Journal of Irrigation Sciences and Engineering
Year:2017 | Volume:40 | Issue:2 |Papers Count:20

The purpose of this study is to compare the scouring hole geometric dimensions for three kinds of spur-dike: permeable, impermeable and bandal-like for submerged conditions by conducting a set of experimental tests. Bandal-like is made by combining permeable and impermeable spur-dikes.Experimental tests were carried out in a straight flume at a constant structure height equal to 12 cm and three angels equal to 60, 90, 120 degrees at a constant flow condition (Fr=0.24, y=16 cm). Results were presented as bed topography, depth, length and width of scour hole. It was found that the ratio of maximum scour to flow depth occurs at 90, 120, 120 degrees for impermeable, permeable and bandal-like spur dike, respectively. Permeable part of bandal-like was found to be effective in decreasing the ratio of maximum scour depth to flow depth and the ratio of scour width to flow depth. The ratio of maximum and minimum scour width to flow depth occurs at 60 and 90 degrees, respectively for three kinds of spur-dikes. The ratio of maximum scour length to flow depth in impermeable, permeable and bandal-like occurs at 90, 60 and 60 degrees, respectively. Impermeable part of bandal-like was found to be effective in increasing the ratio of maximum scour length to flow depth.

Stilling basin is one of the dissipated energy structures in water transfer systems that its dimensions depend on the characteristics of hydraulic jump. In present study, six legs elements have been used in different permeability on basin bed and the changes of shear stress, sequent depth and the length of jump have been investigated. Experiments were conducted in a rectangular flume of 7.5 m long and 0.3 m wide and six legs elements were arranged on the bed of flume with density percent 36, 63 and 100 in such a way that the incoming water jet was just above the elements surface. The incoming Froude number was in the range of 5.3 to 8.1 and during each test the water surface profile and characteristics of hydraulic jump type A were measured. The results indicate that the most reduction of sequent depth ratio and dimensionless length of jump occur when the density of elements is 36%. In this study, relations have been presented for the sequent depth of hydraulic jump and shear force coefficient of bed as a function of the Froude Number for six legs elements.

Since the withdrawal of the observation wells at the plains done for the point, it is necessary to calculate the average groundwater level and also generalization the estimated water level from collected point to the surface of plain. The aim of this study is an investigation on the application of combined geostatistics method with optimized artificial neural networks by genetic algorithm in interpolation of groundwater level over Dezful and Zeidoon plains located in the Khozestan province. The obtained results from Cokriging, Kriging and IDW methods indicated that Cokriging with the Gaussian variogram and cross-variogram in Dezful Plain, and Kriging with the Gaussian variogram in Zeidoon plain are the best geostatistical methods for estimation the groundwater level and combined with artificial neural networks. Also the results of combination these two models showed that optimized model by genetic algorithm have better evaluation criteria than geostatistical methods and proposed as an effective combined model for estimation of the groundwater level. So that an application of this optimized combined method in Zeidoon plain with fewer observation wells was better than Dezful plain.

Nitaret is one of the stable components of nitrogen in the nature. Nitrate compounds are highly soluble and can easily imported to the surface and groundwaters and finally lead to be polluted of them. Denitrification is one of permanent removal methods of nitrate from terrestrial and aquatic ecosystems. In this study, denitrification process and nitrate removal rate changes with time in a column experimental study was evaluated on two types of denitrification beds, first type was a mixture of bagasse and soil (30 % of the volume of bagasse and 70% of the volume of soil) and second type was only soil without bagasse. All experiments were performed under saturation conditions (anaerobic conditions). The influent nitrate concentraion to the all beds was considered an average of 45 mg/l. With sampling of inflow and outflow of the columns, nitrate removal changes were assessed over a period of three months. The maximum percentage of nitrate removal in columns with mixture of soil and bagasse were occurred in the end of the experiment (94%) and in columns without the bagasse were ocured in the first of the experiment (89%).The results showed that sugar cane bagasse as a carbonic source can be very useful in the design of carbonic filters and denitrification walls for nitrate favorable removal of inlet concentrated solutions. Overall, the results confirm that the denitrification process is one of the main mechanisms of biological nitrate removal from anaerobic enviroments.

