Journal of Irrigation Sciences and Engineering
Year:2017 | Volume:40 | Issue:1 |Papers Count:21

Estimation the exact amount of water that is used for evapotranspiration, is the major factor in planning for achieving higher production and its most important parameter of management of water in plants. In terms of lack of access to accurate data lysimeters may use the FAO- Penman-Monteith method as the standard method to evaluate the experimental results. In this study using 15 years of weather data of Ahvaz (1998-2012) evaporation pan coefficient has been calculated with the equations of Orang, Snyder, Cuenca, Allen and Pruitt and their results were compared with the FAO Penman-Monteith. Also for choosing the best model, between five coefficient of determination parameters, Root mean square error, the mean absolute error, the slope and width of the source rank test was performed and the results showed for daily and seasonal pan coefficient calculation is better to use Allen and Pruitt and in ten-day use Snyder in Ahvaz climate.

Gravity current is a phenomenon caused by density difference between two fluids and due to this phenomenon the fine sediments can be moved to the body dam and as a result causes for many serious problems for dam intake. Therefore, controlling the flow can reduce the potential problems. In this study a permeable obstacle was used to evaluate the performance of permeable obstacles for control of turbidity current. The variables were the porosity percentage of the obstacle and different concentrations of the currents. The gravity current discharges and concentrations were measured upstream and downstream of the obstacle. The results of the measured discharges showed that the obstacle efficiency in control of gravity current reduces with increasing porosity. The results of the measured concentrations also showed the same conclusion. The final results of the review sediment load and view similar trend was confirmed. After calculating water entrainment to the gravity current passing through the permeable obstacle, it was observed that with increasing porosity of permeable obstacle, the volume of water entrainment is reduced. Therefore it can be concluded due to lower volume of water entrainment, processing efficiency in controlling the gravity current using the permeable obstacle is reduced. Also, the maximum efficiency of the controlling the gravity current was measured about 73.2%.

Scouring is a natural phenomenon that arises from the erosive action of flow field in the alluvial streams. Bridge failure caused by fully scouring of the piers and abutment makes completely clear the necessity of investigating in the case of scour prediction and ways to protect against it. One of the ways to reduce scour is utilizing the six-based elements (A-JACKS) around the abutment. In this study, the impact of the structure known as six-based elements on the control of the maximum scour depth of the bridge abutment was investigated as well as the scope of locating the six-based elements in order to safeguard the bridge abutment in front of the scour has been studied. The tests were performed with Froude numbers of 0.18, 0.208, 0.235, and 0.25 and in 4 placement scopes (W) of 4, 6.5, 8.5 and 10.6 cm.The scour was decreased one hundred percent in the Froude numbers of 0.18 and 0.208, and scopes of two-row (W2), three-row (W3) and four-row (W4). Froude number of 0.235 and scopes of three-row (W3) and four-row (W4) reduced fully the scour and the Froude number of 0.25 and scope range of four-row (W4) controlled 98.55% of the scour. In comparison with the performance of two scopes, the maximum six-based elements namely W3 and W4 were observed in the maximum Froude number that only have 7.47% difference in the reduction rate of the scour and have completely the same performance in the two Froude numbers of 0.18 and 0.208. In conclusion, it can be stated that the use of W3 range is most optimal mode of replacing elements around the abutment, because it has approximate performance to W4, but the cost and time of its construction is low.

Having unsteady flow in water supply systems due to the change from one stable state to another stable state is inevitable. On the other hand, over time, the various causes lead to the pipeline leakage or even a pipe fracture. So, with presence of leak, investigation of characteristics of unsteady flow that is an integral part of the hydraulic system will be of particular important. In current study, the fast unsteady flow that is one of the most damaging types of flow is simulated by laboratory considering leak in pipeline and with respect to that, the impact of leakage characteristics such as size and location of the leak on the hydraulic properties of unsteady flow will be evaluated. The experiments were carried on a tank, pipes and valve system that made of 63 mm polyethylene pipe with length of 47 meters and a height of 5 m for static water head in tank. A total of 3 discharges, 4 leakage diameters, 4 leakage positions and 2 fasten time of valve were tested that illustrate gradual valve fastening cannot show the leakage in pipeline system. Peak pressure drop in the first period of wave increases with increasing diameter and slope of the pressure drop caused by a leak in the first peak are faster for the leaks that nearer to the valve. Also, the pressure wave damping slope is steeper in the case of leakage with a greater diameter than leakage with a smaller diameter.

