مجله پژوهش آب ایران
پیاپی 15 (پاییز و زمستان 1393)

Accurate water delivery ensures equity in water distribution and enhances the optimum usage of water resources. Nowadays, modern water measurement equipment could increase the accuracy of water delivery; however, the cost of investment and operation as well as the needs of the skillful operator restrict the widespread use of these equipment. Therefore, the traditional water measurement structures are widely used in irrigation networks. In this research, a new form of the flow measurement flume with a trapezoidal cross-section and an invert elevation coincide with the main conduit bottom was experimentally investigated. The design criteria for such flumes were presented hereafter. The proposed structure, which is classified as a long throated flume, is easily applicable in existing networks. The main advantages of the proposed structure are prevention of sediment accumulation and rather low backwater effects, and with such low backwater effects the critical depth could be established in flume section. Based on the compiled data, a method for calculating the required energy grade line in the approach channel and the structure head loss were presented.

Analysis of non-laminar flows in coarse alluvial beds have many applications in different fields such as oil and gas, civil and geology engineering. Since the Darcy equation doesn’t work for analyzing turbulent and transitional flows, we are forced to use nonlinear relationships, divided into two groups of exponential and binomial. The binomial relationship has more accuracy in a vast domain of speed variations than exponential relationship, as its validity has been confirmed through dimensional analysis and Navier- Stokes's equations. Until now, the non-Darcy flow analysis in conditions with relatively parallel flow lines, for free surface and under-pressure states, has been evaluated by many researchers. The researches carried out about the analysis of non-Darcy under pressure flow with convergent lines indicated that a) the behavior of this flow is different from the one with relatively parallel flow lines, b) the binomial relationship works well in the analysis of this flow, with a great accuracy. In this research, an experimental setup with a semi cylindrical shape with a diameter of 6 m and height of 3 m was constructed. The results of experimental research showed the behavior of radial flows with free surface differs from convergent under-pressure flow and from that of non-Darcy flow with relatively parallel streamlines.

In this research, the effect of applying sacrificial piles on local scour around square piers is studied. The sacrificial piles are placed at upstream of a bridge pier for the purpose of protecting it from local scour by deflecting the high-velocity flow, reducing vortex system power and creating a wake pressure region behind themselves. In this study, the effect of size of sacrificial piles and spacing between them was investigated in a 7.3 m long, 0.56 m wide and 0.6 m deep flume, under clear-water condition. The diameter (D) of square pier was 40 mm. The experiments were conducted on three sizes of sacrificial pile’s diameters (d) of 32, 27 and 20 mm, and three different distance of 2.8D, 2.95D and 3.1D from the upstream face of the pier with Froude number equal to 0.13, 0.16 and 0.19. The result showed that in a given distance with increasing the sacrificial pile diameter, the scour depth reduces, significantly. Also, in all of the circumstances, the scour depth increased with increasing the Froude number. Furthermore, the results showed that the best location of sacrificial pile was at a distance equal to 3.1D of the pier (X), that led to a significant reduction in local scour about 70 to 132% related to pile diameter and flow intensity.

Runoff causes soil loss and finally leads to sedimentation in water bodies. Water erosion as a selective process; generally removes the smaller components of soil particles with lower density. Organic amendments increase the soil infiltration rate and finally reduce the runoff and soil loss, but quantification of their effects on runoff parameters has less been attended. The present research was therefore conducted to study the effects of rice straw mulch as a conservation treatment on runoff threshold and coefficient for sandy-loam soils taken from the Alborz summer rangeland, north of Iran under laboratory conditions. Experiments were conducted by using straw mulch with an amount of 0.5 kg m-2 for simulated rainfall intensities of 30, 50, 70 and 90 mmh-1 and the slope of 30 %. Results showed that the straw mulch increased the runoff threshold and decreased the runoff coefficient significantly (p=0.01). The mulching treatment in the rainfall intensity of 90 mmh-1 with the amount of 110.10 % was the highest increase rate of runoff threshold compared with other intensities. The treatment of rainfall intensity of 30 mm h-1 had the lowest reduction rate of runoff coefficient with the amount of 19.36 %.

