flow behavior and characteristics.

Although the evidence for anthropogenic climate change is overwhelming, it is still standard practice to preface the statement by saying; most climate scientists believe that increasing concentrations of greenhouse gases have led to changes in climate. According to the fifth IPCC report, increasing concentrations of CO2 and other greenhouse gases has led to fundamental changes due to anthropogenic activities in the global climate over the course of the last century. These changes in the climate will lead to changes in water demands of existing irrigation networks. In the agricultural sector, there are multiple variables which will be affected by climate change. For instance, evapotranspiration is controlled by climatic variables (such as temperature, precipitation, net radiation, wind speed and relative humidity), and changes in climatic regimes can affect hydrological processes, yield production, and the development of agricultural activities. Given the importance of agriculture, there is a significant need to understand the implications of climate change on agriculture, to explore different adaptation options and performance and vulnerability assessments of irrigation networks to impacts and adaptation to climate change. Therefore, the analysis of climate change impacts and adaptation strategies to maintain the performance and stability of irrigation systems, as well as improve their efficiency, are necessary. The goal of this paper is to investigate the effects of climate change on performance of irrigation networks, through a case study of a sprinkler irrigation network in Bilesavar, in Northern Iran.The Bilesavar irrigation network is located in the Moghan plain in Ardebil province, North of Iran (48o15’ to 48o20’ East longitude and 39o 21’ to 39o 28’ North latitude). The Bilesavar irrigation district is 3, 200 ha, with 21 field units or sectors and cropping patterns that are devoted to a wide range of crops such as wheat (40%), barley (15%), alfalfa (20%), cotton (20%) and lentil (5%). Also, the general circulation models (GCMs) are used to estimate the future climate change due to continuous increase of greenhouse gas concentrations in the atmosphere, The outputs of GCMs cannot be used directly for climate change studies, and they do not provide a direct estimation of the hydrological response to climate change. As a result, downscaling techniques are used to convert the coarse spatial resolution of the outputs of GCMs into finer resolutions, which may involve the generation of point/station data of a specific area using GCM climatic output variables. This study used a statistical downscaling method, SDSM, which has been widely applied to downscale GCMs. In this study, the output from the Hadley GCM3 model (HadCM3) was utilized to downscale temperature and rainfall data for the study area. The HadCM3 model is one of the major models used in the IPCC Third and Fourth Assessments, and it also contributed to the Fifth Assessment. Precipitation and temperature data under A2 and B2 scenarios were produced using HadCM3 in the case study for future periods 2010-39 and 2050-80. Then the potential evapotranspiration was considered as new network water demand, with this assumption that the water supply of Bilesavar’s network there will be no restrictions in the future, and entered to Water Gems model for assessing the performance of irrigation network. Finally, the network performance was evaluated on technical and management approach. The results of temperature and precipitation downscaling showed that the most critical changes of temperature and precipitation will be occurred in June and July months under scenario A2 for 2010-39. In general, scenario A2 results in more increases in temperature than B2 in each time period, and according to these scenarios, higher temperatures will be seen in 2050-79 compared to 2010-39. As compared with the base period, the temperature will be increased 2.1 to 2.3oC (for 2010-39); 4.9 to 5.1 (for 2050-80) and precipitation will be decreased 21.1 and 38.4 percent (for 2010-39); and 52.1 and 57.9 (for 2050-80) in June and July, respectively. For ETo, scenario A2 results in a higher increase in ETo compared to B2 in all considered periods and ETo is around 6% higher than the baseline for 2010-39 and 12 % for 2050-79. Overall, the situation will be more unfavorable in the months with peak water demand, and the conditions will be more extreme (less precipitation, more temperature and ETo). The results showed that with increasing water demand in the Bilesavar network, assessment indicators such as equity and adequacy of pressure distribution have declined 16.7 and 21.5 percent in comparison with baseline.

Different equations have been introduced for estimating grass reference evapotranspiration (ETo) that are in the range of easy to very complex equation of energy balance. Empirical ETo equations have remained in popular use because of simplicity and the smaller number of input parameters needed for computation. The Hargreaves−Samani (1985) equation is one of the empirical equations which widely used by researchers for estimating the ETo. The most important parameters in estimating ETo are temperature and solar radiation (Rs). The RS has a key role in energy balance in the ground-atmosphere system and is a key parameter in calculating ETo. Hargreaves and Samani (1982) recommended a simple equation to estimate solar radiation (Rs): R_S=(KT) (R_a)[(TD)]Ù0.5 (1) Combining equation 1 with the original Hargreaves equation (Hansen et al, 1979) resulted in a simplified equation which requires only temperature and latitude (Hargreaves and Samani, 1982, 1985). The simplified equation is as: ET_o=0.0135 (KT) (R_a) (TD)Ù0.5 (T+17.8) (2)In the above equations, TD is the difference between maximum and minimum daily air temperature (Tmax-Tmin) (oC) for weekly or monthly periods; Ra is extraterrestrial radiation (mm/day); KT is empirical coefficient and T is the average daily air temperature (oC). The equation 2 and its empirical coefficient (KT) were investigated in various studies and its application in ETo proper estimation was validated. Ever now it was not done any study about the effect of solar radiation estimation methods on the results of Hargreaves-Samani ETo equation in Shahrekord plain. In the present study, the effect of 8 radiation estimation models on estimating ETo by Hargreaves-Samani model based on lysimeter measurements was investigated. This study was carried out in the agricultural station of Shahrekord in Charmahal-va-Bakhtiari province in Karoon basin, Iran. The experimental site is characterized with cold semi humid climate, altitude 2070 m above sea level, mean annual air temperature equals to 12.02oC and average annual precipitation of 321.5 mm (Mahdavi et al, 2011). The present study was done by using a volumetric lysimeter planted with alfalfa in the Agricultural Research Center of Charmahal-va-Bakhtiari province in 2011. The date of the beginning and end of the measurement was on 21 April and 22 October 2011, respectively. In the next of the lysimeter, a drainage water measuring hole was constructed. The time of irrigation was based on 50% of maximum allowable depletion (MAD) of soil moisture and this amount was applied based on measuring the soil moisture in depth of 180 centimeters of the lysimeter. Meteorological data used in this study were collected from the weather station of Agricultural Research Center of Shahrekord in 2011. The used meteorological variables were maximum, minimum and average daily air temperature, solar radiation (RS), precipitation, wind speed, soil temperature, dew point temperature, sunshine hours, relative humidity, cloudiness ratio and evaporation from pan. The amount of Rs was calculated from 8 estimation models including Hargreaves-Samani (HS), Doorenbos- Pruitt, Annandale et al, Allen, Ertekin-Yaldiz, Samani, Goodin et al and Mahmood-Hubbard. Then ETo calculated from HS equation based on the Rs resulted from the radiation models was compared with ETo measured by lysimeter. For evaluating model accuracy, some indices include mean bias error (MBE), root mean square error (RMSE), relative error (RE), coefficient of determination (R2), index of agreement (d) and model efficiency (ME) were used.The results showed that the Hargreaves-Samani equation had underestimation based on more Rs models. With respect to differences related to lysimeter data, the Goodin et al and Ertekin-Yaldiz models had the poorest results. Also ETo calculated from Mahmood-Hubbard and Annandale et al models had the best results with 8% and 10% underestimation, respectively. With respect to all the evaluation criteria, it can be concluded that the Mahmood-Hubbard is the best solar radiation model with respect to effecting on calculating ETo in the climate of the present study and the Annandale et al model is in the next order. Also the Goodin et al and Samani are the poorest models in the solar radiation estimation.The Mahmood-Hubbard model generally has more physically base and obtained under various conditions and 9 years data. For this reason, probably the model had the best results in calculating ETo. Also the Annandale et al model takes into account the effect of elevation and reduced thickness of the atmosphere on the primary Hargreaves-Samani model and because the area of study (Shahrekord plain) is a region of high elevation, therefore the Annandale et al model has been a proper model in second order in estimating ETo. The poor result of the Goodin et al model was probably because of obtaining the coefficients of this model under limited conditions.

