WATER AND SOIL SCIENCE (AGRICULTURAL SCIENCE)
Year:2020 | Volume:29 | Issue:4|Papers Count:15

In this study the effect of chute bed roughness height on energy dissipation has been investigated. First effective parameters were identified and then a general dimensionless relationship was developed. A series of tests were conducted by a physical model using the bed slopes of 25 and 35 degrees and four different uniform roughness heights (3. 38, 7, 12. 7 and 38. 1 mm) having uniform particle sizes on the bed. Total of 80 tests were conducted with flow discharges range between 4 and 40 L s-1 and Froude number between 4. 5 and 9. A relationship was developed for prediction of energy slope on this type roughened bed chutes and the results obtained were compared with the results of previous works. Energy dissipation per unit length of the roughened chute was 7 to 38% greater than that of the smooth chute (without roughness).

Hydraulic characteristics of wide channels differ from narrow channels due to the higher ratios of width to depth, b/h. In this research, using a physical model of a rigid boundary channel having 60m length, 1. 5m width and a bed slope of 0. 001 with b/h ratio of 12 to 56, hydraulic characteristics of wide channels including: stagedischarge relationship, velocity and shear stress distributions were experimentally considered. The results indicate that the maximum velocity in the wide channel was occurred nearby the water surface. Investigation of the vertical velocity distribution reveals that the flow velocity follows the well-known logarithm distribution law. The also results show that the shear stress was maximized in the centerline of channel section, and the dimensionless shear stress was increased by increasing the ratio of b/h. In ratios of b/h less than 30, the dimensionless bed shear stress value is less than 0. 9 and in case of b/h greater than 30, it is greater than 0. 9. A comparison of the results for wide channels and channels with an optimal width of b/h=2, reveals that the relationship between b/h and shear stress in narrow channels is linear, while in wide channels a power relationship is governing. Moreover, in wide channel sections, the percentage of shear force on the walls (%SFW), due to the low depth of flow which is less than 10 and negligible, so that to contribute the walls to the shear stress can be ignored for design purposes.

The Lake Urmia basin in North West of Iran is one of the important basins of this country due to its climatological, economical, ecological and environmental condition. In this study in order to discover the likely causes of the lake shrinkage, trends of the two effective factors on its inflows (precipitation and rivers discharge), were investigated. For this purpose, rain gauges and hydrometric stations data at seasonal and annual scale across the basin were collected. Long time-series of variables were prepared and their trends were analyzed using the Mann-Kendall and seasonal Kendall test. According to the results although annual precipitation indicated decreasing or increasing trends at some stations, but most of them were not significant at 0. 05 probability level. Despite lack of significant, decreasing trend for annual precipitation across the basin, the majority of hydrometric stations showed significant decreasing trend in the annual stream flow data at 0. 05 probability level. Therefore, from statistical point of view, the significant decline at annual discharge of the streams draining into the lake and the shrinkage of the lake cannot be attributed to decline at annual precipitation. Therefore, some other causes such as increase in evapotranspiration due to atmospheric warm-up. Over-extraction of aquifers, extensive landuse changes, impoundment of water behind numerous dams and decline at the lake inflows might be effective on the Lake Urmia shrinkage.

In order to evaluate the effects of phosphorus (P) fertilizer and contaminations of lead (Pb) and zinc (Zn) on root Pb, Zn, and P concentrations, pyromorphite (Pb5(PO4)3Cl, F, OH)) formation in a calcareous soil, an experiment was conducted as factorial on the basis of completely randomized design with three replications under greenhouse and laboratory conditions with three factors of Pb at four levels (0, 200, 400, and 800 mg kg − 1 soil as Pb(NO3)2), Zn at three levels (0, 25, and 250 mg kg − 1 soil as ZnSO4. 7H2O) and P at three levels (0, 50, and 500 mg kg − 1 soil as Ca(H2PO4). 2H2O). At the end of the rice growth period, root Pb, Zn, and P concentrations were measured. The treatment of Pb800P500Zn250 was subjected to X-ray diffraction (XRD) analysis for pyromorphite formation. The results showed that application of P fertilizer resulted in reducing the average root Pb and Zn concentrations by 15 and 2%, respectively. The application of Zn fertilizer resulted in reducing the average root Pb and P concentrations by 13 and 6%, respectively. The XRD results showed the formation of poorly crystalline chloropyromorphite. Also, in Pb and Zn polluted soils, application of P fertilizer could decrease mobility and bioavailability of these metals and restrict their uptake by plant.

