Showing 168 results for Rai
K. , and M. R. Nosrati, M. Amini, A. Haddadchi, Zare3,
Volume 20, Issue 78 (1-2017)
Abstract
Accelerated soil erosion in Iran causes on-site and off-site effects and identifying of sediment sources and determination of their contribution in sediment yield is necessary for effective sediment control strategies in river basin. In spite of increasing sediment fingerprinting studies uncertainty associated with magnetic susceptibility properties has not been fully incorporated in models yet. The objective of this study is determination of the relative contribution of sediment sources using magnetic susceptibility properties (High frequency, Low frequency and Frequency dependence) incorporated in uncertainty mixing model. For this purpose, 25 bed sediment samples were collected from the outlet of drainage basin and outlet of sub-basins and their magnetic susceptibility was measured and calculated. The results of Kruskal–Wallis test and discriminant function analysis showed that magnetic susceptibility properties can be used as optimum set of tracers in the uncertainty mixing model. The results of Bayesian mixing model indicated that mean (uncertainty range) relative contribution of Sparan, Joyband and Boyoukchay are 92 (83.9-94.8), 2.8 (0.2-10.7), 5.7 (0.2- 10.5) percent, respectively. According to these results, the highest amount of sediment yield is related to Sparan sub-basin and these results could be used in soil conservation and management planning.
Seyyed S. M. A. Maddahzadeh., K, Esmaili, B. Ghahraman,
Volume 21, Issue 1 (6-2017)
Abstract
Bi-level drainage system is a type of underground drainage systems, in which adjacent drainage lines are installed at different depths. In the Hydraulics Laboratory, Ferdowsi University of Mashhad, a model was built, that include a cube tank 2 meters in length, width and height of 1 meters was made of galvanized. In this model, two rows 20 cm apart from each other drains were installed. As drainage, a pipe of three layers to the outer diameter of 16 mm was made of PVC. Within this model of stratified soil was used as a soil layer of low permeability with a hydraulic conductivity of 1.15 cm per hour, thickness of 20 cm soil layer between two light soil layer with 30-cm thickness for bottom layer and 20 cm for the top layer with a hydraulic conductivity of 1.55 cm per hour. For accurate measurement of the water table Behavior in the soil at each point of the model, some piezometer distance of 10 cm from each other on the floor model was installed. After Outfit of model with blow-off valve, Experiments with a heavy irrigation for different intervals between depths of 30 and 50 cm were used in drainage and water table elevation values as observed values were extracted from the model. The results show that the values obtained from Upadhyaya and Chauhan Equation only in small area of water table profiles, which include an area of between the two drainage, are consistent with observed and with a wider distance between deep and shallow drainage, time of drop in water table increased.
M. Foroumadi, A. R. Vaezi,
Volume 21, Issue 2 (8-2017)
Abstract
Rill erosion is the first step in soil erosion process in the hillslopes, particularly in arid and semiarid regions. This study was conducted to investigate the role of rainfall intensity and raindrop impact on the physical properties of soils and particle detachment capacity (Dc) in a marl soil. Marl soil samples were filled into the flumes with 4 m long and 0.9 m wide and exposed to simulated rainfalls with different intensity varying from 10 mm h-1 to 100 mm h-1. Particle Size Distribution (PSD), aggregate size, porosity, crust thickness, and Dc were determined in each rainfall simulation. The results found that the physical soil properties i.e. PSD, aggregate size, porosity and crust thickness (P< 0.000) were significantly influenced by different rainfall intensities. Also, the rainfall intensity was also an important factor in controlling Dc in the soil. Rainfall intensity of 30 mm.h-1 was recognized as the threshold rainfall intensity for transporting soil particles in the marl soil and rill erosion. An increase in the rainfall intensity was attributed to the increases in the raindrop impacts and in consequence aggregate breakdown, and higher production of concentrated flows in the rills. Raindrop impact is the most important characteristics of the rainfall in the rill erosion and Dc in the marl soil.
