مجله آبیاری و زهکشی ایران
سال نهم شماره 5 (آذر و دی 1394)

Soil erosion and surface runoff generation is a serious environmental threat to sustainable development and agriculture, that may lead to a reduced soil fertility, nutrient loss, and reduced plant performance in the agricultural areas. In recent years, the use of modeling is introduced as a means to evaluate the impact of erosion reduction measures. SWAT is a conceptual and distribution model developed to predict and estimate surface runoff, sediment brought, qualitative characteristics of water, as well as to predict the effects of different management measures in the basin. The aim of this study was to investigate the usefulness of SWAT model to estimate the average daily flow rate and calibrate and validate the model in Atrak watershed at Khorasan Razavi North Khorasan provinces. Calibration and uncertainty analysis of the model were performed using SUFI-2. Indicators P-factor, R-factor, br2, and r2 were used in order to assess the ability of SWAT model to simulate Atrak watershed runoff. Runoff data of six hydrometric stations in 1975-1991 were used for calibration and validation of this basin. The results showed that the monthly runoff at calibration stage, the coefficients P-factor, R-factor, br2, and r2 in output basin was 0.73, 1.15, 0.53, and 0.56, and in the validation stage was 0.77, 1.3, 0.48 and 0.58, respectively. The best results were obtained in Shirabad station and the weakest results in Gharehkahnbandi station. Overall calibration results show that the SWAT model can be a useful tool in river flow rate simulation.

Pivot weirs are used in irrigation networks in order to regulate water surface elevation and flow measurements. Few studies have been reported on head-discharge relation of mentioned structure under submerged flow condition. In this study, one equation based on energy and critical depth equations is proposed to determine discharge equation. To determine the coefficients of these equations, measured data in an experimental model on the three pivot weirs with different three side contractions compiled with the USBR (United States Bureau of Reclamation) experimental data of data, the discharge coefficient was estimated for and submerged flow condition . Comparisons of experimental results with presented relation indicatest he range of error for the proposed equation was less than ±20% , where the submergence factor was between 0.2 and 0.9 , which in comparison to Brater and King’ relation with ±40% error has a good accuracy.

Understanding of the fate of pollutants, disposed of in streams, is a matter of concern in recent years for the effective control of pollution. Transverse mixing of the pollutants in open channels is arguably more important than the longitudinal mixing and near-field mixing. Several attempts have been made to establish the relationship between the transverse mixing coefficient and bulk channel and flow parameters such as width, depth, shear velocity, friction factor, curvature and sinuosity. The training and testing of this model are accomplished using a set of available published filed data. Several statistical and graphical criteria are used to check the accuracy of the model. The proposed ANN approach produces satisfactory results (R2=0.82, RMSE 0.103) in the best try in comparison to linear model.

Remote sensing is a suitable method for estimating of actual evapotranspiration (AET) especially in large scales. As the estimation of AET with both high temporal and spatial resolution is impossible for most sensors such as MODIS and Landsat, it is necessary that the AET maps derived from a sensor were downscaled to another sensor using downscaling methods. The objectives of this study were to use of different scaling factors simultaneously for input parameters of SEBAL included surface albedo, normalized difference vegetation index (NDVI) and land surface temperature (LST) for spatial downscaling of AET maps derived based-MODIS (1000 m) images to Landsat images (30 m) and also temporal downscaling of AET maps derived based Landsat (16 day) images to MODIS (daily) images using input/output regression and input/output subtraction methods in a part of Mashhad plain. The results showed that the zero band emissivity of Landsat and LST of MODIS images had the best performance in spatial downscaling of AET maps. NDVI and LST of Landsat images as a scaling factor had not a good performance in spatial downscaling of AET maps in summer and spring, respectively. Considering the results of this study, it can be concluded that the zero band emissivity of Landsat and LST of MODIS images as a scaling factor for spatial downscaling of AET maps and input regression method for temporal downscaling of AET maps are suitable in Mashhad plain.

