Ali Bakhtiarizadeh; Mohammad Najafzadeh; Sedigheh Mohamadi
Abstract
Introduction
The groundwater aquifer is one of the most vital resources, being considered more important in the countries (e.g., Iran) located in hot and dry areas. One of the ways to prevent contamination of groundwater resources is to focus on their vulnerability. So, a trustworthy assessment of groundwater ...
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Introduction
The groundwater aquifer is one of the most vital resources, being considered more important in the countries (e.g., Iran) located in hot and dry areas. One of the ways to prevent contamination of groundwater resources is to focus on their vulnerability. So, a trustworthy assessment of groundwater vulnerability is useful to determine the contamination points of the aquifer for effective protection and management of groundwater resources.
Materials and methods
In this research, DRASTIC index was applied to evaluate groundwater susceptibility while considering effects of land use and nitrate pollution for Kerman-Baghein Plain located in Kerman Province. In this regard, seven parameters including the depth of the water table, net feeding of aquifer, aquifer texture, surface soil texture, topography, impact of the vadose zone, and hydraulic conductivity were employed to calculate the DRASTIC index. It should be noted that this index has previously been applied by researchers for assessment of the vulnerability of the aquifer against groundwater pollution in different regions. However, despite the complexities in the underground water system and the opinions of experts in assigning the rank and weight of the parameters in this index and the difference in the conditions prevailing in the studied areas, it has always prompted researchers to take practical steps to improve this index. This improvement has been carried out in a number of studies by adding other parameters (e.g., land use and the effect of nitrate) to the parameters of the DRASTIC index. Therefore, in the present research, the parameters of land use and potential risk associated with land use have been used to compute the Composite DRASTIC index (CD) and Nitrate Vulnerability Index (NVI) in the Arc/GIS software environment, respectively. In this way, the CD index was obtained by adding the land use parameter to the DRASTIC index and the NVI index by multiplying the raster map of the potential risk rating related to the land use in the DRASTIC index. It should be noted that according to the land use map evaluation, this plain includes 54% of low-density pastures, 24% of irrigated agriculture, 10% of hand-planted forests, 6% of bare and desert lands, 5% of residential areas, and 1% of claypans. After the evaluation of three vulnerability criteria using all three indices DRASTIC, CD and NVI, their correlation with Ggroundwater Contamination Risk (GCR) was also investigated.
Results and discussion
The results revealed that the correlation of the DRASTIC index with the risk of underground water pollution is 8%, the CD index is 30% and the NVI index is 54%, with a probability of 99%, they show a significant correlation. The results indicated that the addition of the land use parameter caused to increase the correlation of vulnerability with the risk of groundwater pollution, and multiplying the potential risk associated with land use led to further increase of the correlation. As a result, the NVI index was selected as the superior index compared to the other two indices.
Conclusion
The results of the NVI index of Kerman-Baghin Plain indicated that this plain is divided into two categories including very low vulnerability with an area of 1528.07 km2 (75.52 %) having an NVI value of less than 70 and low vulnerability with an area of 495.33 km2 (24.48 %) having NVI value from 70 to 110. Taken together, in order to properly manage the groundwater resources and prevent the pollution of these resources, it is recommended to prohibit the establishment of industries and the cultivation of agricultural sector causing the pollution in areas with low vulnerability.
Mahtab Safari Shad; Mahmoud Habibnejad Roshan; Karim Solaimani; Alireza Ildoromi; Hossein Zeinivand
Abstract
Many of the environmental problems are caused by the changes in the main components of the hydrological cycle. However, water balance modeling can help to better understanding the components of the hydrological cycle in order to develop appropriate management options. The purpose of this study is to ...