Heavy metals pollution is a topic with worldwide concern because of its high toxicity to human beings, animals, and plants. The clay minerals, being important constituents of soil, have been playing this role always by taking up various contaminants as water flows over soil or penetrate underground. The high specific surface area, chemical and mechanical stability, layered structure, high cation exchange capacity (CEC), Bronsted and Lewis acidity, etc., have made the clays excellent materials for adsorption. In this study, retention process of Cd (II) contaminant using Bentonite and Nanoclay Cloisite Na+ investigated. Based on data obtained in this study it can be concluded that the retention capacity of Nanoclay Cloisite Na+ is much more than Bentonite for Cd ions, because of high specific surface area and high cation exchange capacity of Nanoclay Cloisite Na+.

The fertility of agricultural land is a function of the amount of organic material available in the soil. Due to the low amount of this material in the agriculture soil, use of organic materials is important. Biochar is a kind of organic materials which has high stable properties, in recent years attracts the attention of researchers. The goal of this research was to study the effect of sugarcane bagasse biochar on some chemical properties of a sandy loam soil. For this purpose, from prepared biochar in different temperatures of 200-600°C, biochar products in temperature of 300 °C which had the highest stable organic matter yield index (7.2%) was selected as the optimum biochar. Then the effect of this organic matter, after mixing it with a sandy loam soil at 4 levels (0, 2, 5 and 10 g per kg soil), on chemical characteristics of this soil, such as organic carbon, total nitrogen, available phosphorus, cation and anion exchange capacity were determined. The results showed that the addition of sugarcane bagasse biochar in all levels caused increasing significant of organic carbon, total nitrogen, available phosphorus, anion exchange capacity, EC, cation Exchange capacity and decreased pH of the soil. Sugarcane bagasse biochar with treatment of 10 g per kg soil showed greatest impact on anion exchange capacity of the soil (7.4 times compared to the control) and the lowest impact on the reduction of soil pH (0.01 times compared to the control).

Based on water deficits and the severe limitation of water in the country, one of the basic steps for the management, planning and water supply in available and developed projects of catchments, is estimation the maximum yield values. As flow regime in catchments is usually regular and affected by the series and parallel dams, use of appropriate and applicable methods are necessary. In this research, a yield model based on linear programming, for three reservoirs- Zohre catchment in south-west of Iran, has developed. The base of this model is including reservoir storage continuity equations, stream flow expressions in each reservoir, water allocation equations, and storage capacity limitation. The objective function is the maximization of total monthly yield for a long-term period of inflow that can be released from reservoir dams to supply demands in water resource systems. After implementing of the yield model, the modified shortage index in the water resource system has improved in comparison to Standard Operating Policy (SOP) and it has been effective in adjusting severe deficit. The results showed that the reliability for satisfying demands in developed future condition of zohre water resource system is about 83% and the yield is about 65% of demands.

Evapotranspiration is one of the most important parameters in the Planning and operation of reservoirs, designing of irrigation systems. The practical importance of accurate estimates of evaporation and the complexity of effect phenomenon, shows the use of new methods of data mining. In this study, the simulation of pan evaporation in Tabriz station using multiple regression models were investigated. Meteorological data, including maximum and minimum air temperature, dew point, maximum and minimum air relative humidity, number of sunshine hours and Daily wind speed during (1992-2012) were used in synoptic Tabriz stations. Various models of multiple linear regression and nonlinear one were derived for Tabriz station. The selected multiple linear regression model were tested by Ridge Regression method to be considered multi-collinearity among inputs in the model. Variance inflation factor, values for each variable were calculated. The results showed that all Variance inflation factor, s had the value less than 10. In addition, the ratio lmax/lmax for two- variable selected model was 3.34. Therefore, there was no multi-collinearity in the selected multiple linear regression model f (Tmin, n). Durbin-Watson statistic for the selected model was 1.45 that shows the reliability of the selected multiple linear regression model. RMSE and R2 values of the selected models (multiple linear regression and Non- Linear Regression) was calculated as 2.45 and 0.67 and 2.58 and 0.65, respectively. This results demonstrate the ability of regression techniques to estimate Pan evaporation in Tabriz station.

