Mahmoudreza Tabatabaei; Amin Salehpour Jam; Jamal Mosaffaie
Abstract
IntroductionThe cycle of soil erosion (including removal, transport and deposition) that controls the sedimentation of watersheds, includes a set of complex and highly nonlinear processes. On the other hand, the factors influencing sedimentation in watersheds are very diverse, and according to the specific ...
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IntroductionThe cycle of soil erosion (including removal, transport and deposition) that controls the sedimentation of watersheds, includes a set of complex and highly nonlinear processes. On the other hand, the factors influencing sedimentation in watersheds are very diverse, and according to the specific conditions of climate, soil, vegetation, geology, topography, etc., in each basin, the weight and role of each of the mentioned factors in sediment production is very different. Accurately determining and measuring these factors and making mathematical relationships between them are often difficult, expensive, time-consuming and error-prone, and this is the case with the use of models based on computational intelligence and the use of a limited number of basin dynamic variables, it is possible to simulate the behavior of the watershed in sediment production. Regardless of the type of intelligent models, in most of the conducted research (especially in internal research), the simulation of suspended sediment is mainly based on the discharge variable and the role of variables such as precipitation (especially precipitation obtained from satellite images), which are effective in the sedimentation of basins, have received less attention. In addition to precipitation, the skewness of sediment measurement data is also one of the issues that lack of recognition and attention will reduce the efficiency of estimator models. In the present study, the role of variable daily rainfall (taken from CHIRPS satellite) in the simulation of suspended sediment of Qarachai River has been investigated. Materials and methodsMulti-layer perceptron artificial neural network was used in order to simulate the daily suspended sediment concentration of Qarachai River (at the Ramian hydrometer station in Golestan province). In this regard, the variables of discharge and previous discarge (in instantaneous and daily scales) as well as the average daily and previous rainfall of the basin (taken from CHIRPS satellite) for a statistical period of 37 years (1980-2017) as variables model input was used. In order to increase the generalization power of the models, self-organized mapping neural network (for data clustering) and gamma test was used to find the best combination of input variables. In order to improve the efficiency of network training, a variety of activation and loss functions as well as the overfitting prevention algorithm were used. In order to investigate the effect of using activation and loss functions in suspended sediment estimation, different scenarios were considered, which led to the construction of 9 models. After that, using validation indicators, the effectiveness of the models in simulating suspended sediment was investigated and compared, and then the best model was selected. Results and discussionThe results obtained from the present research showed that among the different models, the neural network model with Huber's activation function and ReLU loss function, having the average absolute value of the error equal to 368 mg/l, the root mean square error equal to 597 mg per liter, the Nash-Sutcliffe coefficient of 0.87 and the percent bias -2.2% were selected as the best model. The results also showed that the use of the rainfall variable (as one of the important factors in causing erosion and sediment transfer in the basin) has improved the efficiency of the models, therefore, considering the ease of using CHIRPS satellite rainfall data, it is suggested in order to simulate the suspended sediment of rivers, this data is also used along with other predictive variables. ConclusionIn the simulation of suspended sediment, discharge variable is often used as the only predicting variable of suspended sediment, while in basins with rainy, or rainy-snow regimes, the role of precipitation in the production of surface runoff and soil erosion is very important and plays an important role in the production and transport of sediment in the basin. In this regard, although the use of rainfall data obtained from ground rain gauge stations has played an effective role in increasing the efficiency of data-based models in estimating suspended sediment, however, the preparation of hundreds of spatial distribution layers of daily rainfall from the data point data of ground stations, the use of this variable in the simulation of the suspended sediment of the basin has been faced with many problems (such as the lack or inappropriateness of the spatial distribution of rain gauge stations, statistical deficiencies, the use of inappropriate interpolation methods and time-consuming calculations). Therefore, in practice, the variable of river flow is often used as a predictor of sediment, and precipitation is used less often. One of the solutions to the problem mentioned in the present study is the use of CHIRPS satellite data, which was investigated for the first time in this study. These data, available since 1981, can easily be used to simulate suspended sediment or other applications related to watersheds. Another important point that needs to be taken into account in the simulation of suspended sediment is the presence of high skewness in sediment measurement data (both suspended sediment and flow rate), which lack of attention in the process of training (or recalibration) and testing the models leads to It will lead to the construction of weak models in terms of efficiency and the existence of uncertainty in the accuracy of their results. In this regard, it is necessary to use logarithmic transformations or suitable functions of activation and loss in the training process, which in this research, two functions, ReLU and Huber, were proposed respectively. Another important point is to pay attention to the generalization power of data-based models, which is largely dependent on the data used in their calibration or training process. These data should be selected in such a way that while they are representative of the data in the entire statistical period, they are similar and have the same distribution with other data sets (such as cross-validation or test sets). According to the results obtained from the present research and in order to increase the efficiency of artificial neural network models in estimating the suspended sediment of watershed hydrometric stations, it is suggested to use the experiences obtained in this research in other sediment measuring stations of the country.
