فصلنامه علوم و مهندسی آبیاری
سال چهل و چهارم شماره 2 (تابستان 1400)

The current study investigated the longitudinal flow velocity profile upstream of an orifice for different water depths using the FLOW-3D model. Experimental design was used along with LES, Laminar, and  turbulence models to calibrate the model. The obtained results indicated that turbulence models had almost high and equal accuracy for predicting longitudinal velocity profiles. For various depths upstream of the orifice, the general form of the longitudinal velocity profile followed an exponential function with high accuracy. Moreover, at larger-distance upstream of the orifice, the transverse velocity profile became uniform. Eventually, it was found that with the rise in the depth upstream of the orifice by eight times, the shear stress created on the bed increased by 148%.

The use of sprinkler irrigation systems have been significantly expanded over the last decades in Iran. Among the sprinkler irrigation systems, solid set systems have recently aroused much attention. However, fewer studies focused on the performance of mechanized sprinkler systems such as wheel move (WM) and linear moving system (LM). In this research, LM system and six WM systems were evaluated under two different climatic conditions, so that 12 and 8 field assessment tests were conducted for the WM and LM systems, respectively. Three indicators including Christiansen's uniformity coefficient (CU), distribution uniformity of low quarter (DUlq), and application efficiency of low quarter (AELQ) were used to describe the performance of the selected irrigation systems. As for WM systems, the calculated CU averages were 77.9% and 64.7% for low and high wind speed conditions, respectively, and also the number for LM system shown to be 81.7% and 72.3%, respectively. Regarding the same conditions, the AELQ averages for WM systems were seen to be 59.9% and 38.6%, respectively, and for LM system were 70.2% and 54.3%, respectively. The increase in the wind speed led to a reduction in water distribution uniformity, and however, wind effect on the performance of the WM systems was more than the LM system. Thus, it deserves to be pointed out that the LM system is an appropriate option compared to the WM system in various climatic conditions. Water pressure, sprinklers distance, and irrigation program were identified as the other factors, affecting the performance of sprinkler irrigation systems.

Flow aeration in chute spillway is one of the most effective and economic ways to prevent cavitation damage. Surface damage is significantly reduced when very small values of air are scattered in a water prism. A structure known as an aerator may be used for this purpose. Besides, ramp angle is one of the factors influencing aerator efficiency. In this research, the value of air entraining the flow through the Jarreh Dam’s spillway at the ramp angles of 6, 8 and 10 degrees, as three different scenarios, was simulated using the Flow-3D software. In order to validate the results of the inlet air into the flowing fluid at a ramp angle of 6 degrees, the observational results of the dam spillway physical model from the laboratory of TAMAB Company in Iran were used. According to the results, raising the ramp angle increases the inlet air to the water jet nappe, and a ten-degree ramp angle provides the best aeration efficiency. The Flow-3D model can also simulate the two-phase water-air flow on spillways, according to the results.

Continuous-time, distributed parameter hydrologic models like SWAT have opened several opportunities to boost watershed modeling accuracy. This study has described the essential parameterization issues involved when predicting watershed stream runoff using SWAT. Understanding these issues is expected to guide to improved SWAT runoff prediction performance. This research describes the important parameterization issues involved when modeling watershed hydrology for runoff prediction using SWAT, emphasizing the thanks to improving model performance without resorting to the tedious and arbitrary parameter by parameter calibration. The Bakhtegan watershed was used to illustrate runoff prediction's sensitivity to spatial variability, watershed decomposition, and spatial and temporal adjustment of curve numbers and return flow contribution. The SWAT model finishes hydrological simulation with good performance calibration (2006 to 2012) and validation (2013) periods. SWAT was also conversant in predict runoff from Bakhtegan that has extensive subsurface drainage. If properly validated, the study showed that the SWAT model would be used effectively in testing management scenarios within the Bakhtegan watershed. The result showed that the Nash–Sutcliffe of calibration and the validation between simulated and observed are 0.71 and 0.74, respectively. The SWAT model application, supported by GIS technology, proved to be a flexible and reliable water decision-making tool.