Rainfall intensity, antecedent soil moisture condition and slope steepness are among the main important physico-climatic factors whose individual or interactive effects determine the hydrological response of a watershed to a rainfall event. The present research was conducted to study the individual and interactive effects of rainfall intensity and antecedent soil moisture contents on runoff threshold and coefficient under laboratory conditions in four rainfall intensities of 30, 50, 70 and 90 mm h-1 and five antecedent soil moisture contents of 12, 19, 29, 36 and 44 volumetric percent in sandy-loam soils taken from a summer rangeland in the Alborz Mountains, Northern Iran. The results showed the significant correlation (p<0.01) between rainfall intensity and antecedent soil moisture, and runoff threshold with correlation coefficients of -0.709 and -0.628 and runoff coefficient of 0.517 and 0.804, respectively. The significant antagonistic interaction between rainfall intensity and antecedent soil moisture content on runoff threshold was confirmed. Separation of treatment levels also confirmed the existence of significant turning points in runoff threshold and coefficient at the rainfall intensities about 40 and 60 mm h-1, respectively, and in the runoff threshold at the antecedent soil moisture content between 12 and 19 volumetric percent.

Many of the reservoirs in the world are faced with acute sedimentation problems and in many cases the sedimentation led to closure of the sluice gates and it intensifies accumulation of sediment in these reservoirs. According to international reports, one of the most effective ways to removal of the deposited sediment from large reservoirs is partial Flushing. But this method erodes a small amount of sediment around the sluiceway and it cannot solve the sedimentation problems, completely. In this study, with knowledge about vortex flow around the sluiceway, there vortices were increased by using a specific structure in order to increase partial Flushing. The results show that with using a semi-cylinder structure, the flushing efficiency will increase up to 16.4 times. Therefore, the proposed method can be applied in the large reservoirs and in the reservoirs with serious conditions, for sluicing a significant amount of sediments out of the reservoir, in a short time, with a low loss in water resources.

One method to increase efficiency of energy dissipation in the flip bucket spillway is installation of deflector. Deflector is a wedge-shaped structure which creates changes in part of flow trajectory. In this study, flow in the bucket with approach channel were divided into two parts by deflector. For the purpose of this study, after setting up the physical model, experiments were conducted at three Froude numbers equal to 2.6, 3.4 and 4.3 by using deflectors with 3, 6, 9 cm length, and 12˚,22˚, 32˚ and 42˚angles. Analysis of data showed that the clashing of these two flow trajectories increased energy dissipation in flip bucket. Energy dissipation by using deflector was 62.1% which is 29% more than the case without deflector. Also using of deflector led to decrease the ratio of jump length to bucket radius. The maximum decrease was 41.7% compared to the without deflector case.

In arid and semi-arid regions, sub-surface flow of a river can be a potential of water supply.. Different methods have already been used to divert surface and subsurface water in the rivers. In this research, an experimental model of the intake was built in Hydraulic Laboratory in Water Engineering Department of Ferdowsi University for diverting surface and subsurface flow from the river and the effective factors on the amount of diverted flow were investigated. Results showed a direct relationship between the flow rate and the water level above each drain and the drained flow rate increases with increasing distance between the drains. The discharge of drains varies along the porous media, as it decreases at first and then increases. The lowest discharge was belong to middle drain. The assessment of different drains arrangement indicated that the installation of two rows of the drains in two depths gives higher efficiency. Finally, a regression mathematical model was developed for designing the subsurface intake with porous medium and drainage system.

The most important factor in shortening the useful life of dams is settling of fine sediment. A lot of dam’s reservoirs were filled by sediment due to this process and became useless. One of the most important phenomena that affect on sedimentation process is density current, so recognize the effective process in this phenomenon is very important for researchers and their management in dam’s reservoirs. Changing in successive cross sections inclusive convergences and expansions are the effective parameters on hydraulic of density current. The role of these factors in the density current phenomenon should be specified and the effective works done for management of reservoir sedimentation. So, in this research, we tried to investigate water entrainment of density currents in converging sections. The Experiments were carried out in a flume with changeable bed slope with three convergence angles (8, 16 and 25 degree), three discharges (0.58, 0.98 and 1.28 lit/s), three concentrations (10, 16 and 25 gr/lit) and three bed slopes (0.009, 0.0125 and 0.016). The Results showed that increasing of converging angle will increase water entrainment. Finally an equation is presented for water entrainment in convergent angles.