In this study downscaling of temperature was down in Tajan Plain located in the province of Mazandaran. The result of atmospheric general circulation models was obtained with HadCM3 climate model under scenario A2. Since the output of atmospheric general circulation models has a low locative resolution, should be downscaled in the area or Basin level that it was conducted with statistical method. The statistical methods used included of downscaling SDSM 5.5. And artificial neural network model. In this study, by using the average daily temperature data of Kordkheil Station during the30-year statistic Period (1971-2001) and the large-scale variables NCEP, as inputs to the neural network and SDSM model, simulation and downscaling was down respectively of the maximum and minimum temperature in the last period to determine models error. To this end were used of the features and functions available in the programming software MATLAB. Then To evaluate the performance of the models, were used the statistical criteria including of correlation coefficient, coefficient of declaration and root mean square error between observed and predicted values of temperature. The obtained results show the appropriate performance of SDSM model for downscaling temperature Than the ANN model. So that the error percentage of SDSM model is lower and the correlation coefficient is more than the ANN model. The best Structure of neural network to simulate of maximum temperature is perceptron model with four hidden layer with the 5-5-6-6 architecture and for the minimum temperature Variable is perceptron model with three hidden layer with 5.3.1 architecture.

A review over the rainfall-runoff studies shows that, humid regions have received worth more attention than arid and semi-arid regions. So that, in this study, the rainfall-runoff process of an arid and semi-arid district, namely; Bar Arye Watershed with an area of about 112km2 and a mean annual precipitation of 307mm was simulated by using the spatially distributed rainfall-runoff model, WetSpa which has the ability to be connected to the geographical information systems. The period from 2003 to 2008 was applied for modeling. In the present study, according to Nash-Sutcliff criteria with the value of 0.69% for the validation phases it was indicated that the model has shown a good performance in modeling the rainfall-runoff. The rainfall-runoff coefficients of the observed and simulated values were equal to 0.59 and 0.57, respectively. This shows that the model has a good performance in estimating the values of runoff.

Nowaday, the impact of global warming and climate change because of the increased effects of greenhouse gases in the atmosphere has been observed in many natural systems. All the general circulation models of the atmosphere predict warmer future for the earth. Hydrological processes such as rainfall and river flows as one of the main sources of water supply basins could be affected in such circumstances. Due to the low spatial resolution or simplification of some micro-scale phenomena in atmospheric general circulation models, these models cannot be employed for accurate approximation of the climate of the considered area, therefore, their output must be down scaled to the meteorological station range. In this study, the data of HadCM3 general circulation model down scaling with the use of LARS-WG model under two scenarios A2 and A1B and Parameters of daily rainfall, minimum temperature and maximum temperature of the Sufi-Chi basin generated for three periods (2011-203, 2046-2065-, 2080-2099). To assess the effect of climate change on runoff is used from artificial neural networks and genetic programming of intelligent model. The results indicate that the rainfall will increase in 2011-2030 and will decrease in the further future. Also the maximum and minimum temperatures will gradual increase in three periods of future and the amount of runoff will decrease in future than current time.

Rain water harvesting methods is the include of management methods in order to encounter and compatibility with the conditions of the lack of water. Base of these methods, is allocating surfaces of the earth in order to collecting, storing and reusing rain water for designing goals at the times needed. The necessity of the implementation of the plan is that We' re seeing that in any relatively intense rainfall occurs, The Eclipse occurs on roads and utilities and the damage to the House, that is required to a big city like Tabriz to have a macro system to reduce any damages caused by the floods and also be able to take maximum advantage of this current of water. In present research, In order to increase accuracy in using the methods of estimating runoff, facilitate the access and reduce the cost of transferring, the study area was divided to 4 sub drainage basin. Runoff derived of the four zones was computed with the SCS method. The volume of the reservoirs were designed with the use of the method of runoff frequency analysis for different seasons and with different return periods. Comparing green landscape monthly water requirement with rain water of Tabriz, clears that reservoirs are able to provide about 48 percent of the need for green landscape and the rest of the need, can be provided through the underground water and the incoming water supply to the city.

Water and fertilizer are the most important inputs for producing agricultural crops. Simulation models that quantify effects of water and fertility on yield at the farm scale are valuable tools in water and irrigation management. The AquaCrop model, which has recently been developed by FAO, predicts crop productivity and water requirement under water and fertility stress conditions. In this research, capability of AquaCrop model in simulation of Corn yield response to different levels of water and fertility was studied in Karaj. A field experiment was carried out in 2008 and 2010 years. A factorial design based on randomized complete block design accomplished with four levels (60, 80, 100, and 120%) of the irrigation water requirement and four levels (0, 60, 80 and 100%) of the recommended fertilizer value. Sensitivity analysis showed that the model was sensitive to initial moisture content, time from sowing to start senescence, Reference harvest index (HIo), normalized water productivity (WP*) and maximum coefficient for transpiration (KcTr) more than other parameters. Results showed that the AquaCrop model was able to simulate the grain yield under water and fertility stress, in both years. The normalized maximum error (ME), normalized root mean square error (nRMSE) and coefficient of determination (R2) were calculated 24.77, 9.27 and 0.92 respectively, in validation year. The model was able to simulate the grain yield and crop evapotranspiration (ETC) in non-water stresses (ME, nRMSE an R2 were 9.9, 6.21 and 0.97, respectively) and non-fertility stresses (ME, nRMSE an R2 were 9.9, 6.21 and 0.97, respectively) satisfactory, but it was not satisfactory in simulating sever irrigation and fertility stress. Most deviations from observed data in severe water treatments (ME, nRMSE an R2 were 24.72, 16.61 and 0.66, respectively) occurred.