Dr. S. Akhavan, N. Delavar, Dr. A. M. Mehnatkesh,
Volume 21, Issue 2 (8-2017)
Abstract
The aim of this study was to investigate the climate change impacts on some factors affecting rainfed wheat growth such as effective rainfall, planting date and length of growing season in four stations located in Chaharmahal and Bakhtiari province. Firstly, it is necessary to predict future (2046-2065) climatic conditions. For this purpose, the output of HADCM3 general circulation model was used under three scenarios of A1B, A2 and B1. The data were downscaled by LARS-WG model. After simulating the climatic parameters in mention period, the effective rainfall during the wheat growing season was calculated by Food and Agriculture Organization method. Also, the optimum planting date was defined according to the date of the first rain (at least 10 mm in case of continuing for next days). The wheat's growth stages were determined by Growing Degree Days method. The results indicated a rise in temperature for four stations. On average, it is expected that the annual temperature increase by 1.8°C compared with the baseline period (2010-1990). Total annual precipitation in Shahrekord, Koohrang and Borujen will decrease 2.2, 7.8 and 3.6 per cent respectively. About Lordegan it will increase by 2.7 per cent. Also, the results showed that in three stations of Shahrekord, Koohrang and Borujen, the amount of effective rainfall in November will increase compared to baseline, but in Lordegan it will reduce. So, in the first three stations, in most years, planting date was obtained earlier than baseline, but in Lordegan it was later than baseline. The Length of growing season will reduce in Shahrekord, Borujen and Lordegan stations, 12 days on average and in Koohrang about 13 days.
M. Golabi, M. Albaji, A. Naseri,
Volume 21, Issue 3 (11-2017)
Abstract
In the present study Hydrus-1D software was used to simulate electrical conductivity, pH and sodium, potassium, calcium, magnesium, chloride and sulfate ions. Field experiments were performed at the Sugarcane Research Center located in south of Ahvaz on sugarcane varieties CP48-103 with four water treatments (one treatment was Karun river water and three treatments were diluted drainage water) and three replications. The samples were collected from 0-30, 30-60 and 60-90 cm soil depth before irrigation and electrical conductivity and anions and cations of soil were measured in the laboratory. Sensitivity analysis and calibration were first performed with the aim of verifying the Hydrus-1D software. The sensitivity analysis indicated that the software had maximum sensitivity to the saturated volumetric water content. Minimum sensitivity was for the inverse of the air-entry suction, tortuosity parameter, residual volumetric water contents and moderate sensitivity was for hydraulic conductivity at natural saturation. Also, the software did not show any sensitivity to empirical parameter related to the pore size distribution that is reflected in the slope of water retention curve. In calibration stage the amount of hydraulic conductivity at natural saturation, residual volumetric water contents, saturation volumetric water contents, the inverse of the air-entry suction, empirical parameter related to the pore size distribution and tortuosity were obtained as 18 (cm/day), 0.04 (cm3/cm3), 0.63(cm3/cm3), 0.012 (cm-1), 1.2 and 0.6 respectively. The results showed that the coefficient of determination of all parameters was more than 0.85 which confirms the appropriate capabilities of the model in simulation of electrical conductivity, pH, anions and cations. In the modeling carried out the amount of NRMSE was between 11 and 18 percent which indicates good performance of the model. The Nash-Sutcliffe efficiency criterion was obtained 0.72 to 0.8 that indicates a good match of the model with reality. The coefficient of residual mass in this paper was positive for electrical conductivity, pH and sodium, potassium, calcium, magnesium and negative for chloride and sulfate. The positive and negative coefficient of the residual mass shows less and over estimation of the model.