Bridge pier's local scouring is known to be a destructive factor in river engineering science. This phenomenon is widespread in river intersecting structures such as bridge piers, spur dykes, and downstream river structures. Extensive research has been conducted to reduce and control destructive phenomena, and many solutions have been proposed. These solutions are divided into two parts, namely, direct and indirect protection. In this study, the direct method was studied by defining scenarios. Since many bridges are affected by scouring during the operation, in the present study, the collar method, which is known as a direct protection method, in the case of flexible and permeable, is suggested. The technique is presented an adjustable chain collar, three times bigger than the pier's width (w/d=3), and its effect is investigated in clear water conditions. In the defined scenarios, three different diameters of the chain as CI=5 mm, CII=10 mm, and CIII=15 mm were used to control chain shapes' effect, and three dimensionless flow parameters (U/Uc 0.73, 0.85, and 0.96) were selected to investigate the effect of flow conditions. According to the results, the scour depth is related to changes in the diameter of the collar chain, as the final scour depth decreases by increasing the diameter of the chain from CI to CIII. Therefore, in the best conditions, for CIII, the dimensionless ratio of scouring reduction ( ) is equal to 71% near to inception motion parameter (U/Uc=0.96).

Due to the essential role of groundwater resources as useable and depleting water resources, the study and management of groundwater exploitation are of great importance. Proper management of groundwater resources needs knowledge of the spatial variability of groundwater level and groundwater salinity over the study area. To obtain such information, appropriate interpolation and mapping of groundwater level and groundwater salinity based on a limited number of observations is needed. The purpose of the present study is to evaluate Ordinary Kriging and IDW interpolation techniques for estimating groundwater level and groundwater salinity in Salman Farsi Sugarcane Plantation (West of Iran). The results showed that the prediction accuracy of the Ordinary Kriging model for groundwater level and groundwater salinity parameters was higher than the IDW model. To this aim, the Root Mean Square Error (RMSE) value was calculated to simulate the groundwater level in Ordinary Kriging and IDW method by 1.02 and 2.14, respectively, and to simulate the salinity of groundwater by 1.45 and 2.79. Due to the acceptable accuracy of the results of the Kriging model, planners can, by updating the data of this model, use it to predict the quantity and quality of groundwater parameters.

The  amount  of water  and  fertilizers  used in  the  production  of vegetables,  specifically  tomatoes,  is  high. This experiment was carried out to investigative of effects of yield, nutrient solution efficiency,Vegetative growth, and stomatal gas exchanges of two greenhouse tomato cultivars (V4-22, Amira) in open and closed hydroponic systems, as split-plot design based on completely randomized block design with three 3 replications at Shahid Chamran University of Ahvaz. The results showed that the effect of the hydroponic system had a significant effect on the efficiency rate of nutrient solution usage, fruit length, fruit firmness, leaf area, plant height, stomatal conductance and leaf temperature (P≤%5). The highest fruit length, fruit firmness, leaf area, plant height, stomatal conductance, and leaf temperature were measured in the open hydroponic system. The water productivity per performance in closed hydroponic system was greater than (approximately 55%) open hydroponic system. The highest and lowest water productivity biomass were obtained in the closed system and open system (48.91 and 34.42 kg/m3), respectively. The highest and lowest crop yields were measured in V4-22 and Amira cultivar (3874.29 and 3648.70 g per plant), respectively. Based on the results, the open hydroponic system has increased the characteristics such as plant height, leaf area, number of leaves and stomatal conductance, but the performance of the product in these two hydroponic systems is not different and also the closed hydroponic system reduces nutrient solution consumption up to 96% and fertilizer consumption up to 97%.

