Journal of Water and Soil Conservation
Year:2018 | Volume:25 | Issue:3 |Papers Count:20

Water hammer” is one of the phenomena that causes damage in the pipe system and reduces their useful life. Various numerical methods have been used to analyze this problem. In all numerical methods, for calculating the variables that are the velocity and pressure values due to the sudden discontinuity of the flow and motion of the pressure wave along the pipe, the continuum environment of the problem must be discretized in some way. With calculating these aberrations before designing of the structures accurately, appropriate measures can be taken to reduce tensions caused by the water-hammer phenomenon. Background and Objectives: The conventional method to numerically solve the differential equations that describe this phenomenon is the method of characteristic lines. In general, in conventional methods where have been developed correctly, such as finite element, finite volume and finite difference, discretization of the spatial domain of the problem is done by gridding. Despite the useful use of these methods in many scientific fields, gridding is a costly and troublesome process, especially on problems with complex boundaries. That is the main motive for the creation of meshless methods. In these methods, the spatial domain of the problem is simply discretized by a number of points. Materials and Methods: In the present study, for modeling classical water-hammer in a system including valve, pipe and reservoir, a collocated discrete least squares method is used. In the proposed approach implicit Crank-Nicolson method for time discretization is used to provide conditions for problem solving stability. In this method, the velocity and pressure values on the x-t plane are calculated directly from the previous time step simultaneously. This method is quite matrix and the solution process is accomplished including several simple algebraic operations on matrices. Results: In this study, at first this numerical method is described generally then governing equations are calculated and several experiments on water hammer in the form of the problem have been modeled by this method, also the hydraulic analysis of problems and calculation steps for calculating accurate answers are fully described and the results are verified with exact answers and other numerical methods such as MOC method and numerical method used by “ Zielk” and the computational average error was estimated to be less than 5% by total squared error criterion. So this method can be considered as a precise, simple and low-cost numerical method for modeling waterhammer phenomena. Conclusion: Important properties of the Meshless numerical method included no need to integrate, complete mathematical math operations and meshless space makes it one of the most accurate methods for numerical solution of water hammer phenomenon in the pipe system.

Background and Objectives: Due to lack of available water resources and the continuous increase in the water demands, construction of new dams seems to be inevitable. Dams are infrastructures for water storage and supply, especially in drought periods. If the operation of the reservoir is optimized, the purposes of dam construction is efficiently supplied. Since the optimum operation of large water resource systems are time consuming, complex and sometimes unattainable, the use of alternative methods of optimization models seems to be a good solution which are accurately acceptable and give near-optimum answer. Nohob Dam is one of these dams which are implementing at Khar-Rud River at the Qazvin province. The aim of the operation of this dam is to store Khar-Rud river flows and adjust to meet water rights for agricultural lands located downstream and artificial recharge of Qazvin plain. The aim of this study was to investigate the water allocation to agriculture and environmental uses and artificial recharge of aquifers in drought conditions using MODSIM model. Materials and Methods: The operation of the dam was simulated using the MODSIM model for a long period of 50-year and during the periods of 1965 to 2015, as well as a 17-year hydrological drought period during the periods of 1998 to 2015, which is determined on the basis of average changes in river discharge relative to the long-term average. Simulation was conducted monthly for four options of “ before the sedimentation” , “ 20-year sedimentation” , “ 50-year sedimentation” and “ no-reservoir conditions” . Water allocation priorities are as follows: 1-environmental requirements, 2-agricultural water rights and 3-artificial recharge. Reducing Khar-Rud water volume at the dam site from the years 1998 to 2015, has caused the loss of Nohob dam performance for various reasons, including drought and water withdraw from upstream, so that the needs of any water consuming sections is not supplied. Results: By comparing the results of sedimentation options, it is identified that in 20-year sedimentation conditions, the reservoir has the best performance, which is due to the low dead volume compared to the useful volume of the reservoir in these conditions. By comparing reservoir performance with no-reservoir conditions with the other sedimentation options, it can be concluded that the dam construction will not have much effect on improving the water distribution conditions and the amount of supply in these conditions will not be significantly improved. In order to evaluate the simulation results of the operation of the reservoir, various parameters, such as, supply percentages, reliability, resilience and vulnerability were used. Also, the simulation results showed that in long-term simulation (50-year) and drought conditions, the dam construction would slightly change the increase in the volume and temporal water supply and demand in the region, so that the percentage of provision of the total demands of water in 20-year and 50-year sedimentation conditions are reduced from 77. 4 to 37. 6% and 73. 7 to 35. 8%, respectively and for no-reservoir conditions, it is decreased from to 58. 8 to 34. 1%. By continuing the drought conditions and increasing water supply up to 1-2% as compared to the no-reservoir conditions, the dam construction and the continuation of its implementation is completely unjustified. Conclusion: In general, it can be concluded that in the drought conditions, construction of the dam to improve the water distribution conditions is not justified and perhaps its application is only to control the sudden flooding and prevent the damage caused by the flood at downstream of the dam.