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Many of the environmental problems are caused by the changes in the main components of the hydrological cycle. However, water balance modeling can help to better understanding the components of the hydrological cycle in order to develop appropriate management options. The purpose of this study is to calculate three important components of surface water balance using the WetSpass model and evaluate the model in Hamadan-Bahar Watershed located in Hamadan Province on a monthly time scale. The results of the model evaluation in the study showed that the coefficient of determination between the observed and simulated runoff in the calibration and validation period is equal to 0.79 and 0.83, respectively. Groundwater nutrition assessment was also performed according to manual calculations of the variable for 2012-2013. Then, the results of Kramer correlation coefficient between spatial distribution maps of runoff, actual evapotranspiration and groundwater recharge were investigated with input maps of the model. In general, due to the importance of evapotranspiration in water balance calculations, the evaporation and transpiration maps of the model were evaluated separately for different uses. The evaluation results confirmed the capability of the WetSpass model in simulating runoff, evapotranspiration and groundwater feeding with an acceptable accuracy. The results of spatial distribution maps of runoff, actual evapotranspiration and groundwater recharge indicate a high correlation between evapotranspiration component with land use (0.54), soil texture (0.45), evapotranspiration potential (0.42) and temperature (0.31). Also, these results indicate a high correlation between runoff components with land use (0.62) and soil texture (0.58), and average correlations between groundwater recharge component with land use (0.32) and soil texture (0.34). Therefore, land use and soil texture were the first and second factors affecting the distribution of surface balance components, respectively.
hamzeh saeediyan; Hamidreza Moradi
Abstract
By determining the threshold of runoff and erosion by rain simulator, it can be determined rainfall amount that causes runoff in different conditions with more speed and accuracy and lower cost. After determining the threshold of runoff and erosion in each region, using biological methods and operations ...
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By determining the threshold of runoff and erosion by rain simulator, it can be determined rainfall amount that causes runoff in different conditions with more speed and accuracy and lower cost. After determining the threshold of runoff and erosion in each region, using biological methods and operations can prevent the conversion of runoff to flood. In this research, considering that the threshold of runoff and erosion occurs simultaneously and mistakenly only the term of runoff threshold is used in different researches and do care less about erosion threshold and in order to determine the most important factors affecting the simultaneous threshold of runoff and erosion of different land uses of Aghajari and Gachsaran formations, part of Margha and Kuhe Gach watersheds of Izeh city with an area of 1609 and 1202 Hectare selected. This study was conducted to determine the relationship between runoff and erosion threshold using a rain simulator with some soil physical and chemical properties such as very fine sand percentage, sand, clay, silt, pH, electrical conductance, moisture, calcium carbonate and organic matter in different land uses of Aghajari and Gachsaran formations. Then, sampling was done at 13 points and with three replicates in Aghajari and Gachsaran formations at different rainfall intensities of 0.75, 1, and 1.25 mm/min in 3 land uses of rangeland, residential area, and agricultural land using a rain simulator. SPSS and EXCEL soft wares were used for statistical analysis. The most important factors affecting runoff and erosion threshold were identified by multivariate regression. In general, in Gachsaran formation in all three land uses, clay and calcium carbonate showed the highest role in increasing the threshold of runoff and erosion. The most roles in reducing runoff and erosion threshold showed very fine sand and moisture content in Gachsaran Formation. However, in the Aghajari Formation, in all three land uses, the highest role in increasing the threshold of runoff and erosion, showed clay and organic matter. In addition, the most roles in reducing the threshold of runoff and erosion in the Aghajari formation showed very fine sand and soil sand and salinity.
Nosrat Aghazadeh; Manochehr Chitsazan; Yahya Mirzaee; Hamed Ebrahimi
Abstract
Due to various sources of contamination in the urban aquifers, the potential for pollution of groundwater resources is high. Thus, the vulnerability of groundwater resources can be very effective in identifying vulnerabilities and sensitive groundwater aquifers. The aim of this study was to present a ...
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Due to various sources of contamination in the urban aquifers, the potential for pollution of groundwater resources is high. Thus, the vulnerability of groundwater resources can be very effective in identifying vulnerabilities and sensitive groundwater aquifers. The aim of this study was to present a modified DRASTIC Model to determine groundwater vulnerability in Urmia urban aquifer. To this end, parameters with low impact such as slope and aquifer media were ignored from the DRASTIC Model. Instead, land use, urbanization index, water value and pollution sources were added to the model. Also, the impact of unsaturated zone media and recharge layers were corrected. Results of the modified DRAST-VUL Model in the study area demonstrate that in most areas, the risk of pollution is low to moderate and the vulnerability in 29% of study area is high due to agricultural and industrial activities and low groundwater depth. Considering the results, the vulnerability index is the most sensitive measure to the parameter of pollutant sources, land use and the unsaturated zone. The sensitivity of the model to recharge, transmissivity and water value parameters were low due to the increase of impermeable surface in urban area. Based on positive results obtained from model validation through nitrate, the proposed model can be considered as an effective tool for the protection, revention and optimal utilization of groundwater resources in the study area. Also, this vulnerability model can be used for other urban aquifers.