For accurate simulation of transport in natural rivers, some revisions have to perform in classical advection dispersion equation and some terms for considering of transient storage zones added to this equation. In this study a new and comprehensive model that merges numerical schemes with higher order accuracy (QUICK scheme) for solution of advection dispersion equation with transient storage zones in rivers with irregular cross sections at unsteady flow regime is presented. The presented method is verified by analytical solution, hypothetical example and two sets of real data. The results of verification implied that presented model have reasonable accuracy in simulation of contaminant transport in this condition. Also with implementation of model in the case of pure advection and comparing the results with two other numerical model results that use from centered difference method in spatial discretization of equations the ability of presented model in more accurate simulation in this case is shown. Results show that presented model in this study, is an applicable model and could be suggested as alternative for common present models at contaminant transport studies in natural rivers and streams.

Solar radiation is an essential factor in irrigation scheduling, hydrological cycle, crop growth simulation models and estimation of reference evapotranspiration. The aim of the present research was to investigate the accuracy of solar radiation estimation models and their effects on reference evapotranspiration. For this purpose, the meteorological data of 4 synoptic stations including Urmia, Takab, Salmas and Mahabad in West of Urmia lake catchment in daily scale were used. Solar radiation was estimated using seven models including, Hargreaves- Samani, Allen, Self-Calibrating, Samani, Annandale, Bristow-Campbell and Angstrom- Prescott. Then, the obtained values were used in FAO- Penman- Monteith equation to estimate the reference evapotranspiration. In order to evaluate the models' accuracy, the statistical indicators including root mean square error, mean bias error and determination coefficient were used. The evaluation results of the models showed that the Angstrom- Prescott model had the best performance, and the Samani method was the weakest method in the studied stations. The average values of the root mean square error for the Angstrom- Prescott and Samani methods in the studied region were obtained 0.48 and 1.43 mm/day, respectively.

A density current is a (two-phase) flow of a fluid of density which is caused essentially by the influence of a density difference on the gravity. The previous experimental studies have been focused on investigation into properties of gravity current in straight channels. This paper presents a series of experiments in which saline gravity currents flowed through in physical models laboratory of Shahid Chamran University of Ahvaz. Experiments were carried out in 8.5 m length, 20cm width and 70cm height of flume and three radiuses of curvature (40, 80, 120 cm). In this study the effect of three radiuses of curvature of channel bends on density flow behavior were studied. Experiments performed by four discharges(0.5, 0.7, 0.9 and 1.1 L/s) and four concentrations (8, 12, 16, 20 and 40 g/L). An Acoustic Doppler velocimeter (ADV-Vectrino+) was used to record the instantaneous downstream velocity. The Vectrino Velocimeter measures water speed using the Doppler effect. The results show that the elevation of the interface at the outer bank is in every case greater than the one at the inner bank. The results show that due to increasing the relative radius of channel bend decreases elevation of the interface and transverse interfacial slopes. The maximum and minimum superelevation occur in r/b=2 and r/b=6, respectively.

In order to better exploitation of the available water resources and to prevent water crisis increment, predicting the changes in water resources through different methods will be of great importance. In this study, monthly data of water table elevation, consumptions and precipitation during the period of 2001 to 2011 for Ajabshir plain were used to predict the water table elevation through two methods. The first method is to solve the application of partial differential equation for consecutive time steps and the second one is the proposed regression model. The finite difference method was used for the temporal solution of the differential equation which leads to gain a correlation coefficient of 0.9 and an RMSE of 0.41 between estimated and observed values of groundwater levels. To determine the time period for the effects of precipitation and consumptions on the water table elevation, the cross correlation function wasused; which indicated great impact of precipitation and consumptions on water table elevation with one and two lags respectively. Finally the general relationship between these three variables with time period effects through a multivariate nonlinear regression model was obtained via a correlation coefficient of 0.93 and RMSE of 0.35. According to the evaluation criteria derived from two methods, the multivariate regression model was selected.

