Mohammad Ali Zanganeh Asadi; Mahnaz Naemi tabar; Mokhtar karami
Abstract
Desertification is a problem that is currently affecting many countries in the world, including Iran. This problem is seen not only in arid and semi-arid areas, but also parts of semi-humid areas. The purpose of this study is to investigate and zoning the intensity of desertification using the modified ...
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Desertification is a problem that is currently affecting many countries in the world, including Iran. This problem is seen not only in arid and semi-arid areas, but also parts of semi-humid areas. The purpose of this study is to investigate and zoning the intensity of desertification using the modified Medalus Model and hierarchical clustering method in the Baqous Plain of Sabzevar. For this purpose, effective criteria in desertification including climate, vegetation, soil, erosion, and selection management, and the geometric mean of the indicators were calculated. Data layers indicators related to each criterion were prepared using the GIS system. This information was scored based on the Medalus method and from the geometric mean of the indicators of each criterion, the final map of the status of each criterion was prepared and from the geometric mean of the criteria, the current map of the desertification of the region was prepared. Results showed that the criteria of vegetation, climate, and erosion were more effective than other factors in desertification of the region and high sensitivity and critical type was matched with the poverty of vegetation and the dryness of the climate, and work units 1 and 2 have the largest area of desertification types with high intensity. The results also showed that 21% of the study area is in the high sensitivity zone, 28% in the high and critical sensitivity zone, 17% in the low sensitivity zone, 28% in the low and critical sensitivity zone, and 6% in low sensitivity zone to erosion. 55.6% of the results of modified Modalus Model were obtained by significant clustering methods. According to the spatial distribution map of desertification intensity extracted from the model, it can be used as an auxiliary tool against desertification and prevent excessive destruction of the region in the future.
Abdulvahed Khaledi Darvishan; Jalal Faraji; Leila Gholami; Mohsen Khorsand
Abstract
The dynamics of rainfal erosivity (R), crop management (C) and soil erodibility (K) factors compared to the others (topography-LS and land management-P) is the most important note for the correct estimate of soil erosion at different time bases. Spatio-temporal estimates of soil erosion in the representative ...
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The dynamics of rainfal erosivity (R), crop management (C) and soil erodibility (K) factors compared to the others (topography-LS and land management-P) is the most important note for the correct estimate of soil erosion at different time bases. Spatio-temporal estimates of soil erosion in the representative paired watersheds are of particular importance due to their educational functions as well as the possibility of generalizing the results to larger areas of the country. Therefore, in the present study, while examining the dynamics of R, C and K factors in the Khamsan representative paired watershed, the distribution map of soil erosion in seasonal and annual time scales were prepared using RUSLE model for two water years of 2015-2016 and 2017-2018. The results showed that soil erosion in winter with values of 3.94 and 4.95 t ha-1 y-1 accounted for about 49 and 74% of the total erosion of the year, respectively. Considering the melting conditions in calculating the K factor for the winter along with the lack of vegetation in this season led to a higher estimate of soil erosion than other seasons. These results are in consistent with plots soil loss data recorded in different seasons and the higher concentration of suspended sediments in the rivers especially in March. In the water year of 2015-2016, the distribution of rainfalls in the autumn was much higher than in the spring, so that soil erosion in the autumn accounted for about 33% of the total erosion of the year. In the water year of 2017-2018, although the average annual soil erosion was less, but due to more distribution of erosive rainfalls in winter at the same time with the lack of vegetation on the soil surface and the soil melting, the rate of winter erosion was very high.
mohammad hedayatfard; Hamid Gholami; Seyed Masoud Soleimanpour; Arashk Holisaz
Abstract
Gully erosion is one of the most important phenomenons in land degradation and desertification, which upsets the balance of environmental resources and its sustainability. The aim of this study was to determine the effective factors on creation of gully erosion using data mining methods in Bayan Watershed ...