Weirs are used in different ways to control water levels and flow measurement. One of the most effective and economical way to increase the effective length of weir is using labyrinth spillways. The direction of flow of the labyrinth spillways is not perpendicular to the edge of the weir and it is oblique. On the upstream and downstream of the weir, the flow direction of the symmetry axis of labyrinth weirs is parallel. This phenomenon is more common in the downstream overflow because of flow stacking and, thus efficiency of weir is reduced (Hay the Taylor, 1970). Since, study about the using of upstream guide vanes in the direct channel has not been yet published, in this paper, flow guide vanes were used in the upstream of the triangular labyrinth spillway with vertex angles of 45o or 90o. The main purpose is guiding flow on weir wall perpendicularly and study of discharge coefficient.The experiments were conducted in a canal with a length of 7 m, width of 0.32 m and height of 0.36m. The two triangular labyrinth spillways with vertex angle of 45o and 90o were used. The models were made of galvanized sheet with 1 mm thickness and smooth overflow threshold edge. According to previous researchers (w/P³2.5, in this case P is weir height and w is canal width), the height of the weir was considered equal to 12 cm. A direct spillway with the same width was used to calculate the equivalent discharge. Guide vanes were made from galvanized steel plates. The height of guide vanes was 12 cm and their widths were 2, 3, 4 and 5 cm. The width of guide vanes was a coefficient of the length of one side spillway. Spillways were installed at a distance of 4.5 meters from the beginning of the canal. The reason of choosing this distance is that the flow completely developed from 3.5 to 4.5 meters from the beginning of the canal. Height and velocity of upstream water flow were taken at 5 discharges. The upstream depth of water, above the weir and longitudinal profile of the water surface was measured by a depth meter. Acoustic Doppler Velocimeter was used to measure the flow velocity. The tests were conducted in 3 groups: Group I at vertex angle of 45 or 90o, the width of guide vanes were 2, 3, 4 or 5 cm at a direct distance of 8 cm from the weir with 45o wall angle. Group II at vertex angle of 45 or 90o, wall angle guide vanes with weir of 35, 45, 65 or 90 degrees at direct distance of 8 cm from the weir. Group III at vertex angle of 90o, direct distance of 8, 22 or 33 cm from the center.In this study, Group I on the weir at vertex angle of 90 degrees and direct distance of 8 cm from the upstream weir does not positive effect on overflow efficiency, because efficiency in all tests were less than simple triangular labyrinth spillway with vertex angle of 90 degrees. The comparison shows that the highest efficiency occurred on weir with vertex angle of 45 degrees with guide vane width of 2 cm and on weir with vertex angle of 90 degrees without guide vane. In group II at the weir with vertex angle of 90 degrees, existence of guide vanes at direct distance of 8 cm from the weir with all angles of 35, 45, 65 and 90 degrees is reduced efficiency of flow. It is determined by comparing the curve of models, the maximum of efficiency occurred with vertex angle of 45 degrees and wall angle of 35 degrees, and on weir with vertex angle of 90 degrees and wall angle of 35 degrees. In group III, efficiency in all tests were less than simple triangular labyrinth spillway with vertex angle of 90 degrees and adistance of 8, 22 and 33 cm. In triangular labyrinth spillway with small vertex angle, using guide vanes could affect on vertical velocity component and this component could be increased. So at the same time, the flow is passed more quickly from weir crest, discharge is increased then for the same height water, the discharge coefficient increased. It was found that the triangular labyrinth weir with less vertex angle had very disturbance flow with increasing of discharge. These vanes could be guided flow perpendicularly on wall weir and then efficiency was improved.