Davood Nikkami; Samad Shadfar
Abstract
Soil, as one of the components of any ecosystem and an important source of food production, has a very serious role in the continuation of human life. Therefore, the need to support and protect the soil and prevent its erosion is essential. Regarding the amount of soil erosion and sediment yield in the ...
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Soil, as one of the components of any ecosystem and an important source of food production, has a very serious role in the continuation of human life. Therefore, the need to support and protect the soil and prevent its erosion is essential. Regarding the amount of soil erosion and sediment yield in the country, different figures have been mentioned and in some studies, the difference is with several times. These figures vary from less than one to more than five billion tons per year. Therefore, calculating and plotting erosion and sedimet yield maps provides important information that is used in the design of dams, reservoirs, canals, soil protection operations, onsite and offsite erosion damage assessment, and land use planning and land capability assessment projects. Soil erosion map is one of the basic, scientific and applied maps in various executive, research and educational sectors. Due to the need of determining the amount of soil erosion and sediment yield for the entire country and determining the executive priorities in areas with high soil erosion potential, this project was defined and carried out by the Soil Conservation and Watershed Management Research Institute. Accordingly, the watersheds of the seventh category were divided into seven regions or districts, including 1) Eastern Alborz 2) Middle Alborz 3) Western Alborz 4) Central Iran 5) North Zagros 6) Middle Zagros and 7) South Zagros. Long-term sedimen data of 118 hydrometric stations in these areas were analyzed and the amount of sediment in each station was determined by the logged mean load within discharge classes method. According to the amount of river bedload rates and using EPM model, the amount of sediment yield and cosidering sediment delivery ratio of watersheds, the amount of soil erosion were etermined and the soil erosion map of watersheds overlooking hydrometric stations was prepared. Results showed that the average sediment yield and soil erosion in the watersheds overlooking hydrometric stations are 3.3 and 16 tons per hectare per year, respectively. The lowest and highest soil erosion rates of 9 and 32.4 tons per hectare, belong to the Middle Zagros and South Zagros regions, respectively.
Gholamreza Ghahari; Samad Shadfar; Hamid Hosseini Marandi
Abstract
Erosion and sediment resulting from it, is one of the most important factors in watershed management. The estimation of sediment yield and prioritization of watersheds in terms of water erosion is the main objectives of watershed management. One of the ways to estimate soil erosion and sediment yield ...
