پژوهشی
Tohid Rahimpour; Shahram Roostaei; Mahsa Nakhostinrouhi
Volume 4, Issue 13 , March 2018, Pages 1-20
Abstract
Introduction A landslide is a natural phenomenon that often occurs because of falling down or seamless and quick movements of volumes of sediment along the slope. It has such speed and extent that it may influence tens or hundreds of cubic meters of rock and soil together. This phenomenon causes a lot ...
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Introduction A landslide is a natural phenomenon that often occurs because of falling down or seamless and quick movements of volumes of sediment along the slope. It has such speed and extent that it may influence tens or hundreds of cubic meters of rock and soil together. This phenomenon causes a lot of economic damages to forests and their growth, farmlands, gas and power transmission lines, mines, engineering structures, and buildings. One of the best ways to prevent these damages is preparing a landslide hazard map. Methodology The method used for zoning the Sardool Chay Basin is the Analytical Hierarchy Process. This is one of the most comprehensive multi-criteria decision methods, which was first presented in 1980 by Thomas L. Saati. This method is based on weighing each pair of variables with each other. AHP method consists of three main steps including (1) creating an Analytical Hierarchy, (2) comparing pairs of elements in it, and (3) weighing the criteria. The main feature of this method is the use of expert opinions. In AHP,n paired factors are compared with each other and more weight is given to the layer that has the maximum impact on the target set. The paired comparison of a scale, based on1 to 9, for its two components' relative weighing is hierarchical. Discussion In this study, the landslide hazard zonation was used in the Sardool Chaycatchment in order to identify areas with landslide incidence potential. The main factors contributing to the landslide occurrence in this case study consisted of geology, land use, slope, aspect, rainfall, altitude, distance from faults, and distance from stream. Their layers were prepared in ArcGIS software. An Analytical Hierarchy Process in Expert Choice software was used for paired comparisons of criteria and calculation of final weight. The results indicated that the geology criterion, which weighed 0.343, and the slope criterion, which weighed 0.215, had the most influences on landslide occurrence. Conclusion Landslide is one of the most common environmental hazards in mountainous areas of the northwest of Iran. Factors such as slope, rainfall, lithology, and earthquakes can trigger them. One of the best ways to deal with this phenomenon, before the implementation of any project, is the zonation mapping of the area. This study was based on the Sardool Chay catchment, located in Khalkhal, the southern part of Ardabil Province. To this end, 8 factors including geology, land use, slope, aspect, rainfall, altitude, distance from faults, and distance from stream were used. The weighting factors and the Analytical Hierarchy Process (AHP), and the Expert Choice software were used. The results classified the basin into five areas including very high risk of landslides (65 km²), high risk (144 km²), medium risk (202 km²), low risk (142 km²), and very low risk (120 km²). In addition, it indicated that the landslide risk of the Sardool Chay catchment is medium. Comparing the landslide zonation map and points of distribution suggests that the AHP can be a good method of weighing the criteria involved in the happening of the landslide.
پژوهشی
Mahmood Alaei Taleghani; Najmeh Shafiei; Marzyeh Rajabi
Volume 4, Issue 13 , March 2018, Pages 21-41
Abstract
Introduction Groundwater resources, due to being sweet and having chemical compounds, fixed temperatures, lower pollution rates, and higher levels of reliability in supplying water resources, are considered as reliable resources, especially in arid and semi-arid regions. In addition, due to the ecological ...