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.
sohrab jamalpour bergai; hassan ahmadi; Aboalfazl Moeini; mohammad faraji
Abstract
Dust storms is one of the most important environmental hazards, especially in arid and semi-arid climates, which causes irreparable damages to the various dimensions of the environment. The aim of this study was to identify dust sources in south-east Ahwaz, using a remote sensing technique and fuzzy ...
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Dust storms is one of the most important environmental hazards, especially in arid and semi-arid climates, which causes irreparable damages to the various dimensions of the environment. The aim of this study was to identify dust sources in south-east Ahwaz, using a remote sensing technique and fuzzy logic. For this purpose, the satellite images of dust events of Ahwaz City were investigated and the wind characteristic of the study area were studied by plotting the storm rose of Ahvaz Synoptic Station. In the next step, the criteria were categorized into two categories: soil moisture, land surface temperature and vegetation constitute the main layers and land use, spatial data of soil, climate, slope and sedimentology were used as constraint layers. The main layers were extracted from Landsat OLI-TIRS satellite images. The Boolean method were used to standardize the constraint layers, and the fuzzy membership functions were used to standardize the main layers. Also, main layers weighting was done using fuzzy analytic hierarchy process. Finally, the dust sources map was obtained by overlapping the layer. To validate the results, 44 ground control point were selected from the study area that showed high accuracy (81.8%) for identified areas. Based on investigating of satellite image and storm rose of Ahvaz Synoptic Station, the south-east of Ahwaz was recognized as dust-generating source and 145162.01 ha of lands are dust generating sources from which 69343/01 ha (47.77%) belongs to destroyed rangelands and 335.99 ha (0.23%) belongs to Canebrake, contains the highest and lowest level of sources of dust production in the study area, respectively.
Negin Ghaderi; Karim Soleimani; Ataollah Kavian; Mostafa Rashidpoor
Abstract
Urban watersheds due to their development, have more complex hydrological behavior than natural watersheds, and understanding their hydrological response will help to design appropriate flood control facilities. In this study, SWMM model was used to investigate the potential of urban runoff production ...
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Urban watersheds due to their development, have more complex hydrological behavior than natural watersheds, and understanding their hydrological response will help to design appropriate flood control facilities. In this study, SWMM model was used to investigate the potential of urban runoff production in a part of Babolsar urban area. The purpose of this study was to analyze the water availability of rainwater collected during different return periods for urban use. For this purpose, the SWMM model defined 65.65 ha of study area in the form of six hydrological units (from 5.94 to 16.82 ha), six output nodes and four channels were defined, and the height of runoff from 24-hour rainfall was obtained with different return periods. According to these results, the 24-hour rainfall with a 25-year return period is 70.37 mm, of which 33.73 mm for infiltration and 35.60 mm for runoff. Results showed that about 52.1% of rainfall of Babolsar City plan could have the ability to become runoff. The highest runoff coefficient is in the hydrological unit S3, which has a value of 0.637 at the 100 year return period. However, the lowest runoff coefficient is in hydrological unit S1 which has a value of 0.352 at 2-year return period. The results also showed that the runoff coefficient is directly related to the return period and the larger rainfall has a higher runoff coefficient. Through the collection systems, in addition to reducing the flood hazards of Babolsar City, a water supplement that offsets part of household consumption in the non-urban sector, also water resources management can be done.
Ali Seif; Hoda Ghasemieh; Hossein Zeinivand; Mehran Zand
Abstract
Today, with the increase in population, land use has been changed to meet the needs, which has made it more important to know the future status of land use. Investigating land use changes plays a fundamental role in environmental studies, modeling and simulation of land use changes and water resources ...