Subsurface and surface drip irrigation systems have been preferred by most experts, due to their numerous advantages over other irrigation methods. High frequency irrigation systems are difficult to plan and have complex design procedures to achieve sustainable irrigation conditions. At the same time, these production systems are becoming harder, in an effort to maximize the return on valuable and scarce resources such as water and nitrate. Advanced fertigation systems combine drip irrigation and fertilizer application to deliver water and nutrients directly to the roots, with the aim of synchronizing the applications with crop requirement, and keeping up the required concentration and distribution of fertilizer and water in the soil. Hence a clear comprehension of water movement in the soil is important for the design, operation and management of irrigation and fertigation under the surface and subsurface drip irrigation systems. At the same time, it is necessary to assess the performance of these irrigation systems, because considerable leaching can occur near drip lines, even under deficit irrigation conditions. The loss of nutrients, particularly nitrate, from drip irrigation systems can be costly and pose a serious threat for receiving water bodies. The installation depth of laterals in Subsurface Drip Irrigation (SDI) systems is one of the most important design parameters that if disregarded, deep percolation and nitrate losses could be considerable and lead to low system performance and adverse environmental consequences. In this research, in order to achieve the optimal management of these systems, the distribution patterns of moisture and nitrate were analyzed simultaneously. The main objectives were (1) to determine the optimal installation depths of drippers according to distribution uniformity of moisture and nitrate, and (2) to minimize the deep losses in subsurface and surface drip irrigation system.All the equipment was installed in a drip irrigation system in accordance with the actual situation of a farm in the central laboratory of university of Tehran. Water was pumped through the polyethylene pipes (diameters of main, sub main, lateral pipe were 50, 20 16 mm, respectively) and transferred from a tank to emitters. The system consisted of the float (to maintain the water level in the tank) and valves (to direct the flow), filters (to avoid emitter clogging and improve distribution uniformity), a pressure gauge (to keep the pressure constant through all the experiments) and an on-off control valve (to control water flow in container). All experiments were carried out at the constant pressure of 2 bars. In order to regulate discharge rate, a bypass system was also designed to reduce the working pressure of the system. The experiments were carried out in a transparent plexy-glass tank (0.5m´1.22m´3m) for three different soil textures (fine, medium and heavy) with the irrigation intervals of 6hr. The drippers were installed at four different soil depths (0, 15, 30 and 45cm) and were operated with two different outflow rates (2.4 and 4 lit/s). Urea fertilizer was utilized and injected into the final third of irrigation intervals. Nitrate and moisture distribution patterns were monitored in different directions (horizontal, downward and upward) under the surface and subsurface drip irrigations.Considering the distribution uniformity of moisture and nitrate and with the goal of minimizing the deep losses, the optimal installation depths of drippers were determined 30cm for clay soil texture, loamy and sandy. Moreover, in surface drip irrigation systems, the distribution pattern of nitrate extended to the depth of 20, 40 and 40cm, respectively, and did not go beyond the effective soil depth. Considering more gradual distribution of nitrate in clay soil texture (compared to the coarser textures), the injection time was considered longer for these soil samples. But, it is recommended to set the injection time as short as possible in course soil textures to lower nitrate losses. Finally, by considering the losses of water and nitrate in both surface and subsurface drip irrigation systems, the main design variable (Q: discharge rate of emitters (lit/hr), V: volume of applied water (lit), and F: nitrate concentration in fertigation (mg/lit)) were optimized for different treatments. The results showed that considering the optimized design variables could result in minimal moisture and nitrate distribution losses under the surface and subsurface drip irrigation systems. This could be used as a general guideline for all drip irrigation systems.

Flood protection must be taken into account in almost all development projects. Owing to the fact that hazards associated with flooding (such as disruption of services, health impacts, famine and disease), the new approaches in flood risk management are needed. Therefore, it is essential that the selection of flood management option by cost-benefit viewpoint to be shifted to the selection of flood management option by considering the economic, technical, social, and environmental aspects. Due to the complexity of these challenges, water resources planners require a holistic, adaptive, incremental, and sustainable decision-making process, where multiple non-commensurate, competing, and often conflicting objectives (criteria) must be addressed and reconciled. During the past several decades, multi criteria decision making (MCDM), by its philosophical underpinning and the theory, methodology, and practice that have been developed on the basis of its holistic philosophy, has served as a harmonizing agent in technology, society, and policy. Thus, formidability of this method in addressing the flood management alternatives challenges is undeniable fact. In this paper, there are seven flood management measures in Gorganrood Watershed flood management project, including: conservation of natural condition, Golestan Reservoir management, levee construction, diversions-canal construction, flood forecasting and warning system and flood insurance. Prioritization of the alternatives is in demand of evaluation criteria. Each alternative would be prioritized based upon proposed MCDMs to investigate the most conclusive alternative. The flood management project is ranked based on eleven criteria, including: expected average number of casualties, recovery rate, gradual rate, expected annual damage, safety feeling, employment rate, public participation, landscape protection, wildlife habitat conservation, water quality conservation and technical feasibility and performance. These criteria have been classified into four main groups as social, economic, environmental and technical features. Compromise Programming model (CP) is employed to rank these seven alternatives which are compared with simple additive weighted model (SAW). SAW is known to be common method, which is accepted in many researches due to its simplicity. In this method, alternatives are assessed with respect to each criterion, whilst CP defines the best solution as the one in the set of efficient solutions whose point is at the least distance from an ideal point and the aim is to obtain a solution that is as close as possible to some ideal alternative. The results show that by increasing the value of P parameter, the CP model emphasizes on the importance of recovery rate, expected average number of casualties and safety feeling, which categorized in economic, social and technical feasibility, respectively. This result is obtained by assessing the changes in criteria weights while the P parameter increase from P=1 to P=¥. In the proposed model, integration of a flood warning system and flood insurance was chosen as the most conclusive alternative for flood hazard mitigation. This alternative is a combination of a pre and post disaster action. In contrast, SAW model is unable to highlight or discriminate between the criteria. One of the criticisms over MCDM states that different techniques may yield different results when applied to the same problem. An analyst looks for a solution that is closest to the ideal, in which alternatives are evaluated according to all established criteria. Therefore, it is necessary to compare the MCDMs plus assessment of subjectivity with sensitivity analysis of input data. In this study, sensitivity analysis was performed to examine the response of alternatives when the criteria weights changed to its minimum and maximum values. The results show that the CP model has less sensitivity to changes in criteria weights. Due to considering the ideal solution distance, CP model has more sensitivity to economic and technical criteria in comparison with environmental and social criteria. Although SAW model has less sensitivity to changes in criteria weights, it makes no priority between criteria even in sensitivity analysis. It is observed that the change of the MCDM methods produces differences in the final ranking of the alternatives. The discrepancy that appears between the rankings obtained by different MCDM methods, highly depended on the difference in their mathematical modeling while solving a decision problem. Thus, the main focus must lie on the selection of the most appropriate MCDM method to be adopted, not to mention that proper structuring of the decision problem, considering the relevant criteria and decision alternatives are imperative facts on this issue.