A. R. Vaezi, M. Ahmadi,
Volume 21, Issue 3 (11-2017)
Abstract
Modified Universal Soil Loss Equation (MUSLE) is one of soil loss estimation models which has been developed based on the runoff characteristics in the event scale. However, it needs to be evaluated in the plot scale for the semi-arid rainfall events. With this aim, a field study was designed using twenty one plots. Runoff and soil loss were measured using 5-min samples under seven rainfall intensities consisted of 10, 20, 30, 40, 50 60, and 70 mm h-1 for 60 min. Soil loss was estimated using the MUSLE based on the runoff volume (Q) and runoff peak discharge (qp) and the values were compared with the observed values. The estimated soil loss was about 3.89 times bigger than the observed value on average. In order to improve model estimations, the power of rainfall erosivity index was modified from 0.56 to 0.62, (Q qp)0.62. The modification of the MUSLE model improved model efficiency (ME) from -5.5 to 0.47 and decreased the root mean square error from 0.000137 to 0.000031. This study revealed that the MUSLE overestimates soil loss from the small plots in the semi -arid regions. Therefore it is essential to calibrate runoff erosivity index using the data observed in the area. The modified MUSLE can be reliably used to predict soil loss in the small plot scale in semi-arid regions.
Y. Choopan, A. Khashei Siuki, A. Shahidi,
Volume 21, Issue 4 (2-2018)
Abstract
Limited water resource in arid and semi-arid areas is one of the most important problems in the agricultural sector. Therefore, the use of non-conventional water resources becomes more important. For this reason, a study was conducted on barley to evaluate the effect of irrigation with sugar plant wastewater as a factorial randomized complete block design field experiment. Treatments include water well I1, wastewater I2, combined water and wastewater I3 (the ratio of seven to one, according to local practice) in two levels of without water stress S1 and %75 water stress S2 and treatment I1S1 was considered as control. The results showed changes in surface tension of %1 had a statistically significant effect on plant height, grain yield and root length. As well changes of irrigation water in the level of %1 had a statistically significant effect on plant height, grain protein yield and root length. Maximum grain yield was obtained in treatment I1S1 with the weight of 4034 kg per hectare and lowest grain yield was obtained in treatment I2S2 with the weight of 1564 kg per hectare. The lowest and highest percentages of protein content were observed in treatment I1S1 for 12.37% and treatment I2S2 for 13.47%, respectively. The plant height showed the highest amount in control treatment, i.e. 82.87 Cm.
N. Rashidi, M. Naderi, Sh. Ghorbani Dashtaki,
Volume 21, Issue 4 (2-2018)
Abstract
Nowadays application of soil conditioners for mitigation and reduction of runoff is a current method. Considering the advantages of Polyacrylamide (PAM), this study was arranged to evaluate impacts of this soil conditioner on soil infiltration rate, runoff and erosion control. To fulfill the goal, a factorial experiment in a completely randomized design was carried out with four PAM treatments (0, 6, 10, 20 kgha-1), three slope levels (3, 6 and 9 %), three irrigation treatments and three replications. Surficial (0-10 cm) soil samples were collected from Shahrekord University campus and poured into square plots (55×55cm) with 15 cm depth, after pretreatments. The plots were treated with a simulated rainfall intensity of 36 mm.h-1 for 15 minutes and the attributed runoff, sediment load and drained water were collected and measured. The results showed significant differences among the runoff and soil erosion of control and of PAM treated soils. PAM minimized the raindrop negative impacts on soils and improved water infiltration and diminished the attributed runoff. Soil treatment with PAM as a soil conditioner significantly reduced soil erosion and sediment yield in all treatments.
R. Mostafazadeh, Sh. Mirzaei, P. Nadiri,
Volume 21, Issue 4 (2-2018)
Abstract
The SCS-CN developed by the USDA Soil Conservation Service is a widely used technique for estimation of direct runoff from rainfall events. The watershed CN represents the hydrological response of watershed as an indicator of watershed potential runoff generation. The aim of this research is determining the CN from recorded rainfall-runoff events in different seasons and analyzing its relationship with rainfall components in the Jafarabad Watershed, Golestan Province. The CN values of 43 simultaneous storm events were determined using SCS-CN model and the available storm events of each season have been separated and the significant differences of CN values were analyzed using ANOVA method. The Triple Diagram Models provided by Surfer software were used to analyze the relationships of CNs and rainfall components. Results showed that the mean values of CN were 60 for summer and winter seasons and the CN values in the spring and autumn seasons were 50 and 65, respectively. The inter-relationships of CN amounts and rainfall characteristic showed that the high values of CNs were related to high rainfall intensities (>10 mm/hr) and rain-storms with total rainfall more than 40 mm. Also the CN values were about >70 for the storm events with 40-80% runoff coefficient values.