Proportional weirs in which the discharge is linearly related to the head are known as linear proportional weirs. Because of unit power of their head, linear proportional weirs are more preferable than other traditional weirs in some situations. In this research, based on theoretical concepts different linear proportional weirs having inverted triangular, chimney and two inverted triangular sections were designed. Then, the weirs were constructed and their linear relationship was examined experimentally. 180 runs were conducted to compile the data in the discharge range between 1 and 8 l/s. The data proved the presence of linear relationships for all the examined weirs. The results are shown that relative error of 50%, 66% and 73% of experimental data for inverted triangular weir, chimney weir and two inverted triangle weir are between 1%±. Also, it is observed that the two inverted triangular weir performed better than that of other two weirs, that is, the two inverted triangular weir data had the minimum deviation from its proposed relationship.

Partial root-zone drying (PRD) is a new deficit irrigation technique which improves water use efficiency. To evaluate the effect of PRD method on corn, an experiment was conducted at the Research Farm of College of Agriculture, Shahid Bahonar University of Kerman in the spring of 2010 using a randomized complete block design with three replications. The nineteen irrigation treatments were as follows: control, mild water stress (irrigation with 75% ETP), high water stress (irrigation with 50% ETP), fixed every other furrow irrigation (irrigation with 50% ETP) and three partial root-zone drying (change the wet furrows in every irrigation, change the wet furrows in every other irrigation and change the wet furrows in every second irrigations). Every deficit irrigation treatment was applied at three growth stages of corn (all periods of growth, vegetative growth stage and reproductive growth stage). The results showed that the highest WUE for dry forage yield was 2.67, for the biological yield was 6.02 and for grain yield was 2.13 kg/m3. Harvest index was obtained for different treatments between 0.25 and 0.48. In this study, the partial root-zone drying was the best choice to apply deficit irrigation for corn.

In this research, a two dimensional model is developed in order to simulate the dam break based on the finite volume method by using shallow water equations. At first, the shallow water equations are solved by cell-centric finite volume method on unstructured triangular grid. The flow computing method was Harten-Lax_va Leer based on the approximate Riemann solver. For development of the model in solving equations, the Second order spatial (Roe’s upwind) and third order temporal (Runge-Kutta) methods are used. This approach models the existing discontinuities and avoids the instabilities which are formed near dry and wet border. Finally the model is validated through some standard examples. Results showed that the mean percentage error of the model was 2.6 percent in comparison to the standard problems that confirms the model has appropriate performance in simulating dam break.

Decline in groundwater table and annually deficit more than 200 MCM, are the most important challenges in the Neyshabour plain aquifer of Khorasan-e-Razavi province. This research was conducted to study the role of developing the modern irrigation systems on sustainable management of groundwater resources. The effects of existing irrigation practices were evaluated using the Soil-Water-Atmosphere-Plant (SWAP) model. After model calibration, scenario of pressurized irrigation systems development for balancing the recharge and discharge of groundwater was studied. The results showed that change from surface irrigation to pressurized irrigation could cause decrease in water irrigation consumption (0-60%), decrease of deep percolation (2-90%) and improve in water productivity (0-140%). Use of modern irrigation systems for 30% of the total cultivation area of six main crops in the Neyshabour plain can decrease the discharge of groundwater aquifer about 22% without reducing in crop production. This is equal to 43 MCM of groundwater savings in the Neyshabour plain scale. If the results extend to other crops, it is expected that the scenario of pressurized irrigation systems development -without an increase in the area of cultivation- can compensate for 30% of the aquifer deficit in the Neyshabur plain.