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Today, with the increase in population, land use has been changed to meet the needs, which has made it more important to know the future status of land use. Investigating land use changes plays a fundamental role in environmental studies, modeling and simulation of land use changes and water resources management and helps managers in better land use planning. So, in this research, first, the land use map of Rahim-Abad Basin was extracted for 1999 and 2016, using ETM+ and Landsat 8 sensors in ENVI5.3 software environment, with a kappa coefficient of 95% and overall accuracy of 97% that indicates the high accuracy of the 2016 map.Then, the maps of affecting factors on land use change including maps of distance from the road, distance from the river, distance from the city, distance from the village, distance from the fault, geology, soil texture, rainfall, evaporation, elevation digital model, gradient, groundwater level and the amount of solar radiation were prepared in Arc-GIS 10.6.After, using logistic regression, the role of effective factors on land use was determined and the Relative Operating Characteristics curve (ROC) was used to evaluate the logistic regression. Finally, the land use map of the study basin was simulated for 2026 using the CLUE-s model.Results showed that the area under the ROC curve was 0.9, 0.88, 0.9, 0.92 and 0.91 for grasslands, rain-fed lands, irrigated lands, water and, residential zones, respectively, which expresses the acceptable accuracy of the regression method in investigation of affecting factors on land use.Also, the most changes of land use in 2026 would be related to conversion of rangelands to rainfed lands, and 6.47% rangelands would decrease and 18% rainfed lands would increase.
Behzad Hessari; Kamran Kamran
Abstract
Considering the importance of Lake Urmia, the purpose of this research is to survive the human activates on the trend of surface water and groundwater changes in the Urmia plain. For this purpose, the changes in input and output discharge, aquifer drainage and land use changes in the Urmia Plain were ...
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Considering the importance of Lake Urmia, the purpose of this research is to survive the human activates on the trend of surface water and groundwater changes in the Urmia plain. For this purpose, the changes in input and output discharge, aquifer drainage and land use changes in the Urmia Plain were studied on the basis of nine hydrometric stations data (during 1973-1903) and information of 74 piezometers and using satellite images. The test used for trend analysis was Mann-Kendall nonparametric test with considering the effect of autocorrelation. According to the results, the trend of input discharge from the Nazlou-Chay, Rouzh-Chay and Barandoz-Chay sub-basins to the Urmia Plain was decreasing and the negative trend of outlet discharge related to the Rouzh-Chay, Shahr-Chay and Barandoz-Chay sub-basins was significant at 95% confidence level. Comparison of the results the difference between discharge average during after and before 1995 (the year which in it the lake begins to dry) showed that at all stations except Ghassemlou, there is a significant difference between average discharge during these two periods. The value of the statistic (Z = -2.18) indicates a significant decreasing trend at 95% confidence level for the drainage volume of the aquifer reservoir. The results of this study showed that discharge to Lake Urmia in all seasons had a decreasing trend during the studied period and serious actions should be done to manage water resources in the region.
Raziyeh Motamedi; Mahmood Azari; Reza Monsefi
Abstract
Landscape is one of the main factors influencing hydrological processes of the watershed. Changes in structure and spatial pattern of land use play important role in surface runoff and sediment yield. Determining the relationship between landscape patterns and hydrological processes can be used as an ...
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Landscape is one of the main factors influencing hydrological processes of the watershed. Changes in structure and spatial pattern of land use play important role in surface runoff and sediment yield. Determining the relationship between landscape patterns and hydrological processes can be used as an indicator of watershed soil erosion and sediment yield. Therefore, due to the problems in field measurement of sediment yield, its estimation using landscape properties and land use pattern is an appropriate alternative for current estimation methods. The purpose of this research is to determine the relationship between watershed sediment yield and landscape metrics in the selected sub-watersheds of Golestan Province. To this end, suspended sediment concentration data for all hydrometric stations of the studied province were obtained from the relevant resources and appropriate sub-watersheds were selected. Then, using the land use map of Golestan Province, 15 landscape metrics related to sediment yield were determined for different land uses by Fragstats 4.2 software. In order to determine the relationship between watershed sediment yield and landscape metrics, a partial least squares regression was used which combines the methods of principal component analysis and multiple linear regression. The relative importance of landscape metrics was determined through examining the values of Variable Importance for the Projection (VIP) and Regression Coefficients (RCs). The results of this study indicated that the watershed sediment yield is densely associated with land use patterns. The main indices in reducing sediment yield were the Largest Patch Index (LPI), the average of the nearest neighbor distance (ENN-MN) and the average of perimeter-area ratio (PARA –MN) with values of VIPs of 1.296, 1.184 and 1.747, and regression coefficients of -0.014, -0.039, and -0.002, respectively. The main indices in incrising sediment yield were Landscape Shape Index (LSI) and mean patch size (AREA-MN) with regression coefficients of 0.020 and 0.017, respectively. The landscape characteristics in watersheds could account for as much as 71% of the variation in sediment yield of watershed. The results of study showed that the landscape characteristics can be used for watershed sediment yield modeling.