A. R. Vaezi, Y. Mazloom Aliabadi,
Volume 22, Issue 1 (6-2018)
Abstract
Water loss and nutrients loss are one of the important signs of natural resource degradation in the catchments. The amount of loss of these resources is affected by several factors including the characteristics of rainfall. In this study, the data of stream discharge (Q), total dissolve solids (TDS), and total nutrient loss ratio (NR) along with rainfall characteristics were analyzed for the events from1988 to 2002 in the Tahamchai catchment, which is owned by a regional water company. Moreover, soil properties were determined by soil sampling from different points in the catchment surface. Based on the results, there was a significant correlation between Q of the river and rainfall height (r=0.24, p<0.05), while its correlations with the rainfall intensity and duration were not statistically significant. On the one hand, this result was due to the inverse relationship between rainfall intensity and rainfall duration; on the other hand, due to the temporal variations in vthe egetation cover in the area, it controlled Q in the intensive rainfalls. The highest Q was in spring (1.68 m3 sec-1) and March (2.58 m3 sec-1). In this period, rainfall height was high and the rainfalls interval was short. Moreover, vegetation cover was weak, so it could not control surface runoff and reduce Q in the catchment. TDS and NR also significantly varied during the months and their highest values were observed in December (282.55 mg l-1) and (61.77 mg l-1), respectively. Mg2+ had the highest amount of water loss in the catchment area. A negative correlation was found between Q and TDS (r=0.41, p<0.001) and NR (r=0.31, p<0.001). This study revealed that spring and autumn were the sensitive period for water loss and nutrient loss in the catchment, respectively. Therefore, promoting the vegetation cover in early spring and reducing improper agricultural practices (tillage and fertilization) could be substantial strategies contributing to conserving the catchment’s resources.
Y. Abdoli, S. Jafari,
Volume 22, Issue 1 (6-2018)
Abstract
This study was done to evaluate the effect of topography, water table, and irrigation on gypsc soil development and clay mineral diversity in Ram-Hormuz Plain, Khuzestan Province. To localize, 10 profiles in this region that covered all purpose irrigation and topography situation were described. The results showed that the soils could be classified in Entisols, Inceptisols and Aridisols orders. All soil epipedons were ochric and subsurface horizons were cambic, gypsic, and salic. The salic horizons were formed under a low water table. The XRD results showed that smectite, kaolinite, illite, chlorite, palygorskite, vermiculite and sepiolite were the dominant minerals, respectively. Kaolinite and illite were inherited from the parent material, but chlorite was the result of both inheritance and transformation of other clay minerals except uncultivated or non-irrigated soils. Sepiolite was decreased in gypsic horizons, but palygorskite was increased in these horizons. Sepiolite was raised with increasing the depth under the good drainage class; this could be related to neoformation, but it was decreased with depth under the weak drainage class. These results could be due to the instability of this mineral in high moisture and its low Mg activity. There was also a negative correlation correlation between Palygorskite and smectite; this was such that most palygorskite was observed in the surface horizons, but smectite was in the subsurface. Smectite was the dominant clay mineral in the studied soils; it was formed from the weathering of other minerals as well as from neoformed ones in the lowlands. Vermiculite was formed in these soils due to k depletion by leaching or plant absorption. This happened in the illite to smectite transformation process. Therefore, topography and irrigation could be regarded as the main factors putting these soils in high category; also, clay mineral assemblage was different under this situation in these soils.