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Erosion and sediment resulting from it, is one of the most important factors in watershed management. The estimation of sediment yield and prioritization of watersheds in terms of water erosion is the main objectives of watershed management. One of the ways to estimate soil erosion and sediment yield is to use empirical models. The aim of this research is to evaluate the efficiency of the EPM Model in Fars Province. To examine this, five small watersheds were selected in Fars Province. Five basins in which the earth dams and check dams were built were selected. There is no overflow from these dams in rainfall events and the most of them was made near to 10 years. The amount of sediment deposited in upstream of the reservoirs was calculated by means of precision mapping. Deposit bulk density was determined in the field to convert the volume into the weight. In parallel, the sediment yield of the basins was determined by EPM Model. Results showed that the minimum and maximum sediment yield measurements varied from 0.89 to 2.62 tonh-1y-1, but the estimated sediment was between 3.3 to 6 tonh-1y-1. The results of the relative error of estimation of EPM Model in each of the studied basins showed an over estimation in all basins (minimum 121.5 and maximum 447.2 percent). The Relative Root Mean Square Error (RRMSE) of the model was calculated as 2.39, which indicates a too much error of the model. Statistical analysis results comparison of actual sediment yields of watersheds with estimated values by model, using paired t-test, shows that there is a significant difference between these values (t=8.728 and sig.=0.001). According to the presented findings, the results of this model estimation for the investigated areas are not accepted.
Hamzeh Noor; Ali Bagherian Kalat; Aliakbar Abbasi
Abstract
Rangeland exclusion is one of the watershed management methods that is applied for range rehabilitation. However, most rangeland hydrology studies have been focused on exclusion effects on soil loss at plot scale, whereas their effects on sediment yield at micro-watershed in seasonal and annual scales ...
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Rangeland exclusion is one of the watershed management methods that is applied for range rehabilitation. However, most rangeland hydrology studies have been focused on exclusion effects on soil loss at plot scale, whereas their effects on sediment yield at micro-watershed in seasonal and annual scales have rarely been considered. The present study was conducted in two sub-watersheds under exclosure and open grazing treatments, with area of 1.0 and 1.1 ha, respectively, in Sanganeh Watershed, Khorasan Razavi Province, Iran. Runoff and sediment associated with 56 storm events occurred during 2006 to 2016 were estimated at the main outlet of the watershed. The results showed the significant decreasing effect of exclosure treatment on sediment yield at micro-watershed scale (p≤0.05). So that, 582% decrease in sediment yield was obtained in exclosure treatment compared to open grazing. Results also showed seasonal and annual variations of exclosure on hydrological processes so that, maximum and minimum differences in sediment yield among study treatments were founded. The results of this study suggest that livestock grazing management during sensitive seasons as well as rangeland exclosure, if its social problems are resolved, is a practical solution to reduce watershed sedimentation.
Saeed Nabipay Lashkarian; Mahmood Arabkhedri; Samad Shadfar
Abstract
Accelerated soil erosion and the production and transfer of large amounts of sediment are considered as one of the most important issues in many parts of Iran. Having enough knowledge on soil erosion and sediment production as well as identification of critical areas are necessary in order to reduce ...
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Accelerated soil erosion and the production and transfer of large amounts of sediment are considered as one of the most important issues in many parts of Iran. Having enough knowledge on soil erosion and sediment production as well as identification of critical areas are necessary in order to reduce the adverse effects of this problem through soil and water conservation measures. Due to lack of gauge stations in the outlets’ of small watersheds, empirical models are considered as the proper tools for estimating soil erosion and sedimentation. One of these methods which was developed based on Meditranean sediment data, is the Factorial Scoring Model (FSM). Towards this, the main objective of this research is to compare estimated vs. observed sediment yields in some selected regions of Iran. For this purpose, 58 small chatchments equipped by reservoirs in their outlets were selected in Semnan, Central, Isfahan, Chaharmahal and Bakhtiari, West Azarbaijan, Lorestan, Fars, Golestan and Khorasan Razavi Provinces. The comparison of the results showed that all estimates of the original model (before calibration) are several times bigger than observed values obtained by surveying (0.44 to 459.44 t.km-2.y-1). In order to correct the model coefficients for Iran, calibration was performed in two scenarios; once using all data and in the second secenario after allocating data into three geographic regions, which in both cases resulted in significant improvement of estimates. The Nash‐Sutcliffe Efficiency coefficient for all catchments was 0.39, and for Central, Zagros and Northeast regions were 51.1, 0.66 and 0.78, respectively. Based on obtained findings, the application of original FSM must be avoided in study areas. Instead, we strongly recommend using calibrated models based on observational values for different geographic regions.