Background and Objectives: Phosphorus (P) is one of the essential elements for plant growth, which is considered as one of the potential sources of water pollution due to its excessive use as chemical fertilizers and also due to discharge of municipal and industrial wastewater into water resources. P has high spatial and temporal variations due to factors such as rainfall intensity, land use, slope and soil erosion. The aim of this study was to investigate the temporal variations of phosphorus pollution at various regions along the Siahroud river, located in Guilan province. Materials and Methods: The study was conducted in the Siahroud watershed of Rasht with different land uses including forest (Jokolbandan and Saravan regions) as well as agricultural (Jokolbandan region), industrial (Saravan and University regions) and urban area (Gil and Golsar regions). Water samples were collected from the various regions of the river with different land uses during ten months. The contents of total, dissolved and suspended solids, along with total, soluble and particulate P were measured in water samples. Total P was measured by potassium persulfate digestion method. Nitrogen content was also determined according to Kjeldahl method in the samples taken on December, January, February and March. Results: The results showed higher level of P pollution in the urban (Golsar with the value of 0. 261 mg. L-1) and industrial regions compared to other regions of the river. In winter, most of soluble P discharge was observed from the agricultural areas, while in summer the highest the urban areas. The maximum P pollution (0. 296 mg. L-1) was related to the Golsar region. In addition, the high level of total P in Jokolbandan (0. 188 mg. L-1) can be due to the destruction of forest and the steepness of slope in this region. The majority of the solid particles discharged from the watershed were also in the form of suspended solids (annual average, 503 mg. L-1). The results of the mean comparison showed that there was a significant difference in the spatial variations of the concentration of various forms of P including total, soluble and particulate P and the highest amount of P was observed at the end of the river. Furthermore, the results showed that there was no significant difference between soluble and particulate P in the study area. The results showed an exponential relationship (R2 = 0. 54) between soluble phosphorus concentration and soluble solids. It was also observed that the output of phosphorus is also a function of time and the amount and form of P output significantly change with monthly variations. Conclusion: In general, the rate of P pollution increased from the upstream to the downstream and showed high temporal variations. While soil erosion was recognized as the reason for high levels of P pollution in agriculture regions such as Sangar in rainy season, the discharge of municipal and industrial wastewater into the river was the reason for P pollution in the urban areas. Therefore, control of soil erosion in agricultural lands and preventing municipal and industrial wastewater discharge into the river will effectively reduce P pollution.

Background and Objectives: Cadmium (Cd) is one of the most common soil pollutants that can adversely affect all living organisms. Therefore, proper remediation is necessary to reduce metal availability in soil. Considering higher reactivity and adsorption capacity of nano-material compared to ordinary-sized materials, with the development of various nanotechnology applications in human life, the evaluation of the effectiveness of nanoparticles in remediation of polluted soils has been considered by researchers. However, up to now, there is no reported information about heavy metal immobilization by nHAP in calcareous soils. This experiment was conducted to investigate efficiency of nHAP on stabilization of Cd in polluted soil. Materials and Methods: This experiment was conducted in a completely randomized design with factorial experiment and three replications. First, the soils were contaminated with Cd at three levels (0, 20 and 40 mg kg-1 using CdCl2) and then were incubated for one month in 70% field capacity. Then, nHAP was applied to soils at three levels (0, 0. 25 and 1%). After 30 days incubation, Cd was fractionated by sequential extraction and analyzed for DTPA extractable form. To quantify the effect of nHAP in binding intensity and mobility of loaded Cd, the reduced partition index (IR) and mobility factor were used. Results: The results of sequential extraction showed that nHAP application significantly reduced concentration of Cd in the exchangeable and organic fraction and increased in the carbonate fraction, while there was no change for Cd in the residual fraction. The results of extraction with DTPA experiment indicated that at 40 mg kg-1 of Cd both of the levels of nHAP application decreased DTPA-extractable Cd, but at 20 mg kg-1 of Cd, addition of nHAP at 0. 25% level did not significantly reduced concentration of DTPA extractable Cd. It was also found that efficiency of nHAP increased when Cd loading quantities to soils increased. However, the role of nHAP in the reducing of bioavailability was not very large. The results also illustrated that the IR value increased when Cd and nHAP loading quantities to soils increased, demonstrating a decrease of availability and mobility of Cd in soil. Application of nHAP caused reduction of the mobility factor of Cd indicating decreasing availability and environmental risk of Cd. Conclusion: On the basis of results obtained in this study, it can be stated that although the nHAP addition has somewhat stabilized and reduced the mobility of Cd in the soil, it seems that the effect of nHAP on decreasing Cd was not considerable. Therefore, further studies should be carried out more on the feasibility of application of nHAP at the widespread level and the economic status of its application.