Runoff is a main component of water balance in the watershed scale which its accurate estimation helps to better hydrological simulation of watershed. In this study, the SWAT (Soil Water Assessment Tool) model was used to simulate runoff in Neyshabour watershed with area of 9500 km2 for the 2007 to 2010 period. To this means, SWAT model was calibrated based on measured runoff data at three hydrometric stations (Andarab, Kharve Majmoo and Hossein Abad) during 2000-2007. Calibration, uncertainty and sensitivity analysis were done using SUFI-2 algorithm. According to the results, parameters such as fraction of transmission losses, moisture condition curve number and factors related to snowmelt showed the greatest sensitivity to run off estimation. The model calibration in all three stations; Andarab, Kharve Majmoo and Hossein Abad, was evaluated as appropriate by referring the values of 0. 84, 0. 77 and 0. 92 for the NashSutcliff efficiency coefficient, respectively, although underestimations for the peak amounts of hydrographs were observed relatively. The values of the mentioned coefficient were obtained as 0. 92, 0. 66 and 0. 71 for the validation period at the stations of Andarab, Kharve Majmoo and Hossein Abad, respectively. Also root mean square error values varied between 0. 46 to 0. 57 m3/s and 0. 06 to 0. 19 m3/s in the same three hydrometric stations for the calibration and validation periods, respectively. The results showed that considering the crop management concepts significantly improved runoff estimation.

Occurrence of the vortex in hydraulic structures as a natural problem has negative effects on the performance of the intakes. In order to better understanding this complex phenomenon, in addition to macroscopic studies on critical submergence and anti-vortex devices, microscopic studies are also employed to investigate the hydraulic properties of a vortex. In the present study, a strong air-core vortex under critical submergence condition was created on a vertical bottom intake at a wide flume then the three-dimensional velocity components of the flow were measured by a particle tracking velocimetry method. By analyzing the velocity components and water surface profile, the changes of the hydraulic characteristics of the vortex in the flow path were identified and a new information from a 3D vortex structure with the air core was obtained. Based on the results, it was found that the Particle Tracking Velocimetry (PTV) method can provide useful and new information about distribution of the velocity components in the vortex structure.

Successive sluice gates are utilized to deliver a relatively constant amount of flow rate for a range of water levels variations at the upstream of the water distribution channels. In this study, the flow through successive sluice gates in four different models with five input flow depths were simulated and investigated using FLOW-3D software. Comparison between the numerical and experimental results indicated that the differences of the output flow rates were less than 10%. Therefore, the accuracy of simulated models was desirable. After validation of models, the output flow rate was calculated for each model and compared with design flow rate. Comparing the output flow rates of models with the design flow rate indicated that in the all investigated cases, there was an approximate difference of 8 percent. Therefore, the successive sluice gates showed acceptable accuracy in delivery of constant flow rate during variation of water depth at upstream of the channel. Also, the evaluation of energy dissipation in the models showed that the energy dissipation was negligible when just the first gate was active. But by increasing the depth of input flow and utilization of the next gates, the rate of energy dissipation caused by the flow through successive sluice gates was increased to about 15-22 percent. Therefore, in addition to precise flow regulation, this structure was also effective in energy dissipation if input flow depths were high.

In this study the HBV hydrological model and runoff indices have been applied to investigate the impacts of climate change on runoff in the ArazKoose watershed. Therefore, the projected future temperature and precipitation under the three representative concentration pathways (RCPs) 2. 5, 4. 5 and 8. 5 scenarios for the first future epoch (2031-2051) and the second future epoch (2051-2071) were incorporated into the calibrated HBV model. The Dynamic Dimension Selection (DDS) optimization technique was used to calibrate the HBV model’ s input data of precipitation, potential evapotranspiration and temperature in daily scale. Daily flow data from 1986 to 1999 and from 2006 to 2009 were used to calibrate and validate the model, respectively. The Support Vector Machine (SVM) model projected the evapotranspiration in two future epochs. Future runoff simulations compared to the base period with respect to hydrological indices of flow duration curves indicating a decreasing trend in monthly runoff of ArazKoose watershed. Furthermore, projected extreme events resulted in decreasing high flow and low flow by 60% and 25%, respectively, in the future when compared to the baseline period. While, the annual mean flow projected to increase by 25% than that of historical period in two scenarios except in RCP8. 5.