S. Parvini, Z. Jafarian, A. Kavian,
Volume 22, Issue 2 (9-2018)
Abstract
Due to the lack of necessary equipment for measuring and recording changes in watershed runoff and flood situation after the implementation of corrective actions, using hydrologic models is considered as an efficient tool to assess the undertaken actions and simulate the behavior of the watershed before and after the implementation of these measures. The present study aimed to simulate the effects of corrective actions on runoff components using HEC- HMS hydrological models in the form of a rangeland and watershed plan in 2006 and the predicting plan of applicable operations in a region in the Meikhoran watershed, Kermanshah. For this purpose, three scenarios including the conditions before running the rangeland and watershed plan, the conditions after running the project and requirements and enforcement actions resulting from the proposed location map were considered in the spring of 2006. First, a map of the curve number (CN) changes was prepared under all three scenarios caused by the vegetation changes and by implementing HEC-HMS model, the curve number criteria, the peak discharge and flood volume were determined to assess the changes in hydrological basins and their values for all three scenarios were calculated and compared. The results showed that the HEC- HMS model for the base period (first scenario) with Nash-Sutcliffe coefficient 0/551 and the coefficient of determination 0/63 had an acceptable accuracy in predicting runoff. Nash-Sutcliffe coefficient for the second and third scenarios was 766/0 and 0/777, respectively. Also, the results showed that in the second scenario, there was an 8/85 and 7/74% decrease in the peak flows and runoff volumes, respectively, and these values for the proposed operation were estimated to be 12.84% and 6.33%, respectively. Overall, the results indicated the considerable impact of rangelands and watershed management (third scenario) on the reduction of effective runoff components, particularly flood peak, on the basis of the location model.
F. Jahanbakhshi, M. R. Ekhtesasi, A. Talebi, M. Piri,
Volume 22, Issue 2 (9-2018)
Abstract
One of the main sources of runoff in arid and semi-arid mountainous highlands is typically composed of before Quaternary formations. Since the structure and lithology of formations are different, varying formations can have different significance in terms of runoff and sediment. The present study aimed to investigate the sediment production potential and the runoff generation threshold on three formations (Shirkooh Granite, Shale, Sandstone and Conglomerate of Sangestan and Taft Limestone) in Shirkooh mountain slopes. The 60 mm/h rainfall intensity with the 40 minute continuity, according to region rainfall records, and the ability of the rainfall simulator were selected as the basis for the study. Field experiments were conducted in dry conditions based on one square meter plot on rocky slopes with a gradient of 20 to 22 percent and a maximum thickness of 30 cm of soil. The results showed that in 60 mm/h rainfall intensity, the minimum rainfall to produce runoff on Sangestan, Shirkooh and, Taft, was 10, 10.7 and 16.7 mm, respectively. The maximum amount of the sediment was measured on Sangestan, Taft and Shirkooh, respectively. Statistical tests related to runoff and sediment production on all three formations confirmed a significant difference at the 5 % level. In terms of the time required to start runoff, the minimum time was for Sangestan, Shirkooh and Taft, respectively. According to the results, in terms of the potential for runoff generation and sediment production, Sangestan, Shirkooh and Taft can be ranked from high to low levels.
M. Noshadi, S. Karimi,
Volume 22, Issue 3 (11-2018)
Abstract
The growth of world population and the demand for agricultural products can be regarded as one of the important issues that humanity has ever faced. There are serious concerns regarding surface and ground water pollution by nitrates because of using nitrogen fertilizers in the agriculture. Improving agricultural water management systems can reduce nitrate in drainage outflow and therefore, reduce the environmental pollution. This research was conducted to evaluate the effect of the controlled drainage and nitrogen fertilizer on nitrate leaching and environment pollution as a factorial randomized complete block design in Shiraz College of Agriculture. The treatments consisted of three fertilizer levels; 0, 200 and 300 kgN/ha, and three water table depths: free drainage, control water table at 60cm (CD60) and 90 cm (CD90) depths, respectively. According to the results, the value of drainage water and nitrate losses in the controlled drainage toward free drainage were significantly increased. The mean reduction of drainage water in CD60 and CD90, as compared to free drainage, was 59.3 and 35.7%, respectively. The decrease nitrate losses, as compared to free drainage, was 72 and 44%, respectively. The total value of nitrate leaching in 200 and 300 kgN/ha fertilizer treatments was 1.86 and 2.48 times of 0 kgN/ ha.