Nowadays, due to drought and lack of water, using of low quality water have been addressed especially from wastewater that before was considered as a source of pollution. Now it considers as a source of nutrients for irrigation of plants. This study tried to investigate the effect of different quality of irrigation water mainly; dairy effluent farm and water wells (W) as control with surface irrigation methods on the performance of maize 704 single cross in 2013 in Shahrekord University. In this study, treatments were effluent of four parts of Saman dairy industrial farms named DEsep, DEshir, DEkol, DEsalon. All growth and yield indexes was measured such as plant height, stem diameter, leaf numbers, wet and dry weight, number of ears per plant, number of kernels per corn and the percentage of dried treatment. The result shows that the mentioned parameters observed was maximum as 148.63, 2.29, 308.01, 80.14, and 28.05 in DEshir, respectively. It was minimum as 74.75, 1.63, 117.1, 17.50 and 10.84 in DEsep, respectively. The results show a significant effects of dairy effluent farm on plant yield, and it can conclude that dairy effluent farm can be a suitable alternative for chemical fertilizers. In this study, the controlled treatment (W) that was irrigated just by well water, because of the lack of nutrient supply, in terms of yield was lower than dairy effluent farm treatment. It seems that the macro and micro nutrients in dairy effluent farm, especially nitrogen can increase stem elongation and stem diameter. As a result, the wet and dry weight increase with the use of consumption of dairy effluent farm.

Modeling of the rainfall-runoff process is important. The Results of the rainfall-runoff models have been used directly on issues such as water resource management, flood control and design of hydraulic structures. According to variety of accessible rainfall runoff models, selecting an appropriate model for a basin is important in terms of productivity and water resources management. In this study the performance of two rainfall-runoff models, IHACRES and GR2M in simulation of monthly flow were evaluated in Darhe Tkaht basin between 2000 and 2013 time. The models in the study region were calibrated and validated. The error between observed and simulated flow values was estimated based on the criteria Nash, root mean square error and the total flow volume error. Simulations is indicative satisfactory performance of two models in monthly flow simulation. In addition, the results show that the HACRES model simulate monthly flow with The Nash coefficient 0.7 and RMSE 0.56, better than the GR2M model.

Snow is a form of precipitation that plays a key role in runoff generation at mountain climate watersheds. Because of a time delay between the snowfall and its melting process, the generated runoff has a differnet behavior than other form runoff generations. DarbandSamalghan is one of the important mountain climate watersheds in North Khorsan province that its snowmelt runoff has a significant influence in the watershed streamflow. In this study a snowmelt runoff model (WinSRM) applied for runoff simulation during the two water year 2010-11 as calibration and 2011-12 for validation by using the MODIS satellite data. The model can estimate the snowmelt runoff using metorogical, hydrological and physical characterstics of the watershed as well as provinding the output simulations in diffrenet form of charts and values. The results showed a good agreement between the simulated and observed streamflow data. The determination coefficient and difference volume were 0.88 and -3.3 % for the first year, and 0.72 and 0.3 for the next year of simulation respectively. Finally, results of this study indicated the high capability of the WinSRM model and this model can be applied for the other watersheds in the region.

Since the characteristics of density current is affected by different parameters, the effect of discharge rate changes, gradient and the concentration of density current on speed of the forehead and also the speed distribution in density current's body have been investigated by physical and three-dimensional mathematical model (Flow-3d) in this research. For these purposes, different tests in the form of salty density current were done with three inflow discharge rates (0.7, 1 and 1.3 liters per second) and three different slopes (0, 1 and 2.2 percent). As well as to evaluate the effect of density changes on the flow characteristics, the concentration of 10, 15 and 20 grams per liter were used. In order to measure the speed of the forehead, velocity distribution in the body and its changes with flow, density and different slopes, video camera and ultrasound profiler speedometer were used in this study. Then, forehead speed and velocity distribution in the current's body were achieved using six different turbulence models which are available on the software of "Flow-3D". Comparing the results of physical and mathematical model showed that Eddy turbulence model and laminar flow mode have better accuracy in relation to other turbulent models. It should be noted that Reynolds number on experiments are at the range of 2000-4000.