Tayebeh Irani; Mir Hassan Miryaghoubzadeh
Abstract
Land use is referred to the use of land in existing condition that includes all uses in different parts. Land use change is affected by several factors. In this research, land use Changes in the Zarrinehroud watershed and its effect on water quality were investigated in three periods (1987, 2004 and ...
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Land use is referred to the use of land in existing condition that includes all uses in different parts. Land use change is affected by several factors. In this research, land use Changes in the Zarrinehroud watershed and its effect on water quality were investigated in three periods (1987, 2004 and 2013) using Landsat satellite TM and OLI sensors. The results indicate that land use changes in the watershed is going to reduce of pasture and increasing of agriculture. Wilcox and Schuler diagrams were used to evaluate the chemical quality of agricultural water, and drinking water, respectively. Based on the Wilcox diagram, only year 2004 (dry period) was on the C3-S1 class and the remaining years were on the C2-S1 class. Based on the Schuler diagram, the year 2004 (dry period) is considered acceptable in the drinking category and the remaining years are in good drinking category and have no restrictions on drinking. Water quality assessment of the Zarrinehroud watershed shows a decrease in water quality, as a result of increasing the EC, TDS and SAR characteristics in year 2004 that indicates a decrease in river water quality due to land use change and accordance with the occurrence of droughts in the year 2003-2004.
Aliakbar Noroozi; Ziaoddin Shoaei
Abstract
Wind erosion is one of the important processes of desertification in arid and semi-arid regions. This process causes destruction in the land, soil and water resources and etc. Dust phenomenon is one of the major consequences of wind erosion in the world and Iran, particularly in the west and south west ...
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Wind erosion is one of the important processes of desertification in arid and semi-arid regions. This process causes destruction in the land, soil and water resources and etc. Dust phenomenon is one of the major consequences of wind erosion in the world and Iran, particularly in the west and south west of the country. Therefore, the present study aimed to identify areas of dust generation potential in the Khozestan, Iran using the combination of statistical methods, remote sensing and modeling. The statistical results showed that the most frequent occurrence of this phenomenon happened between 2008 and 2009. Most dust events happened in the seasonal scale, late spring and early summer and in the monthly scale, happened in May, June and July. Dust detection on satellite images and study their concentration using indicators AOD and BTD represents the greatest concentration of dust in the west and south west regions of the Khuzestan province, since 80 percent of these dust occurred in these zones. Tracking of dust showed that during the warm period, most dust happened from north west-south east and west-east and during the cold period, especially at the end of period, the northern-southern dust affected the province. The assessment of land use change showed the reduction in the irrigated areas, vegetation and arid lands increased in 2015, especially for the half of area of western Khuzestan. These features and physiographic features such as erodible formations, saline soils and marshy, low soil moisture and high changes in land use, indicates the presence of dust prone areas and potential for west and southern province.
Ata Amini; Rangin Haydari; Majid Hosseini; Nader Jalali
Abstract
The land use programming is vital since inappropriate land use can endanger soil and water resources in a region and reduce their quality and quantity for future generations. While land development based on its ability are always facing limitations. This research is conducted with a sustainable approach ...