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Gully erosion is one of the most important phenomenons in land degradation and desertification, which upsets the balance of environmental resources and its sustainability. The aim of this study was to determine the effective factors on creation of gully erosion using data mining methods in Bayan Watershed in the north of Fars Province. K-Means clustering algorithms and CART decision tree were used to model gully erosion. The estimated accuracy based on the parameters affecting the creation area in the final model is 100% for the educational data set and 71.43% for the experimental data set. Results from measuring different variables from 40 selected gullies, including a target variable (creation area) and twelve predictive variables, like creation slope, vegetation, bare soil, surface gravel, surface litter, EC, pH, SAR, OM, clay, silt and sand in field and laboratory operations and the use of data mining techniques, showed that the creation of gullies in this watershed is a function of silt, acidity, bare soil, gravel and organic matter. These results showed the effect of vegetation and consequently, the presence of adequate organic matter in the soil as the most appropriate method for controlling gullies and the destructive and intensifying effect of bare lands without vegetation in intensifying gully erosion. Therefore, it is necessary to establish and establish permanent and compatible vegetation, to stabilize and improve soil structure and increase organic matter, and control and management programs, in lands with more silt, to be operated more carefully.
Majid Kazemzadeh; Ali Salajegheh; Arash Malekian; Abdolmajid Liaghat
Abstract
On average, 70 percent of the precipitation that reach Earth's surface, returns to the atmosphere through evapotranspiration, and this rate reaches 90 percent in arid areas. Meanwhile, watershed measures directly related to water, soil and plant, and ultimately to evapotranspiration on the natural resources ...
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On average, 70 percent of the precipitation that reach Earth's surface, returns to the atmosphere through evapotranspiration, and this rate reaches 90 percent in arid areas. Meanwhile, watershed measures directly related to water, soil and plant, and ultimately to evapotranspiration on the natural resources region (ecochydrology). In this study, in order to study the effect of biological activities of watersheds (enhancement and increase of vegetation) on the process of soil moisture and evapotranspiration changes, paired watersheds of Taleghan, Alborz Province were selected. In order to calculate evapotranspiration by soil moisture balance method, soil moisture monitoring points were selected using field and laboratory studies in three main areas (northwest, eastern and southeast) and three replications and at three depths of 0-20, 40-20 and 40 -60 cm during plant growth period in 2017. Data were analyzed by ANOVA method, and Duncan test. The results showed that the actual evapotranspiration in the treated watershed and control watersheds were not statistically significant and, respectively, they showed 181 mm and 159 mm in a period of growth. In other words, the actual evapotranspiration value in the treated watershed was 14% higher than the control one during the growth period. Also, the results showed that evapotranspiration under different aspect slopes had a significant difference. The total actual evapotranspiration in the northwestern slopes were 229 and 226 mm, in east slopes were 207 and 171 and in the southeastern slopes were 109 and 80 mm in the treated and control watersheds, respectively.
Seyed Masoud Soleimanpour; Majid Soufi; Mohammad Javad Rousta; Samad Shadfar; Ladan Jowkar; Hojatollah Keshavarzi
Abstract
Gully erosion is one of the main types of water erosion and is known as one of the destroying forms of land degradation and soil loss in the world. Therefore, knowing the most effective factors on extending this type of erosion is utmost important. Beside, management and control of gully erosion require ...
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Gully erosion is one of the main types of water erosion and is known as one of the destroying forms of land degradation and soil loss in the world. Therefore, knowing the most effective factors on extending this type of erosion is utmost important. Beside, management and control of gully erosion require knowing the most effective factors on gullies extension. So, the present study was performed to determine the most effective factors on gullies in Khorrambid Watershed, North of Fars Province through measuring the permanent gullies during 13 years (2004-2016). Results showed that the average of gully length extension was 21.67 m throughout this period. This data indicated that the length of gully extension was 1.67 m per year. Further, it is determined that the length expansion of permanent gullies in this region was a function of bare soil and saturated electrical conductivity, using SPSS and backward multivariable regression. In conclusion, it is suggested different management solutions to increase the soil resistance against the erosion be prioritized in management and implementation plans such as increasing adoptable cover vegetation for the natural condition of the region and exclude the area to restore vegetation cover and pay more attention to control erosion in gully head cuts.
