فصلنامه مهندسی منابع آب
پیاپی 20 (بهار 1393)

All the geophysical phenomena including river networks and flow time series are fractal events inherently and fractal patterns can be investigated through their behaviors. A non-linear system like a river basin can well be analyzed by a non-linear measure such as the fractal analysis. A bilateral study is held on the fractal properties of the river network and the river flow time series. A moving window technique is utilized to scan the fractal properties of them. Results depict both events follow the same strategy regarding to the fractal properties. Both the river network and the time series fractal dimension tend to saturate in a distinct value.

Time-variation of scour depth around abutments is more complicated due to the three-dimensional vortex flow. In this study، variation of the scour depth with time around abutments was investigated experimentally under clear-water conditions. The Nonlinear Regression (NLR)، neuro-fuzzy inference system (ANFIS) and artificial neural networks (ANN) were employed to predict the time variation of scour depth at intermediate and short abutment. Statistical analysis showed that، although the presented regression method (R2=0. 957، RMSE=0. 049 and MAE=0. 035) provided a better prediction compared to previous equations but the ANFIS (R2=0. 961، RMSE=0. 041and MAE=0. 025) produces a more accurate result. Statistical measurements showed that ANFIS as well as ANNs can be considered as a robust technique to predict the temporal scour depth at the short and intermediate abutment.

Prediction and control flood is essential in water resource management. Studying and analysis on this problem is done using flood routing methods in hydraulic science. The Muskingum model is one of the best methods in the hydrologic flood routing rivers. In order to estimate of the Muskingum parameters have been used experiential methods as trial and error method، least squares. Genetic algorithm is one of the estimation methods of the parameters. Comparison between experiential methods results and genetic algorithm show that Genetic algorithm method is benefit and easy method for estimated the Muskingum parameters. The determining of objective function is most important in this method (GA). In this paper، different objective functions have been selected for linear and non-linear Muskingum models and are optimized using genetic algorithm then the effects of objective function are investigated on prediction of Muskingum parameters and computational output discharge. Comparison between computational hydrograph of output discharge and experimental result show that the effects of objective function on result prediction predominate in the linear Muskingum model whereas these are virtually negligible in non-linear Muskingum model.

Eutrophication is one of the most important problems which affect quality of the reserved waters in dams. In this research، using CE-QUAL-W2 software in three states of low water، normal and high water، water quality condition of Baft dam reservoir was measured in terms of monthly changes in phosphate and nitrate. Although the results of the simulation indicate low concentration of phosphate and nitrate in the Baft dam reservoir، these low concentrations given the different eutrophication indices (Chapra Index، Meybeck Index، Carelson Index، and Vollenweider diagram) places Baft dam reservoir in the nutritive area. In addition، in terms of nitrate concentration، Baft dam reservoir is positioned in the interstitial area. And in terms of drinking and agricultural consumptions، the Baft dam reservoir has no problem، yet finding a solution to prevent the Baft dam reservoir from entering the nutritive area which may strongly affect the water quality is necessary. Considering the thermal stratification peak in late August and start of the dam reservoir mixing in February، for preventing the Baft dam reservoir from entering the extremely nutritive area، some suitable solutions can be proposed including: reducing water stay in the dam by quick impoundment from lower layers in late August and impoundment from the lower layers in late December، preventing entry of rural sewages and agricultural waters from upstream of the Baft dam reservoir.

Some Experiments were conducted in water research center، for five specific discharge and four tail water depth to investigate effects of parameters like specific discharge and tail water depth. To carry out the experiments we made use of the hydraulic model of Azad dam. Measured parameters are: Maximum depth of scour، distance of maximum scour depth from bucket، the maximum length of scour hole and maximum width of scour hole. By using nonlinear regression analysis to predict the scour hole dimensions some relations were achieved. These relations were tested by applying experimental data from other investigators. in this research The results have showed the relative ability of the presented relations. Scour wide and the place of maximum depth are estimated appropriately by using of these relations. The relation of maximum depth is compared with another famous relations and showed weaker results. The best results was for Martins B relation.

Water scarcity is a growing global problem and increasing population pressures، living standards and the growing demand for environmental quality have evoked all the governments to represent better solutions about water resources management. In addition، there are growing political ties for reducing water use in agriculture that follow enough environmental benefits and increase the welfare of other water consumers. This further increases the economic analysis to check the behavior of farmers using mathematical programming techniques and has been followed the application of Positive Mathematical Programming (PMP) especially. Despite. The method used in this study is one of the PMP methods that used for deficit irrigation technique that haven’t been observed in the reference period. This method applied in Fars province that faces water shortages and the reduction of groundwater levels to evaluate the price increase and quantity reduction of available irrigation water. Applied policies include increased 5، 10، 20 and 30 percent in water irrigation prices and reduced 10، 15، 25 and 30 percent in the amount of available irrigation water policies. The results showed that increased costs and reduced available irrigation water are effective in accepting deficit irrigation. Additionally، the impacts of quota policies are more than price increase policies

Standardized Precipitation Index (SPI) has been widely used for evaluation of drought. Different time scales of SPI could be used e. g.، 3، 6، 9، 12، 18، 24 and 48-months. SPI 12-month is used for evaluation of drought condition and vulnerability of drought in the study area. SPI 12-month was computed in 28 stations based on 30 years of data period in the study area. Spatial distribution of SPI 12-month was analyzed using different interpolation techniques of geostatistics. The precise interpolation technique was selected based on the cross-validation criteria. In order to access vulnerability of the study area in drought، two years were selected as end-members (1378-79 and 1377-78 for minimum and maximum precipitation، respectively) and 1376-77 was selected as average climatological condition due to annual precipitation values. The results show that in extreme year (1377-78)، more than 99٪ of the study area leave from the drought condition. However in minimum condition of annual precipitation (1378-79)، more than 98٪ of the study area belongs to drought. As a results، Yazd، Taft، Mehriz، Bafgh، Naibandan and Kharanagh show high vulnerability to drought in the Yazd Province.

Infiltration is one the most important parameters in surface irrigation which its accurate measurement is obvious. It could potentially affected by different parameters such as bed slope، discharge، cross section and roughness coefficient. In this research، Kostiakov-Louis equation (KLE) was employed using two-point method، in order to measure the soil infiltration rate. This study was carried out in research field of Shahrekord University، Shahrekord، Iran. A completely randomized block design was employed with three treatments and three replications. The effect of changes in furrow bed slope and shape is evaluated on the soil moisture distribution، soil infiltration rate and cumulative infiltration. Statistical analysis was performed using the LSD test. The results show that the lowest infiltration rate (0. 00052 cubic meters per minute) and cumulative infiltration value (0. 5 cubic meters per meter) were observed in variable furrow bed slope. The changes in the slope were significant (P<0. 01) on soil infiltration rate and soil basic infiltration rate (). There is no correlation between cross section variation and KLE parameters including k، a and (P<0. 01). The result shows that soil moisture distribution was more uniform in variable cross sections than other treatments