Alireza Habibi; Hamidreza Peyrowan
Abstract
The erosion rate ranking of geological formations can be a useful way for identifying and prioritizing the watershed sub-basins and it is important in view of decision making and management of the watersheds. Therefore, the present research was conducted with the aim of prioritizing the implementation ...
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The erosion rate ranking of geological formations can be a useful way for identifying and prioritizing the watershed sub-basins and it is important in view of decision making and management of the watersheds. Therefore, the present research was conducted with the aim of prioritizing the implementation of soil conservation operations in the Hablehrood sub-basins in northern Garmsar based on the degree of sensitivity of rock units to erosion. The method is based on the expert opinions and rainfall simulator experiment and comparison of the obtained results with erosion and sediment estimations of empirical models such as PSIAC, EPM and SWAT. Results showed that erosion rate ranking of the sub-basins based on the results of rainfall simulator conformed to the output of the three mentioned models in 12 sub-basins of 21 sub-basins and in other six sub-basins with two models, and in the remaining three sub-basins, it only conformed to one model output. Rainfall simulation results showed the highest correlation with the PSIAC model with a specific sediment yield of 9.2 t km-2 and based on the results of the observation data of the Bonkouh sediment-debit station, a special sediment of 8.02 t km-2 without considering the bedload, it became clear that the PSIAC model provided the most reliable estimate of sediment yield. Thus, matching the results of rainfall simulator in the erosion rate ranking of sub-basins with the PSIAC model shows that the rainfall simulator study on lithology units quite reliable with a 90% confidence level for erosion ranking classification of sub-basins and it can be used in similar basins.
Farzad Heidari; Razieh Saboohi
Abstract
Marl formations have problems in watersheds due to high sediment yield. The purpose of this research is the marls classification of Isfahan province according to erodibility indices and their physical and chemical properties. In this regard, region marl units were identified and their sediment yield ...
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Marl formations have problems in watersheds due to high sediment yield. The purpose of this research is the marls classification of Isfahan province according to erodibility indices and their physical and chemical properties. In this regard, region marl units were identified and their sediment yield was measured using rainfall simulator. Then, based on erosion type, they were sampled and soil physical and chemical properties were analyzed. Cluster analysis statistical method was used to classify marl units. Statistical analysis was performed by three sets of data including chemical, physical and both chemical and physical accompanied by slope and measured sediment from six mmh-1 rainfall in each step of the analysis. Results showed that the most important similarity factors in marls are chemical properties and the effect of climate. According to information obtained from investigations, climate is the most effective factor of differences among marl units in this province. In addition to its direct impact on creation and evolution of marls, it affects on other parameters directly and indirectly and choosing either of these parameters is related to climate.
arezoo kheyrkhah
Abstract
Correct and consistent uses of natural resources preserve this valuable wealth. Using optimization knowledge can assist us to achieve this object. Thus, this study aims to compare linear programming as a classical method of optimization with genetic evolutionary algorithm for land use optimization of ...
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Correct and consistent uses of natural resources preserve this valuable wealth. Using optimization knowledge can assist us to achieve this object. Thus, this study aims to compare linear programming as a classical method of optimization with genetic evolutionary algorithm for land use optimization of the Bayg watershed. Results showed that linear programming reduced dry farming acreage and increased the acreage of irrigated agriculture. After minimization, surface runoff and sediment yield declined by 1.16, 12.91 percent, respectively. Genetic algorithm led to an increase in rangeland, irrigated agriculture and horticulture acreages, while almond orchard and dry farming acreages were reduced. Furthermore, surface runoff and sediment yield declined by 13.95 and 31.99 percent, respectively. Linear programming acted stronger in satisfying the constraints, as compared with genetic algorithm. The constraint “total acreage” was satisfied by linear programming, while genetic algorithm could not meet this constraint. Sensitivity analysis of linear programming showed that the most critical factor in minimizing runoff and sediment yield function was the coefficient of dry farming with a reduced cost of 67.52. Results also established that the constraints “total acreage and minimum acreage of rangeland” with the shadow prices of 397.40 and 233.28, respectively had the highest negative impact on the optimal solution. Meanwhile, the constraints “maximum acreages of irrigated horticulture and almonds garden” with the shadow prices of -134.97 and -118.44, respectively had the highest positive impact on the optimal solution. As a general conclusion it can be stated that in land use optimization problems with a large number of constraints, genetic algorithm show poorer performance in satisfying constraints, as compared with linear programming.