Background and Objectives: Groundwater is one of the most valuable water resources owing to its quantity and quality. Measuring water level is a basic and essential step in any groundwater study. Since the measured data are derived only from a limited number of observation points and, at the same time, they must be extended to the whole surface of the zone, it is essential to determine optimal location of measuring network. Accordingly, for reduction of observation wells, a number of them were eliminated in such a way that the remaining wells have an optimal combination. Materials and Methods: Dezfoul-Andimeshk plain, located in north of Khouzestan province, was investigated as a case study. Kriging, as the best linear unbiased estimator, was used for interpolation of groundwater level. Based on the measured data of 76 studied observation wells, a theoretical variogram was fitted to empirical variogram points. To achieve the optimal combination, tabu search algorithm (a meta-heuristic algorithm) was used. Two computer programs including GSLIB and MATLAB were used for Kriging and tabu search, respectively. By connecting these two programs and providing conditions for the exchange of information between them, a model called optimizer model was developed to provide the ability to optimize the groundwater level measurement network. The observation points are distributed in such a way that minimize the variance estimation error limited to the plain extent. Results: Optimization model was implemented for five completely different modes. For the first to third cases, which aimed only at verifying the model, the optimal selection of one, two, and three observation wells was presented, which, by comparing the complete search method, verified the functionality of the model was confirmed. In the fourth and fifth cases, the optimal selection of 50 and 60 out of 76 observation wells were presented for which the groundwater levels were compared and the results showed that there exists a good match between the groundwater surface results in comparison with those of whole wells (76 wells). Conclusion: Due to the fact that the variogram of the region is an isotropic variogram, the distribution of wells is uniform in different directions. This is tangible for the first to third cases in which the number of wells is small. The results of optimization of 50 and 60 observation wells without any interference during the optimization process were automatically achieved by the model. The comparison of the groundwater level confirms the accuracy of the model results. Also, the results showed a great deal of time saving through the use of the present model.

Background and Objectives: Lead (Pb) is considered to be particularly toxic and responsible for significant decreases in biological activities in soils. Phytoremediation is an emerging and low-cost technology that utilizes plants to remove, transform, or stabilize contaminants located in water, sediments, or soils. The success of phytoremediation depends on the interactions between rhizosphere macro and microorganisms and plant roots. Among these organisms, the role of earthworms, mycorrhizal fungi, and plant growth promoters' rhizobacteria have been considered. In this study, we have evaluated and compared the combined effects of earthworms and bacteria on root colonization and plant growth in a contaminated soil. Materials and Methods: Three plant species seeds (Zea mays (maize); Cynodon dactylon (bermudagrass) and Stachys inflata), after surface-sterilization and germination were transplanted into each plastic pot contained 4 kg of contaminated soil (collected from bama mining area located in the southwest of Isfahan) that already autoclaved at 121 oC for 2 h. A completely randomized design with 2×2×2 factorial treatment combination was used with the following factors: with or without earthworm treatments (Eisenia foetida), with or without arbuscular mycorrhizal (AM) fungal treatments and with or without rhizobacteria. After about three (bermudagrass and maize) and four (Stachys inflata) month growth in greenhouse condition, plant shoots were harvested. Pb and phosphorus (P) concentration, root colonization, spore abundance and root colonized length were determined. Results: In general, inoculation of these organisms differently affected root colonization, spore abundance, soil phosphorus (P) availability and plant growth, and showed variable results depending upon plant species and soil organisms involved. The significant and negative correlations between soil P availability and root colonization for all the plants (maize: r=-0. 48, P<0. 05; bermudagrass: r=-0. 74, P<0. 001 and Stachys inflata: r=-0. 65, P<0. 01) suggests that the increased P availability would mainly be responsible for the decreases of root colonization in the presence of earthworms or rhizobacteria. But the negative correlation between available Pb and colonization only showed in C. dactylon and demonstrated that the negative effects of Pb on mycorrhizal symbiosis depends on plant sensitivity on the toxicity of Pb. Furthermore, among all mycorrhizal symbiosis determined in this study, the spore abundance had a lower change between co-inoculation. The correlations between spore abundance and root colonization were also different for the three plant species (maize: ns; bermudagrass: r=-0. 76, P<0. 001 and S. inflata: r=-0. 67, P<0. 01), showing that spore abundance could not be a suitable index for mycorrhizal dependency, and that it depends on plant species and soil organisms considered. Conclusion: This study showed that increasing the availability of soil P and Pb could be one of the decrease factors in root colonization, but the negative Pb effects depend on plant sensitivity. Furthermore, root colonization may not alone be a suitable index for plant growth and could be different with plant species and soil P or Pb concentrations. Furthermore, the relationship between plant growth and mycorrhizal symbiosis was higher in plant sensitive to Pb toxicity.

Background and Objectives: In the present study, HYDRUS1D software was used to estimate the hydraulic parameters of the Van Genuchten-Moalem model and simulation of water infiltration in soil of four stations of Gonbad University, Artificial Lake, Kalaleh and Negin Shahr with loam soil texture by reverse method. Materials and Methods: For this purpose, three groups with a different selected number of hydraulic parameters were defined for the optimization process. In the first group, only the cumulative penetration data measured as software input was used. In the second group, the soil moisture content measured at 0. 3 atmospheres (FC) and in the third group, the amount of moisture in the 15 atmospheric suction (PWP) was used as supplementary data for the inverse solution along with the data cumulative infiltration. After optimization of hydraulic parameters of soil, the water infiltration changes along with time were simulated using HYDRUS1D software. Results: In Kalaleh station, optimized parameters ø s, ø r and α value were obtained 0. 34, 0. 027 and 0. 014, respectively. In Neginshar, optimized parameters α , n and ks parameters were obtained 0. 0075, 1. 52 and 0. 012 cm/min, respectively. In Artificial Lake optimized parameters α , n and ks parameters were 0. 011, 1. 39 and 0. 016 cm/min, respectively. In Gonbad University station optimized parameters value were ks and α value 0. 011cm/min and 0. 005, respectively. After optimizing the hydraulic parameters of the soil, using HYDRUS software, water infiltration along with time was simulated. The result showed that Hydrus software predicted the data to be slightly higher than the actual amount. The results showed that at all stations, the R2 value is high, indicating a high correlation between field data and Hydrus software. In the Kalaleh station, there was a greater correlation between field infiltration data and Hydrus software with high R2 coefficient (0. 997) and the predicted data by the software was approximately identical with field data. At Negin shahr station, the difference between field data and Hydrus software simulated data was higher. Conclusion: According to the results Hydrus software simulated cumulative infiltration well and with over time, the infiltration rate was slightly higher than field data. At all stations, the R2 value is high, indicating a high correlation between field data and Hydrus software.