Imperfect knowledge due to unpredictable climatic conditions leads to uncertainty in decision making in agriculture. Therefore, a probabilistic analysis of the various possibilities besides increasing flexibility in decision-making can also enhance the reliability of decisions. Using Tabriz Synoptic station’s data, the values ofthe crop (TriticumAestivum L.) evapotranspiration and effective rainfall in mid to late season in the study area (Tabriz plain) were estimated. Analyzing the effective rainfall and crop evapotranspiration as probabilistic variables, a reliable method for estimating the irrigation water requirement was described using the “probability distributionfunctions”.By examining 12 different probability distribution function, it was found that the log normal distribution function achieves the best results for the monthly precipitation data with values greater than 30 mm, but there is no unique probability distribution function for evapotranspiration data.This method can also provide a general formula for calculations of irrigation water requirement with different probability levelsduringthe growing season. Results showed thatthe reported values of irrigation requirement in the NETWAT program that is atthe 50 % probability level andused in most of irrigation projects in Iran, were different the calculated values in this study.According to similar reports in different researches, the represented method is recommended for more precise estimation of irrigation water requirements (with different probabilities) especially in critical situations (with high evapotranspiration and low rainfall values) or for crops that are sensitive to water stress in 80% probabilitylevelor higher.

Surface energy balance algorithm for land (SEBAL) is one of the actual evapotranspiration predictor algorithms which are based on remote sensing. To determine outgoing long wave radiation from land surface in this algorithm, an index named soil adjusted vegetation index (SAVI) is used. In calculating SAVI, an equation consists an empirical coefficient (L) calibrated based on Idaho satellite images, USA, is used. In this study using MODIS satellite images of neyshabour watershed during 2009 to 2013, the mentioned coefficient was calibrated. The results showed the proposed value nearly L=0.5 for all areas may not evaluate adequately and it is better to calibrate this coefficient before using in SEBAL algorithm in each area. The results showed the trend of SAVI changes and thus determine the optimum value of L coefficient is sensitive to the time of satellite images and it is better to use the months with appropriate vegetation cover on the land surface. The results also showed the values of SAVI index are more sensitive to lower values of L coefficient. Results’ analysis showed the proposed value of 0.2 for L coefficient application in studies related to SEBAL algorithm in this area is properly assessed.

where there is not adequate space to build other types of spillways, morning glory spillways are use to pass the excess water from the headwater to the dam downstream. Creation of strong vortices in the entrance is among the main problems faced with these types of spillways. One of the effective methods of controlling the vortex is using the vortex breaker blades, which are used in this spillway to increase the discharge rate and coefficient. In this paper, the physical model was constructed and the effect of shapes triangular, rectangular and baleen body of anti-vortex blades on the discharge coefficient of the morning glory spillway was examined by conducting 91 experiments. The results showed that the baleen shape of vortex breaker blade has the greatest impact on increasing the efficiency of the spillway discharge coefficient. The results indicate that the airfoil type anti vortex blade in contrast to rectangular and triangular type have a greater effect on increasing the discharge efficiency in a way that in the best condition (L/D=0.25) and the constant submerged ratio (H/R=cte), airfoil type, rectangular and triangular increased the discharge coefficient by 52, 39 and 32 percent respectively.

Furrow irrigation is the most common type of surface irrigation. Determination of the advance and recession time in the field requires the accurate measurement and that could be costly and time consuming. For this purpose, using the appropriate model can be useful. In this study, Sirmod, WinSRFR, Furdev and Pozal models are used to simulate the furrow irrigation. To evaluate these models, the results of field experiments in lighttextured, heavy-textured and medium-textured soils were utilized. The experiments have been performed in summer 1393 on Kerman University experimental farm in light-textured soil and in summer 1376on two experimental farms in Mashhad and Dezfoolin medium and heavy-textured soils. Using the mentioned models, advance time, recession time and infiltration depth were calculated and compared with the measured data. The results showed that Pozal model has the highest error. Also, Sirmod model has the highest accuracy in calculation of advance and recession time in light-textured soil. The errors are 0.344 and 0.53 percent for advance time and recession time, respectively. This model also has the highest precision in heavy-textured soil. Furdev model computations in advance and recession time at light-textured soil is less accurate than the other models. Based on the results, the WinSRFR model with 1.53 percent error has the lower error in the calculation of the infiltration depth in light-textured soils.