Elnaz Azartaj; Ali rasoulzadeh; Ali Asghari
Abstract
Soil and water are the most valuable national resources. Unfortunately in recent decade, due to land use change and vegetation cover degradation, most of the rainfall changed into runoff and in addition to loss of this vital resource, causes abundant loss of life and property by creating enormous floods. ...
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Soil and water are the most valuable national resources. Unfortunately in recent decade, due to land use change and vegetation cover degradation, most of the rainfall changed into runoff and in addition to loss of this vital resource, causes abundant loss of life and property by creating enormous floods. The aim of this study is to assess the effect of land use change from range land to agriculture with different percent of vegetation cover on runoff and soil erosion. For this purpose, three types of land use included preserved range land with 100 percent of vegetation cover; range land with 50 percent of vegetation cover and agricultural land (range land changed to agriculture) were identified in the study area. Then, in each land use, three slopes were determined (10, 15 and 24%). This study was carried out split plot experiment based on completely randomized design. In each land use and slope, runoff and erosion were measured in plots randomly using rainfall simulator with 1.5 mm.min-1 intensity and 15 min duration with 3 replicates. Results showed that the maximum of runoff, sediment mass and sediment density were in the range land changed to agriculture with 24% slope and the minimum of them were in the preserved range land with 10% slope. Also the results showed that the change of range lands to agricultures increase runoff 5 times. In the other hand, with increasing slope from 10 percent to 24 percent, runoff increased 1.7 times. Runoff coefficient was determined for 3 land uses and 3 slopes level. The maximum and minimum runoff coefficient were found 0.72 and 0.06 for the range land changed to agriculture with 24% slope and preserved range land with 10% slope, respectively.
Nadergholi Ebrahimi; Reza Sokouti Oskoee
Abstract
Mountainous rivers have characterized by steep slope, roughness due to bedrock and coarse aggregation, bed and marginal vegetation as well as severe and rapid spatial displacement of the surface substrate morphology. The protection role of vegetation in the river bank is known as an economic and environmental ...
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Mountainous rivers have characterized by steep slope, roughness due to bedrock and coarse aggregation, bed and marginal vegetation as well as severe and rapid spatial displacement of the surface substrate morphology. The protection role of vegetation in the river bank is known as an economic and environmental option that decreases hydraulic conductivity power of the river through the rising of roughness coefficient and rising water level. This study aimed to estimate the flow resistance and roughness coefficient of the river that is affected by the physical and biophysical factors of the Shahr-chay River bed in West Azerbaijan in three selected river reach. Results showed that none of the proposed equations for estimation of roughness coefficient depend on energy slope, but in general, without affecting flow, roughness coefficient in mountain streams depends only on the degree of submergence. Marginal trees can affect Froude number by increasing margin pressure and friction forces, also, enhancing the hydraulic depth, less than critical depth. It was also found the equation for estimating roughness coefficient both with and without marginal trees, have different coefficients and can provides roughness coefficient prediction possibility for mountainous rivers. Comparing the obtained relations both with and without its fringe of trees showed that fringe trees can increase the flow depth and roughness coefficient. Coefficient of determination of all mathematical relations was above 0.99 and calculated relative error was 0.001- 0.008 that demonstrates the suitability of the model to estimate the roughness coefficient.
Abolghasem Dadrasi Sabzevar; Ali Ghazanchian; Mohammad Namaki
Abstract
Social and economical evaluation of watershed management activities, is an important criterion for its validation. The main objective of present study was, identification and analysis of socio-economic impacts of watershed management operations implimented in Gosh village wich is located in 60 km north ...