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Introduction Groundwater resources, due to being sweet and having chemical compounds, fixed temperatures, lower pollution rates, and higher levels of reliability in supplying water resources, are considered as reliable resources, especially in arid and semi-arid regions. In addition, due to the ecological potential of the region, it is an important and effective phenomenon in the economic development, ecological diversity, and community health. Relying on groundwater resources, especially in dry and semi-arid lands, has led many scholars to study how to form or access them. The main objectives of this research are to investigate the effective role of geomorphologic factors in the potential of underground water resources in the region and the possibility of proper management of water resources in the studied basin and to be more knowledgeable about groundwater issues,. Therefore, studying and identifying the hydro geomorphology of the area and the factors affecting the aquifers is essential. The study area is located in the geographical boundary of the west of the country in the northeast hillside of the Zagros range. The area of Meiandareh, with an area of 329 km2, is located in the northern part of Kermanshah Province. Methodology The method used in this research was based on the analytical and weight-empirical analysis carried out in separate steps. First, an inferential method was used to determine the direction and amount of groundwater flow, the role of nutrition of various geomorphological phenomena in the plain, the position of the piezometer wells, and the groundwater level map for the plain. Second, weighing index based on expert opinion and expert of Delphi-completed questionnaire of various weighted layers were used. Finally, the potential of the plain and its favorable regions were studied using the pairwise G.I.S. software. Discussion In the maps of the groundwater level of the plain, it was indicated that while the maximum level in the eastern margin of the eastern part of the region at the beginning of the apple flank was about 25 m, in the boundary of the Ghareh Souz River and flood plains, it was about 3 m. Thus, the groundwater flows from the northern and eastern parts to the central parts and outlet of the basin. Indeed, the farther from the heights, the lower the thickness and the higher the level of the stairway. Therefore, the river is located in the Al-Qaer plain line and plays the role of the drainage of the plain and the outlet of the water of the upper land. In 1382, the water table was the lowest with a depth of 3-16 m. In 2009, however, it was the highest water table with a depth of 3.17-25 m. it was also shown that there was a decline in the amount of the groundwater since 1388 in comparison to 1382 due to harvesting. Conclusion The map obtained from the composition of the layers indicated the importance or weight of each zone in the groundwater potential. The final configuration was divided into three classes with a very suitable, appropriate, and inappropriate potential. Regarding the results and the status of discharge, the eastern and central boundaries of the middle reaches have high potential for the artificial feeding of groundwater. There is also a lower risk for drilling wells. In general, the aquifer of the plain is considered as the limit of humidity and rainfall absorption and water supply required by the middle reaches plain. Physical weathering of the rocks and proper rangeland cover caused plenty of gaps and increased groundwater nutrition in this area. It seems that one of the important reasons for water guidance in the axis of the plain of the navy building and the direction of the slopes of the China's flanks is the drainage of the surface water and the underground water. However, the volume of groundwater in the plain is the only function. The result of the study of water behavior in exploratory and piezoelectric wells has shown that the low drainage density plays the main role in feeding plain in flood plains, coniferous fringes of eastern plains, slopes of 0-2%, and low altitudes. These lands are usually highly influential and because of the fertility and access to surface and underground water resources, the establishment of the demographic and agricultural lands can be seen within them. A significant level of plain lands is flood plain, which plays a very important role in the nutrition of groundwater resources of the plain. According to the maps, the depth of the groundwater level, the main flow of underground water in the plain are from north to south, which indicates that the main river plain in this region plain and evacuates underground water from the area. Sedimentary plain with infiltration infrastructure and young alluvial coverage is the most potential area for water resources in Meiandareh.
پژوهشی
Mohamad Sharifi Paichoon; Fatemeh Parnoon
Volume 4, Issue 13 , March 2018, Pages 43-62
Abstract
Introduction Rivers' channels tend to change due to different factors such as lithology, discharges, floods, sedimentation, and humans. Of all factors, understanding the morphological features of a river and its major controlling factors is importance in its control and regulation. The morphological ...