In this study, the methods of Elliott and Walker two-point, Shepard et al., Valiantzas et al. one-point, Ebrahimian et al. two-point and NRCS were evaluated and the two new two-point methods were proposed based on Kostiakov and Kostiakov-Lewis equations. For this purpose, five data sets measured in the field under different conditions, e.g. length, slope and inflow discharge were used. Advance and recession phases were simulated using a hydrodynamic model (SIRMOD software) and mentioned infiltration equations’ parameters. The results showed that the second proposed and Valiantzas et al. methods had the lowest (7.98%) and the highest (24.09%) relative error in estimating total infiltrated volume, respectively. The second proposed and NRCS methods had the highest (23.2) and the lowest (1.07) standard error in prediction of advance and recession phases, respectively. The second proposed and Valiantzas et al. methods with average efficiency equal to 0.79 and 0.7 had the highest and the lowest accuracy in prediction of advance phase, respectively. Also, the NRCS and Ebrahimian et al. methods with average efficiency equal to 0.89 and 0.83 had the highest and the lowest accuracy in prediction of recession phase, respectively. The second proposed and Valiantzas et al. methods with an average coefficient of residual mass equal to 0.19 and 0.45 had the highest and the lowest accuracy in prediction of recession phase, respectively.

Bridge scour (contraction, pier and abutment scour) is one of the main factors of bridge failure. The bridge abutment scour has been reported to be one of the main causes of bridge failure around the world. Therefore, during the past decades, it has been trying to introduce new practical and economical methods for controlling abutment scour of the existing bridges. In this study, the effect of submerged vane on the scour abutment has been experimentally investigated. Different alternatives, including number of vanes, vane locations and different angle of vane have been studied under different flow conditions. The results were compared with tests without vane to find out the reduction of the scour depth. The results showed that the vane can decrease the score depth up to 89 percent. It was also found that a single submerged vane attached to the upstream corner of abutment with an angle of 40 degrees is the most effective alternative. The submerged vane was found to be highly effective in moving the scour away from around the abutment.

Stilling basins are one of the common structures for dissipating the kinetic energy in high speed flows. Among all types of stilling basins, the basins with the inverse slope of the bottom, because of its appropriate performance regarding the hydraulic jump’s parameters, are suitable alternatives for classic stilling basins. Since the weight of the hydraulic jump on the reverse slope affected the resultant forces on the volume control, extracting the mathematical equation for the profile of hydraulic jump and the actual length is necessary for accurate estimating of this component. Therefore, it would be worthwhile to find a solution that could consider an actual profile for the hydraulic jump and also remove the length of jump as an unknown from final equation. In this research, the linear, quarter-elliptic and parabolic profiles were considered to extract explicit equations for estimating the sequent depth of hydraulic jump on adverse slope. Comparing the results of extracted equations with experimental data showed that the theoretical equations based on the parabolic and linear profiles had lower error than the elliptic profile in estimating the sequent depth of hydraulic jump.

Limited water resources, shows the need for efficient use of water in agriculture. In this research, in order to increase water use efficiency of Cotton by using municipal wastewater, a field experiment was conducted at the experimental farm of Jopar Agriculture and Natural Resources Research Center in Kerman province during the 2011 growing season. The treatments were laid out in a strip split plot based on a Randomized Complete Block Design with three replications. The treatments were comprised of four levels of irrigation, including 100, 85, 70 and 55 percent of the crop water requirement in the main plot and subplot consisted of two irrigation systems (surface drip irrigation system (S1), subsurface drip irrigation system (S2)) and two water quality (groundwater (Q1) and wastewater (Q2)). The results showed that wastewater application had a significant effect on crop yield, water use efficiency and morphological traits. So that the crop yield and WUE increase 9 percent. Also that drought stress had significant effects on crop yield and crop yield components, and sever stress treatment (55 percent moisture depletion) caused 29 percent crop yield reduction. In comparison with surface drip irrigation system (S1), subsurface drip irrigation system (S2) caused increase all of the measured traits. The results of this study show that application of subsurface drip irrigation system and deficit irrigation for Cotton cultivation in Kerman with 85 percent of the cr...