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Social and economical evaluation of watershed management activities, is an important criterion for its validation. The main objective of present study was, identification and analysis of socio-economic impacts of watershed management operations implimented in Gosh village wich is located in 60 km north of Mashhad. The sample data of this study was consisted of 38 extension workers were randomly selected from the study area based on Cochran’s sampling methodology. The research instrument consisted of three parts in Likert scale. The validity of the questionnaire was analyzed and reliability coefficient was calculated for the questionnaire using Cronbach's alpha ratio of 0.745. These amounts showed that questionnaire has an acceptable ability for data gathering. Factor analysis was the major statistical method. The results offactor analysis indicated that socio-economic effective parameters are increasing garden and farm area, increasing qanats water discharge, increasing rangeland area, and preventing lands flood damages. These four factors, in general, had more than 60 percent of the total variance. Final results indicated that watershed management activities have improved qanats water discharge by flood control and aquifer rechrge and increased the area of Agricultural and garden lands. Also, conseving activities in rangelands caused improving of vegetation cover density and the area of rangelands.
Nadergholi Ebrahimi; Azim Shirdeli; Ebrahim Nikkhah Javan; Majid Hosseini
Abstract
The riverbed and margin vegetation causes to increase in roughness against flow, decrease in average flow velocity, reduce water-energy, and alterations in layer velocity distribution (the flow velocity profile) across the river. In current experimental research, the effect of branching vegetation on ...
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The riverbed and margin vegetation causes to increase in roughness against flow, decrease in average flow velocity, reduce water-energy, and alterations in layer velocity distribution (the flow velocity profile) across the river. In current experimental research, the effect of branching vegetation on the stream flow and bed formation is analyzed. The flow conditions are examined in experimental channel with 7 meter length, 25 cm width and height through different flow rates (3,5,7 lit/s) and slopes under different(0.001, 0.003, 0.005) and densities of vegetation (50, 25 and 12 percent). According to the processed data, it can be implicated that the difference between flow level, substrate, and rate is affected by the types of vegetation density; thereby existence of vegetation causes resistance to flow and depth increment. In all experiments, through the vegetation density increment, the bed erosion increases compared with the primary condition in which the most and least alterations are observed in 50 and 12-percent density, respectively. In the condition of equal flow rate with density increment, the flow depth is increased. The bed particle displacement in the section covered by vegetation is increased through density increment in which flow level in 50 is more than 25 and 12-percent density, as well as, flow substrate erosion and alteration whereas sediment (particles accumulation) is appeared frequently under less density at the end of section covered by vegetation.
Mansour Jahantigh
Abstract
Duststorms occur generally in Sistan region. So, it limits the development of the region. Many factors play especial role on duststorms such as removal of vegetation cover due to automobile transportation. The aim of this research was to identify car transportation role in producing dust storm. For this ...
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Duststorms occur generally in Sistan region. So, it limits the development of the region. Many factors play especial role on duststorms such as removal of vegetation cover due to automobile transportation. The aim of this research was to identify car transportation role in producing dust storm. For this reason, three sites with different characteristics were chosen and in each area, two sites of 600 and 300 m length and wide respectively were selected with and without car transportation. Three soil samples were taken randomly from the first, mid and the end of the sites of each location and they were analyzed for pH, EC, CaCO3, organic carbon, moisture, calcium and vegetation cover. The soil erosion measured according to the Universal Soil Loss Equation. The results showed that the car transportation areas have less amount of clay, vegetation cover, topography, soil surface roughness, organic carbon, but, they have an increase in soil small particles with less than 0.84 mm in diameter, pH, EC, CaCo3and land length which they have especial effect on wind erosion of the region. Results also show that the amount of soil erosion is 15.8-216.3 tonsperhectare in study area.
Mehran Lashanizand; Kianfar Payamani; Shahla Ahmadi; Iraj Veyskarami
Abstract
There is a very close relationship between two distributions of climate and vegetation maps. But, the relation between climate and vegetation is not clear. Therefore, the main objective of this research is to determine the effect of main climatic factors on distribution of main vegetal species and its ...