Reference crop evapotranspiration is one of the most important and effective factors for optimizing agricultural water consumption and water resources management. Forecasting of daily reference evapotranspiration can be used for short-term planning of irrigation water requirements. In recent years the use of artificial neural networks and wavelet-neural hybrid model has become very popular in the forecasting of hydrological parameters. The aim of the present study is to use artificial neural network and wavelet-neural network models to forecast reference evapotranspiration in the range of 1 to 28 days ahead at Tabriz synoptic station. For this purpose, a 10-year period (2000 to 2009), 7 years (2000-2006) for training and 3 years (2007- 2009) to test and validation were considered. To create daily reference evapotranspiration time series at the given period, standard equation Penman-Monteith 56 is used. Different combinations of input data (various delays) and various mother wavelets were used. Results of reference evapotranspiration forecasts for a one day ahead, showed that the wavelet-ANN model (RMSE=0.07 mm/day and R=0.999) compared to the artificial neural network model (RMSE=0.69 mm/day and R=0.964) has higher accuracy in forecasting of reference evapotranspiration. The results showed that the use of time delays of 1 to 7 (M7) and 1 to 6 (M6) days can provide the highest accuracy and fewer delays and delays from one year to two years can reduce the accuracy of the models. Comparison of mother wavelets showed that Meyer wavelet due to greater complexity and similarity to the time series of reference evapotranspiration would increase the accuracy of forecasting. To forecast reference evapotranspiration in 2 to 28 days ahead, the wavelet-neural network with Meyer wavelet model was used. The results showed that the increasing of the forecasting period from 2 to 28 days would decrease the accuracy of models (R is ranged from 0.997 to 0.929 for 2 and 28 days ahead). Also, at forecasting 2 to 12 days, annual delays reduced the accuracy of the model, while at 13 to 28-day annual delay increased the accuracy of models. Finally, to compare the models, statistically, t and F tests were performed to compare the mean and variance. The comparison showed that in all the proposed models, at 99 and 95 percent levels, there was no significant difference between the results and observations. The results of this study can be used in irrigation scheduling at study area.

This paper studied flow pattern in attractive and repelling modes of a spur dike (30 degree angle to the flow) by changing the submergence percentage of the spur (0, 15 and 25% of depth at the channel entrance). The simulation was made by SSIIM modeling. In this study, streamlines, secondary flow strength and flow separation and reattachment zones were addressed. The numerical results were compared with experimental data and the comparison showed that the numerical results were in a relatively good agreement with the experimental data. The results indicated that by increasing the submergence percentage, the amount of jumps in secondary flow strength decreased in repelling mode and increased in attractive mode. Moreover, the streamlines at the upstream of the repelling spur dike were more deflected than in the case of the attractive spur dike.

In this article, the role of imports and exports of major agricultural products on amount of virtual water trade, net virtual water import (NVWI), and country water indices included water footprint (WF), water scarcity (WS), water dependency (WD), and water self-sufficiency (WSS) in agricultural sector was studied for a five-year period (1388- 1384). The results show that the volume of imported virtual water to Iran during the mentioned period for 16 major crops was three times more than the volume of exported virtual water for 16 major crops (about 125.8 and 37.9 billion cubic meters, respectively). This means that the NVWI in this period was positive. It is noted that sever increasing in positive NVWI in the two last years of this period has been accrued due to population increasing and drought events in most provinces of the country. Also, Annual meanly country water footprint in agricultural sector is 104.8 billion cubic meters in this period and with average annual 17.6 billion cubic meters through NVWI, Iran has been saved the same amount of its internal water resourecs. Calculated indices of WS, WD and WSS in Iran showed that the average annual intensity of water use in agricultural sector in the mentioned period has been 67.1% which is high (WS index close to 100). Average annual country's agricultural dependency on imports of virtual water (WD) has been 16.8%. This percentage indicates that if the country instead of importing agricultural products, produce those amount into country, an average of about 16.8% should be added to the water consumption in the agricultural sector. Also, average annual Iran's selfsufficiency to water (WSS) has been estimated about 83.2%.

