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Most previous laboratory studies of local scour at bridge abutments were performed in rectangular channels in which the distributions of flow velocity and bed shear stress were considered uniform in the transverse direction. In reality however, bridge abutments are usually located in the floodplain zone of rivers where velocity and shear stress distributions are directly affected by the lateral momentum transfer. The influence of channel geometry and lateral momentum transfer in compound flow field on scouring phenomenon, however, has not been fully investigated and understood as yet. This paper presents the results of an experimental study performed to investigate the impact of both sediment size and lateral momentum transfer on local scour at abutments terminating in the floodplain of a compound channel. It is shown that, by accounting for lateral momentum transfer at small floodplain/main channel depth ratios (yalH<0.3), estimates of maximum local scour depth are increased by up to 30% . In relation to the sediment size, earlier studies of scouring around circular bridge piers proposed a limit for the relative size of sediment (pier diameter/median size of bed material) beyond which the sediment size has no effect on the equilibrium scour depth (Ettema, 1980; Chiew, 1984). The results of the current laboratory studies, however, indicated that the limit established for circular bridge piers might not be appropriate for the abutment case installed in the floodplain zones; further studies are required to draw a more general conclusion regarding the effects of relative grain size in the abutment case.

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Cohesive sediment transport remains a complicated subject that hydraulic engineers are frequently faced with in water-related engineering problems. This is primarily affected by the macroscopic aspects of water-sediment system characteristics. In this paper a 1-D mathematical model was developed to be employed in predicting the cohesive sediment transport under simultaneous conditions of erosion and deposition. This model is based on the convection-diffusion equation with proper source and sink terms and dispersion coefficient. The equation developed in the model has been solved by applying the finite volume approach. The model has been calibrated by employing the optimization technique using laboratory experimental data. For optimization, the transformed Powel's method has been employed. The data were collected in a flume of 10 m length, 0.30 m width and 0.45 m height. The applied discharges and concentrations were between 3 to 5lit/sec and 7 to 15 lit sec-1, respectively. The performance of this model has been assessed using two data sets: a set obtained in this study, and another provided by other researchers. The model shows good agreement with both data sets. The results obtained suggest that the deposition and erosion are functions of flow concentration, flow depth and shear stress exerted on bed.

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A subsurface drainage network mainly carries unsteady flow and data are not usually available for model parameters calibration in such networks. In the present research, the finite volume method using the time splitting scheme was employed to develop a computer code for solving the one dimensional unsteady flow equations. Using corrugated sub drainage pipes, an experimental prototype setup was constructed to examine the numerical model response in predicting the observed unsteady data in such circumstances. The experimental setup components and the model parameters were calibrated in place based on steady state flow condition. The results revealed satisfactory performance by the abovementioned method and the scheme employed and justified its validity for field application.

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This paper evaluates the efficiency of using surface water simulation results to improve the accuracy of groundwater simulation due to improving the accuracy of its input boundary conditions. The three most important data sets of boundary conditions in groundwater flow simulation are groundwater recharge, evapotranspiration rates and their regional distributions that little information is usually available about them. Moreover, the incorrect definition of these values can lead to uncertain groundwater modeling that is not applicable for groundwater resources management. In the most of previous studies done in Iran, percentage of the average regional precipitation and the local pan evaporation data (available from local weather stations) are used as the regional groundwater recharge and evapotranspiration rates, respectively but they have high uncertainty in their quantities and spatial distributions. In this research in order to solve this problem, the values of groundwater recharge and evapotranspiration rates and their regional distributions, obtained from SWAT modeling results, were used as the related input boundary conditions data in groundwater flow simulation using MODFLOW model. SWAT model is a comprehensive watershed model that calculates these values in each Hydrologic Response Unit (HRU). The study aquifer in this research was Silakhor shallow aquifer with the area of 590 km2 located in Lorestan province of Iran. The annual water table depth in different locations of this aquifer had been reported from 0.75 to 40 meter. Using this approach for improving boundary conditions in groundwater simulation and its evaluation was carried out for first time in Iran. The SWAT model was run for a period of 7 years from 2002 to 2008. After calibration and verification of the model using hydrodynamic data of Silakhor and Tire-Doroud gauging stations, the values of groundwater recharge and evapotranspiration rates in each HRU were extracted. The MODFLOW model was run for the period of 9 months of 2009 using these simulated boundary conditions and the other required information. For comparison of the calculated values with the observed values of water table depths in the 20 piezometers for the period of 9 months of 2009, the Root Mean Square Error (RMSE) and Mean Absolute Errors (MAE) were obtained 1m and less than 1m, respectively. In continuous of this research, the values of 5, 10 and 15 percent of regional average precipitation and the evaporation data in Silakhor pan evaporation gauging station were used as usual boundary condition for groundwater simulation using the MODFLOW model. For comparison of the simulated values of water tables depths obtained from this usual approach with the observed ones, the both of RMSE and MAE values were calculated more than 1 meter. Therefore this research showed that using integrated SWAT-MODFLOW models was more applicable in the groundwater simulation in the study aquifer.

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Shortage of irrigation water is a crucial problem especially in arid and semiarid regions; therefore, application of wastewater in agriculture in such regions seems to be an indispensable solution. A field experiment was conducted in non-agricultural soil to investigate the effect of Treated Municipal Wastewater (TMW) on the yield and fiber quality of cotton (Gossypium hirsutum L.) crop. The treatments consisted of surface irrigation by different mixtures and as well, through different intervals of freshwater plus TMW. Two additional treatments, namely, irrigation with freshwater and with TMW were considered as control. The experimental design was a randomized complete block one with eight treatments and three replications. The results indicated that cotton yield, number of bolls per m², Leaf Area Index (LAI) and plant height were significantly higher when the crop irrigated with TMW rather than with freshwater. The crop yields in TMW vs. freshwater treatments were about 2,200 and 780 kg lint ha^-1, respectively. There were no significant differences observed between interval and mixture treatments when the same percentages of freshwater and TMW applied. Also there was no significant detrimental effect observed on the characteristics of cotton fiber quality when the crop irrigated with TMW.