Operation of reservoirs is influenced by lots of goals and generally many of these objectives are inconsistent with each other. The inflows of reservoir and storage volumes are uncertain, which lead to increase the complexity of the operation of the reservoirs. Utilization of optimization methods to determine the operational policy of the reservoirs is an important issue in the planning and management of water resources. Heuristic techniques have been developed as a tool in the optimization of complex systems. In this study, in order to evaluate the ability of the HSA in solving the problem of reservoir operation, and also to present the algorithm's efficiency in solving the problems with a large number of decision variables, optimization of the Dez dam reservoir operation is considered for a long time period (40 years). The goal is supplying the agricultural water demand of downstream. The global optimum value of the objective function was calculated 10. 55 by application of the Lingo software and 19. 78 by use of the HAS algorithm. The results of HSA were compared with HBMO and ACO algorithms and it was revealed that the HSA could present a better solution than HBMO and ACO algorithms. So, the use of this algorithm for optimal operation of reservoirs with more complex objective function and a greater number of reservoirs, could be recommended.

Study of the changes in precipitation regimes is very important in proper water resources management. In this research, in order to analyze the state of precipitation and annual dry spell periods, the trends of SPI, Annual Maximum Dry Spells length and Annual Number of Dry Spell Periods indices were studied. For this purpose, daily precipitation data of five synoptic stations in northwest of Iran (Urmia, Tabriz, Ardebil, Khoy and Maragheh) having a 34-year data record (1981-2014), were used. After examining the homogeneity and normality of the data, the significance of autocorrelation in each of the time series was tested. According to outcome of Mann-Kendall test, all three indices had a decreasing trend in the most of stations. Decreasing trend in the two AMDSL and ANDSPs indices reflects improvement of spell and number of dry periods, and decreasing trend of SPI index indicates reduction of precipitation. So, we can conclude that despite of the reduction in precipitation in the region, rainfall distribution has improved over the years. Decreasing trend of the two SPI, and ANDSP indices is significant in Maragheh and MannKendall test criteria (Zm) for SPI, and ANDSP indices were-3. 622 and-2. 408 respectively (P<0. 05). In order to identify the change points of the trends of series, sequential Mann-Kendall technique were used. The results indicated the occurrence of significant jump in Maragheh station.

The ogee spillway with a curve axis has a longer crest length than the spillway with linear crest. Therefore, in a specific reservoir water level, it can discharge higher flow rate compared to a straight one and due to this reason is preferred in applicable plans. In this study, physical model of Germi-Chai spillway which include an ogee crest with a curve axis and converging training walls was constructed in scale of 1: 50. The SCWMRI Soil Conservation and Watershed Management Research Institute, has led a research effort on it. For each of the convergence angles, including 60 and 90 ̊ in both symmetrical and asymmetrical situations, flow characteristics such as discharge, water surfaces, depths and distributions of pressure were investigated in the downstream channel of the spillway. Experiments conducted in varying flow discharge from 30% to 177% of design discharge. Based on visual observation, at the toe and the end of straight portions of the spillway face, due to converging training walls, interference streamlines occurred which led to generate a rooster tail phenomenon. It was observed that in the convergence angle of 90° , rooster tail had been witnessed up to slightly more than 118% Qd. However, it saw nearly 147% Qd in 60° convergences. Moreover, it should be emphasized that due to asymmetric angles, closest wall to the rooster tail had more static pressure.