Clean water is the most important need of human life to create safe conditions for human life. Pure water resources scarcity and high costs often hinder access to treatment plant which is vital to human societies. This research aimed to evaluate agricultural drain water quality from paddy fields after harvest and drain water treatment to reduce some harmful drain water parameters. In this study the performance of four types of biofilters consists of wood sawdust, rice husk, charcoal and tea wastes were evaluated. Data were taken at intervals of ten-day period from drain water of paddy fields to study the parameters of nitrate, phosphate, pH and EC. Observations showed that all four biofilters types in some cases reduced the pollutant amounts. These increase and decrease depends on many things which the most important factors were pollutant concentration in drain water and air temperature. Among the four types of biofilter, sawdust biofilter had relatively a better performance e.g. nitrate was reduced from 4.54 to 0.25 mg l-1. Economical comparison showed that sawdust biofilter was better than other four types of biofilter, e.g. sawdust biofilter is 80% cheaper than charcoal biofilter.

Estimation of discharge coefficient for lopac gates plays an important role in determining the discharge of such structure, as a flow control and regulation structure. The present research provides semi-analytical equations to estimate the discharge coefficient for submerged lopac gates for different conditions. The results indicate that the discharge coefficient depends on gate opening and submergence ratios. Theoretical equations for estimating the discharge coefficient were calibrated with experimental information for the conditions of without transition and with gradual and sudden transitions. The results show that the discharge coefficient of lopac gates with transition is less than that of without transition. The proposed equations for the discharge coefficient have maximum of 10% error. Comparing the results of theoretical equations with previous investigation also demonstrates the efficiency of present equations for estimating the discharge coefficient of submerged lopac gates.

Demand management as a way to control consumption and manage water resource is concerned. Farm data of Mashhad- Chenaran plain through questionnaires and interviews was collected from 130  representatives in 2013. All of them divided to two group of water consumption, mean’s that low consumption (<10000 m3/ha) and high consumption(10000 m3/ha ≤). Then mathematical programming model with due attention to four scenarios of water deficit (10, 20, 30 and 40%) was run for each group. Also sensitivity analysis was applied to study effect of water price on demand of water. Result showed while this strategy of water deficit make  99 and 33.6 million cubic meters of excess water in the two groups, the income of farmers increases 15.2 and 6.2 % in low and high consumption group respectively. Result of sensitivity analysis of water price showed that increase of water price does not cause significant changes in water use at low consumption group, but is different in high consumption group. Therefore, non pricing policy for example education, promotion and design of crop pattern is recommendable for low consumption group. For high consumption group, if increase of water price to extent water trading and to use water resources sustainability, water pricing policy is suggested. As well as paying subsidies to farmers may encourage them to non exploitation of surplus water.

Planning for optimal operation in irrigation network is an efficient solution in water saving, increasing in cultivation and improving agriculture performance. Problem of water delivery scheduling in irrigation network is a multi-objective, multi-variable, and multi-constraint problem. Solving such problem needs powerful optimization methods. Evolutionary algorithms are major group of search algorithms that are used for finding a suitable answer using current evolutionary rules in nature. In this research the provided delivery and distribution program in irrigation network is optimized using Imperial Comparative Algorithms (ICA) and PSO and are compared with genetic algorithm results. In this research the delivery and distribution program in distribution channel branches are provided so that the various objects such as decreasing in distributor channel capacity and decreasing in time needed for complete the irrigation program optimize as a single and two objectives. In this program, first branch numbers, upper and lower limit of delivery discharge to per branch and branch coverage, gross irrigation requirement, irrigation interval and block numbers as input are defined to the model. By running the model, the best intermittent of branches in per block, minimum of distributer channel capacity and minimum irrigation duration in optimum conditions define to the model as outputs. To control and considering of developed program, the optimum delivery program in downstream irrigation network of Jiroft diversion dam using this model is provided. The results show that in two-objective optimum status for irrigation supply of the network, Imperialist Competitive Algorithm performance is better than the other two algorithms so that the maximum discharge is 1381 cubic meter per second and maximum irrigation duration is 236 hours.