Asghar Azizian; Amir Samadi
Abstract
River bed materials are of great importance in construction works as one of the most valuable resources due to their economical costs and ease of extraction. This has caused the rivers to be subjected to profound changes due to excessive, improper and non-standard harvesting by effective activities ...
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River bed materials are of great importance in construction works as one of the most valuable resources due to their economical costs and ease of extraction. This has caused the rivers to be subjected to profound changes due to excessive, improper and non-standard harvesting by effective activities of human apart from their natural changes. Hence, replacement of river resources with other resources such as mountain mines can be considered as an essential way to protect the rivers. Considering the importance of this issue, the present study has evaluated the potential of sediment production and delivery in Qaen and Ferdows’ rivers sub-basins using a combination of GIS and geomorphological models. The results obtained from the studied basins indicated that the geomorphologic models are capable of identifying areas susceptible to sediment production. According to calculations performed by the geomorphologic model, the southern and south-western parts of Ferdows and northern parts of Qaen Basins in Southern Khorasan Province have good potential for harvesting. Moreover, sediment quality assessment showed that most of materials in these areas are coarse grains and therefore require far less processing.
Hossein Kheirfam; Seyed Hamidreza Sadeghi
Abstract
Measurment of river sediment transport in different temporal and hydrological conditions is important in hydraulics, hydrology and soil and water conservation science and engineering. Bed load is rarely measured because of difficulties and low efficiency of conventional samplers. The present study was ...
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Measurment of river sediment transport in different temporal and hydrological conditions is important in hydraulics, hydrology and soil and water conservation science and engineering. Bed load is rarely measured because of difficulties and low efficiency of conventional samplers. The present study was carried out in order to design a bed load sampler based on the conditions prevailing in the mountainous rivers flumes. The sampler with dimensions of 120 cm length, 60 cm height and 60 cm width was designed and subsequently fabricated. The accuracy of sampler was evaluated through comparing the bed loads estimations made by the designed equipment and those measured by collecting the whole discharged runoff to a 300 liters water tank installed at the outlet flume and with the help of statistical criteria. The t-test, relative erorr (RE) and relative bias (RBIAS) criteria were then used for statistical analyses. The results showed that the mean mesured bed load by water tank and designed sampler were 0.00635 and 0.0064 gl-1, respectively with no siqnificant differece (p<0.0763). In overall, the designed sampler had a high accuracy and efficiency in river bed load measurement with relative erorr and relative bias of about 8.5% and 0.107, respectively.
Heshmatolah Agharazi; Aliakbar Davudirad; Mahdi Mardian; Majid Soufi
Abstract
Recognition of effective processes of erosion, especially, threshold is one of the most important strategies in water and soil resources management. Gully erosion is one of the most important sources of sediment yield in watersheds that is defined as different thresholds like area-slope or topography. ...
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Recognition of effective processes of erosion, especially, threshold is one of the most important strategies in water and soil resources management. Gully erosion is one of the most important sources of sediment yield in watersheds that is defined as different thresholds like area-slope or topography. In this paper, the area- slope threshold was investigated in Zahirabad Watershed in Markazi province, Iran. First, based on field surveys and digital elevation model, morphometric characteristics of 14 gullies were measured, accompanied by soil sampling and vegetation cover measurements. Second, homogeneous groups of gullies were defined by factor and cluster analysis and power relations of area-slope was prepared. Results demonstrated that there was no considerable correlation between area and slope of gully watersheds. So, coefficient of determination of creation point and head-cut of gullies were 0.111 and 0.181, respectively. According to the results, the dominant process in creation and head cut development of gullies in Zahirabad was related to flow concentration and rill erosion of high slopes. Considering the prevail of loamy texture of soils land use changes and deterioration of vegetation cover, it is suggested to investigate the optimization of land use schemas, and land cover improvement on sloppy lands with the objective of gully control.
