فصلنامه علوم و مهندسی آبیاری
سال سی و هفتم شماره 4 (زمستان 1393)

Among surface irrigation methods, furrow irrigation is most common and adaptable method. Longitudinal slope in furrow irrigation is generally uniform and constant along the furrow. In order to access more application efficiency and more uniformity of water distribution and control runoff and deep percolation in furrow irrigation, several techniques such as surge irrigation and cut-back irrigation is used that all is need applying special equipment during operation. This study was conducted to investigate the effects changing of longitudinal slope furrow from linear to planar (concave or convex) on the parameters of the furrow irrigation. In this way an experiment with completely randomized design with three replications was taken place in the experimental field of Shahrekord University during the summer 2010. The treatments were furrows with uniform, concave and convex longitudinal slope. Indexes such as time advance, time recession and outflow was measured. Coefficients of infiltration equation were calculated by two-point method of Elliott – Walker. The indexes such as application efficiency and uniformity of water distribution in all treatments were calculated and compared statistically by SAS software. The results of this study shows application efficiency and uniformity of water distribution in the concave slope treatment was 73 and 92 percent, respectively. Corresponding values of control treatment (70 and 90 percent) were significantly different and so on that of convex slope treatment with quantity of 63 and 86 percent, respectively. Therefore it can be concluded that in furrow irrigation the assessment indexes and productivity are improved by applying the longitudinal concave slope.

The estimated evapotranspiration of landscape with crop coefficient values should be set up relating with shadow, density modification and regulation of certain plant species which are estimated. Nowadays, according to three coefficients surplus are compared by evapotranspiration landscape plants, it is the problem to accurate calculation crop evapotranspiration of these parameters which are so high, and need high accuracy and will be demanded the using of proper methods. However one of the newest methods of estimating evapotranspiration is using large-scale satellite images which is in this research we would tried to use the satellite images by Sebal models and synoptic stations Mashhad in evapotranspiration rate of landscape (Mashhad Mellat Park). This parameter is with Kimberly Penman (1972), FAO Penman Mantis 56, radiation (FAO 24), Blani Criddle modified, Hargrive Samani, Prystly Taylor, Makking (1957), Turc, and the 24th FAO Penman 1948 Penman method compared with Sebal methods. The values of landscape coefficient obtained in this research have a close relationship with vegetation index and increased together the value of evapotranspiration calculated by Sebal method in warm months is more than calculated in other methods. This research is showed that by using coefficient obtained in Sebal model have showed the better results than Limp model. The Results show that differences between the values of reference evapotranspiration calculated by above methods with Lysimeter data of Ferdowsi University in May. Therefore the results given by the linear regression equation of Laysymetr were closed. Landscape coefficient obtained in this study, is closed relationship with vegetation index and increasing together. Sebal evapotranspiration values method is gram per month type and more than the values calculated by other relationships. This study showed that the using of this model coefficient obtained is better results in Sebal coefficient and better than limp model. These results show that Hargrive, Samani, Blani Criddle and Tork models are less accuracy and against them Prystly and Taylor, radiation and FAO 56 Penman Mantis and FAO are better than other methods and are close to Sebal model data. Therefore, to calculate the evapotranspiration Mashhad landscape or regions with similar climates could be used three methods to set Prystly Taylor, radiation and FAO 56, Penman Mantis models accompany with landscape coefficients which presented in this study.

In the conventional methods of flood frequency analysis, the flood peak variable is just considered and assumed that this variable follows some specific parametric distribution function. This assumption would restrict us and lead us to the limited available information to evaluate the flood risk. It is well known that a flood event has three variables of flood peak, volume and duration which are random in nature and are mutually dependent. In this research, the concept of the Copula function is briefly introduced and then used to modeling the dependency structure of the flood variables of the Karun River at the Ahvaz hydrometric stationand then estimate their joint probability distribution. We use three well-known and appropriate copulas, including Ali–Mikhail–Haq, Cook–Johnson and Gumbel–Hougaard which belong to the Archimedean class of copulas, to modeling the joint probability distribution of the flood variables, where the marginal distributions of the flood’s variables are selected from the parametric and non-parametric distributions. The Gumbel–Hougaard family led to better modeling of different combination of flood’s variables based on goodness of fit criteria. The selected copula is used to estimate conditional cumulative distribution function and joint return periods which lead to better estimation of flood risk.

In present study, the near-wake flow around the bridge piers of a circular section has been numerically analyzed. Numerical simulation was carried out using Fluent, and the numerical results were verified by the different researcher's experimental and numerical data. In order to consider the accuracy of numerical results, the flow pattern around the pier, the Strouhal number and the drag coefficient, obtained with Fluent, have been compared with available numerical and experimental data. Also, three turbulent models, k-ε , RSM, and LES, were used to apply the flow turbulence effects and the hydrodynamic parameters, the near-wake flow, the flow separation angle, shedding of the vortices at downstream of the cylindrical piers, and the distribution of the bed shear stress around the pier, have been investigated for three turbulent models. The numerical results show that RSM turbulent model is an accurate model for simulating and modeling the turbulence effects of these kinds of the flows.