In order to dong this study, daily data of 34 meteorological variables during 1/1/1961 to 30/6/2013 from Urmiah synoptic station has been used. Cluster Analysis with Ward method applied on the Euclidean distance. The numbers of clusters determined by quality control inter group's variance Indices. The results show that clustering air mass to seven groups is the optimum. The second air mass is the most rainiest air mass which its rainy occurrence probability equal to 65.7% and the amount of precipitation per day equal to 6.6 mm. The fourth air mass is the hottest and drier air mass which has observed in the one third of year’s day. The fourth air mass with the occurrence index of 0.89 and with persistency of 9 days is the most stable air mass. While the third air mass with the occurrence index of 0.43 and with persistency of 1.7 days is the most unstable air mass. The third air mass with sequantality of 21.1% is the most agreeable air mass which occurs after the second air mass subsequently. Daily variety of air mass index get highest value during winter season (69%) while it gets to zero in some days of July and August which indicates a certain air mass (the fourth).

Achieving sustainable water resources has been considered as the biggest challenge of sustainable agriculture among the majority of countries across the world. Obviously, preserving water resources requires optimization of water consumption in different sectors, particularly in agricultural section. This study has been carried out with the aim of water use management reform via applying deficit irrigation techniques in order to promote potato plant productivity and water use efficiency (WUE) indicator in Shahrekord area. Accordingly, management indicators' quantities such as application efficiency, distribution uniformity and irrigation adequacy were measured and compared at the rates 60, 80, 100 and 120 percent supplying conditions of potato water requirement in the form of a complete randomized block design with three replications from June to October 2014. Determining aforementioned management indicators requires sufficient knowledge of the distribution pattern and amount of percolated water. In this regards, mentioned management indicators were determined by designing and installation of the six simple WFD devices at the beginning, middle and end of each furrow in two different depths. The distribution pattern and the amount of percolated water along the furrows were followed, measured and evaluated. Based on the results of this research, the average application efficiency of mentioned water treatments were calculated as 81.26, 68.09, 56.26 and 46.92, respectively. While, the lowest levels of adequacy efficiency and distribution were equal with 86.29 and 75.56% which was related to 60 percent treatment, respectively. Eventually, the findings indicated that irrigation management of potato farm in the study region will bring about the highest water use efficiency (WUE=1.83KG / M3) with considering MAD of 47 percent and water application equal to 80 percent of water requirement.

Flood is a stochastic phenomenon and successful and construction of economic dam in flood discharge system is very important. In recent years, non-linear overflows, as a solution, helped designers and engineers of water sciences. In this study, new non-linear overflow weirs as Crown Wheel spillways are introduced. Discharge coefficient tests were performed under various scenarios geometry of the overflow in order to investigate the ability of the hydraulic overflow flood discharge. To study the effect of the slope floor of inlet and outlet keys (Z) on the current discharge coefficient, the slope of 1: 0.5, 1: 1 and 1: 1.5 (Horizontal: Vertical) were designed and built. Then in each of the three phase variation in the slope floor of inlet and outlet keys (Z), four types of spillway with a crest length of two, four, six and eight cycles were designed, built and tested. The results indicated that by increasing the slope of inlet and outlet keys (Z), discharge flow rate will be increased. This also increases the number of cycles at low heads, leading to an increase in the flow discharge coefficient. In large heads, the feature of vortex breaking in overflows with the less number of cycles is noticeable. The results showed that the coefficient of discharge in Crown Wheel spillway is to 2.2 bigger than in a circular vertical sharp edged weir. Due to the small dimensions of this type of overflow compared to similar types, this nonlinear overflows can be considered as an efficient and economic flood discharge system for introduction to the scientific community of the country.

