Journal of Irrigation Sciences and Engineering
Year:2013 | Volume:36 | Issue:2|Papers Count:12

Lateral intake is a hydraulic structure which is used for diversion of some portion of water from a river.In this paper because of the importance of sediment entry to the intake, flow patterns and the most important factors affecting the sediment entry has been studied. Stream tube is the most important parameter in flow and sediment diversion. Stream tube is a part of main channel that divert sediment and flow to intake. Stream tube dimensions at different depths have a significant impact on sediment diversion into the intake. Most of previous studies have been conducted on rectangular canal. In this study experimental tests are conducted in trapezoidal canal with four different bank slopes. Three components of flow velocity at three different flow depths was measured using ADV velocity meter. Using data the streamline were plotted and stream tube dimension were determined. The results show that the stream tube dimensions for trapezoidal canal is different than it is in rectangular canal for the same discharge ratio. It was found that the bottom stream tube width is less than it is in rectangular canal. Since sediment concentration at lower layer is high, for the same flow discharge ratio sediment entry to the intake is reduced when the canal banks are inclined.

Hydraulic condition of stilling basin, in particular, the flow rate passing through chute spillway, as well as the location of hydraulic jump plays an important role on velocity fluctuations in a stilling basin. In this study, effects of the hydraulic jump location and flow discharge in stilling basin on the velocity fluctuations are evaluated. The experiments were performed in a 1:30 scale model of Glabar Dam spillway for discharges of 221.7, 355.8, 450 and 592.5 (m3/s). The discharges ranges are for 1.000 to 10.000 years return period. The flow velocities in different locations inside of stilling basin have been measured near the wall and centre of basin. The experiment results show that flow velocity fluctuations are considerably affected by the discharge and the location of the hydraulic jump. The most energy lost was in discharge 355.8 (m3/s) where jump was on the shut blocks. The lost was nearly 93% after the jump compared to the energy before the jump.

Construction of dams in rivers is cause of sediment accumulation behind the dams and therefore clear water flowing downstream. Flowing of water with high capacity of sediment and low in sediment load will affect downstream morphological parameters of the river. In the present study, morphological changes of Karkh river in the segment located downstream of the Karkheh reservoir is analyzed with the aids of a mathematical model.The length of the river reach was about 200 km located between Paaipol station and Hamidieh station.GSTARS3 model is developed version of the stream tube model for simulating the alluvial rivers presented by the river hydraulics and sedimentation branch of USBR. The hydraulic data of the river between 1998 and 2009 (12 years period) and measured cross sections in 2005 are used. Calibration of the model showed that the Ackers-White and Laursen-Madden are suitable sediment transport equation for this river. By using these equations for a priod of 10 years, the changes of the sediment and morphological parameters such as the variations of the cross sectional and longitudinal profiles, bed slope of the river were analyzed and discussed.In this period the greatest change in slope at the interval of the Upper Karkheh Basin has been observed.

In this research, an analytical model is developed to determine the influence of the bank stability on the stable width and depth of alluvial gravel-bed rivers with cohesive banks. The formulation of the model is based on the assumption that the stable width corresponds with an optimum condition that is equivalent to the maximum bed load transporting capacity. The optimum condition develops when the channel banks are at their limiting stability with respect to either mass failure or fluvial erosion. Two basic channel types are identified: bank-height and bank shear constrained. A method for estimating the critical bank shear stress based on model calibration is proposed. Analysis of field data indicates that the effect of the bank vegetation on bank stability can be expressed in terms of the critical bank shear stress. The average critical bank shear stress value calculated for river banks covered by vegetation with well-developed root networks was found to be approximately three times that obtained from rivers with weakly vegetated banks.

One of the ways of water supply is used from river resource. Flow diversion from river has been foretime from the methods of water supply for different consumptions, yet, common methods has always created many problems in this case. A new idea offering decrease a lot of problems of river flow diversion. Applying bottom racks in bottom intakes to divert water from the mountain river with steep slopes and coarse sediments has been one of the most common methods in water diversion. Problems due to Exploitation on diversion channel propose new idea of bottom intake with porous medium. In order to experiments on a physical model done to investigate the hydraulic conditions of flow in bottom intake with porous medium upstream and influence procedure of that on the diversion rate and to study the different situations affect of inflow conditions of discharge and intake geometric on the profiles of water surface and velocity.Experimental results show that the diverted discharge of porous medium depend on surface slope of intake, grain size distribution of porous media, and inflow discharge to porous medium intake. As the surface slope increase, the diverted discharge decrease. when increasing the inflow discharge, the rate of diverted discharge increases gradually and then reaches to a constant value. Grain size distribution has also significant effect on diverted discharge and coarser grains divert greater discharges.