Any change in the pipe discharge, caused by valve closure or shutting off the pump, results in fluctuations in velocity and pressure of the flow; which develops transient flow in the water conveyance system. This flow causes various risks by creating rapid and short waves. A model composed of a reservoir, a polyethylene pipe and check valve was made to examine hydraulic transient flow in branched pipe lines. The model was made in the laboratory of hydraulic and physical models of water science faculty in Shahid Chamran university. The experiment were done on different length and diameter ration of branch to mainline in a constant discharge of 4 lit/s. the data acquired of installed pressure transducers in different points of the model were used to demonstrate how pressure wave transformed and became transient and the results are presented in the following diagrams. As maximum and minimum pressures downstream the branches decrease significantly in compare with the system without branching, some equations were proposed for estimating the maximum and minimum pressures downstream the branches.

The currently most widely used erosion models are poorly based on physical principles and lack the ability to describe erosion of the consolidated sediment bed at increased shear stresses e.g. during a storm. There is a need for a new modeling approach that is both fast and accurate. A new erosion formulation is proposed that regards the bed shear stress as a stochastic variable and allows erosion only when the actual bed shear stress exceeds the actual yield strength at the interface. There is a formulation that relates the actual yield strength to the density and the cohesion. In the formula, is assumed that the potential erosion flux is the same as entrainment flux of fluid mud under turbulent flow. The formulation needs eight physical input parameters. The five shear strength parameters can be determined from standard consolidation experiments in a settling column as well as soil mechanical tests. The other two physical parameters have to be determined by means of relation concerning to erosion on fluid mud and shear parameter. For the last parameter, namely coefficient of the probability distribution of the bed shear stress, No standardized laboratory tests are yet available and should be estimated during calibration process. The formula has been validated on short term erosion experiments performed in a straight flume on the bed sediments of the junction of Sefidrud dam reservoir and Ghezel Ozan river. These erosion experiments have been performed on the same beds that were measured in the consolidation experiments used to validate the parameterization. In the straight flume seven experiments have been performed. The model can simulate the results from the flume experiment well. The simulations show the same characteristic exponential decay evolution of the eroded material height. Moreover, the model can be calibrated well in a qualitative sense.

In recent decades spur dike has been one of the methods for bank protection and sediment deposition in rivers. In fact the spur dikes decrease the erosion and sediment potential rate of flow between them by improving the flow hydraulic conditions and controlling the shear velocities. Spur dike construction creates new conditions in river, which causes scour around the spur dike. Having knowledge about the amount of scour and sedimentation patterns around the spurs, helps for better and improved design of dikes. Therefore in this study the scour and sedimentation patterns around a Series of permeable and impermeable spur dikes is investigated. The experiments were carried out under the conditions of clear water and the percent of permeability of 0%(closed)to 50% in a flume with 0.56m-wide,7.3m- long and 0.6m-depth. The results show that the maximum depth of scour around the series of spur dikes and the amount of deposition between spurs reduced with increasing the spur permeability.

According to the present heavy metal pollution is a universal phenomenon, thus concerns about long-term effects of these metals, is increasing. The heavy metal cadmium as a toxic element exposure in humans can cause a variety of symptoms, because of its ability to accumulate in various tissues. The objective of this research was to evaluating the performance of the reverse osmosis system in cadmium removal from drinking water. The standard solution made in laboratory scale, then the removal efficiency of cadmium by semi-permeable membrane for reverse osmosis system (model: FT-30), under the influence of parameters concentration, pH and pressure were investigated. The results of this study showed that in the standard temperature 20 ºC , the concentration 50 ppb, pressure 350 (Kpa) and pH of about 6.8, cadmium removal efficiency by reverse osmosis system was above 98 percent. Thus, can be concluded that reverse osmosis, an ideal method to cadmium removal in areas with contaminated water to this metal.

Sedimentationin the dam reservoirs reduces storage volume sand as a result the useful life of the dam reduced.In deep dam reservoir the turbidity current usually are the reason of transport and deposition of sediment. If turbidity current completely stopped in middle regions of reservoir or not to allow deposition in sensitive areas, sediment deposition will decreased near dam wall and the main tasks of the dam will not be disrupt. Roughen the bed is a technique for changing the turbidity current hydraulic or slow it.Therefor in present research has been investigated the body velocity distribution of the density current on the bed with cylinder roughness and has been provided a relation for maximum velocity of body. A series of gravity currents experiment were performed into 35 cm width flume with 9 m length. The experiments developed as salinity fluid flow with 3 concentrations of 10, 15 and 20 lit/s in slop bed renge of 0.5, 1.25 and 2% and 3 roughness height of 25, 40 and 55 mm. The result indicates that the bed slope is in direct relationship with body velocity. Increasing the bed slop causes the maximum body velocity is closer the bed. And increases Roughness height reduces body velocity to certain extent.