Background and Objectives: One of the main limiting factors of the development of Iran's agricultural sector is the shortage of water resources. The annual recharge of groundwater aquifers due to atmospheric precipitation has not been able to compensate for this amount of reduction in groundwater level. Also, farmers do not have enough economic incentives to minimize negative environmental effects, such as reducing groundwater aquifers level. Therefore, most decision-making issues in natural resources such as water resources management face the problem of the existence of conflicting objectives, such as maximizing economic benefits and minimizing negative environmental impacts. According to this, in the present study, the game theory method was used to manage the groundwater resources. Materials and Methods: The statistical population of this study is the total wells water of Gorgan. In current study 88 questionnaires was completed by using stratified random sampling. The information required includes the production costs and agricultural water wells information in the 2014-2015. Accordingly, five scenarios for the exploitation of groundwater were considered. In order to estimate the economic benefits and environmental impacts, farmers' net income and groundwater resources exploitation were used respectively. The optimal application of groundwater resources was then determined by Non-symmetric Nash equilibrium method. Results: Based on the results of this study, the optimal crop area and the net income of farmers were decreased by declining groundwater exploitation for irrigation. Furthermore, the results of this study showed that when economic profit is considered as the only target, groundwater exploitation is at its highest level of 579 million cubic meters and when environmental goals are considered as the only target, the optimal groundwater scenario is in the minimum volume of groundwater exploitation as 66 million cubic meters. When the same weight is considered for environmental and economic goals, the best scenario for exploitation of groundwater resources is 246 million cubic meters and farmers' income is 2340000 million Iranian Rials per year. Conclusion: According to the results of sampling, farmers' exploitation from the groundwater resources of the region is wasteful. Although this operation in the short run has led to an increase in net profits, but it will lead to irreversible damage to the hydropower potential of the region and the environment in the long run. Also, the results of this study showed that the optimum exploitation from groundwater by game theory model should be less than the current exploitation. The results of optimal cropping pattern showed that the optimum cropping area is reduced by decreasing the used water.

Background and Objectives: In during the past decades, the study of pollutants transfer in saturation zone has become an important issue due to its chemical and physical effects on subsurface water. On the other hand, the increasing application rate of nitrogen fertilizers has been considered as a serious threat to groundwater and human health due to its high dynamic nature in soil. Brigham and Fried-Combernous models have been proposed for the dispersivity calculation in short and long travel distances, respectively and are the most significant models of persistent contaminant transport in homogeneous saturated porous media under constant flow. The purpose of this study was the evaluation and comparison of Fried-Combernous and Brigham mathematical models to calculate nitrate dispersivity in homogeneous saturated sandy soils under laboratory conditions. Materials and Methods: In order to study the dispersivity using Fried-Combernous and Brigham models, pure potassium nitrate salt solution was added to sandy soil columns (in the three size of coarse, medium and fine and distance transmission of 80, 40 and 20 cm) as persistent contaminant under the sustainable regime with concentration of 160 (mg⁄ lit). The concentration of output nitrate were then measured in three different porosity volumes and Breakthrough curves were plotted for each column to obtain all required parameters. Results: Experimental data analyze by analytical Fried-Combernous and Brigham models revealed that there is a significant difference between the dispersivity of fine sandy soil and dispersivity of coarse and medium sandy soil in both models. So with increasing in the average travel distance in medium and coarse sand, nitrate dispersivity increased. Investigation of the calculated values of β parameter for fine sand showed that this parameter increases dramatically with increasing travel distance. This represents a higher pollutants velocity transition than the water velocity in the pores at the shorter distances in fine sand. Therefore the travel distance increases with increasing dispersivity. Conclusion: Evaluation of the results revealed that unlike long travel distance, the results of Fried-Combernous and Brigham models were different and therefore, it could not be generalized to long travel distances indicating that the Fried-Combernous model was not efficient enough for short travel distances.