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Introduction Rivers' channels tend to change due to different factors such as lithology, discharges, floods, sedimentation, and humans. Of all factors, understanding the morphological features of a river and its major controlling factors is importance in its control and regulation. The morphological features and geometric characteristics such as change in the length and width of the river, wavelength, arc length, arc angle, and sinuosity are the most important factors that should be considered to study and mange a river. Many investigations have been done to study the changes in the morphology of the rivers and the geometrical parameters. For example, Leopold and Wolman (1957), based on structural viewpoint, divided rivers to three groups including braiding, meandering, and relatively straight channels. Singh (2014) studied morphological changes of the Ganga River during 10 years using GIS. Iranian researchers (Ahmadian,2001; Ghafari et al., 2004; Hafezi Moghadas et al., 2012 ; Maghsoudi et al., 2010; Shahbazi et al., 2009) have also investigated the morphological and geometrical parameters of different rivers. In the current research, the changes in the geometrical parameters of the Qaresou River between 1959 and 2015 were evaluated. This river is located between latitude of 34° 30’ N to 34° 54’ and Longtitude of 46° 22’ E to 47° 22’ within Kermanshah’ Province in the west of Iran. It is one of the sub catchments of the Karkhe basin. It has a land extended about 5278 km2, with a maximum of 3360 m and a minimum of 1270 m height. The average precipitation of the basin fluctuates between 300 to 800 mm in a year. Three rivers which flow into the Qaresou includes Mereg, Qaresou, and Razavar rivers. Methodology In this research, to study the morphology of the Qaresou River and its geometric parameters and changes, the aerial photos (1955) and satellite images IRS (2015) were used. In fact, the photos were the best tools to compare the rate of changes in the morphology of the channel for about 60 years. First, the photos and images were scanned and georeferenced. Then, the river was digitized with high exactness. Next, using AutoCAD Software, the geometric parameters such as wavelength, arc length, arc angle, amplitude, sinuosity, central angle, and meandering were evaluated. Finally, through comparing geometric parameters between two periods, the rate of changes for about 60 years was calculated. Results and Discussion Evaluation of the geometric parameters of the Qaresou River was based on using drawing circles tangent with meanders of the river for both periods. The findings showed that the pattern of the river and some geomorphological and geometrical characteristics were changed during the time. For example, the number of meanders had reduced from 535 in 1959 to 379 in 2014. Also, the central angle, as a criteria to divide and determine the development of the meander in a river, was evaluated. This criteria showed a reduction in the average of the central angles in all segments of the river except its first segment with an increase in its width because of higher erosion. In addition, during this period, 60 years, the river has tended to a straight pattern. The changes in the radius of the meanders also reduced in all segments except the first one. However, at first, the pattern of the river changed to develop in the meanders. Besides, the curvature coefficient of the river reduced in all segments except the third one. Finally, there was an increase in the wavelength and the length of the channel between the years 1959 and 2015. Conclusion The result showed that although the frequencies of the arc in all segments reduced during the statistical periods, the geometric parameters fluctuated. For example, in the first segment, the wavelength increased 96 m and the length of the channel increased 31 m. Also, the curvature coefficient reached from 1/83 to 2/38. The radius of the meander increased about 38%. The central angle increased 40%. The increase in the geometric parameters showed grubbing in the river bed and increasing in the curvature of the river. In the fifth segment, in contrast, all geometric parameters declined. For example, the wavelength and the length of the channel respectively declined 31 and 15 m. In addition, the curvature coefficient was also decreased 3%. There was also a decline in the flow water of the channel. Therefore, the river follows a natural process of digging in the upstream and sedimentation in the downstream. Near Kermanshah city, the slope of the channel tends to the least and the river starts to leave all sediments, which leads to displacement in the channel.
پژوهشی
Mohammad Akbarian; Siavosh Shayan
Volume 4, Issue 13 , March 2018, Pages 63-78
Abstract
Extended Abstract
Introduction
Each part of a shore should be thouroughly considered with its hydrodynamic, lithodynamic, geological, geomorphological, and other peculiarities. In modern conditions, anthropogenic factors should also be included. Only such a multilateral approach can produce results ...