Davood Nikkami; Reza Sokouti Oskuee; Ebrahim Brooshkeh; Faniz Heshmati
Abstract
Eroded soil particles within watershed areas are transported in three shape of dissolved, suspended and bed loads by river water discharge. Knowing the amount of suspended and bed loads are necessary in estimating sediment yield of watersheds. Usually, suspended load is measured daily in hydrometric ...
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Eroded soil particles within watershed areas are transported in three shape of dissolved, suspended and bed loads by river water discharge. Knowing the amount of suspended and bed loads are necessary in estimating sediment yield of watersheds. Usually, suspended load is measured daily in hydrometric stations, while this does not happen for bed load. Although, there are many differences between geology formations, rainfall intensities and water discharges of watersheds, the amount of bed loads are considered as a constant unique coefficient of suspended load. So, there would be highly errors in watersheds’ sediment load estimates. In this research, after collecting bed and suspended load data of three hydrometric stations of Badlan on Alandchay, Pol Yazdakan on Ghotourchay and Mazraeh on Baroonchay Rivers in Western Azerbaijan, the data were analyzed and best relations were fitted between bed load and suspended loads. According to statistical analysis all data had high coefficient of correlation at the level of 99 percent and the best equations were chosen accordingly. The ratio of bed to suspended load in Yazdakan, Badlan and Mazraeh stations were 79, 49 and 13 percent, respectively. This ratio was 47 percent for all three stations.
Saeed Nabipay Lashkarian; Seyed Ali Asghar Hashemi; Samad Shadfar
Abstract
Erosion and sedimentation are main challenges in Iran, which cause the reduction of soil quality and quantity. Soil conservation and watershed management activities should be implemented to reduce the impact of these phenomena. Therefore, the knowledge of critical area is necessary through the learning ...
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Erosion and sedimentation are main challenges in Iran, which cause the reduction of soil quality and quantity. Soil conservation and watershed management activities should be implemented to reduce the impact of these phenomena. Therefore, the knowledge of critical area is necessary through the learning the amount of sedimentation and erosion. Because of lack of sediment measurement stations in more watershed outlets in Iran and insufficient data, empirical models are proper tools for data layers generation. Factorial Scoring Model (FSM) is one of the experimental models which has been recently developed out of the country. The main objective of this research is to compare sediment yield estimated by FSM model and observed values. So, in order to evaluate the model, nine small dams of 10 years old with no overflows were selected from in Semnan province. For modeling sediment yield, topography, lithology, gully, catchment shape and vegetation cover of related catchments were studied and required data layers were prepared and scoring indexes were given and finally, the calibrated model was presented. Estimated model values were then compared with measured values. Results showed that main model equation does not have sufficient efficiency. Also, results demonstrated that calibrated FSM model has conformity with observed sediment values at 84 percent.
Mehdi Bashari; Seyed Hamid Reza Sadeghi; Abdolsaleh Rangavar
Abstract
Investigation of effective factors on soil erosion and their variability analysis is essential for soil and water conservation projects. The present research was carried out to survey the role of two north and south facing slope plots on soil erosion on storm basis at Sanganeh watershed located in Khorasan ...
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Investigation of effective factors on soil erosion and their variability analysis is essential for soil and water conservation projects. The present research was carried out to survey the role of two north and south facing slope plots on soil erosion on storm basis at Sanganeh watershed located in Khorasan Razavi province, Iran. The study was conducted using a pair of small plots with dimensions of 2×2 meters. The plots were be designed using metal sheets and their outlet was directed towards collecting tanks. These plots were established close to each other at two different aspects. The generated runoff and sediment from plots caused by 12 storm events during October 2006 and May 2007 were collected and sediment concentration was ultimately calculated. The results of sediment concentration analysis verified a significant difference (p<0.01) between soil erosion study plots with very low quantities in plots installed in northern aspect. The difference was clearly associated with effect of slope aspects on vegetation cover.