Direct outlets from rivers are the most common structures to supply water for agriculture, industry and drinking water uses. Among the various methods of river intake, construction of a diversion dam and lateral intake is the most common way to supply water for irrigation network. This method is based on diverting a part of the river flow using a diversion dam. Since the river flows often contain sediment load, sedimentation usually occurs near the intake structure. Consequently, during the time it causes blocking the intake inlet and decreasing capacity of intake canal. Many researches have been done about the optimal design for connection between a main canal and the intake inlet and also different methods have been suggested to control sedimentation. Often they have not considered the diversion dam in the vicinity of intake inlet. However, the comprehending of flow and sedimentation patterns requires the attention to all components of a flow diversion system. Nowadays, with progression of numerical models, the application of numerical simulation of flow pattern in such structures is provided. Among numerous released software for numerical simulation, the Fluent is a powerful software for analysis and simulation of fluid flow which widely used by researchers. In the Fluent the users can define new physical properties and boundary condition with especial functions. This software uses a finite-volume method for solving the Reynolds averaged Navier- Stokes equations.In this research, three-dimensional simulation of flow pattern in the lateral intake, with taking into account diversion dam structure, dividing wall, sluice way and entrance sill height was done by using the Fluent. The results of numerical model are validated with experimental tests which had been carried out in the Irrigation and Reclamation laboratory of Tehran University. Then different characteristics of the flow separation zone, flow patterns, vortex, and secondary flows were compared. The experimental tests consist of a Plexiglas flume with a lateral canal, main canal, diversion dam structure, dividing wall, and sluice way. The main canal consists of a rectangular cross-section with a width of 0.90 m, height 0.60m and 18m in length. The lateral intake with 0.4 m in length and width was installed at 120o (at the left side) to the main canal. The longitudinal slope of the flume was set to 0.0008. The diversion canal and sluice way were perpendicular to flow alignment of the main canal. The width and height of diversion dam are 0.6 and 0.27 m, respectively. The lateral intake was separated of diversion dam with the sluice way. It is 0.29 m in length and 0.1 m width. In the first, the canal invert was covered with sediment, and then flow characteristics were measured at different levels and the diversion ratios of 0.5 and 0.65. In this study, the magnitude of flow velocity (z velocity) near the intake and sluice way is used for verification of numerical simulation. The 3D geometries and meshes of intake system were generated by using the Meshing Tool of Gambit software. Computational domain was built with 218000 grid nodes. In this study, the governing equations are discretized by first order upwind method and the pressure is decomposed from the velocity by SIMPLE algorithm. The standard k-ε turbulent model is used to describe the flow separation. The Volume of Fluid (VOF) method is used to track the fluid interfaces. The considered boundary and initial conditions included: (1) inlet velocity condition and a water depth of 23 centimeters is assumed at the main canal inlet, (2) the outflow condition is used at the intake outlet, and (3) it is assumed that the sluice way is closed.The results of numerical model showed that the flow pattern in the vicinity of the intake canal has been simulated good. Comparison of small amounts of z velocity between experimental and numerical models, particularly in diversion ratio equal to 0.5, indicated suitable model reliability for simulation in the lateral intake. The result showed that the average error rate of the numerical model at three different levels was about 13%. After model verification, impacts of shape of the entrance intake on the flow pattern formed at the intake inlet have been studied. The results of the numerical model for angled upstream wall inlet, revealed that the low-velocity zone was removed from this region, as the width of the eddy zone has been reduced from about %8 to near zero.

With the popularity of complex hydrologic models, the time taken to run these models is increasing substantially. Also, in order to apply a precise runoff modeling in a watershed, the efficient parameter calibration is of importance while reviewing and producing runoff data. Comparing and evaluating the efficiency of different optimization algorithms for calibrating these hydrologic models is now becoming a nontrivial issue. In the present research, particle swarm optimization (PSO) algorithm is utilized for parameter calibration of the Soil and Water Assessment Tool (SWAT) Version 2009, in Sanjabi watershed. SWAT is a semi distribution hydrological model. This model is a river basin scale model developed to quantify the impact of land management practices in large and complex watersheds. In fact, SWAT model is capable to predict the impact of land management practice on water, sediment and agricultural chemical yields in large complex watersheds with varying soils, land use and management conditions over long periods of time. SWAT is widely used in assessing soil erosion prevention and control, non-point source pollution control and regional management in watersheds. Sanjabi watershed is located in Kermanshah province in west of Iran. For this purpose, SWAT model was run by applying required information layers such as land use, Dem layers and rain and temperature data in Sanjabi basin in the period of 1995-2004. The hydrological model's performance entirely depends on the optimality of the calibration of the model's parameters which their real values are not available. To calibrate SWAT parameters, SWAT-CUP (SWAT Calibration and Uncertainty Procedures) program is used herein. The SWAT-CUP package is a program designed to integrate the various calibration/uncertainty analysis programs for SWAT using the same interface. This program links SUFI2, PSO, GLUE, ParaSol, and MCMC procedures to SWAT. Since the number of SWAT parameters is relatively large, the procedure of sensitivity analysis has been done firstly and thereafter most of sensitive parameters have been calibrated. Sensitivity analysis was performed herein for 22 more important flow parameters (in 1995-2004 period) by connecting the output of SWAT model to the PSO algorithm in SWAT-CUP package. The sensitivity of flow parameters was determined in PSO procedure by P-Value and t-State. The most sensitive parameters were, ranked by importance degree, are as follows: SOL_BD (Soil bulk density), GW_Dealy (Delay time for aquifer recharge), ESCO (Soil evaporation compensation coefficient), SOL_AWC (Available soil water capacity), CN2 (Moisture condition II curve number), RCHRG_DP (Deep aquifer percolation fraction), ALPHA_BNK (Base flow alpha factor for bank storage) and CH_K2 (Effective hydraulic conductivity in main channel alluvium). As a result of sensitivity analysis, the most eight sensitive parameters were selected for optimization purposes. So, the best value of these most sensitive parameters has been calibrated utilizing the PSO algorithm in SWAT-CUP.4000 simulations of PSO have been performed (4 iterations with 1000 simulations) to obtain the best value of these SWAT parameters. The objective function considered in this research was Nash-Sutcliffe (NS) simulation efficiency. After calibrating the SWAT model in a specified period, the optimum values of calibrated parameters have been fixed in the model and the model was validated for a period extending from 2005 to 2007.In order to assess SWAT simulation performance, in addition to NS, two more criteria, including R2 (coefficient of determination) and RMSE (root mean square error) have been used. The value of Nash-Sutcliffe objective function (NS) for calibration and validation period was obtained 0.58 and 0.60, respectively. The evaluation results of the model show that the values of R2 and RMSE for calibration period are 0.65 and 6.74 m3/s, respectively, and for validation period are 0.67 and 3.66 m3/s, respectively. If the obtained NS value of SWAT simulations was equal or higher than 0.75, the model considered to be accurate in predicting flood flows, the results of the model is satisfactory when NS value is between 0.36 and 0.75 and the results of the model is not satisfactory when NS value obtained less than 0.36. So the obtained results of SWAT simulation herein showed the desired accuracy of SWAT for runoff simulation was calibrated by PSO. Results show the high accuracy of SWAT model for runoff simulation in Sanjabi watershed. Therefore, SWAT model can be used to predict future surface runoff in Sanjabi watershed and other watersheds in Iran (after calibrating model for watersheds). Having knowledge of the results of the SWAT model in each watershed can play an effective role in water resource planning for local and regional planners.