In the recent years, many downscaling techniques have been developed for projection of station-scale meteorological variables from large-scale atmospheric variables by general circulation models (GCMs). In this study, the performance of three downscaling methods, including support vector machines (SVM), decision tree (M5) and K-nearest neighbor (KNN) methods of data mining models, were compared in downscaling precipitation simulated by NCEP general circulation models in the Kermanshah station. Simulation was performed between daily precipitation of Kermanshah station and NCEP model output parameters during the period of 1961 to 1991, and its result was tested during the period 1992-2001. The results of this study showed that the mean and standard deviation of output of the data mining models are less than the observed data and these models cant predict extreme values well. However, the KNN method gives better results than other considered methods.

Due to the importance of base flow in hydrologic processes and vital role in water resources management, estimation of base flow is an important issue. Graphical methods used to determine the base flow, significantly underestimate the contribution of this component. The results of isotopic and hydrochemical tracer methods in the humid regions, indicates a high proportion of groundwater component in runoff generation. The aim of this study is to investigate the role of groundwater flow in runoff generation processes in the arid and semiarid karstic Abolabbas basin, using isotopic techniques and hydrochemical tracers. For this purpose, during the winter of 2010-2011, three rainfall events with different antecedent moisture and intensity were selected and the corresponding floods were sampled. Hydrochemical parameters were measured in water quality laboratory of the water sciences faculty of Shahid Chamran University and Oxygen-18 isotopic content was measured in the stable isotope laboratory of Ottawa University. The results show that for all considered rainfall events, the contribution of groundwater component in runoff generation was considerably larger than the rainfall, due to karst development in the Abolabbas basin. The results also showed that the surface runoff component is minor for low moisture conditions, and it increases in the high moisture conditions.

Although the trickle irrigation systems have a high level of technology, but often unable to provide their potential advantages for several reasons. Therefore, evaluation of irrigation systems can discover their strengths and weaknesses and provide better operation by selecting and modifying management methods. In this study, 11 trickle irrigation systems were selected and evaluated in Kurdistan province. The measurements were performed according to the instructions released by the U.S. Soil Conservation service. The results showed that in most of the systems, the discharge of the drippers were less than their nominal discharge due to the unsuitability of the pressure, clogging and high coefficient of variation of the drippers. The ratio of wet area to total area was between 3.8 to 55 percentages. Emission Uniformity of systems was between 16.59 to 79.4 percentages. Application efficiency of low quarter of the fields varied from 16.6 to 79.3 percentages. Based on this index, only two farms had moderate performance and the performance of the rest were poor. The reasons of poor performance of systems can be imputed to the unsuitability pressure of systems, the pressure difference in the system, the large coefficient of variation of the drippers and weak management of the systems operation.

Inappropriate water use efficiency is one of the most important problems in agricultural section. The lack of farmer’s knowledge about the amount of crop water requirement and proper irrigation principals lead to excessive use of water in agricultural section. For this purpose in the present study water use amounts, water use efficiency and crop yields for Maize and Potato were estimated in 9 fields of Boroujen, Khanmirza and Shahrekord plains located in Chaharmahal and Bakhtyari province. Furthermore, economic analysis has been conducted among the fields to assess common management of this area. The results showed that water use efficiency with considering the dry weight of the crop, for the Boroujen, Khanmirza and Shahrekord plains were in average 0.51, 2.57 and 2 kg/m3, respectively. Highest net income per unit volume of water (9250Rials), belonged to Dehsahra farm located in Khanmirza plain. At this farm the used water was 30% less than the required water and so, this maximum net income was obtained due to high crop yield and less use of water in this field. The lowest net income per unit volume of water (1010Rials), belonged to Konark farm located in Boroujen plain in which the irrigation water was used 134% more than the crop water requirement. The highest and lowest values of benefit-cost ratio (B/C) (2.97 and 0.28) have been obtained from Dehsahra and Konark farms located in Khanmirza.