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The land use programming is vital since inappropriate land use can endanger soil and water resources in a region and reduce their quality and quantity for future generations. While land development based on its ability are always facing limitations. This research is conducted with a sustainable approach to manage water resources and land programming in line with make optimal use of limited land, soil and water in the watershed. For this purpose, the required information to prepare a development model based on the land potential, were collected. Using the ArcGIS software, essential maps including map of slope, altitude, driving directions, land form, hydrographic, soil and vegetation, and density, were derived. By combining layers of information, the lands abilities were extracted in term of 107 ecological units. The meteorological data, hydrometer and the sources and consumptions of water resources of the watershed were collected and analyzed. The results showed that 88.2 percent and 11.6 percent are currently the area of agriculture and orchards. While the watershed potential for these practices are as 78.9 and 19.1, respectively. However, lack of attention to the potential water resources of the region, which is mostly as groundwater, caused a drop in groundwater level about 0.85 m per year and consequently the risk of soil and water resources in the region. The results indicate the importance of integrated water resources management and natural potentials in sustainable development in the watershed.
Keivan Khorrami; Ghorban Vahab Zadeh; Karim Soleimani; Reza Talaei
Abstract
The use of groundwater is one of the ways to overcome the seasonal shortages of water.Underground dam that can be noted as one of the techniques to help the improvement of water resources management and increase the efficiency of these resources, is one of the water storage practices to use the groundwater. ...
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The use of groundwater is one of the ways to overcome the seasonal shortages of water.Underground dam that can be noted as one of the techniques to help the improvement of water resources management and increase the efficiency of these resources, is one of the water storage practices to use the groundwater. . It is a simple method for the collection and storage of water in arid and semi-arid areas. In this study, selection of suitable areas of underground dam in Gharasou watershed is investigated. Many factors are influenced in determining the suitable areas of underground dam. In this research, physiography, geology, hydrology, hydrogeology and land use of the watershed were investigated and analyzed with the use of information, maps, reports, required data and geographic information system. Then, derived maps from different stages were combined and finally suitable areas and streams for construction of underground dam were mapped. Results showed that about 30 percent of Gharasou watershed is suitable for construction of underground dam.
Ebrahim Boroshkeh; Mahmoud Arabkhedri
Abstract
Sediment yield estimation for small basins is essential in watershed management planning projects. However, almost all of these basins are ungauged. In this study, in order to determine a range for specific sediment yield and to develop a regression model for estimating annual sediment yield, sedimentation ...
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Sediment yield estimation for small basins is essential in watershed management planning projects. However, almost all of these basins are ungauged. In this study, in order to determine a range for specific sediment yield and to develop a regression model for estimating annual sediment yield, sedimentation behind small dams within 25 basins in Western Azerbaijan province, were measured. The selected basins with an area ranged 29 to 1200 ha, cover a range of lithology, land uses and climates and all of the sediments had been trapped behind the check dams. The specific sediment yields showed a two digit differences ranged 0.12 and 12 . However, the weighted average of specific sediment yield for all basins was calculated a low value of 1.3. Study of relationship between annual sediment yield and 18 characteristics of watersheds using correlation matrix showed that the sediment yield is significantly affected by geologic erodibility, basin area and land use factors. From several regression models which were developed, an equation including two independent variables, geologic erodibility and basin area, with a high determination coefficient (R2=0.899) was chosen.
Ravanbakhsh Raisian; Amir Hossein Charkhabi; Mohammad Nekoueimehr
Abstract
One of the main factors accelerating soil erosion in the watersheds in Iran is improper management including overgrazing and improper land use changes of pastures into agriculture. This problem is true in the whole Karoon watershed. Therefore, the objective was to study the effects of land use changes ...
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One of the main factors accelerating soil erosion in the watersheds in Iran is improper management including overgrazing and improper land use changes of pastures into agriculture. This problem is true in the whole Karoon watershed. Therefore, the objective was to study the effects of land use changes on soil loss in Gorgak sub-watershed. The statistical design was split plot design with pasture and rain fed agriculture as main factors. A drop maker rainfall simulator with 40 mm/hr intensity and 30-minute rainfall period was used on five field locationsunder two soil moisture conditions of air-dry and field capacity and three slope classes of 10-20, 20-30, and 30-40%. A total of 180 sediment and runoff measurements were made using the above rainfall simulator under field conditions for two land use systems of rain fed cereal and overgrazed pastures. All the measurements were done in triplicates (5 fields x 2 land uses×2 moisture content×3 slope classes×3 replicates = 180 plots). The results showed the soil loss under overgrazed and air-dry soil condition was 45.6 times more than the rain fed agricultureunder the similar soil moisture condition. However, the results showed the soil loss under overgrazed and field capacity soil moisture condition was 2.33 times more than the rain fed agriculture under similar soil moisture condition. Once the soil loss was compared for different slope classes of 10-20, 20-30, and 30-40 slope percent, the results indicated the soil loss under overgrazed and air-dry soil condition were 4.77, 5.19, and 2.34 times more than the rain fed agriculture under similar soil moisture condition. Overall, soil loss under overgrazed conditionwas 3.38 times more than rain fed agriculture. Therefore, although most soil conservationists generally believe that the rain fed agriculture in Iran is very improper managed and it has high soil erosion rates but the results of this study showed the overgrazed pastures in the north Karoon watershed need much more priority for any soil loss measures and controls.