Background and Objectives: One of the ways to predict and estimate the amount of runoff from rainfall is the use of hydrological models. Calibration process is a critical step which should be carried out carefully to optimize the model parameters. Multi-objective optimization algorithms as one of the most important and practical topics in various fields of study could be employed to achieve a reasonable calibration. The purpose of these algorithms is to determine the values of model parameters to find the best possible solution and achieve different goals. Materials and Methods: In this study, Multi-objective optimization algorithm (AMALGAM) used to calibrate conceptual daily hydrologic model (MILC). MILC model employs the Soil Conservation Service-Curve Number method for abstraction (SCS-CN) for estimation of losses, the geomorphological Instantaneous Unit Hydrograph (GIUH) for routing of rainfall excess of catchment. This paper applies a four-objective calibration strategy focusing on peak flows (NSE), low flows (TRMSE), water balance (ROCE) and flashiness (SFDCE) to parameter estimation of MILC model. After calibration process, a trade-off point extracted from Paretofront was selected to include the appropriate values of all four objectives simultaneously. This point is applied to verify the validation period. Results: The obtained values during the validation period (0. 71 ≤ NSE ≤ 0. 78) indicate that the MILC model has good performance to simulate the amount of peak flows but according to ROCE and SFDCE values it has weak performances to simulate the balance water and median flow respectively. Conclusion: The values obtained for the TRMSE target function during the periodic verification period were 1. 22 to 1. 22 (TRMSE = 0 in optimal mode), which indicates that the simulations are suitable for low flows. Multi-objective optimization algorithm for the automatic calibration process of rainfall-runoff model, due to the use of multiple objective functions that target each part of the hydro graph of the basin, challenges the model in simulating all current flows in the basin. This issue shows the importance of using multi-objective algorithms to calibrate hydrologic models. Also, the intelligent selection of multi-objective functions in the calibration process of the model plays a key role in understanding the model more fully by using multi-objective algorithms instead of single-objective for the calibration process.

Background and Objectives: Soil surface temperature has a key role in the mass and energy interchange between soil and atmosphere and it is an important input parameter for running the heat, water and carbon balance estimating models in the soil-plant-atmosphere system and weather and climate simulating models as well at the regional and global scales and the whole soil surface energy balance components are affected by soil surface temperature. Instead of the high important and remarkable application of soil surface temperature, its measurements is performed just in the synoptic meteorological stations and in an imperfect manner (just the minimum daily soil surface temperature) and so, it is essential to simulate this important variable by appropriate methods. Materials and Methods: In this research, two methods including soil surface energy balance model and satellite images were used to estimating daily mean soil surface temperature in the Sararoud-Kermanshah agro-meteorological station which has the recorded data of both maximum and minimum soil surface temperature at the 2013 to 2014 time period. Estimating daily mean soil surface temperature based on the satellite images was performed by considering the MODIS sensor images at four different times including 22: 30, 1: 30; 10: 30 and 13: 30 using the MRT software and for running the soil surface energy balance model, the daily meteorological data including air temperature, wind speed, sunshine and relative humidity along with some soil physical properties were used as the model inputs and the efficiency of these methods was evaluated using some evaluating error indices. Results: By applying the MODIS sensor images, the results showed that from different combination cases of soil surface temperature at the mentioned imaging times, calculating daily mean soil surface temperature based on the averaging of soil surface temperatures at 22: 30, 1: 30 and 10: 30 times was led to gaining the highest agreement with soil surface temperature observations and the absolute error and determination coefficient of this method to estimating daily mean soil surface temperature were 2. 1 ° C and 0. 93, respectively. Using the soil surface energy balance model to estimating daily mean soil surface temperature, the absolute error and determination coefficient were 1. 8° C and 0. 96, respectively. The results of the seasonal time series analysis showed that by using the soil surface energy balance model and satellite images, the highest agreement between calculated and observed values was occurred at summer and winter, respectively. Conclusion: The overall results of this research showed reasonable and appropriate accuracy of both applied methods. However, the soil surface energy balance model is suggested because of its higher accuracy. Therefore, it is possible to adopt the applied methodology of this research to simulate the mean soil surface temperature in different regions and the estimated values of the daily mean soil surface temperature could be used to different applications such as soil temperature and moisture simulating models as an input variable.

Background and Objectives: Urmia Lake, as an important water ecosystem, is located in the northwest of Iran. Over the past 14 years, the average of Urmia Lake water surface level has decreased to 1272. 2 m and it means that the difference between the ecological level of the lake and the present water level is 2-meter. Drying of the Urmia Lake will cause serious problems and crises for the watershed, adjacent provinces and the country. In this research, direct and indirect effective parameters in prediction of the lake level such as evaporation, input runoff to the lake, precipitation, temperature, wind, mean air humidity and water level in the previous month have been employed. The comparison of the efficiency of two models namely the Bayesian network, which is a probabilistic model under conditions of uncertainty and the machine algorithm of Least Square Support Vector Machine (LS-SVM) is the main objective of the present research. Materials and Methods: In the present research, two methods including least squares support vector machine and Bayesian were employed in the modeling process. In this study, effective factors in predicting Urmia lake water level in the previous month as inputs for the used models and water level in the present month as outputs were investigated. Results: The analysis of hydrometric stations data showed that the data of only 4 stations among 13 stations are fitted to the normal distribution. Comparison and investigation of the results of two model by examining the coefficients R2, RMSE, MBE and Nash-Sutcliff indicated superiority of the least squared vector machine model compared to the Bayesian network. These values for the superior model were 92. 3%, 0. 082, 0. 122 and 0. 86, respectively. Conclusion: In this research, the criteria for evaluating and comparing the accuracy of the two model in prediction based on R2, RMSE, MBE and Nash-Sutcliff criteria indicated that the least square vector machine is superior to the Bayesian model. However, the important point in comparing the two model is that the nature of the least squares support vector machine is a machine, however, the nature of the Bayesian network is a probabilistic model under uncertainty conditions in which the normal distribution is used to train network variables because the nature of events is random. Therefore, in this research, the use of Bayesian network model is recommended to the least-squares support vector machine model.