Maximum Allowable Depletion (MAD) by affecting on number of irrigation in growing season and irrigation use reduction can be used as a managerial tool to save water. The purpose of this study was to investigate the effect of MAD in irrigation interval, applied irrigation water, top and root growth of grass under subsurface drip irrigation system. Three irrigation treatments which were MAD equal to 40% (W1), 60% (W2), and 80% (W3) arranged in a randomized complete blocks statistical design with three replications in 2012 and 2013 in Isfahan University of Technology. The soil moisture was measured daily using Moisture Meter GMK-770S in the root zone depth of grass to manage irrigation. The apparent parameters and root parameters of grass were collected periodically. These parameters were analyzed by Duncan's multiple range test and the results showed that the irrigation treatments had no significant effect on the root growth parameters and top weight. In the depth of 0-13 cm the maximum root volumetric density and fresh and dry root weighted density were occurred in W1, W2 and W3 treatments, respectively. On the average, 80.14% of the mentioned parameters were in of 0-5 cm depth and 19.86% of them were in of 5-13 cm depth. The maximum (3.93 g/day) and minimum (3.21/day) dry biomass were observed in W1 and W3 treatments, respectively. Overall, the results indicated that although the increment of MAD to 80% in a clay-loam soil slightly decreased the shoot and root growth of mix sport grass under a subsurface drip irrigation system, it is a reasonable management solution with the aim of conserving water in the water shortage condition which had the least negative effect on apparent parameters of grass.

The basic equation of Gradually Varied Flow (GVF) describes the variation of water depth with flow process. Several methods have been developed for numerical solution of the water surface profile in GVF and one of the challenges of numerical integration is determining the appropriate integration spatial step size. In this paper a novel Adaptive Newton-Raphson method is developed for numerical solution of the GVF equation. In this method the spatial steps are determined by using error estimation during calculation, this procedure is smart and increases accuracy and speed of computation the water surface profile in GVF. Several examples were analyzed using the proposed method and compared with the results of previous researches and the accuracy of the proposed method was evaluated. The results indicate good accuracy of the proposed method in comparison with other methods. As shown in one of examples presented in the paper, the obtained results from 10 step of developed Adaptive Newton-Raphson method approximately equal with 90 step of standard direct step method.

Many nonlinear models have been developed based on the mean errors modeling. However, the non-linear models with Autoregressive conditional heteoscedasticity are based on variance modeling. These models are combined with linear models, partly to increase the accuracy of modeling and predictions. In this study, using data from the Urmia Lake water level data for the period 1973-2012, the models with autocorrelation moving average and Bilinear model and two combined models (Autoregressive conditional heteoscedasticity) and (Bilinear conditional heteoscedasticity) were evaluated. To select the ARMA family models, AICC test were used and regression coefficient (r) and root mean square error (RMSE) tests were used for validation models. The results of validation the ARMA, BL, ARMA-ARCH and BL-ARCH models showed the correlation coefficient of 0.707, 0.618, 0.792 and 0.704 and the mean square root equal 2.838, 4.309, 2.031 and 4.11 between observed and modeling data respectively. Also the results showed that model accuracy increased with combining both linear and nonlinear models, but with combining two nonlinear models is caused reduce the accuracy of the models. Overall the results showed that by combining ARMA and ARCH models, the model error decreased about 28 percentage and combining two non-linear models caused increased model error about 2 percentage.

The discharge coefficient of morning glory spillway is decreased with eddies created by vortex at the inlet part of weir. However, a series of specific blades can reduce vortices which result in the spillway efficiency is increased. Hence, in this research numerical modeling of installed breaker blade on morning glory spillway was evaluated using Flow-3D model. To achieve these purposes, morning glory spillway was modeled without and with blades 3, 4 and 6 blades at 45 degree angle. To simulate the turbulence fluctuations, the modified k-e model (RNG k-e) was used and its results were compared to the experimental data. Results showed that by installing blades, the discharge coefficient increases up to 42 percent with 25 percent decreasing in the upstream water level. Moreover, among the three different arrangements of blades, the six-blade model was found to have more satisfactory results than other models. In comparison to control model, for H/D between 0 to 0.1 and 0.1 to 0.2 the discharge coefficient has been increased 40 and 57 percent for six-blade arrangement, respectively.

