Journal of Water Resources Engineering
Year:2012 | Volume:5 | Issue:12|Papers Count:8

Flow at the river bend is completely three dimensional, complicated and related to the ratio of curvature radius to river width. Studies on bend river development depict that flow pattern in the curves have different behaviors. Therefore, curved channels with different development rate are simulated by numerical model of Delft 3D and results such as, flow pattern, longitudinal profile, transverse profile, secondary flow power, have obtained at a curve of the river. Results have been verified by the same laboratory model that has run at Tarbiat Modares Laboratory. As a result, answers reached by numerical model had accordance with laboratory result. Results show that whatever the ratio of curvature radius to bent width decrease the secondary flow power will be increased and the longitudinal current will more strongly affect on flow pattern.

Limited water resources and the climatic conditions of Iran are the main problem in increasing agricultural production. Drip irrigation methods are an ideal solution for the optimal use of water resources due to their high potential efficiency of water distribution. In the present study, the condition and performance of the 8 drip irrigation systems implemented in Sarbaz region were evaluated and parameter uniformity coefficient (CU), distribution uniformity (DU), application potential efficiency of low quarter (PELQ) and application efficiency of low quarter (AELQ), Emission uniformity (EU) and the maximum pressure difference (DP max) calculated in trickle irrigation system were 93.31, 89.51, 68.66, 72.6, 76.5 and 42.85 percent, respectively. In order to better analyze dripper discharge, the variation curve in the lateral pipes on manifold has drawn. In system AW1, there has been excessive irrigation needs. And there was a deepwater loss in the system. While in the rest of the system, the water requirements are far less than the amount of irrigation and deficit irrigation was done unintentionally.In general, it can be said that the key problems of trickle irrigation systems in Sarbaz region are due to the lack of care in design, implementation, management and maintenance of systems, inefficiency of pressure and its inconsistent distribution and lack of wetted area because inefficient trickle layout.

Development of water resources is not possible in arid areas, so production increase is only possible with management improvement and the irrigation efficiency would be increased afterward. Deficit irrigation is an important solution for irrigation efficiency improvement and optimal use of water resources, especially in arid areas. Nowadays, software facilitates selection and design of various scenarios in irrigation management. So, in this project, Aqua Crop model was calibrated and the simulations accuracy was verified for Sunflower product indices. Aqua Crop model calibration was done with comparing the results of field studies and model simulations. Statistical test results showed that the model has high accuracy in simulation. The values of Er for water productivity Yield, water productivity Biomass, Yield and Biomass are: 4.3, 7.24, 20.85 and 24.66, respectively.

In the present study, the flow field on stepped spillways in the skimming flow regime was modeled using free surface models of VOF and Mixture developed in Fluent software. Standard k- e, RNG k-e, Realizable k-e and RSM turbulence models were used to resolve the Reynolds stresses. The results of concentration and velocity distribution were compared with those from an experimental study carried out by Hansson and Toombes in 2002 using a physical model set up in the hydraulic Laboratory at the University of Queensland. Comparing the results of VOF and Mixture models shows that the results obtained from the numerical modeling using the above-mentioned turbulence models, are in relative adaptation to each other and laboratory results. In general, the model of Standard k-e presents worse results for concentration distribution in high discharges, but it acts like the other models in lower discharges. The results of velocity distribution obtained from Standard k-e turbulence model using both methods of VOF and Mixture are more suitable results. The air and water flow pattern formed in models of Mixture and VOF are the same, but convergence time of the Mixture model is shorter than that of VOF model. RSM turbulence model privileges the longest convergence time and the Standard k-e model has the shortest convergence time in both models of VOF and Mixture. In addition, among the different meshes, the Tri pave discordant mesh brings about the best results.

The information of the temporal variations of the beginning and the end of a precipitation trend is important for estimating climate changes. In this study, the sequential Mann Kendall nonparametric test was used to determine changes in time of annual precipitation for synoptic stations in Fars province. This sequential test is useful to trend analysis of a time sub-series. The results indicated that in Abadeh station, a downward trend of precipitation has been begun in 1980 and 2005 and this downward trend in 1985 and 1990 is statistically significant at 5% level. In 1955 and 2007 a downward precipitation trend was beginning in Shiraz Station. In this station, a significant downward trend has been occurred in precipitation of years 1962, 1963, 1964, 1966, 1971 and 1973 at 10% level. In Fasa station, a downward trend of precipitation was beginning in 1970 and 1997 such that the minimum value of the sequential Mann Kendall test statistics is happened in 2010 and therefore, the downward trend of precipitation is much strong in this year.

Zahedan plain is one of the sub basins of Mond river that is located in Fars province. The area of this basin is 1246 km2. This research focuses on surface and ground water resources and water balance in Zahedan plain. Thus, the total recharge of aquifer is 415.242 MCM and the total volume discharge is 423.127 MCM and mean annual decrease of aquifer volume is -7.854 MCM. In the recent years, due to drought and an increase usage of water resources, water level has decreased. Due to the exploitation limits on the plains and the negative water balance of the plain and the significant decrease in the water level in the plain there is no possibility to develop the alluvium aquifer in this area. In order to supply drinking and industrial water needs in this area, the utilization of wells can be changed from agriculture to drinking and industrial water or via water supply from Salman Farsi dam. There is drinking water limitation because of water resources quality of Zahedan plain as the southern parts of plain is affected by Razak plaster-marli formation in terms of sulfate ion. Overall, more than 60 percent of plain water has inadequate to bad quality. Water resources of this plain contains chloride sodium. The total average of dissolved salts is equal to 3078 mg per liter and the average electrical conductivity is equal to 4707 micro siemens per cm that indicating poor quality of water plain.

There has been always a question whether the natural phenomenon could be studied when outburst. Nonlinear adaptable intensity has made them suitable for analyzing the nature behaviors. In a multifractal outlook, we have studied the river flow conducts when flooding. A new method has been presented for multifractal analysis of the river flow. The wavelet coefficients are used to construct the Legendre spectrum instead of the raw flow time series. Using this method besides utilizing the preprocessing algorithms for the time series has led to a more efficient multifractal analysis than the previous studies. Forty years of monthly River flow data in three stations of Ghar-e-Aghaj River have been used for this study. The results indicate on two significant points. The first is that De-noising the signals affects the multifractal behaviors of the river flow significantly. The more important result depicts that the river flow is multifractal intensively and the anomalies like the flood would turn it to monofractal during their occurrence period. In other words changing from multifractal to monofractal condition is the river flow response to the changing of its stable condition.

According to this reality that in Iran, especially in Khuzestan, there are many rivers, and also due to extensive dam construction in this area, it is important to determine the rate of sediment transport. Simulation of sediment transport in Dez River (between Harmaleh & Bamdezh reach) has been carried out by HEC-RAS 4.0 and GSTARS 2.1 models. In this paper, models were run by theoretical sediment transport relations to compare the results of laboratory data, and determine the best relation for calculating the river sediment. It compares the two model outputs and depicts the difference between one-dimensional and quasi two-dimensional models and also the results of sensitivity analysis on these models. At last, the rate of sediment transport was estimated.