In this study, the hydrogeological and geological conditions of ground water storage reservoirs in margin of Gharehchay River were considered in determining appropriate locations of aquifer layers by interpreting geophysical measurements. The water table in the margin and along with Gharehchay River is semi-deep and deep. Sediment’s diameter decrease and conductivity of solutions increase when we go far away from the river, toward the North. The appropriate zones for forming groundwater reservoirs with thickness of 50 to over 60 m were specified based on the geoelectric mapping. The sediment layer depth reduces when go toward Northern and Southern highlands. In these zones aquifer thickness is less than 20 meters.

Seepage is one of the important problems in design, construction and operation of earth dams, for its influence on stability of dams and water losses from the dam reservoir. Nowadays, many softwares have been provided for solving the seepage equation using numerical methods. In this study, we tried to evaluate and compare the ability of two finite element based softwares, MSEEP and PLAXIS, for solving seepage equations in earth dams. For this purpose, the Karkheh earth dam was selected as a case study. The results confirmed the high ability of these software for simulating and estimating the seepage through homogeneous dams bodies, but the error of the results for the inhomogeneous section of the Karkheh earth dam was very high for MSEEP (50 percent), while the error of PLAXIS model was very small (3 percent). This showed the higher ability of PLAXIS model in solving complex problems of seepage.

Streamflow simulation is one of the main issues in hydrology which is usually studied using rainfall-runoff models. In this research, IHACRES model was applied to simulate daily and monthly streamflow in Navroud catchment located in Guilan Province. Model performance was evaluated using different error criteria. The results showed that the model could simulate daily and monthly streamflows with high accuracy. Comparison of daily and monthly results indicated that the monthly streamflow simulation was more precise than daily ones. Generally based on Bias index, the model underestimates the streamflow in the calibration period (in average 20.2 mm/year) and overestimates it in the validation period (in average 77.5 mm/year). The results showed that during simulation period, effective rainfall was about two-third of total rainfall over the catchment.

In order to increase water use efficiency of Corn, a field experiment was carried out at the experimental farm of Agriculture and Natural Resources Research Center of Orzoueyeh located in Kerman province during the 2010 growing season using a completely randomized block design with three replications. Four irrigation treatments (net water requirement (control) and suctions of 1/2 FC, 1/5 FC and 1/8FC) were applied on single cross 704 cultivar. The results showed that water use volume were decreased in the three suction treatments of 1/2 FC, 1/5 FC and 1/8FC in comparison with control treatment, 11, 13 and 17 percent, respectively. While, the crop yield of the mentioned treatments reduced compared to the control, 4/5, 28 and 34 percent, respectively. However, water use efficiency was increased in the suction of 1/2 FC treatment compared to the control about 6/5 percent that shows the superiority of this treatment than other treatments. The weight of 1000 seeds, number of kernels on rows, number of rows of kernels on Ear in the suction of 1/2 FC treatment in comparison with control treatment were 5, 6.5 and 6.5 percent, respectively. Therefore, it appears that the application of deficit irrigation method for Corn cultivation in Orzoueyeh, Kerman can be a suitable way for saving water and increasing water use efficiency during drought periods.

The present paper tries to discuss about the importance of getting accurate knowledge of flow properties for predicting and analyzing the governing nature of the river flow. With regard to the important effect of the flow velocity and shear stress forces on river bank erosion, we applied a two-dimensional numerical model, namely CCHE2D, to simulate river flow pattern at a meandering river reach, Khoshk-e-Rud River of Farsan, located 30 Km west of Shahrekord city. For this purpose, at first, we designed the model geometry and mesh grid by using the topographic maps of the studied location. In the next step, the measured properties of the river flow were entered into the model and the Depth-Average, Two-Dimensional Hydrodynamic Model was run. The model outputs such as depth and velocity distribution of flow were extracted from the river bend section. Based on the obtained results the calculated and observed flow velocity values at three cross sections were 0.90, 0.914, 0.978; 1.01, 1.02 and 1.174, respectively. The calculated and observed values of flow depth were 0.937, 1.016, 0.892; 0.947, 0.839 and 0.890, respectively. It can be concluded that the values calculated by the model have a good compatibility with observed data at the considered meandering river reach.