To prevent flooding and water logging condition and to provide cultivation condition for fall and winter seasons, installation of subsurface drainage is necessary in large areas of Northern Iran paddy fields. The correct design of depth and spacing of drainage systems causes minimum negative effects of drainage water on the environment. In this research, the effects of different drainage systems on the Sodium, Chloride and Sulfate of drainage water in 4.5 ha of paddy fields of Sari Agricultural Sciences and Natural Resources University (SANRU) during two successive growing seasons of rice and canola have been investigated. The experimental treatments were: Four subsurface drainage systems including drainage system with 0.9 m drain depth and 30 m drain spacing with mineral envelope (D0.9 L30), 0.65 m drain depth and 30 m drain spacing with mineral envelope (D0.65 L30), 0.65 m drain depth and 15 m drain spacing with mineral envelope (D0.65 L15S), and 0.65 m drain depth and 15 m drain spacing with Geotextile envelope (D0.65L15F) and a bi-level subsurface drainage system with 15 m drain spacing and drain depths of 0.65 and 0.9 m as alternate depths (Bi-level). During the study period, Na, Cl and SO4 of drainage water were measured. Based on the results, by increasing drain spacing from 15 m to 30 m, the average Na, Cl and SO4 of drainage water decreased. Also, the minimum Na, Cl and SO4 concentration and total dissolved drained were for D0.9L30 treatment. So, it can be concluded that this drainage system had less environmental effect with respect to other drainage systems, from drain water quality point of view.

In a catchment, deposition of the erosion process is influenced by factors such as degraded pastures, land use change, agriculture non-normative and others may occur. That causes problems such as sedimentation in reservoirs, reducing their, effective volume reduction and water quality. For sustainable and watershed management and to prevent soil loss and sediment in the river and basin, It also plans to build watershed protection is required to estimate suspended sediments in rivers. In the present study, in order to select the most appropriate method for estimating suspended sediment in hydrometric stations Barzu, Babaaman, Ghatlesh, Darband, Aghmazar, Tabarok Abad on the river Atrak, The corresponding data flow and sediment discharge during the period were collected and analyzed. The relationship between water discharge and sediment load values based on five linear model, linear combination (multi-line), linear correction FAO, middle class and graphical methods (tangent to the line of maximum concentration), to select the appropriate model the best prediction based on the statistical indicators. In order to, the index of root mean square error (RMSE), coefficient of determination (R2), the estimated mean of the observations (r), coefficient of variation (Cv), the root mean square error of the estimated mean (GSD), the correlation coefficient between estimated and observed sediment (R), mean absolute error (MAE) and mean bias error (MBE) was used. Results showed intermediate model categories in Tabarok abad station, linear model in aghmazar and barzu station, Model drawing (maximum concentration) in Babaaman and Ghatlesh station, hybrid model (multi-line) in Darband station, among the models tested was the lowest rates and the best mean square error in estimating the predicted precipitation stations is studied.

Importance of determining unsaturated soils hydraulic properties in solute transport and water flow is always regarded by soil science engineers. Among these properties is the hydraulic conductivity that should be determined at different suction. Unsaturated hydraulic conductivity is estimated using the traditional Wooding analysis at steady state condition for tension disc. Estimating of hydraulic parameters using numerical solution of flow equations and the parameter optimization with inverse solution method is one of the conventional methods that its accuracy is dependent on soil type.In this study, saturated and unsaturated hydraulic conductivity was measured in 5 suctions 20, 15, 10, 5 and 0 cm from experiment tension disc on four samples of cylindrical clay soil with diameter of 56 cm and height of 75 cm. Then, the results of tension disc were compared with inverse solution. TheHydrus 2D/3D model was used for inverse solution with Van Genuchten-Mualem method. Optimization process was done based time, cumulative infiltration data, saturated hydraulic conductivity and α parameters obtained from the analysis of the tension disc. Then the optimizedparameters in 2D were used for 3D model simulation. The average standard error of optimized θr, n and L was obtained 0.011, 0.078 and 0.117, respectively. The results showed that the unsaturated hydraulic conductivity obtained from the model is less than the values ​​measured by tension disc. However, the low suctionsindicated betteragreement than higher suctions. Additionally, the maximum and minimum value ofsimulation error ofunsaturated hydraulic conductivity was found in suctions 5 and 20 cm equal to 6.50% and 60.0%, respectively.