Groundwater is one of the most important water resources and its qualitative study is very important for water resources protection and planning. Also, qualitative parameters measuring of the ground water is costly and time consumer. Models will be reduced the cost of water qualitative estimations and it will be provided a data bank to manage water resources. In this study, Artificial Neural Network (ANN) has been used to simulate ground water salinity on the Caspian southern coasts (Mazandaran Province). So, a comprehensive data bank of water qualitative experiments has been provided and then quantitative values of the effective factors on ground water salinity, such as: Water conductivity of aquifer formation, surface water salinity, slope and elevation (topography) and the distance from Caspian Sea were estimated. The efficiency of Artificial Neural Network (ANN) has been considered through two parameters: Median Root of Square of the Error (RMSE) and co efficiency between the actual and desirable outputs (R). The results showed that co efficiency between the actual and desirable outputs (R) is 0.75 in the best network structure. surface water salinity, water conductivity of aquifer formation and distance from Sea are the best inputs for simulating ground water salinity and those are the most important factors on ground water salinity in Mazandaran Province Coasts.

The flux of water in unsaturated soils plays an important role in analysis of hydraulic structures. In addition, water infiltration from the soil surface and flux through the soil column are important processes in hydrologic cycles, which they were predicted using the Richards’ equation. The objective of the present research was to apply a novel numerical technique called Localized Differential Quadrature Method (LDQM) for modeling water flow in unsaturated soils. Up to now, LDQM has been used in many investigations and has been claimed as highly accurate, stable and efficient method. The 1-D Richards’ equation was used as a simple mathematical model. At first, the governing equation and associated initial and boundary conditions were described. Then the implementation of the method for discretization of governing equations was discussed. An analytical solution data and experimental measurements were employed for evaluation of the results. It was concluded that, LDQM has high accuracy and efficiency. The application of the method for 2D and 3D cases is recommended for future researches.

The fluvial suspended sediment concentration (SSC) which is directly and traditionally measured in the most times is costly and time consuming. Also, in some situations it has some human errors and also is calculated and recorded in a discontinuous time and spatial scale. MODIS data, because of high temporal resolution and accessibility are proper tools to estimate fluvial SSC.In this research, the relationship between spectral reflectance of red and near infra red bands of MODIS sensor, their band ratios and their simultaneous fluvial SSC data have been evaluated.Regarding with this, in a period of 9 years the SSC data of Mollasani hydrometry station (2003-2011) and simultaneous daily MODIS images (red and infra red bands with 250m spatial resolution) have been used.In order to understand the relationship between data, the correlation between the SSC and all simultaneous images for the entire period (all seasons together) was investigated and derived results showed a low correlation among them.In the next stage, the data of wet season (22 Nov to 20 Apr) for entire statistical period were evaluated and results showed a high correlation between SSC and water spectral reflectance (r=%88).To make a regression relation, some linear and nonlinear relations were statistically considered and eventually a linear relation with having suitable parameters (R2=0.77, Sig.=0, F=43) was calibrated (a=1.27, b=0.242, n=15). The calibrated relation then was validated using leave one out cross validation (LOOCV) method (RMSE=55 mg/l, RRMSE=%26). In summary, despite the insufficient number of fluvial SSC data, the existence of cloud and aerosol in the images and also other influencing parameters in spectral reflectance of Karun river, the results showed good performance of MODIS images in estimating daily fluvial SSC in large rivers in wet season.

Existence of healthy water sources without poisonous and dangerous pollutant is a significant requirement for a healthy and sustainable society. It is well known that heavy metals such as cadmium and nickel in environment are a serious threat to plants, animals and human because of their bioaccumulation, nonbiodegradable property and toxicity even at low concentrations. This metals were entered from industrial wastes consume oil, urban waste water to environment. in this study, nano particle bagasse fly ash was used to removal of Cd (II) and Ni (II) from contaminated waters by batch adsorption experiments.First experiments related to pH were carried out on aqueous solution at the concentration 5 ppm, amount of adsorbent 10 g/L, contact time 12 hours with pH of the solution varying from 3 to 8. The pH0=6 was founded to be the optimum for the removal of Cd (II) and Ni (II) ions by BFA. The equilibrium time was determined to be 15 min for Cd (II) and Ni (II). The batch adsorption experiments were done at the lab temperature, optimal pH and equilibrium time. Adsorption efficiency were obtained at different initial concentrations (C0=2-20mg/l). The experimental adsorption data were fitted to the Langmuir, Freundlich, Redlich-Peterson (R-P) and Langmmuir-Freundlich isotherm models. The R-P model represent the equilibrium data better than other models.

Although the empirical models of base flow separation meet the engineering desires in evaluating the volume of storm runoff or total drainage of a basin, however, they do not offer an actual understanding of the existing processes. The common runoff models often assume that the groundwater base flow into the river during wet season is minor. The tracing isotopic methods show that it is not the case and it has caused a close look at the runoff generation processes. In this study, during the winter 2010-2011, three rainfall events with different antecedent moisture and intensity and the corresponding flood were sampled to analyze isotopic composition in stable isotope laboratory of Ottawa University. Results showed that surface runoff component was minor for the low moisture conditions, and it increased for the high moisture conditions. Also, the contribution of groundwater component to total runoff was considerably large due to karst development in the Abolabas basin.