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Extended Abstract
Introduction
Each part of a shore should be thouroughly considered with its hydrodynamic, lithodynamic, geological, geomorphological, and other peculiarities. In modern conditions, anthropogenic factors should also be included. Only such a multilateral approach can produce results which reflect the actual situation as closely as possible. Arid lands and coastal zones are the most favourable areas for wind processes. The analysis of the forms and coastal conditions provides a valuable key for coastal management. A beach can be composed of a wide variety of materials of many sizes and shapes. The river load is one of the hydrological elements that affects the beach. Particle size windows (PSWs) are interpreted as reflecting different modes of sediment transport and deposition. In a related research on western Makoran coastal plain, Shayan et.al (2014) found that the distribution of the internal sand masses on the plain was affected by the extent of the old beds and floodplain that were exposed to the prevailing wind rather than wind function. The aim of this study was to identify the effect of river’s flows on sedimentological characteristics of the shoreline in the western part of Mokran coastal plain, Iran. The major process that formed coastal plains were fluvial processes. In semi arid areas, the geomorphological impacts of dams are very major. The purpose here was to identify the consequences of dam construction on vegetation and aeolian geomorphology with an emphasis on the ecogeomorphology of the western part of Makran coastal plain. The study area is located at 25o31’-25o50’N, 57o52’-59o02’E, in the western part of the coastal plain of Makoran, the southern part of Iran, the northern part of the Oman Sea, and the eastern part of Strait of Hormoz. In general, the region under research could be assumed a dry land with very low rain, windy, sand storm, torrent shower, thunder-storm, higher humidity, and hazy down (Akbarian et al., 2006). Geologically, it is affected by Mokran (Makoran) region's general construction and it is mainly composed of shaile, marl, and sandstone layers.
Methodology
Research data included spatial distributions of coastal lanforms, rivers' hydrodinamic data, data of surface morphometric specialy slope, and type of vegetation. Maps of geology and topography, satellite imagery, aerial photos, GPS and computer softwares such as Freehand and ArcGIS were used. Morphodynamic changes of the rivers were investigated by using hydrometric station's data, comparing the satelite images and areal photos, and gathering the results of other studies. The Coastal plain's topographical and geological charecteristics, the distribution map of landfoms, the vegetatin cover, and coastal dunes were also studied. Then, based on the geomorphological analysis and information from field works, the possible ecogeomorphological consequences of dam construction were studied.
Discussion
The exploitation of coastal rivers have had an enormously negative impact on coastal zone and a deleterious effect on the natural dynamics of river loads. The basins leading to the Coastal Plains of Sedijch, Gabric, and Jagin have high sedimentation discharge. According to the results, the hydrodynamic effects of these rivers have a special effect on the formation of plain landforms. The sources of the sedimentation of sand masses and the establishment of forest cover on adjacent coastal plain are affected by river’s hydrodynamic. Once dams constructions on these rivers are complete, sediment load virtually comes to an end. In the near future, major changes can be expected at the mouth of the rivers and along the coastal zones of this region. However, dams could cause serious environmental damage in the downstream of these rivers. They may increase the severity of wind erosion, the performance of waves in sediment drift along the coastline. They will also have negative effect on the amount of forest cover on upland of these coastal plains and especially mangrove wetlands.
These results are consistent with the following researchers. According to Nanson and Croke (1992), as a result of environmental modifications on rivers, flood plains affected by major rivers evolve over time. In a study of hydrology, geomorphology and vegetation in the southeastern coastal rivers of the United States, Hop (2000) concluded that the vegetation diversity of the coastal plain has adapted to long flood periods and anaerobic conditions. Based on Berkun (2014), the natural course of fluvial alluvium transport is almost completely altered because of planned and constructed dams and coastal protection measures. Decreasing volume of sediment carried to the sea cause intensification of the shore erosion (Berkun, 2012). Sulimanirad et al. (2011) stated that the habitat of the protected area of Gabrij (the whole range of Gabriel coastal wetlands, Jengin, and Sourgelm) is threatened and possibly destroyed due to the construction of a dam on the Jegin River, camel grazing and the destruction of mangroves.