Determination of the field-saturated hydraulic conductivity can result in very high variability. So, analysis and simulation of hydrological processes such as runoff from rain requires a lot of data of field-saturated hydraulic conductivity even on a small scale. To identify this variability as well as its source, eight widely used measurement methods were compared: (Double-ring, Single-ring, Guelph permeameter, Tension infiltrometer, BESTslope, BESTintercept, Wu1 and Wu2) to evaluate the BEST method. In the single-ring method was used a metal cylinder with a radius of 10 cm. It was found that the maximum and minimum estimates of hydraulic conductivity are in Wu1 method (0.104 cm/min) and tension infiltrometer (0.0063 cm/min), respectively. The methods of double-ring, single-ring and Tension infiltrometer were not statistically significant differences at 5%. BEST methods were not statistically significant differences but BESTintercept method 28% more than BESTslope method. According to the experiment data, Kfs was estimated using the BESTintercept method is closer to reality than BESTslope method. In generally, the BEST methods can be a good alternative to estimate field-saturated hydraulic conductivity and prevent from a lot of field measurements.

Different models are provided for estimation of evapotranspiration that the main difference between them is the number of meteorological parameters needed, but due to the lake of the reliable long-term data in some stations, use of model with little data is needed and it will be necessary to help planners. The Simulation of EvapoTranspiration of Applied Water (SIMETAW) model is used for simulation of weather data from climatic records and estimation of reference and crop evapotranspiration with the simulation data. In this study, using the monthly values of four synoptic stations (Rasht: Very wet climate; Shahrekord: Semi arid climate; Ahvaz: Arid climate and Sanandaj: Moderate climate) in the period of 1961 to 2001, the ability of model for simulation of climate variables (maximum temperature, minimum temperature, dew point temperature, wind speed, solar radiation and precipitation) and potential evapotranspiration was evaluated and daily Et0 simulated using meteorological data, were compared with calculated values of potential evapotranspiration from observed meteorological data. To compare the results, were used from Coefficient of Determination (R2), Root Mean Square Error (RMSE) and index of agreement (d). The results showed that model simulations in all stations has acceptable accuracy. The highest accuracy in simulation maximum temperature (R2=0.9954) and precipitation (R2=0.3716) related to mediterranean climate, minimum temperature (R2=0.9947) and dew point temperature (R2=0.9942) Related to humid climate, wind speed (R2=0.8094) related to dry climate and solar radiation (R2=0.9902) related to semi-arid climate. The highest accuracy of SIMETAW model in simulated evapotranspiration related to Mediterranean climate (R2=0.9936), semi-arid climate (R2=0.9935), dry climate (R2=0.9903) and very wet climate (R2=0.9846) Respectively. Given the high correlation between simulated and observed values, SIMETAW model can be used for simulation of the climate data and estimate the potential evapotranspiration, net irrigation requirement and also filling the gaps in four climatic regions.

Every year, natural disasters and catastrophes such as hurricanes and tsunamis cause coasts destruction and bring irreparable damages to the life and properties of people. Recent approaches of coastal protection are based on environmental balance and stabilization. the new method of coastal protection is planting coastal forest lines known as green belt. Coastal green belt confronting toward coastal protection and damage reduction is through increasing the resistance to incoming wave to the coast and absorbing part of its force. Hence, the aim of present study is to investigate the effect of coastal vegetation density on variations of destructive solitary breaking waves force and drag coefficient of coastal forest. To this purpose, a sloping coast and a coastal vegetation model were installed in a flume equipped with a frictionless force measurement system. The experiments were conducted in four different coast slopes in both with coastal vegetation and without coastal vegetation model (three coastal vegetation density). The results indicated that the presence of coastal green belt reduce the destructive force of the waves to a bout 60 percent on average.

Due to accuray of numerical methods and constitutive equations, a comparison of these methods with the classical methods of dynamic analysis of earthfill dams seems necessary. The results of Seed-Makdisi, Sarma and Ambrasys-Sarma analysis of a homogenous dam are compared with those of Quake/W and Slope/W softwares. A code is developed for calculating permanent displacements based on Newmark double integration method. The results of linear and equivalent linear models show that, due to unrealistic linear assumption of the behaviour of the material, the calculated accelerations are high and the analytical methods are overdesign. This is due to realistic constitutive models. Also, in homogenous dam, as the assumed critical wedge in analytical methods is different from that calculated in numerical analyses, the critical acceleration estimated is different too (0.45g in Ambrasys-Sarma method compared to 0.26g in equivalent linear model for a wedge of 0.6h depth). This shows that realistic models must be utilized. In the developed code first the average aceleration of assumed wedge is calculated using acceleration calculated with finite element codes utilizing modern constitutive models and consequently the permanent displacements are calculated. The results show that the current methods are overestimating. Also, the assumed critical wedges are unrealestic and pass through the dam core. While the critical wedges pass through downstream shell. The permanent displacement of a wedge with 0.6h depth is estimated to be 3 cm compared to zero in Sarma method. The developed code was used for dynamic analysis of Balarud earthfill dams.