Journal of Water Resources Engineering
Year:2014 | Volume:7 | Issue:22|Papers Count:9

Drought is a natural phenomenon with high frequency in arid and semi-arid regions of Iran, especially in the Province of Fars. Monitoring and evaluation of drought is a basic need for agriculture and water resources management to reduce its adverse effects. Reconnaissance drought index (RDI) is one of the agricultural drought indices used to categorize drought intensity. In this study, agricultural drought return period for wheat for the Province of Fars was assessed based on RDI. Twelve synoptic weather stations, with the minimum of 10 years data were selected for this purpose. Evapotranspiration was calculated based on the Penman- Monteith method, and the drought intensityof normalized and standardized RDI for each year was calculated. The results showed that the most severe drought in the Province of Fars occurred in the 2007-2008 hydrological year. After classifying the wheat drought intensity, the results indicated that the normal drought was the most prevalent in all of the selected stations. Also, zoning maps of wheat drought with the return periods of 2, 5, 10, 25 and 50 years were prepared for the Province of Fars. The results showed that the wheat agricultural drought for the Province of Fars is normal in the return periods of 2 and 5 years; however, it was different for the frequency of 10, 25 and 50 years.

Reaching a compromise between stakeholders of reservoir systems is one of the delicate and complicated subjects in water resources management. Game theories in general, and the Nash conflict resolution model in particular, are such methods that consider the existing conflicts and utility functions of each stakeholder, and search for an optimum solution in the decision space. In this research, optimal operation of a three-reservoir system has been considered with hydroelectric energy generation as well as supplying downstream demands objectives. To specify the effects of the defined objectives, stakeholders of each reservoir and their utilities were introduced simultaneously. Afterwards, all objectives were considered separately. Results showed that the utility of stakeholders for each reservoir in separated objectives was increased. In the next step, to compromise between different stakeholders (hydroelectric energy generation and supplying downstream demands), stakeholders' utility was used in the Nash function. As a result, a solution was reached through which most of the utilities for all stakeholders were provided at the same time. Next, the reservoirs systems were divided into the parallel upstream reservoirs and a single downstream reservoir. Each reservoir's stakeholders tried to generate more hydroelectric energy and supply as much flow as the downstream demands. Results show that the total system utilities equaled to 5.872 units in the last step, which was 0.472% more than total system utilities of the separated reservoirs.

The wetted perimeter's roughness, the radius of curvature and its ratio to the bottom width affect the flow velocity and its patterns. This laboratory study was conducted in a 90° sharp bend flume with a rectangular cross-sectional area, and the radius of curvature to the bottom with ratio of 2. The experiments were conducted under a constant Froude No. of 0.17 with 3 wall roughnesses of 0.5, 2.0 and 5.0 mm. The three components of the flow velocity were measured at 480 points. The flow lines in the high velocity zone of 30° to 60° were mostly deflected towards the inner wall and along the channel depth. However, they gradually turned towards the outer wall where the deflection angle exceeded 60o. Further, the main rotational cell of the secondary flow was formed close to the inner wall at all 3 roughnesses at the 60o alignment of the bend. An increase in the wall roughness delayed the decay of the rotational cell at the bend's termination. It was also observed that the bed shear stress was increased in the highly stressed area with an increase in the wall roughness. The area delimited by the 70o and 80o was singled out showing the highest shear stress. Moreover, it was established that the secondary flow strength at any cross sectional area decreased with an increased in the wall roughness.

Runoff prediction in un-gauged catchments is of importance for designing hydraulic structures. Some rainfall runoff models such as Clark requires time-area diagram of catchments. In this study, a novel method to derive time-area diagram using Nash's instantaneous unit hydrograph model is presented. This method was compared to time-area equation already introduced by USACE (1999). The values of parameters n and k were obtained as n=4.7 and k=te/7.4. The results were validated using the existing time-area diagrams in Kasilian and Jafarabad, Iran and Ajay and Godawri, India. Moreover, the time- area diagrams derived from the new method were converted to direct runoff hydrographs using Clark model. The hydrographs were compared with observed ones. The average efficiency coefficients for Ajay and Godawri are 0.96 and 0.78, respectively. The errors in peak discharge estimation vary between 14 to 22 percent and 4 to 17.5 percent for Kasilian and Ajay, respectively.