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There is a very close relationship between two distributions of climate and vegetation maps. But, the relation between climate and vegetation is not clear. Therefore, the main objective of this research is to determine the effect of main climatic factors on distribution of main vegetal species and its zonation in Iran. For this purpose, 51 synoptic stations with 30-year data (1976-2005) or more were selected and their meteorological data were extracted. Using principal components techniques, 269 climatic variables were considered and the numbers of variables reduced to 14 factors with eigenvalues more than one that represent 96.4% of the total variance. The first three factors (the thermal component, moisture and precipitation, respectively) had the most influence on the climate, so, they were considered for climate zonation criteria. These three components were rasterized within ArcGIS using Kriging interpolation method. Resulted raster map was used to create the climatic zonation map by unsupervised clustering technique. Finally, ecological climate zonationmap was derived using two climate parameters (temperature and humidity) and elevation map of country and by using unsupervised clustering technique. This map shows that the boundaries of ecological climate regions are mainly based on climatic (temperature and humidity) and landform factors (elevation). Another result of the research was that most ecological climatic zones were related to the low elevation areas of the country (below 1200 m) and the rate of high ecological climatic areas (above 2400 m) were very low.
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.
Ali Rezaei
Volume 2, Issue 1 , May 2010, , Pages 11-17
Abstract
Increasing runoff coefficient and flood intensity and extending dry land areas over the country basins are due to the destruction of vegetation cover. For monitoring the trend of temporal variation, maximum peak flows and maximum 24 hr rainfall data have been gathered from all climatologic and hydrometric ...
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Increasing runoff coefficient and flood intensity and extending dry land areas over the country basins are due to the destruction of vegetation cover. For monitoring the trend of temporal variation, maximum peak flows and maximum 24 hr rainfall data have been gathered from all climatologic and hydrometric stations of Ghizilozan basin. The acquisition data repaired and standardized within a period of 30 years. Then the data were divided into three categories with period of 10 years and finally six categories with period of 10 to 30 years were produced. The mean of variables for every period was calculated based on two years return period by fitting the distribution function of Pearson type III to selected data series. The mean of every category plotted with time period and fitted a line to them. The results showed that based on Kendall’s Tau method, there are significant and positive harmonizing between measured variations respect to time only in two climatology stations named Gitoo and Salamatabad and so two hydrometry stations named Sarcham and Dehgolan and in the others there aren’t any positive or negative harmonizing of data variations respect to time. But the slope of regression line of maximum 24 h of annual rainfall as an index of climate variations to the time, equal 0.031 and in contrast the slope of regression line of peak flow to time equal 0.059. Therefore, the slope of peak flow is 1.9 times of maximum 24 h of annual rainfall with time. This finding says that the vegetation cover because of dry land extending is destroyed and runoff coefficient and flood intensity is increased at studied basin.
Abolghasem Dadrasi; Shahrokh Hakimkhani; Abdolsaleh Ranghavar
Volume 1, Issue 4 , February 2010, , Pages 227-239
Abstract
The fact that there are so many erosion models makes it necessary to critically select one of them as all have some limitations. Models are formulations of processes and logics as represented by the modeler. The formulations may be representations of either simple processes or complicated ones as the ...
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The fact that there are so many erosion models makes it necessary to critically select one of them as all have some limitations. Models are formulations of processes and logics as represented by the modeler. The formulations may be representations of either simple processes or complicated ones as the modeler deems necessary to solve a specific problem. These variables must be derived by a procedure of calibration for a specific case. The Soil erosion model of Morgan, Morgan and Finny (1982) from a large list of soil erosion models, have been applied to test the validity of the model in Sanganeh research station, Mashhad, Iran. After a field survey, plots with sheet erosion, were selected and their data was collected. Rainfall, slope and soil data were derived from station archive, vegetation cover and root depths were determined from field observations and some other parameters were tested on site. Soil loss was calculated by using overland flow for each plot after each rainfall and the measured records were compared with model estimations. The results show that in most plots, predictions deviated from the observations and in 28.21% of plots the results seem acceptable. The final result of present research shows that the model performs reasonably well for plots with lower density of vegetation cover (less than 20%), steep area with more than 40 percent, and soil depths of less than 10 centimeter.