M. Yazdekhasti, M. Shayannejad, H. Eshghizadeh, M. Feizi,
Volume 22, Issue 3 (11-2018)
Abstract
Due to the dry climate and limitation of fresh water resources, using fresh and salt water is a solution for crop production under salinity conditions. This study was conducted at Isfahan University of Technology as a randomized complete block design with three replications and five irrigation management treatments in 2014. The treatments included irrigation with saline water (with the salinity of 5 dS/m, based on the relative yield of 75%), irrigation with fresh water (municipal water), alternate irrigation (irrigation with saline water and the next irrigation with fresh water), conjunctive irrigation (half of irrigation with saline water and the other one with fresh water) and irrigation with fresh water to reach the raceme stage, and irrigation with saline water. The maximum wet yield, dry yield and grain yield were related to the fresh water treatment with 4.14, 2.45 and 0.588 kg/m2 and the minimum values were obtained for water their water treated with 1.34, 0.765 and 0.0957 kg/m2 respectively. The conjunctive treatment had the highest yield after fresh water treatment. The various statistical indices showed that this model could be used for sorghum in Isfahan. The determination coefficient for yield was 0.65.The priority of model for yield simulation was salt water at the last stage, alternate irrigation, saline water, conjunctive irrigation and fresh water treatments, respectively.
M. R. Mirzaei, S. Ruy,
Volume 22, Issue 4 (3-2019)
Abstract
Preferential flow is of great importance in the environment and the human health. So, rapid water transportation and consequently, pollutants and pesticides leak out and get into the groundwater, making it very difficult to measure and quantify. To quantify and describe the preferential flow, two gravity-driven models were used: 1) kinematic wave model (KW) introduced by Germann in 1985), and 2) kinematic dispersive wave (KDW) model developed by applying a second-order correction to the Germann’s model by Di Pietro et al. in 2003. So, the experimental data was obtained using the laboratory mini-rainfall-simulator over cylindrical soil samples at the laboratory. Their parameters were obtained using Solver add-ins in the Excel software. Then, the results were compared using the root-mean-square error (RMSE). The results showed that the KDW model could better predict the preferential flow (with lower RMSE). Also, the regression results showed 1) there was no significant relation between the preferential flow and the total porosity, and 2) there is a significant relation between the preferential flow and the macrospores.