In general, the Density current is motion of a fluid with a density into relatively stationary fluid with different density. The difference in density may be caused by the suspended materials, dissolved materials, temperature, or a combination of them. In fact, since these currents occur because difference in specific weight or the effects of gravity on density, these may called gravity current too. When the density of entry fluid is more than the density of stationary fluid, then the dense fluid will move beneath the stationary fluid and called underflow density current. In this paper, the effect of cylindrical obstacles on the controlling of density current is experimentally studied.Laboratory equipment consists of two main parts: the flume and mixing system. Experiments were performed in a flume with the length of 7.8 m, 0.34m in width and 0.7m in height and the bed slope was variable. The flume was divided into two parts by a sluice gate. The water level in the flume was fixed by a 66 cm spillway installed at the end of the flume. The flume was filled with clear water before starting the experiments. The level of dense fluid and clear water in both sides of the gate are balanced, the gate was opened 5cm suddenly. The total number of 27 experiments with the bed slope of 0.5, 1.25 and 2 percent and with concentrations of 10, 15 and 20 g/L were performed. Discharge of entry dense fluid was controlled almost 1L/s by using an electromagnetic flow meter during the experiments. Cylindrical obstacles were installed on 4 meter of the flume- 1.5m from the sluice gate to 5.5m from the sluice gate. The obstacles were made from P.V.C material with a diameter equal to 1 cm and the height was 30 cm. The arrangement of the obstacles was staggering. The obstacle height was more than the density current head in all experiments. At first, nine experiments, the distance between two obstacles within a row (perpendicular to current direction) and the distance between two consecutive rows of obstacles were 8 and 8 cm, respectively. In second nine experiments, these distances were 4 and 8 cm, respectively. At last nine experiments, these distances were 4 and 4 cm, respectively. Inside the obstacles, four sections named 1, 2, 3 and 4 at spacing of 0.75, 1.5, 2.25 and 3 meters from the first row of obstacle are selected to measure the hydraulic parameters. The distribution of concentration in the head of density current was measured directly by using four siphons in sections 1, 2, 3 and 4. Also, the velocity of the head was measured in mentioned sections. Wake space and vortex caused around obstacles can effect on hydraulic of density currents. Impact rate and the flow lines encounter will increase at the space between two obstacles and lead to increase friction and resistive force and also increasing mixing rate. The best longitudinal distance to attach next obstacles is wake space length. In fact, by attaching of the next obstacle at end of wake space the possibility of parallel and uniform flow lines is reduced very much and flow lines is encounter together during the experiment. Impact and encounter of flow lines are important to increase the rate of mixing. In this research, for increasing the obstacle effect, they are attached to the bed as stagger form.The results showed the head velocity and height decreases in the beds with obstacles in comparison with the bed without obstacles. When the number of obstacles are increased, the reduction rate of head height and velocity goes up. The discharge of the head is reduced along the flume in the beds with obstacles. This reduction rate is more intensified as the number of obstacles increases. Mixing rate of head increase in the beds with obstacles in comparison with the bed without obstacles. Reduction of height and velocity in the bed with arrangement 4´4 of obstacles is more than bed with arrangement 4´8. So in the bed with arrangement 4´8 of obstacles is more than a bed with arrangement 8´8. Reduction of discharge of head in bed with arrangement 4´4 of obstacles is more than them. Reduction rate of height, velocity, discharge and mixing at all arrangements decrease by increasing slope of bed and density.

Scour happening around bridge piers is one of the major reasons to bridge destruction. At present, there are various methods to prevent bridge bases scouring. One method is to set protector boards (collars) around bridge piers. The collar is like that a thin plane surface that surrounding the pier. Many experimental studies were done to illustrate the hydraulic function of collar to protect pier against scour, and also many researchers have examined numerical approachs and developed many packages such as SSIIM, FLUENT, FLOW3D, etc. Collars protect the bed against the vortex system around the bases and it reduces the amount of water scouring. In this study, Lozenge, Square and Circle collars with slight thickness have been used to reduce scouring around bridge bases. In the conducted tests, the diameters of the used collars have been considered twice the base diameter. Various discharges have been considered for these tests and median size of bed grain is considered equal to 1.8 millimeters uniformly (d50=1.8 mm). In order to examine the effect of collar to control scour around the bridge pier in a direct channel, a laboratory model is constructed. The experiments were done in Soil Conservation and Watershed Management Research Institute. They were performed in a flume made of glasses for wall and floor partition with a length of 6 meters, almost 30 cm width and 30 cm height. There was a valve for flow depth control at the end of the flume. In all experiments, to eliminate the effect of flume walls on local scour; pier diameter must not be longer than 10% of flume width according to Chiew and Melville (1987). Considering Raudkivi and Ettema (1983), the standard canal width shall be 6.25 times of pier diameter minimally so the effect of channel wall on pier of local scouring has been eliminated. Therefore, the pier with the width of 21, 30 and 40 mm is used in this study. The collars diameter was fixed twice the pier diameter. The depth of water was constant and equal to three and half times of pier diameters. The time of every test were chosen about one hundred minuets since about 85% of final scouring after 5 hours was occurred in 100 minutes. The experiments have achieved with clear water and discharge was measured by triangular weir adjusted at the end of the flume. The critical velocity of bed material was calculated by Shields diagram. The profile indicator device was used to determine of the bed surface and scour hole dimensions, and then plotted these data by Surfer 11 package.In general, in the experiments equipped with a collar, it was observed that scouring started due to vortexes activities at the back of the pier. Rising vortexes make grooves beside the base margins so scouring continues by horseshoe vortexes through the development and extension of these groves to pier front and then it penetrates to base underneath and this process digs a scour hole in pier front.Results showed that the pattern of scouring have directly related to collar’s shape in each pier. Through the use of circle and square collars, the scouring location happened in near the piers, on the other hand, when the lozenge collar was used, scouring happened in a certain place in each pier. By using various collar shapes, the dimensions of the formed hole and hill were different.The results of using 3 different diameters cylindrical piers and 3 different collar shapes, showed that the scour dimensions directly related to the pier diameter. In such a way that the amount of scouring increases by increasing the pier diameter. In other words, holes and hills are made in a larger region. The results also showed that scour pattern was directly associated with the collar shape. So that the use of circle and square collars lead to occur the scouring location near the pier, however, when the lozenge collar was used the scour hole was formed in a farther distance from the pier. The ratio of the distance of the maximum scouring to the depth of the scour in the lozenge collar, is approximately 52% more than the circle and the square collars. The height of the maximum sedimentation by using the lozenge collar, is 58% less than the circular and square collars.