Conclusion
The present study showed that water and sediment discharge of rivers and their hydrodynamic has a special role in the formation of coastal landforms, specially on aeolian landforms, and the stablishment of mangrove on lagoon and Persian Gulf-Oman(Sahara-Sendi) forest habitat on upland deltas. Lake of fluvial processes in the long period will probably have destructive consequences on the ecology and geomorphology of this coastal region.
پژوهشی
Narjes Bay; Shima Niko; Vahid Feizi; Haydeh Ara
Volume 4, Issue 13 , March 2018, Pages 79-97
Abstract
Abstract
Introduction
Drought, with its gradual, tranquil, and crawling occurrence, is one of the most important natural disasters that affects various aspects of human life. This phenomenon, as a disastrous climatic phenomenon, directly affects communities through changes in their access to water ...
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Abstract
Introduction
Drought, with its gradual, tranquil, and crawling occurrence, is one of the most important natural disasters that affects various aspects of human life. This phenomenon, as a disastrous climatic phenomenon, directly affects communities through changes in their access to water resources. One of the most important effects of drought on water resources is the reduction and drop in groundwater aquifers and the decrease in river flow rates. The hydrological drought, with the effects of periods of atmospheric drops, affects the sources of groundwater or surface water supplies such as river flows, reservoirs, lakes, and groundwater. Therefore, the effect of the rainfall shortage on the components of the hydrological system such as soil moisture, river flow, surface of reservoirs, and groundwater is seen after a long time. Climatological drought with a time lag in one place leads to a hydrological drought which, consequently, leads to water stress. Determining the starting and ending dates of droughts, their severity, continuity, spatial distribution, assessment, and quantification is one of the most important issues in the study area. Accordingly, the main objective of this research was to determine the extent of the continuity of meteorological and hydrological droughts and the relationship between them.
Methodology
The Gorganroud River watershed forms 48% of Golestan Province with an area of 11393.1 km2. It is located in the geographical range of '36 ° 36 'to 37 ° 37' the northern latitude and '00 ° 54 'to '29 ° 56 the eastern altitude. It is located in the national scale of the Gorgan River basin in the north of the country. From the south east to the eastern Alborz, from the east to mount Aladagh and mount Glydiyah, from the north to the Atrak basin, and from the west to the Caspian Sea and the Gharasso basin. The Gorganroud River has 17 main branches that are connected in different parts and, ultimately, flood the Caspian Sea. The basin is used as a forest in the south and east, but in the north and west, alluvial plains are exploited in agriculture and pasture. In order to study droughts, the standardized precipitation index (SPI) and standardized water-level index (SWI) were used. The data used in this study was extracted from 16 meteorological stations and 31 piezometric wells, with a common statistical period of 30 years (1362-1392). To analyze the droughts' trend, seven scales of 1, 3, 6, 12, 24, and 48 were used in a monthly and annual scales. In this study, to reconstruct the statistical errors and homogenize the data, acorrelation and normal ratio methods were used. Then, the SPI and SWI indices and the quantitative analysis of droughts of basin were used to evaluate the trend of rainfall and underground water in different spatial and temporal scales.
Result
According to the calculations and checking the map of the annual extent of meteorological drought, the western and eastern regions of the basin were affected by drought more than other regions. In addition, according to the map of the annual extent of the groundwater droughts, the southwestern, western, and northern parts were affected by drought more than other regions. Considering the duration of the meteorological drought, the northeastern, western, and southwestern parts had longer durations than other regions. Considering the duration of the groundwater drought, the northern, southwestern, and central parts of the basin had the longest duration.
پژوهشی
maryam khosravian; AliReza Entezari; Abolfazl Rahmani; Mohmmad Baaghide
Volume 4, Issue 13 , March 2018, Pages 99-120
Abstract
Expanded Abstract
Introduction
It is very difficult and costly to collect information about the continuous changes of vegetation by conventional methods. With the development of the satellite technology, the satellite imagery has provided extensive access to information about ground sources. The detection ...