Water dynamic in wetted volume of soil around emitter is one of the primary information for designing the irrigation systems and management of water and chemical substances. In fact, for particular kind of soil, knowing the evolution and gradual change of the shape of the wetted volume is necessary for estimation of the distance of emitters from each other and irrigation duration. Most of the numerical and analytical models used for prediction of wetting pattern need determining the pounding area from high cost experimental tests. These models predict unreliable results if the discharge of emitter is more than infiltration of soil. In this paper, a new model for coupling surface (Navier-Stokes, VOF) and subsurface flow equations (Richards) is presented. The method can use for simulation of both two phase air-water surface flow along with wetting pattern inside the soil in surface drip irrigation. In this model, Richards equation is discretized with finite volume method and coupled with two phases Navier-Stokes equations based on the new coupling algorithm. To demonstrate the accuracy of the model the results of new method for two different soil texture and discharge are compared with experimental data and numerical results of HYDRUS software. Furthermore, statistical indexes such as mean error and root mean square error and model efficiency are evaluated for the model. The results indicated that the presented model has the high ability in simulation of wetted pattern, and its accuracy is more than HYDRUS software.

The purpose of this study is to evaluate the land use changes on flood hydrograph at Abolabbas basin during the period of 1990-2009. In this paper, the techniques of Remote sensing, Geographic Information System (GIS) and HEC-HMS hydrologic model was used to achieve the purpose intended. At the first step, Landsat satellite images used for the preparation the land use maps of 1990 and 2009, Then images were classified using artificial network algorithm with fine accuracy in eight class of land use. Then these land use maps with the hydrologic soil map were integrated using GIS tools to produce CN maps of 1990 and 2009. The HEC-HMS rainfall-runoff model using of the SCS-CN method for estimating runoff in Abolabbas basin was calibrated and validated for 4 storms occurred at study area. Results of the simulation showed that changes in land use that occurred in the direction the reduction in the level of forest and increased level of rangelands and residential areas has caused peak flow and flood volume during the study period increased 5.5 and 5.1 percent, respectively. On the other hand the results showed, this land use change not affect on the time of peak in flood hydrograph.

The SALTMED is one of the models that can be used for simulation of soil moisture distribution and crop yield under different conditions. This study was carried out to evaluate the performance of SALTMED model for simulation of crop yield and soil moisture distribution under maize cultivation (KSC 704) and irrigation with saline water in research field of Water Sciences Engineering Faculty, Shahid Chamran University of Ahvaz, Iran. This experiment performed in February 2014 to June 2014. The experiments were arranged according to a randomized complete block design with split plot layout. After calibration and verification of model with the control treatment data (irrigation with Karoon river water with EC: 2.5 dS.m-1), soil moisture distribution, crop yield and biological yield simulated for S1, S2, S3 and S4 treatments (irrigation water salinity: 3.5, 4.5, 5.5 and 6.5 dS.m-1, respectively). According to the calculations of soil moisture distribution prediction, model has a highest accuracy in depth of 60- 90 cm and model accuracy decreased in depth of 90- 120 cm. Accuracy of model increased withincreasing the salinity of irrigation water. In simulation of crop yield and biological yield, coefficient of determination respectively was 0.93 and 0.82 and show model has better accuracy in simulation biological yield. According to the results, model simulates soil moisture, crop yield and biological yield with high accuracy.

In this study, experimental model was used in order to evaluate the effect of diameter and length of drive pipe on ram pumps characteristic curves. To do so, after developing a ram pump device with inner diameter of 51mm and the construction of ancillary equipment, tests were carried out in six scenarios by changing the ratio of length to diameter of drive pipe in amounts of equal to 100, 200, 300, 400, 500 and 600. In each scenario with a change in supply head of pumping system and delivered of its, the ram pump performance was evaluated and quantities of pumping discharge (q), wasting discharge (Q) and frequency of impulse valve (n) were recorded. By analyzing the results and evaluating the dependent parameters versus effective independent parameters on the ram pump performance, the ram pump characteristic curves including relative pumping discharge (q/QT), relative wasting discharge (Q/QT) and impulse valve parameter (nD/v0) versus pressure head ratio (h/hm) per each of length to diameter ratios of drive pipe (L/D) were presented, and general equation of pump efficiency were determined. The result showed that along with increasing the length of drive pipe to 400 times of its diameter, the ram pump made is able to pump water to a height equal to twice supply head with efficiency of 48 percent.