Samad Shadfar; Mojtaba Yamani; Mohammad Namaki
Abstract
One of the hillslope movement processes is land sliding which causes both human loss and economic damages. Factors such as structural and dynamic developed landforms , forests clearing, incorrect technical principals in construction and maintenance of rural and forest roads, lack proper management and ...
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One of the hillslope movement processes is land sliding which causes both human loss and economic damages. Factors such as structural and dynamic developed landforms , forests clearing, incorrect technical principals in construction and maintenance of rural and forest roads, lack proper management and using existing resource causes much damages to rural settlements, construction activities, forest, rangeland, and agriculture lands every year. Landslide Hazard Zonation is the first step for proper land management to overcome these problems. To prepare LHZ, several thematic layers such as lithology, slope, elevation, land use, distance from faults and distance form drainage were digitally prepared. Landslide distribution map of the area was prepared through Arial photos interpretation and also field checks. The thematic layers were integrated using information value, area density and LNRF models in a GIS environment. Finally to validate the results, a sub-basin was selected as a control area and the calculated weights for this sub-basin were applied for the rest of the catchments. The result of this investigation indicates that most of the landslide occurred in pdr, Js lithological units composed of marl, clay and silt layers, slope class 30- 50 and on elevation 2000- 2500 m. Also, most of the instability are on rangeland and occurred in a distance of 0-300 m from drainage network. The research shows that the estimated percentage of high hazard class is 79, 63, and 66 percent for area density, LNRF, and information value models respectively.
Mohammad Hemmati; Davood Nikkami; Hassan Ahmadi; Gholamreza Zehtabian; Mohammad Jafari
Volume 1, Issue 1 , May 2009, , Pages 21-31
Abstract
Soil is one of the four elements of life and one of the most important agricultural and rangeland production factors. Soil erosion has impact on fertility of upstream lands and indirectly causes downstream damages. On a global scale, more than 50% of rangelands and about 80% of farmlands are significantly ...
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Soil is one of the four elements of life and one of the most important agricultural and rangeland production factors. Soil erosion has impact on fertility of upstream lands and indirectly causes downstream damages. On a global scale, more than 50% of rangelands and about 80% of farmlands are significantly suffering from soil erosion and sedimentation phenomenon. Despite of agricultural benefits of rainwater, its erosive energy in the primary stages, detaches soil particles and creates surface runoff which has the most severe impacts on soil erosion. The effective energy in this shape of erosion is called rainfall erosivity, which is rainfall erosion potential and depends on rainfall physical characteristics. Some different indices are developed for quantification of rainfall erosivity. Some indices emphasise on the amount of rainfall or rain intensity. Worldwide investigations show that applying a certain index, like EI60 in USLE equation has not sufficient credit and according to climatic condition the best rainfall erosivity index should be determined. In this research, after establishing 21 erosion plots in Kaboudeh Oliya village, Kermanshah city, on two land use types of dry farming of 6, 12, 16 and 17 percent slopes and rangelands on 25, 35 and 45 percent slopes with three repetitions, 15 rainfall events which produced surface runoff were monitored by a recording rain gauge and the amount of surface runoff and sediment were measured. According to the literature, 45 rainfall erosivity indices were chosen to be compared. For facilitating and increasing accuracy of calculations on rainfall erosivity indices, a computer program was developed to analyze and extract necessary factors from each storm. The result showed that in the study area, EI60 is the best rainfall erosivity index and has maximum correlation coefficient of 0.721 with soil loss.