Background and Objectives: Weirs and orifices (gates) are among the hydraulic structures that are used to control water level and flow discharge, respectively. They are also extensively used for flow discharge measurement. One of the most important reasons for using these structures as measuring instruments is having a simple stage-discharge relationship. Also, in cases where flow is heavily sediment-laden or carries considerable loads and floating objects, the combination of these two structures improves system performance. One of suitable solution that can be used to increase the efficiency of weir-orifice structures is compound weir-orifice. There are very limited investigations in this regard. Materials and Methods: This study was conducted with the aim of investigating the discharge coefficient for combined compound weir (triangular-rectangular)-orifice structures. The experiments were carried out in a rectangular flume with length of 10 m and width of 0. 40 m. In these experiments, triangular notch weirs with angles of 45, 60 and 90 degrees and rectangular orifices were used. The width of rectangular weir in upper section was 40 cm. Results: The results of this study showed that for compound weirs at all angles, with increasing weir height ratio (relation of head water on compound weir to the weir height), discharge coefficient of compound weir increases. In spite of high variations of head water on the weir as well as triangle weir's angles, variation in discharge coefficient was relatively low and ranges from 0. 58-0. 61. This fact indicates the importance of precise estimation of discharge coefficient for compound weirs. Furthermore, it was found that by increasing the angle of the triangle weir, the discharge coefficient increases while for compound weir-orifice structure, the discharge coefficient decreases. The opening height of orifice is also effective on the discharge coefficient of combined compound weir-orifice structures so that with increasing of this parameter, discharge coefficient decreases. It is also found that the discharge coefficient of combined compound weir-orifice structures is slightly lower than the discharge coefficient of the compound weirs without orifice. Conclusion: According to the results obtained in this study, one can properly estimate the discharge coefficient of combined compound weir-orifice structures given the simple data such as geometry of compound weir and orifice and also the flow depth in upstream of the weir and hence, utilize this structure in the main irrigation networks and canals. In this case, the proper control of water surface elevation by compound weir as well as suspended sediment transport through the orifice would be achieved.

Background and Objectives: Water limitation is one of the most important inhibitors of crop production, so choosing an optimal and superior strategy is essential for using water in conditions of water shortage. Khuzestan province has been ranked third with 13. 8 percent of the total date production of the country. Therefore, using pressurized irrigation methods with the goal of optimal utilization of water resources is inevitable. This research was carried out with the aim of investigating the possibility of utilizing subsurface drip irrigation systems in date orchard and determining the most suitable irrigation treatments in terms of yield and water use efficiency in Zahedi cultivar. Materials and Methods: The treatments consisted of the amount of water consumed by subsurface drip irrigation in three levels based on 75, 100 and 125% water requirement and in surface drip irrigation based on 100% water requirement. Data analysis was performed using a complete randomized block design with three replications. This research was carried out on Zahedi date palm cultivar at Behbahan Agricultural Research Station during three years (2013-2015). Results: In the number of fruits in the cluster, treatments of 75, 100 and 125% of crop water requirement and surface drip irrigation, respectively, with 1438. 1, 1336. 8, 1492. 8 and 1449. 8 of fruits in the common cluster were in same place. The surface treatment and 75% of water requirement respectively had the highest yield of 8569. 6 and 7802. 2 kg / ha, but the difference between mean treatments was not significant. The water use efficiency under 75% of the water requirement treatment was highest with the production of 7444 kg of dates per cubic meter of water. The 75% water requirement treatment had the lowest moisture content and the final rating was 8. 7%. The 75% water requirement treatment with 13. 7 N / m2 had the highest rigidity and loneliness was in the first place. In the index of total soluble solids, 75, 100 and 125% treatments of subsurface drip irrigation and surface drip treatments were respectively 60. 2, 59. 5, 59. 9 and 60. 2 at the same place. Conclusion: Optimizing water use and reducing it to 6116. 53 cubic meters per hectare in 75% water treatment resulted in saving water consumption. As this treatment decreased 20. 4, 19. 7 and 39. 4% of water use, respectively, compared to the surface drip and 100 and 125% water treatments. This amount of water consumption reduce has not resulted in significant alteration of the quantitative traits and some qualitative traits such as pH, soluble solids and sugar content in sub-surface drip treatments. Considering the insignificant impact of irrigation levels in subsurface drip treatments, it is possible to use other irrigation treatments such as 50 and 60% water requirement in future studies of subsurface drip irrigation.