S. Salehi, Sh. Esmael Zade, Gh. Panahi, K. Esmaili,
Volume 22, Issue 4 (3-2019)
Abstract
The effect of the uplift force in the hydraulics structures is against stability. So, determining and controlling this force can be very important. One of the ways to achieve this purpose is to decrease this force by using the hole drains; in this way, we can build perpendicular pipes with different diameters, leading to the durability of the structure. Therefore, an experimental model of concrete dam was constructed in the hydraulic laboratory. The dam's model was divided into five sections by using 4-hole drains with a thickness equal to the dam's foundation. By running experiments with the maximum water level at the upstream, dam hole drains were opened in their position. Hydraulic potential was estimated by using the Piezometer built in the flume body. Finally, by opening some hole drains, the uplift force was calculated from the equipotential lines. Therefore, the best case (which had the minimum force) was determined, which was a/L=0.4, to create the most proper hole drain in the dam foundation. (a: distance of drain to heel and L: length of the dam's foundation). To place the hole drain in this position, by applying the zero potential in this position, the up lift force was increased
S. Abdi, A. Pirzad,
Volume 23, Issue 1 (6-2019)
Abstract
Water stress is one of the most important factors limiting the growth and production of crops in arid and semi-arid regions. To evaluate the effect of mycorrhizal fungi species on the growth and yield (quantity and quality) of Onobrychis sativa under water deficit condition, a greenhouse factorial experiment based on completely randomized design (CRD) with three replications was conducted in 2014. Treatments included five species of mycorrhizal fungi (Fanelormis mosseae, Rhizophagus intraradices, Claroideoglomus claroideum, Funneliformis caledonius, Glomus versiforme and non-mycorrhizal control) and two levels of irrigation (irrigation at 80% [well watering] and 50% [water deficit] field capacity [FC]). The highest grain yield (9.187 g/plant) was obtained from the stressed plants inoculated with Rh. intraradices with the same grain yield of F. mosseae inoculated plants (8.867 g/plant). With a significant reduction in the grain yield of stressed plants, mycorrhizal relationships even increased the yield more than the well-watered plants. Despite the decreases in the grain protein and phosphorous of water-deficit stressed mycorrhizal plants, the highest grain protein content was obtained from the plants inoculated with G. versiforme, and the highest grain phosphorus content was obtained from the plants inoculated with F. mosseae. Mycorrhizal symbiosis enhanced the yield and the quality of Sanfoin grain in water deficit stressed plants due to reducing root volume against the stimulating root elongation. In this way, the species G. versiforme exhibited the greatest positive effect.
A. Sharifnezhad, M. Kashefipour, M. Ghomeshi,
Volume 23, Issue 1 (6-2019)
Abstract
Study of Turbidity Current, as one of the most important phenomena affecting the sedimentation in the reservoirs of dams, is essential. Since most of the research studies have been conducted under experimental conditions on rigid beds, the effect of erodible bed and the formation of the bed form on the turbidity current specifications is not yet clear. Therefore, in this Research, the study of the turbidity current in two conditions of rigid and mobile bed was conducted in order to determine water entrainment specification and the effective hydraulic parameters. The results showed that water entrainment changes depended on the variation of bed roughness and the type of bed form. Also, water entrainment of turbidity current was initially reduced by about 25% with the change in the bed shear stress, relative to the rigid bed, due to formation of small bed forms; then, it increased by about 30%, forming the larger bed forms; finally it decreased with increasing the flow strength and removing the bed forms. In addition, comparison of the results of the present study with previous research showed that the formation of bed forms increased water entrainment in a constant Richardson number up to 50%.
A. Kavian , A. Alipour, K. Soleimani, L. Gholami,
Volume 23, Issue 1 (6-2019)
Abstract
Nowadays, acid rain serves as one of the most serious environmental problems has affected many regions in the world. This phenomenon is characterized by many environmental impacts, such as soil contamination and degradation. Acid rain immediately affects soil, causing soil particles to breakdown and be dispersed; this is the first step to initiate the soil erosion. Therefore, in this study, the effect of different pH levels of acid rain (at different levels) on the soil splash was investigated under laboratory conditions using a rain simulator and a cup splash. In the experiments, acid rains, with the pH values of 3.75, 4.25, 5.25 and normal rains at three intensities of 40, 60 and 80 mmh-1, were studied; finally, a number of 36 samples were taken for statistical analyses. SPSS 23 and EXCEL 2013 software and one way and two-way ANOVA were used for the statistical analysis at a confidence level of 95%. The results showed that at the intensities of 40 and 60 mmh-1, the splash rate was significantly different in all pH treatments, and the acid rain with pH of 3.75 showed the highest splash rate. However, no significant difference was found at the rain intensity of 80 mmh-1, despite the higher splash rate at the pH of 4.25 and 5.25 treatments. Also, the results of the comparison of the means showed that the soil splash rate was also increased with enhancing rain intensity. Finally, the two-way ANOVA test showed that the simultaneous interaction effects of the two factors of pH and rain intensity on soil splash was not significant.