Spur dikes are rigid hydraulic structures built out from a river bank used in order to protect it from the rushing water. These structures also play significant roles in changing the river's depth, in causing sedimentation, in controlling erosion along the river, and in dealing with some environmental issue. In this paper, the flow pattern around a T-shaped spur dike at a 45 degree position located in a 90 degree bend with a rigid bed has been investigated, while the radius of curvature changes, but geometry of the spur dike (1/l=1) and a discharge of 25 liters per second around it remain constant. The results indicate that as the radius of curvature increases, the vortex downstream becomes smaller in a way that when the central radius increases three times of the channel width, the vortex length decreases three times that of the spur dike length, and its radius reduces as much as 0.9 fold of the spur dike length. The roles of the radius of curvature and the analyses of the results have been discussed in this paper.

Hydraulic analysis of water networks consists of determination of the discharge rate in each pipe and the piezometric head at nodes. Benefiting from the matrices algebra, and developing equations following the Taylor series, the gradient method numerically solves the continuity equation determining simultaneously the flow rate in nodes and energy dissipation in loops. The objective of this study was the hydraulic analysis of water distribution networks based on the matrix form of the Gradient method, comparing the results with the statistical indices, namely: NS, CRM, R2 and RMSE with Hardy Cross, Newton Raphson and Linear theory methods. The indices Values were NS=1, CRM=O, R2=1 and RMSE=O; very close to the ideal values. Following the same reasoning, the gradient method is reliable in predicting the head in unknown nodes and the flow through pipes. Accordingly performance of Gradient was proved in computing head of unknown nodes and discharge through pipes. The obtained results indicated that the Gradient method delivers accurate and reliable output. This ability highly facilitates the design and hydraulic analysis of wide spread networks.

The 15th khordad Dam reservoir with a total volume of 200 million cubic meters is the first dam which was built over a brackish river in Iran. The reservoir was put into service in 1994. In the beginning, the total amount of total dissolved solid of the reservoir's water was 600 mg/lit; it increased to 2500 mg/lit 5 years later. To simulate the temperature and salinity distribution in the reservoir, a two-dimensional width averaged model (CE-QUAL- W2) was used. By using the calibrated model, the effect of water withdrawal location and also the reduction of the entering salinity in the reservoir on the salinity profiles were studied. The result revealed that the location of water withdrawal (1408 and 1430 m above the mean sea level) did not affect the' salinity profiles; hence, this option could not prevent the salinity increase of the reservoir. However, identification of the salinity sources, and prevention of the saline water entry into the Dam Rude may somewhat mitigate the salinity of the pounded water in the reservoir. Results show that with a reduction of 25% in the entering salinity, the rate of increase in the reservoir salinity was small, but with a 50 percent reduction in the entering salinity, there is a possibility of reduction in salinity of the reservoir.

The combined weir- gate is a structure which may replace weir and gate in channels. The semi cylindrical weir- gate has a higher discharge coefficient in comparison with the sharp crested weir- gate because of the curvature on the weir section which the water wedge adheres momentarily. In a weir- gate structure, the rate of the passing flow discharging above the weir and through the gate depends on the structure's position. In the present research, hydraulics of the semi cylindrical weir- gate rotating the flow around the off-center axis, so that the gate opening height remains constant were investigated. The experiments were conducted in a rectangular' and horizontal flume with the length of 5 m and width of 75 mm in the Sari Agricultural Sciences and Natural Resources University Hydraulics laboratory. PVC pipes with 40, 50, 60, 70 and 85 mm diameters were used as semi cylindrical structures. Experimental results illustrate that the maximum and minimum discharge coefficient were observed in the 330 and 90 degree angels, respectively. Furthermore, the maximum and minimum energy loss were observed for the 90 and 180 degree angels. Moreover, the results show that in addition to the angle of the semi cylindrical curvature toward the horizontal line, the structure diameter affected the discharge coefficient and energy loss. In addition, the best relationship for estimating the flow discharge is proposed.

The aim of this study was to evaluate the optimal cropping patterns in the Marvdasht- Korbal Plain and its effects on water resources management in that area. The linear fuzzy and the uneven fuzzy programming have been used in this study. Based on the results achieved using the fuzzy linear programming, the area appropriated for cultivation of barley and sugar beets should be reduced compared to the existing situation. Using the uneven fuzzy programming, the area ear-marked for the cultivation of wheat and barley should be increased, while that for the other crops has to be reduced in comparison with the existing situation. As to the programming efficiency, they both performed less than expected; however, the linear fuzzy was more efficient than the other one. Eight recommendations have been presented for optimization of water consumption.