The salinity of water and soil resources and lack of appropriate quality water resources are major threats to agricultural development in arid and semiarid regions such as Iran, Khouzestan province. The implementation of haloculture projects causes the availability of saline water resources in these areas. Therefore, the study on the effects of salinity on seed generation was the essential aim of current research. In this study, because of the importance of nutrition, medical and industrial of Chia (Salvia hispanica L.), Guar (Cyamopsis tetragonoloba L.), Luffa (Luffa cylindrical L.), and Karela (Momordica charantia L.), the effect of saline water on seed germination indices were evaluated. The seed germination indices consisted of germination percentage (Gp%), the coefficient of the velocity of germination (Gi), seed vigor index (Vi), germination uniformity (GU), salinity tolerance index (STI), dry weight, fresh weight, and the percentage of moisture of the radical and plumule were determined under salinity stress. To achieve the aims of the current study, four salinity levels were used, including Karoon River water (as a control treatment) with an average electrical conductivity of 1.21 dS /m and diluted drain water with an electrical conductivity of 5, 10, 15, 20 dS/m (S1, S2, S3, S4, S5, respectively) in three replications (R1, R2, and R3). The experimental design was completely random. The analysis of variance of measured indices in the experiment showed that the effects of salinity on germination percentage of Guar and Luffa at 1% and Karela and Chia at 5% level of probability were significantly affected by salinity stress. The effect of salinity on the velocity of germination of the studied species was significant. Also, the salinity effect on the seed vigor index of Guar and Chia was significant at the 1% level. Increasing salinity significantly decreased the seed vigor index in the mentioned species. According to the results of this study, among four seeds, Chia and Guar were identified as the most tolerant plant to salinity stress in the seedling stage.

Considering Sefidrud River discharge decrease in the last decade in Guilan province in the north of Iran, groundwater and surface water resources can meet the water demand of rice cultivation in this area. It is evident that irrigation water quality should be considered in rice cultivation. Electrical conductivity (EC) is one of the essential parameters of assessing the quality of groundwater. The purpose of this research is to identify areas at risk of groundwater EC decrease for rice cultivation. For this purpose, zoning and probabilistic maps were prepared by ArcGIS software. The models were evaluated using ME, RMSE, MSE, RMSSE, and ASE statistical indices. The accuracy of the models was very good; the RMSE values for ordinary kriging were between 0.2674 and 0.4172 dS/m, and for indicator kriging, they ranged from 0.2841 and 0.4087 dS/m. The zoning and probabilistic maps showed an increase in EC of more than 1 dS/m from 2002 to 2015. In addition, the highest EC in Guilan province was in the central and eastern parts of the province, including Rasht, Astaneh, and Lahijan cities. More than 30% of groundwater resources were exposed to excessive salinity exceeding rice's tolerance level. Therefore, to prevent the quality mitigation of groundwater resources in the province and prevent yield penalty related to irrigation water salinity, the regional water companies should take appropriate management measures such as a ban on digging new wells or reducing groundwater extraction in hazardous areas.

In the Ardabil Plain, groundwater is one of the most important sources of water supply. Therefore, quality protection and groundwater management are a research priority. Ardabil Plain is in danger due to agricultural activity's excessive consumption of fertilizers in the agricultural sector, livestock, and industrial centers effluent. Therefore, it is necessary to identify and monitor areas with high vulnerability potential. In this study, the vulnerability of the plain is first assessed using the DRASTIC method.  The DRASTIC model is a general method and should calibrate in each area. So, this method was modified by two approaches. In the first approach, sensitivity analysis, and in the second approach, the amount of groundwater supply estimated by the WTF method was used. Then the vulnerability of Ardabil Plain was assessed. The results of the sensitivity analysis showed that the DRASTIC model in the Ardabil Plain area is susceptible to the parameters of Impact of vadose zone (I), Depth of groundwater (D), and aquifer media (A). The results also showed that the conventional model of the DRASTIC did not produce acceptable results compared to the Nitrate map. But calculating the amount of water recharge (R) by the WTF method, the correlation between the vulnerability maps and the Nitrate map was about 75%. In the second method, soil parameters (S) and hydraulic conductivity (C) did not have an acceptable correlation with the nitrate concentration in the groundwater of Ardabil Plain.  These parameters were removed from the initial equation of the DRASTIC method, and the maps were prepared with the remaining parameters and with new weights and ratings, as a result of which the correlation between the new maps and the nitrate map reached about 30%. According to the WTF modified method for the DRASTIC model, the whole of the Ardabil Plain vulnerability maps in four areas was divided, including medium, high, very high, and infinitely highly vulnerable areas, and 25.8, 47.7, 15.1, and 11.4 percent, respectively.