One of the common methods to dissipate energy of the flow passing over a dam is using flip bucket spillways to create free falling jet to the downstream. However, the collision of the falling jet to the downstream bed will cause topography changes due to scour threatening the stability and safety of the hydraulic structures. In case of precise analysis of the downstream topographic conditions due to the falling jet, such structures perform better than other dissipaters. Experimental results show that the dimensions of scour hole are dependent upon upstream water depth, discharge and tail water depth. Due to water and sediment flow complexities and the effect of different geometric-hydraulic parameters on bed profile variations, more studies are needed.In the present study, the effect of flip bucket tooth and upstream gate opening on downstream bed topographic changes due to falling jet was investigated using a flat flume having dimensions of 2m*0.5m*0.5m. The free falling jet was controlled using a sluice gate located upstream of the flume. Falling jet hit a downstream sedimentation basin having dimensions of 2 m long, 1.5 m wide and 0.7 m deep. Tail water depth was controlled using a gate located at the end of the sedimentation basin. Spillway and flip bucket of the Karoon III dam were modeled considering a 1.165 scale. Experiments were carried out on a normal (simple) and slotted flip buckets. Slot dimensions were selected as 2 cm according to USBR (1987) recommendations. To control the water surface level at upstream of the spillway for different discharges, a sluice gate was used at the spillway inlet. To investigate bed topographic changes, sedimentation basin was filled with non-uniform silica sediments with a mean particle diameter of d50=2.76 mm, the geometric standard deviation of s=2.11 mm, uniformity coefficient of Cu=4.07 and a specific gravity of gs=1.52 gr/cm3 according to grading curve up to a depth of 40 centimeters. Researches show that several geometric-hydraulic parameters influence bed topography changes at downstream of the flip buckets. Most important parameters include input flow velocity to the flume (V), tail water depth (Ut), flow density (r_w), kinematic viscosity (m), acceleration of gravity (g), specific or mean diameter of bed particles (d50), bed particles density (r_s), falling jet height from the bucket edge to sediment level (Hw), gate opening height (L), bucket tooth height (h), Manning coefficient of shoot surface (n), flip bucket radius (R), time (t), sedimentation basin width (B) and geometric standard deviation of non-uniform materials (s). Using dimensional analysis and combining dimensionless parameters, the dimensionless densimetric Froude parameter (Frd) is achieved.In this study, after depiction of the longitudinal profile changes of the hole and mound scour due to falling jet, variations of the obtained dimensionless parameters were first investigated. Then, using statistical analysis, experimental relations to estimate the scour hole depth and downstream sediment mound height were presented. For this purpose, the effect of a tooth located at the end of a flip bucket on downstream bed topography changes was experimentally investigated considering different discharges, spillway gate opening percentages and tail water depths. After leveling bed sediment surface at the beginning of each experiment, discharge was adjusted using the electromagnetic flow meter and water depth was controlled using a spillway sluice gate. Besides, tail water depth was stabilized using a gate available at the end of the sedimentation basin and the falling jet was finally released to the basin. In order to determine experiment’s equilibrium time, several primary experiments were carried out considering different discharges in different time periods. By drawing equilibrium time curves, 360 min time duration equal to formation time of 88% of the total scour hole depth was considered as experimental time duration. Therefore, a total of 54 experiments were carried out considering the studied variables in this study. Water jet was released from 57 centimeters height of the bucket end level to the non-uniform bed sediments during 360 minutes experiments. Bed topography changes were measured at the end of each experiment using a dot sounder with 0.01 mm precision and depicted using Surfer V.9.0. By calculating the changes of bed sediment volume, the influence of the slot on reduction of the scoured sediment volume can be evaluated in comparison to the normal condition. It was found that scour hole dimensions enlarge with discharge, but increase in tail water depth shows a descending procedure. In addition, in the case of slotted flip bucket in comparison to the normal one, by increasing gate opening by 33%, the hole volume increased by 125.64 %, and increasing gate opening by 66% and 99%, the hole volume decreased by 45.92 % and 22.85 %, respectively.

Surge irrigation is one of the most advanced methods of surface irrigation that has developed in recent decades. Surge irrigation, introduced by Stringham and Keller (1979), is defined as the intermittent application of water to furrow, rills or borders in a series of relatively short on- and off-time periods of constant or variable time spans. The main advantages of this method compared to irrigation with continuous flow (ordinary) are increasing water use efficiency and uniformity of water distribution. On the other hand, fertigation is the effective method for application of fertilizer and reduce nitrate losses. Fertilizers are widely applied to agricultural fields using surface fertigation. However, there are still no adequate guidelines for the proper design and management of surface fertigation. The proper management of surface irrigation fertigation is important because of the low uniformity of distribution of water in surface irrigation. The efficient application and distribution of water by furrow irrigation is highly dependent on parameters such as inflow rate and inflow hydrograph shape. Determination of fertigation correct indicators in new surface irrigation methods like surge irrigation is imperative. In this research, water and nitrate losses in furrow fertigation with surge and continues flow were evaluated and compared. For this purpose, field experiments were conducted on a soil with clay loam texture at the experimental station of the College of Agriculture and Natural Resources, University of Tehran. Three fertigation treatments with the surge flow included injection fertilizer during all advance cycles, wetting phase and last of the advance cycle plus start of wetting phase tested. Also for continues flow, two treatments included injection fertilizer in the second half of advance phase and wetting phase was applied. Each treatment contained three furrows of which the central furrow was as main furrows and the others as guard furrows. Furrows had 0.75 m distance and 150 m length. The longitudinal slope of furrows varied as it was 0.9% in the first 60m and 0.4% until the end of the furrow. Inflow and outflow were measured by WSC flumes. Six irrigations were performed every seven days, and the third and sixth irrigations were with fertilizers (fertigation experiments). For estimating nitrate losses through surface runoff, water samples were collected from outflow water in five minutes intervals until the end of outflow. After that, water samples from inflow and outflow were analyzed by spectra photometer to estimate the nitrate concentration.Runoff losses of water for first and second fertigation experiments with surge flow amounted to 15.8-21.8% and 13.8-33.4% and for experiments with continuous flow amounted to 9.1- 9.4% and 13.0-15.1%, respectively. Deep percolation losses of water for first and second fertigation experiments with the surge flow were obtained 9.1-14.3% and 14.2-17.0% and for experiments with continuous flow were obtained 33.2-34% and 24.5-25.5%, respectively. Ratio of flow advance rate in first and second surge experiments to continuous was calculated 1.75 and 1.2, respectively. Runoff losses of nitrate for first and second fertigation experiments with the surge flow amounted to 5.1-37.7% and 5.4-47.1% and for experiments with continuous flow amounted to 3.7- 20.2% and 6.0-27.2%, respectively. Deep percolation losses of nitrate were negligible in all experiments. Outflow and inflow nitrate concentration had a time lag of about 15 to 20 minutes. In experiments that fertilizer had injected in wetting phase, this time lag was less than injection in advance phase.Nitrate runoff losses in first fertigation experiments with continuous flow were low compared to surge flow, but there was no significant difference between them in the second fertigation experiments. Decreasing of surge effect and soil consolidation were the main reasons for this result. Conversely, infiltrated nitrate in fertigation experiments with the surge flow was low compared to continuous flow in both experiments. Nitrate runoff losses in experiments that, fertilizer was injected in advance phase was less than that injected in wetting phase. According to average soil depth of field, water and nitrate deep percolation losses were calculated up to 80 cm soil depth for all experiments. Nitrate deep percolation losses were negligible and there was no risk of nitrate leaching in all experiments. Results indicated that the best fertigation management for decrease nitrate runoff losses is injection fertilizer during all advance cycles and second half of advance phase in furrows with surge and continues flow, respectively. As conclusions, nitrate losses were dependent on both the shape of inflow hydrograph and fertigate injection management. It is recommended that the tests conducted on soils with sandy and sandy loam texture.