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Expanded Abstract
Introduction
It is very difficult and costly to collect information about the continuous changes of vegetation by conventional methods. With the development of the satellite technology, the satellite imagery has provided extensive access to information about ground sources. The detection of changes is one of the main factors in the study of the relationship between human activities and the environment. Most remote sensing products are used to evaluate and estimate the bio facial and biochemical parameters of plants from broad bands such as NOAA, AVHRR, SPOT, and TM / ETM. Landsat sensors often consist of three to seven bands. Vegetation indicators are mathematical transformations that are defined based on different gauges of the sensors and designed to evaluate and investigate plants in multi-spectral satellite observations. Lake Parishan Basin is located in Fars Province (Kazeroun city). In recent years, many environmental and human factors have had an adverse effect on its ecosystem. The interference of the agricultural lands with the marginal lands of this lake, the disposal of chemical fertilizers, the flow of pesticides from plant pests to the lake, burning of grasslands, and bogs of the surrounding countryside by profitable individuals in order to expand agricultural lands, are factors that affect its ecosystem. The purpose of this study was to investigate Lake level changes between the years 1989 and 2004.
Materials and Methods
Lake Parishan Basin is located in the geographic coordinates of 29˚ 25ˊ 12˝ to 29˚ 36ˊ 15˝ north latitude and 51˚ 40ˊ 50˝ to 51˚ 48ˊ 20˝ east longitude in Kazeroon, Fars Province. In this study, multispectral sensor data was used to investigate the changes in the lake level. Landsat ETM + 1: 50000 satellite and digital elevation data were used to carry out atmospheric and geometric corrections on satellite data. The Satellite data was interpreted and processed in ENVI 4.1 software and performed in ARC GIS 9.3 Cartographic Mapping Software. The datasets of this study were from Landsat satellite imagery of 1989 and 2004. There has been a very intense occurrence since 2004. The process of drying the lake so that nothing remains in 2007 can be checked using remote sensing techniques. The data processing process was carried out in three stages of pre-processing, processing, and post-processing. Regarding the necessity of geometric correction in detecting water level changes, the topographic maps of 1: 50000 and GPS-controlled points were collected. Using the reference grounding function in the PCI-Geomatica software environment on each image, the control points were made. The pixels were re-evaluated using the nearest neighbor method. In addition, images with an error of 0.39 and 0.42 RMS were correlated.
Results and Discussion
Different indices (SAVI), (NDWI), (NDMI), (MNDWI), (NDVI), and (AWEI) were separately extracted in order to identify distorted lake changes in the period of 1989-2008.The detection and identification of water level was done to study the relevant indicators of water level changes. The level of lake changes between the years 1989 and 2004 was evaluated and extracted in various indices. In addition, an algorithm was designed in ENVI software environment. The results showed that it was incapable of extracting the surface water of the lake. The NDMI index (with the lowest overall accuracy and kappa coefficient) was also considered due to its excessive sensitivity to blue areas.
Conclusion
The changes in the water level of the distressed lake using vegetation and water indices during the period of 1984-2008 were investigated. The results of this study showed that the normalized dispersion index (NDMI) with the lowest overall accuracy and kappa coefficient was unable to extract water from the surface, while the NDWI had the highest accuracy for the extraction of lake water level changes. Accordingly, the Normed Water Difference Index (NDWI) was used to model the spatial and temporal changes in the level of the disturbing lake in the period of 1989-2008. The results of this study also indicated that the decline in the lake water level between 2000 and 2004 was 19,160 m2. Moreover, the decline between 1989 and 1991 and between 1991 and 2000 were respectively 1344010 m2 and 1313000 m2. It was also estimated that the total changes in the water level of the lake amounted to 1494470 m2 between 1989 and 2004.
پژوهشی
Khadijeh Haji; Shahnaz Mirzaei; Raoof Mostafazadeh; Habib Nazarnejad
Volume 4, Issue 13 , March 2018, Pages 121-146
Abstract
Extended Abstract
Considering the relative stability of the physical characteristics of a watershed, the variability of the precipitation over space and time, and the direct relationship between rainfall and runoff, the variations of runoff can be expected and analyzed to understand the nature of variability. ...