Ramin Salmasi; Hamid Reza Peyrowan
Abstract
The most of the soil erosion and sediment yield in the Talkheh Rood watershed are mainly related to marl formations. This study was conducted to evaluate physico- chemical properties of Talkheh Rood marl samples in rill, gully, mass and badland erosion types. For this purpose, marl samples were taken ...
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The most of the soil erosion and sediment yield in the Talkheh Rood watershed are mainly related to marl formations. This study was conducted to evaluate physico- chemical properties of Talkheh Rood marl samples in rill, gully, mass and badland erosion types. For this purpose, marl samples were taken from marl sediment of homogenous work units. Twenty four samples were selected, in total. Some of main physic - chemical properties of these marls were measured in lab. These properties were pH, EC, CEC, Lime, gypsum and OC content, SAR, Na, K, Cl, Ca, Mg, clay, silt and sand percentage. These data were interpreted by ANOVA and mean comparisons analysis methods. Results showed that pH, gypsum content and sand percentage had statistically significant differences between four erosion types. Mean comparison showed that significant difference of pH, was between mass and badland erosions, sand between badland and gully ones, and gypsum, rill and gully, also badland and gully ones.
Seyed Ali Asghar Hashemi; Mahmood Arabkhedri
Volume 2, Issue 1 , May 2010, , Pages 25-34
Abstract
Evaluation of empirical models for sediment yield in watersheds is a necessity. One of the conventional models in Iran is MPSIAC that has been used extensively. Sediment measurement of small dam's reservoirs is one of the methods for evaluation of these models. In this research, 9 small watersheds were ...
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Evaluation of empirical models for sediment yield in watersheds is a necessity. One of the conventional models in Iran is MPSIAC that has been used extensively. Sediment measurement of small dam's reservoirs is one of the methods for evaluation of these models. In this research, 9 small watersheds were selected in Semnan Province. There is an earth small dam at the outlet of each watershed built in the past 10 years. These dams have not spilled since they were built. Therefore total sediment volume discharged from each watershed was entrapped behind the dams. The amount of deposited sediments in these reservoirs was measured by surveying and estimation of apparent Specific Weight which then compared with estimating values of MPSIAC model by paired t-test. The results showed that the difference between the means for estimated volumes of sediment yield by use of MPSIAC model at the level of 5% had no significant difference while the difference between mean weights of sediments at the level of 5% was significant. Also determination of performance and relative root mean square error showed that MPSIAC model has no appropriate efficiency for application in the region.
Hamid Reza Moradi; Nayereh Ghazanfarpour; Sadat Feiznia
Volume 1, Issue 2 , July 2009, , Pages 119-127
Abstract
One of the effective factors in soil erosion is geological formations of the drainage basin from the view points of their erodibility and the amount of runoff and sediment yield. In this investigation a part of Segzi- Kuhpayeh subdrainage, located in Zayandeh-Rood Drainage Basin with 67091.7 ha area ...
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One of the effective factors in soil erosion is geological formations of the drainage basin from the view points of their erodibility and the amount of runoff and sediment yield. In this investigation a part of Segzi- Kuhpayeh subdrainage, located in Zayandeh-Rood Drainage Basin with 67091.7 ha area was chosen for studying erodibility and sediment yield of Quaternary Formations. For doing this, the map of Quaternary Formations was prepared. Then in each unit a field rainfall simulator was used and runoff and sediment were collected from the plots and erodibility and sediment yield factors were obtained. Soil samples were taken adjacent to each micro plot for laboratory tests and the data were analyzed statistically. The results of regression analyses have shown that erodibility and sediment yield are significantly different in various Quaternary Formations. The most important physical and chemical parameters in sediment yield in different formations are Silt, Sand, very Fine Sand, Wetness, Caco3 and in erodibility of different formations are Silt+ very Fine Sand, Caco3, Silt, Clay, very Fine Sand and EC.