The water crisis has become a serious issue in Iran in recent years due to the arid and semi-arid nature of the country. The water issued in the production processes is called "Virtual Water", some of it remains in the product. When these products enter the international markets, virtual water trade happens. Virtual water trade is expected to decrease water use in national and international levels due to the efficient and specialized use of water. Nowadays, the concept of virtual water is an important issue in water resource management. In this paper, the volume of virtual water trade was investigated for six main crops of Hamedan province in four groups: cereal (wheat and barley), vegetables (potato and garlic), industrial (sugar beet), and provender (alfalfa) over the period 2001-2010.The components of crop VWC are the type of water resources used in the crop growth process, including blue water (surface water or groundwater) and green water (effective precipitation). Under a rain-fed scenario, green water is equal to the total VWC of the crop. The VWC of primary crops can be calculated according to the methodology developed as follows:(1)where c, i, j are crops number, city and year, respectively indicates average water requirement (m3/ha), Ac, i, j is Area (ha), TAc, j is Total area (ha), VWCc, j is virtual water (m3/ton), and indicates average yield (ton/ha).The water requirement of crops was calculated by Hargereaves-Samani method and daily meteorology data of Hamedan station (equation 2):(2)where Ra is solar radiation (Mj/m2/day), Tmean is the average air temperature (oC), and Td is Tmax-Tmin (oC).The results showed that the virtual water volume of industrial and vegetables group is lower than 1 kg/m3 and not water-intensive crop with high water use efficiency. Meanwhile, cereal groups with virtual water volume greater than 2 m3/kg are water-intensive crops with low water use efficiency. Furthermore, during 2001-2010, the difference between virtual water exports and imports demonstrated that 1538.4 MCM net water is harvested from water resources of Hamedan province.Table 1- The required parameters for calculating VWC, Total net virtual water trade (TNVW), CWP, Water use intensity (WI), Water dependency (WD), Water self-sufficiency (WSS) of six crops during 2001-2010WSS WD WI WA WU CWP TNVW VWI VWE VWC Parameter100 0.0 17.7 3091 546.1 1.2 -65.9 0.0 65.9 0.8 11.2 9066 Alfalfa100 0.0 16.4 3091 507.6 0.4 -132.8 0.0 132.8 2.5 2.7 634 Barley100 0.0 32.5 3091 1004.7 0.2 -1146.2 213.7 1359.9 4.5 1.7 7169 Wheat100 0.0 0.5 3091 14.3 3.5 -4 0.0 4 0.4 15.8 4561 Garlic100 0.0 8.6 3091 266.4 3.6 -167.5 0.0 167.5 0.3 32.1 8889 Potato100 0.0 2.3 3091 72.4 3.6 -21.9 0.0 21.9 0.3 31.1 8741 Sugar beet100 0.0 13.0 3091 401.9 2.1 -256.4 35.6 292 1.5 15.8 7461 MeanAccording to Table 1, the minimum amount of water requirement belongs to garlic crop with 4560.8 m3/ha and maximum amount of requirement water is equal 9066.3 m3/ha in alfalfa crop. The important point in Table 1 is less the amount of virtual water on alfalfa, potato and sugar beet crops with high water demand, in contrast barley and wheat crops with less water requirement.With consideration of irrigation efficiency about 60%, the actual amount of water harvesting from Hamedan water resources is 2564 MCM. The economic value of virtual water calculations showed that Hamedan province is exported an average of 19547 Rials water out of the province during the years 2001- 2010. Therefore, it is necessary to apply suitable policy to prevent large amounts of water exports. By considering the results of this study, it seems that the increasing trend of agriculture crop exports, especially those with high water requirements in the recent years facing with drought event isn’t compatible with water resource contents.Therefore, reducing the area under cultivation and lower exports of agricultural products, lead to storage of water resources in the province. However, a more appropriate solution is increasing of crop yield. Due to the negative balance of water in the aquifers of the province, it could be based on studies of virtual water, and economic valuation of water, with imported products with high virtual water content, and export products with low levels of virtual water, water use efficiency will be increased. Therefore, for optimal use of water, it should be combined policy of export and import of agricultural products, taking into account the economic benefits.