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Extended Abstract
Considering the relative stability of the physical characteristics of a watershed, the variability of the precipitation over space and time, and the direct relationship between rainfall and runoff, the variations of runoff can be expected and analyzed to understand the nature of variability. Determining changes in the amount of runoff caused by rainfall and detecting the time of rivers' floods can provide a prediction of floods' occurrence and, consequently, reduce their damages. The increasing importance of water resources management in recent years, erosion, and sediment highlights the need for understanding the rivers' behavior and regimes. Regarding the changes in the river flow rate, estimating temporal and spatial variations of runoff changes can be effective in determining and controlling the dependent processes of soil erosion in a watershed and river bank, droughts, floods, and water quality and utilization. The analysis of the river flow variability, its duration and influencing factors, is necessary for an optimal river management/operation as the main sources of water uses.
Methodology
The monthly and annual runoff volumes of different stations were calculated based on the monthly discharge data in different years during the study period. Then, the variability indices were used to study the seasonal variations in the runoff volume at each hydrometric station. Next, using Annual Distribution of Regulating Coefficient and Concentration Rate indices, the seasonal variation in runoff volume of twenty river gauge stations located in Golestan Province were evaluated in 38 years. The values of Annual Distribution of Regulating Coefficient indicated the uniformity/ non-uniformity of changes in runoff volume at the studied river gauge stations. In addition, the annual variation of runoff volume was plotted in triple diagram models based on average runoff volume and time variables. The Kriging method was also used to draw the triple diagram models using two independent variables in a surfer environment. The Annual Distribution of Regulating Coefficient and Concentration Rate indices were considered as dependent variables. The variability of the implemented indices were analyzed over a time period of 38 years.
Results and Discussion
According to discharge data in different years, the monthly and annual runoff volumes of the stations were calculated during the study period. Based on the monthly spatial distribution, the results showed that the maximum amount of runoff volume of the stations were observed in March. The highest amount of surface runoff amounts occurred in Aghghala, Ghazagli, and Basirabad which respectively had an average annual runoff of 33.9, 33.5, and 32.6 million cubic meters. The highest uniformity in runoff occurrence was related to Nodehkhandoz, Tamar, Galikesh, and Gholitappeh stations, respectively with an annual Distribution of Regulating Coefficient of 0.19, 0.21, 0.23, and 0.24. The lowest Rate of runoff concentration was at Nodehkhandoz and Tamar stations respectively with 0.26% and 0.25%. The results also indicated a direct and significant relationship (R2 = 0.60) between Annual Distribution of Regulating Coefficient and Concentration Rate (p < .05). Ramian station had the highest Concentration Rate with a value of 0.62%. The highest significant decreasing and increasing trends, in Mann-Kendall test, were observed at Shirabad and Nodehkhandoz stations
Conclusions
According to the findings, there was a correlation between the annual distribution of regulating coefficient and the concentration rate. The higher values of the Annual Distribution of Regulating Coefficient and the Concentration Rate of runoff volume can be attributed to physiographic properties of watershed such as its slope, vegetation, and soil permeability. In other words, the process of changes in the runoff volume at these stations can indicate the temporal and spatial variations of precipitation, human protection measures such as dam construction in the basin, or the amount of permeability during the statistical period. In conclusion, with the non-uniform distribution of runoff volume in different months of the year, it can be expected that variations between the minimum and maximum values of runoff volume will also be high. Indeed, the higher the uniformity of the monthly distribution of runoff volume, the lower the variations between the minimum and maximum changes in the runoff volume. Variations in the amount of monthly runoff in the studied area can be related to the characteristics of the area, the hydrological response, and land use (agricultural land plowing season), as one of the main factors controlling runoff.
پژوهشی
Seyedeh Nastaran Hashemi; Mohammad Akbarinasab; Taher Safarrad
Volume 4, Issue 13 , March 2018, Pages 147-164
Abstract
Introduction
Remote Sensing is an effective tool for detecting and monitoring plume areas. Landsat8 satellite can be used for marine applications and the reason that it was used in this study was the need for a higher resolution to detect a Plume. The satellite has a resolution of 30 m and there is ...