The aim of this study was investigating the impacts of Bukan ' s Dam construction on hydrological indices based on the Flow Duration Curves (FDCs) of the Zarrinehrood River during the pre (1955-1971) and post-dam (1972-2011) construction periods. For this aim, nineteen hydrologic indices were calculated in four groups of Peak Flow, Flow Duration, Low Flows and Flow Variability. In this regard, the Flow Duration Curves were plotted for both pre and post-dam construction periods. Based on the results, the values of 1-day maximum flow and the average of daily flow in the post-dam construction period decreased by 13% and 7. 5%, respectively. However, the values of the index for 1-day minimum flow in the post-dam period increased by 4. 7 percent. The results showed that at 50% of the flow duration time in post dam construction period the amount of discharge was increased 40%, which related to the impact of the dam on the flow of the Zarrinehrood River. The average magnitude of the rising rate relative to the average flow discharge in the pre and post periods of the dam were 97. 71 and 79. 18 cubic meters per second respectively, which indicated a 18% decrease in the flow of river flooding during the period after the dam construction. In the post-dam period, the average amount of discharge increased in summer season. In conclusion, the construction of the dam had reduced the flood variation related indices and increased the indices of the flow related to the duration components.

Among the soil forming factors, climate by effect on weathering severity and parent material degradation plays a basic role on soil evolution. In order to investigate the effects of climate on soil physicochemical properties and evolution in Ilam province, two regions from a climosequence were selected. The purpose of this study was to compare soil evolution in a climosequence according to the soil indices of clay, iron, aluminum, manganese, and 5 profiles in each land units of Salehabad and Ilam plains were dug, described and sampled. The results of physicochemical analysis of Salehabad and Ilam soil profiles in two regions were different and significant difference were observed within the all parameters except pH and silt. In addition, electrical conductivity increases in Salehabad soils with ustic moisture regime and hyperthermic temperature regime comparing to Ilam soils with xeric moisture and thermic temperature regimes revealed the climate effect on them and changes in soil orders from Inceptisols in Salehabad to Mollisols in Ilam were related to the changes in moisture and temperature regimes. Soil classification showed that Salehabad soils were placed in Gypsic Haplustepts and Ilam soils were placed in Gypsic Calciusteps, Typic Calcixerolls and Typic Haploxerolls subgrops. Based on obtained results the iron, aluminum and manganese amounts in Ilam soil profiles were higher than those in Salehabad ones and less weathering in Salehabad region were happened by drier climate, lower humidity and higher temperature. Additionally, the results showed that the horizons with gypsum did not have potential to store clay and metal oxides, and the soil evolution according to the distribution and amount of iron, aluminum and manganese offered a better understanding of the soils and their forming conditions and the Ilam soils showed further evolution.

For a cost-effective design of wave screen, an accurate estimation of dynamic pressure and wave force is needed. This study investigates the dynamic pressure action on elements of wave screen. The wave screen consists of several horizontal pipes with constant distance between them. This wave screen provides convection, interchanges of seawater within the harbor district, and makes available wave energy absorption effectively. The experimental were done on regular waves with 3 heights and 6 periods of waves at a constant water depth of 0. 6 m. Also 3 difference diameters were considered for wave screen pipes. Dynamic pressures distribution along and around the pipes were measured by the pressure transducers. The results indicated that with increasing of the porosity, the pressure difference was decreased and with increasing of the incident wave height, pressure fluctuation for different porosity was increased. Furthermore, the maximum dynamic pressure fluctuation occurred at the angle more than 45° .

In general, rapid transformation of supercritical flow regime into subcritical flow is accompanied with hydraulic jump. The phenomenon usually occurs at downstream of the hydraulic structures such as ogee spillway. The length of hydraulic jump is one of the most important parameters used to determine the dimension of stilling basins. In current study, a hybrid method for predicting the hydraulic jump length on sloping rough bed was developed. In the other words, the hybrid method (ANFIS-GA) was presented using combination of Adaptive Neuro-Fuzzy Inference Systems (ANFIS) and Genetic Algorithm (GA). In this study, to examine the performance of ANFIS-GA models, the Monte Carlo simulation (MCs) was used. At first, the effective parameters on length of hydraulic jump such as; Froude number in upstream of the hydraulic jump, the ratio of bed roughness, sequent depth ratio, and bed slope, were identified. Next, regarding these parameters, five ANFIS-GA models were defined. Then, the results of the ANFIS-GA models were examined and the superior model was introduced. The superior model predicted the experimental measurements with acceptable accuracy. For example, the Mean Absolute Percentage Error (MAPE) and Root Mean Square Error (RMSE) were respectively computed 4. 520 and 0. 781. In addition, the results of modeling revealed that the Froude number at upstream of hydraulic jump was the most effective parameter in modeling the length of hydraulic jump on sloping rough bed using ANFIS-GA method.