Prediction of scour hole characteristics downstream of structures and water surface regulators is of the most important and most difficult steps in designing the foundation of structures. Considering the hole dimension, the design should be a way to reduce the probability of failure or reversal of the structure. Collision of a water jet to the bed causes an increase of near bed shear stress and leads to the separation of the sediments. At the beginning of this phenomenon, while tail water depth is at minimum level, falling jet penetrated to the vicinity of the alluvial bed then vortices are created. These vortexes penetrate into the pores of the bed particles and cause separation of the particles. By the passage of time and dissipation of flow energy, the local depth of flow will increase and erosion will be reduced. In this case, the sediment particles are carried to downstream as and the suspended load deposit in a relatively short distance from the location of the jet collision. As a result, hill deposit to be formed downstream of the scour hole. The height of this hill is a function of the tail water. Experience has shown that by reducing the tail water depth, the height of the hill would be decreased. The experimental data also show that by changing the nozzle diameter for a constant drop height and tail water depth, the dimensions of the hole will change. Many studies are carried out by researchers to determine characteristics of scour holes formed around hydraulic structures and in most cases, the empirical equations have been presented.The aim of this study was to evaluate the effect of hydraulic parameters of submerging jets, tail water depth and angle of jet, on the dimension of scour hole and sedimentation hill in the submerged pool. The innovation of this study is the use of non-cohesive alluvial materials with uniform particle size in the range of medium gravel. It is worth noting that the diameter of the materials used in the previous researches was in the range of fine sand and fine gravel. The physical model was made in the Hydraulic Models laboratory of Jundi-Shapur University of Technology in order to conduct the tests. This model has the ability to change the angle of the nozzle, to change in the nozzle installation to the upper levels of sediment, and it is capable of changing the amount of tail water depth. For this purpose, a special chariot was made for establishing the nozzle which is capable to shift horizontally, vertically and rotationally. In this research, the nozzle was fixed at angles of 45 and 60 degrees. Nozzle diameter is constant in all stages of the experiments. By installation of this nozzle on top of a metal tank with a length of 2 m, width of 1 m and a height of 1 m, the necessary condition was provided to evaluate the scour depth in the submerged pool. The nozzle edge was installed as submerged for removing the effect of the concentration of the incoming air around the jet. An electromagnetic flow meter device was used to control the rate of flow with an internal diameter of 100 mm and with an accuracy of two percent of full scale (2 % FS) that is made in Megab-Iranmedar company. A Leica Disto-D8laser model was used to record the bed profile. Effective parameters in this study are presented in the equation (1).(1) where is the outflow of the nozzle, is inlet discharge of air to the water jet, is the nozzle diameter, is the outlet jet velocity from nozzle, is the width of the pool, is nozzle angle to the horizontal, is tail water depth, is average diameter of particles, is accelerate of gravity, is viscosity of fluid, is the density of the fluid, is density of sediments and is defining characteristics of the scour hole.In this research, in addition to the variation of the angle of the jet, tail water effect on the scour hole has been also evaluated. The results showed that with increasing depth of tail water, form and deposit style of sedimentation in the scour hole downstream are different. At low depths of tail water, deposit style of sediments is distributed with constant height, approximately. However, with increasing tail water depth, erosion parameter (Ec) reduced and this makes the pattern of turbulence be slow in fluid layers near the bed. The particles which have moved from their places with any form, they are deposited and lose kinetic energy quickly. Experience has shown that in the mentioned condition, the sediments are deposited on the ridge area to form a peak. The results show that by increasing the tail water depth, the erosion parameter value was decreased, and this action reduces the relative scour depth in both of the output angle of the jet. In addition, it is evident that a change in the angle of the jet, a limit of the threshold will be set up on the trend procedure of the relative depth of scour.Results indicated that the trend procedure of all dependent parameters of the scour phenomenon has a direct relationship with erosion parameter (Froude number of jet). By increasing the depth of tail water, formation and shape of sediment deposition will be changed in the downstream of scour hole. In the low tail water depth, method of depositing sediments is distributed by approximately a constant level. By increasing the depth of tail water, the form of sediment deposits will have a peak form. By increasing the depth of tail water, the amount of erosion will be reduced, and consequently, the relative scour depth will be reduced. This is true for all angles of the outlet jet from the nozzle. For erosion parameters larger than 2.82 (Ec>2.82), the value of relative scour depth with an angle of 45 degrees is higher than the value of 60 degrees. For erosion parameter larger than 1.97 (Ec>1.97), the value of relative ridge of sediments under 60 degrees.

At the start of execution of the water pipeline of the Kuhrang River to Morvarid Spring project as one stage pumping, the client was confronted with problems of high time and cost to provide the main components of the project such as high pressure pumps and steel pipe with nominal pressure of 40 bar and also Air Chamber. Therefore, in review of project two alternatives were considered.The Value Engineering was used to compare the time and cost and water hammer rate and the problems of each alternative. In this paper, both of the alternatives have been modeled with pumping station and pipeline at steady and unsteady conditions in Hammer software. Finally the results showed that using Value Engineering can eliminate the air chambers and reduce water hammer risk and also cause reduction about 20 to 30 percent in time and cost of preparing and implementing the various components of the project.

In designing the hydraulic structures with rapid flow, there is the probability of occurrence of cavitation phenomena. To prevent the occurrence of cavitation phenomena, the places where may pressure reduced to vapor pressure of liquid because of increase the flow velocity, should be identified. In this regard, to achieve a quantitative measure, the cavitation index can be used. In this study, two cases have been designed and simulated for Vanyar dam’s spillway using numerical models of computational fluid dynamics (CFD). Then the cavitation index was calculated for each case and finally for the verification, the results of laboratory model are used. For the numerical solution of the 3-dimensional Navier-Stokes equations and 3-dimensional gridding of the spillway, the Fluent and Gambit software are used, respectively. To determine the parameters of the flow field turbulence, the free-surface flow and the separation of momentum equations, the k-e (RNG) turbulence model, the VOF method and the second order upwind method are used, respectively. The results indicated a proper agreement between the Fluent results and experimental model. Also it is found that in none of the considered cases, the cavitation didn’t occur and constructed spillway is safe against this phenomenon.

Seepage flow modeling beneath hydraulic structures on permeable materials is an essential issue that must be considered before construction processes. Because of no detailed studies, followed by inappropriate design some problems such as foundation erosion, seepage and water escape and structure settlement may be occurring. If we couldn’t overcome these problems in designing process, we can utilize a series of auxiliary actions. Some actions for eliminating the piping and reducing the uplift pressure and hydraulic gradient are construction of horizontal apron, cut-off walls and also weep holes. Hence, in this study the effect of the weep hole on uplift pressure and hydraulic gradient has been investigated. For this purpose, the governing equation of flow through porous media has been solved for different setups, by the numerical method of Control Volume. All calculations have been done by the simple and powerful Excel Spreadsheet tools. Results show that, the application of weep hole reduces the uplift pressure and hydraulic gradient. Installation of a weep hole on stilling basin could reduce the cut-off wall depth and this cause a noticeable reduction of project costs. By moving weep hole toward the downstream of stilling basin and getting away from dam toe, its positive impact will be reduced.

In order to have an economic design to reduce uplift pressure in weighted concrete dams, so many methods have been proposed that the most important include: adding horizontal apron, cutoffs in upstream and downstream of the dam and weep hole installation in downstream or proper place between the two cutoffs. These implementations also reduce the exit gradient. The effects of these parameters are the main subject of this study. This study focuses on Yusef Kand Mahabad diversion dam, by study on the dam and its simulation in Seep/W software, effect of number of weep hole on uplift pressure, proper location of weep holes on stilling basin and also the length of the dam cutoffs. Simulation was studied on uplift pressure and exit hydraulic gradient in key points of diversion dam and the overall stability of the dam. In this study, it was observed that creating primary upstream cutoff with 8 m length decreases uplifting force about 63% and decrease exit gradient 79% than the case without cutoff. Creating a weep hole in the stilling basin decreases uplifting force 8% and decrease exit gradient 74% than the case without weep hole. Results demonstrate that suitable location of weep holes can reduce uplift pressure and so the diversion dam design can be safe and economical.