Background and Objectives: Infiltration is one of the important parameters of the soil, which affects many hydrological processes in the watersheds. The importance of the Infiltration has led to various laboratory methods used to measure this process. Various methods have been developed for measuring the infiltration, which are based on the measurement of the vertical flow of water to the soil. One of the standard methods for measuring infiltration, is double-ring infiltrometers method. In this method, it is assumed that the external cylinder prevents lateral flow and creates a completely vertical flow in the soil. Therefore, the present study was conducted to evaluate the double-ring infiltrometers method for measuring the vertical infiltration compared to actual vertical infiltration data simulated using HYDRUS-1D software. Materials and Methods: In this study, in order to evaluate the double-ring infiltration data, infiltration was measured in several regions with different soil textures by double-ring infiltrometers. Then, HYDRUS-1D numerical model was used to simulate infiltration and the vertical infiltration data were obtained through forward solution of the Richards equation. The van Genuchten-Mualem model was used to quantitatively determine soil hydraulic properties of the Richards equation. The hydraulic parameters of van Genuchten-Mualem model were optimized using inverse modeling in the HYDRUS, for each region's soil. Assessment of measured data was performed using mean error (ME), root mean square error (RMSE), coefficient of determination (R2) and normalized mean square root (NRMSE). Results: Comparison of simulated and measured infiltration data showed that double ring infiltration data is much higher than the simulated vertical infiltration data. The measured infiltration data in all soil texture was much different from that of simulated data. The lowest error in the measurement of vertical infiltration was observed in sandy loam soil that is a light texture. The values of coefficient of determination, root mean square error, mean error and normalized mean square root (R2, RMSE, ME and NRMSE) in this texture were 0. 87, 8. 51,-4. 45 and 0. 18, respectively. Conclusion: In measuring the infiltration of a double-rings, the size of the cylinders used, as well as the buffer index, is of great importance. Therefore, the use of cylinders of different sizes influences the final infiltration values. The double-ring infiltrometers method has a lower error in the sandy texture than heavy texture and the contribution of lateral infiltration is less in this texture. Therefore, the double-ring infiltrometers has a higher accuracy in light texture.

Background and Objectives: Aquifers are vulnerable to pollution from industrial and agricultural activities, the share of the agricultural sector is higher than the rest. Nitrogen fertilizers have the highest consumption in agriculture. Nitrate ion with negative charge is not absorbed by soil particles; therefore, it is subjected to surface and ground water leaching which is more intensive in sandy loam. Analytical and numerical models are used to investigate nitrate transport between soil and groundwater and its effect on groundwater contamination. The application of these models depends on the determination of dispersion and retardation factors. Therefore, quantitative estimation of these factors is necessary to solve the problems related to solute and metal transport in the soil. The parameters were estimated by comparing laboratory and field data versus theoretical ones. The objective of this study is to determine dispersion and retardation factors of nitrate and ammonium ions with three different methods including breakthrough curve (BTC), least square and HYDRUS models in a saturated sandy loam soil. Materials and Methods: The study was conducted in the soil columns of 50 centimeter and 10. 5 diameter with three replications. Before leaching, ammonium nitrate fertilizer was added to soil columns with concentration of 10 g per liter. Concentration of nitrate and ammonium in leached water at the end of soil column with time, commonly known as the breakthrough curve (BTC), is determined. BTC as the first method, resulting from a step input of solute is often of sigmoidal shape and the dispersion and retardation factors are determined with this curve. The second method was least square one. In this method an error function model that fits to a breakthrough curve is presented with two unknown parameters. The parameters can be estimated by using laboratory data and a least square method. The last method is HYDRUS model. In HYDRUS model, the convection-dispersion and mobile-immobile models through inverse modeling were used to estimate the parameters. Results: Dispersion and retardation factors for nitrate ion were in the range of 0. 09-0. 15 and 0. 44-0. 48 and for ammonium ion were in the range of 0. 042-0. 053 and 0. 24-0. 37, respectively. Conclusion: For quick and accurate estimation of dispersion and retardation factors from a soil column data, three methods were used in this study. The models applied in this study have almost identical results in estimating dispersion and retardation factors. The nitrate ion has been absorbed into the soil particles more than ammonium ion and consequently has a lower dispersion and retardation factors and less leaching than ammonium ion.

Background and Objectives: Soil health is one of the factors contributing to food security and public health and hence achievement of sustainable agricultural goals. One of the factors affecting soil health is agronomic management. Different agronomic managements have different effects on soil health indicators, so that the positive effect of management of plant remains leads to the improvement of physical, chemical and biological properties of the soil. Considering that till now few studies have evaluated the effect of different types of agricultural management on chemical and biological properties in arid and semi-arid regions of Iran, Therefore this study was designed and conducted to evaluate the effects of different agronomic management on some soil chemical and biological indicators. Materials and Methods: The study was conducted in Research in Shahid Chamran University of Ahvaz. In this research, the effect of some different agronomic management (residual management, agronomic rotation and monoculture) on a number of soil health assessment indicators (pH, EC, microbial respiration, organic matter, active carbon, total nitrogen, available phosphorus, potassium, Iron, Zinc and Manganese was studied. The experiment was conducted in a randomized complete block design with four replications. Mean comparisons were done by Duncan's multiple range test method. Results: The results of analysis of variance showed that the crop management type had a significant effect (P<0. 01) on pH, EC, organic matter, microbial respiration and activate carbon. Monoculture cropping system caused a significant increase in pH (7. 29) and EC (3. 5 dSm-1) compared to the other agronomic management systems. The application of plant debris to crop rotation and monoculture management increased the amount of soil organic matter, microbial respiration and soil activated carbon to 1. 7, 1. 4 and 1. 75 times. Also, the values of these traits in the crop rotation system were more than monoculture management. Also, the management of plant remains with a ratio of 1. 8, 2. 3 and 1. 4 increased the iron, zinc and manganese levels. Conclusion: This study showed that soil EC, pH, organic matter, microbial respiration and activate carbon, total nitrogen, available phosphorus, potassium, iron, zinc and manganese in soil can be used as soil health indicators to evaluate the effects of different agronomic managements on soil health. Crop residue management had more significantly effects on improving soil health indicators than crop rotation and monoculture cropping systems. The soil health indicators were more in crop rotation system compare with monoculture which shows the positive effect of rotation compare with monoculture. In general, the results showed that the crop residue management can improve soil health indicators more than crop rotation and monoculture.