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Introduction
Remote Sensing is an effective tool for detecting and monitoring plume areas. Landsat8 satellite can be used for marine applications and the reason that it was used in this study was the need for a higher resolution to detect a Plume. The satellite has a resolution of 30 m and there is a 16-day spatial resolution. It was the first time that the remote sensing was used to detect the Arvand River's Plume. Because of human population growth and industrialization, there is an increasing pressure on coastal areas and it is important to evaluate the quality of water. Accordingly, remote sensing plays an important role. Considering the vast amount of water covering the surface of the earth, using field measures to study water resources is costly. For this reason, it has taken its place in the processing of satellite imagery. An interesting mesoscale feature of the continental and shelf sea is the plume produced by the continuous discharge of fresh water from a coastal buoyancy source (rivers, estuarine or channel). Coastal plumes resulting from the continuous discharge of brackish or fresh river water are common features ofcontinental and shelf seas. Inside the plumes, a set of physical and chemical processes occur. Plume areas are excellent sources of nutrients. They have a great impact on marine ecosystems. They are identified as water masses with decreased salinity relative to the ambient ocean water. The Arvand River is a permanent river located in the Gulf region and the Oman Sea. The length of its central part is 84 km and its length is about 190 km. The annual average of the discharge is estimated to be 761 to 792 m3 /s. The tides are mixed at the mouth of the Arvand River.
Methodology
In this study, in order to detect the Arvand River plume, Landsat8 satellite images of October 2016 were used. The downloaded images did not have any cloud cover. River plumes with very high sediment loads have been widely studied by remote sensing technology. The suspended sediment increased the radians caused by surface water. It was in the visible and near-infrared region of the electromagnetic spectrum. The amount of impurities based on NDWI index was negative and the water was purer than the positive NDWI. The plume had more suspended sediments than its surrounding waters, so its NDWI index was less than the sea's. The plumes were identified as water masses with decreased salinity relative to the ambient ocean water.
The plume had more radians (energy) than the surrounding waters. Indeed, the NDWI index of the plume had a lower content and the Salinity Ratio Index of the plume was lower. Then, to detect plume verifications, an image of the Sentinel-2 satellite of October 2016 was also produced. The Sentinel-2 satellite in the blue, green, red, and infrared bands had a resolution of 10 m. The Sentinel 2A satellite was launched in 2015. Using the ENVI software, the radiometric correction was first performed on images. After obtaining radiance and reflectance, the NDWI index and Salinity Ratio were calculated. These four conditions were considered for the detection of the plume. Then, using the scatter plot, the thresholds mentioned in the algorithm were determined, Finally, using the decision tree, the subscriptions of these four indicators were extracted and two plume and non-plume were obtained. In addition, in this study, the NSMI index was used to classify suspended material concentration, and the results showed how the plume dispersion was developed based on this index. In addition, to determine the core of the plume and coastal waters, the NSMI index was used. The more the water, the cleaner and purer it is. The NSMI was more negative. When the water had more suspended sediment, the NSMI was more positive. The NSMI had a fluctuation between one to one negative.
Discussion
In this study, the scientific theories in relation to a plume were proved through the indicated indices. Also, through the use of an algorithm and Landsat 8 satellite imagery, successful results were obtained from the Arvand River Plume. In this study, plume and coastal waters were categorized using a decision tree. In addition, four different water zones were determined based on the spectral properties. Providing accurate and up-to-date information on the dynamics of the plume can lead to the better protection of the coast.
Conclusion
The results of this study can be used to monitor water quality. In October, Radian Band 4, Radian Band 2, NDWI, and salinity ratio matched the preconditions. The core of the plume was based on the distance from the river mouth.The Plume Core (the part with the highest concentration of suspended matter) was located adjacent to the mouth of the Arvand River.