Background and Objectives: Rangelands of arid and desert areas despite the insignificant vegetation cover, but due to the large global scale, more than one third of the surface and underground carbon reserves have landed. Organic carbon dioxide management in rangelands requires knowledge of the amount of organic carbon and the affecting factors. The amount of soil organic carbon is the result of the balance between the carbon that is added to the soil and the carbon released from the soil by leaching, carving and erosion. The present study evaluates the changes in soil carbon and how they relate to environmental parameters in dry and semi-arid rangelands. For this purpose, the rangelands of Yansi region of Gonabad have been selected as a model of arid regions of the country. The aim of this study was to study the effect of soil characteristics, land management and vegetation cover on soil organic carbon changes. Therefore, in the present study, the study of the relationship between organic carbon of soil and some soil characteristics and vegetation cover and determining the most important factors affecting soil organic carbon are among the studied variables. Materials and Methods: The study area in the Yancei region is located in the geographical area 20' and 32° to 39' 32° north latitude and 57' 59° to 13' and 60° longitude. Vegetation inventory of the area was carried out using cross-sectional method. The measured environmental parameters were: altitude from the sea level, average annual rainfall, average annual and average annual precipitation, acidity, conductivity, calcium, magnesium, sodium, potassium, phosphorus, carbon Organic and soil texture. To determine the environmental factors affecting soil carbon changes, principal components analysis (PCA) has been used on the values of factors and correlation coefficients as a criterion for the similarity between the plots. Results: The results of main component analysis showed that vegetation, climatic, maternal and altitude parameters have a great role in soil organic carbon control in these rangelands. The soil carbon content was positively correlated with clay (39%), sand (33%), potassium (30%) and magnesium (21%) and negative correlation with altitude (32%), nitrogen (18%), precipitation (39%), moisture content (39%) and coating (34%). Conclusion: In this study, it was determined that in the dry and semi-arid rangelands of Iran, soil organic carbon is primarily affected by rainfall and temperature, soil texture, elevation and vegetation. Therefore, a combination of different factors, especially those mentioned above, is needed to understand and estimate the soil organic carbon levels and without considering the key controller factors together, any estimation of the organic carbon of the soil would be unreliable.

Background and Objectives: The channels and rivers confluence phenomenon is the issue which occure in the irrigation and drainage channels, superficial water accumulative channels, water and waste water refinery and rivers. The aim of this research is to investigate the effect of several installed submerged vanes in tributary channel on controlling and decreasing the erosion at 90 degrees confluence of channels, detecting the best situation and vanes orders by using the simulation software. Materials and Methods: In this research, Flow-3D flow simulation software was used to model the various states of submerged vanes at 90-degree channels confluence. In order to verify the results, the data from the experiments carried out in the laboratory of the civil engineering department of Sharif University of Technology have been used. The experimental model consists of a main channel with a length of 12 meters and a width of 40 cm and a tributary channel of 3 meters in length, the width of the tributary channel is equal to the main channel. The tributary channel is located 6. 35 meters from the beginning of the main channel and is connected to the main channel at a 90-degree angle. The using equations were Navier-Stokes and continuity equations for modeling incompressible flows. For modeling turbulence, the k-w equation model was used. Results: The results of this study showed that software simulation can accurately estimate the scour pattern. So the difference between the maximum depth of scour of numerical and laboratory models in confluence was 1. 4%. Also few modeling were done with angles, dimensions and different locations of vanes to calculate the best conditions of vanes to decrease the depth of scour in channels confluence. The results showed that it is possible to decrease the scour hole dimensions, considering that submerged vanes were installed in the 60 degree (in respect to longitudinal axis of channel), the ratio of the length of the submerged vanes to the channel width was equal to 0. 25, the longitudinal spacing of the submerged vanes was half the width of the channel, the spacing of the submerged vanes from each other was 0. 375 of the channel width and the distance between the installation of the submerged vanes from the intersection of 0. 25 to 0. 375 was the width of the channel; submerged vanes effectively reduce the maximum depth of scour hole at the junction of two channels with a 90 degree angle. Conclusion: The final result of this study shows that if submerged vanes are installed in an appropriate position with optimal dimension in the tributary channel, they can reduce the maximum depth of the scour hole at channel confluences. In this study, the maximum scour depth was reduced by 21% submerged vanes compared to the non submerged vanes.