Showing 26 results for Basin
Dr. Morad Kavianirad, Dr Yadollah Karimi Pour, Dr. Hedayat Fahmi, Mr. Sadegh Karami,
Volume 17, Issue 46 (9-2017)
Abstract
Efforts to provide security have always been of great importance to human being. In recent decades, the security issues of climate change have attracted attentions due to its sustainable consequences on the lives and civilization of humans. Among all countries, the ones which are placed in draught belt, like our country Iran, have hurt a lot because of low precipitations and also mismanagements in water resources control. Climate change show itself by changes in precipitation patterns, reduction of precipitation and increasing of temperature. According to the present data, Iran's central drainage basin which consists of important geopolitical provinces, has been affected by the above mentioned factors. This descriptive-analytic research is carried out based on the effects of climate change on Iran's central basin which provides approximately 48 percent of Iran’s GDP. Continuity of climate changes in this region can make critical problems in social, environmental, economic and political scales and the lives of the citizens would be affected as well. To conclude, the persistence of the current conditions in climate change in the central drainage basin of Iran, would result in challenges through the national stability and security.
Nader Parvin,
Volume 17, Issue 46 (9-2017)
Abstract
studying and identifying the middle levels change affecting the formation of a circular pattern creation is inevitable. In this study, the annual rainfall data for selected stations Zab River Basin during the period 2015-1986 were the standard time. After indexing and spatial-temporal threshold, 184 days without rainfall were selected in the wet period of three severe drought in the region. Level 500 HP height data located in the range of 0 to 80 degrees northern latitude and eastern longitude on dry days as a matrix S_Mode were used and these data using principal component analysis were processed using modern statistical methods. Based on the correlation matrix, the main focus of the 500 HP topography of the basin dry days were identified and analyzed. The results show that, in the happening time of dry days, twelve atmospheric middle levels of height change focus have been effective. In this regard, the following two centers having the highest anomalies (R≥0.7) are detected according to the high levels of the atmosphere: 1) the center of Eurasia-Africa, 2) the center of West Africa, respectively, 48% and 10% of the total area of the study. Such changes in middle atmospheric levels cause to strengthen and deepen the traffic axis and on the ridges. In the meantime, the change of first center has the highest impact on creation of stability and domination of dryness in days of Zab River Basin.
Mrs Malihe Mohammadnia, Dr Gholamabbas Fallah,
Volume 18, Issue 48 (3-2018)
Abstract
Landslide, due to its dangerous nature in mountainous areas, usually causes morphology to suddenly collapse and causes major damage to residential areas, roads, agricultural lands, and so on. In this study, using the AHP model and fuzzy logic operators, we evaluated and zoned the landslide sensitivity in the Pseudogene basin in Razavi Khorasan province. The eight main criteria of elevation, slope, tilt direction, distance from the waterway, distance from the road, distance from the fault, geology and land use associated with the occurrence of landslide phenomena were examined in total. The sub-criteria were weighted and fuzzy using the Frequency Ratio Model. The weight of the criteria was also determined using the AHP model. Then the landslide susceptibility map was prepared using fuzzy operators 9 / 0.8 / 0 and 0.7 and verified using the ROC curve. The results showed that the gradient factor had the most effect and land use factor had the least effect on the occurrence of slip in the basin. Validation results of the model showed a 90% accuracy of the landslide sensitivity map with a 0.7% operator in the basin. Therefore, the fuzzy gamma model with the 7th operator provides the best form of landslide susceptibility map in the Pseudogene basin.
Shamsollah Asgari, Amir Safari, ,
Volume 18, Issue 50 (3-2018)
Abstract
One of the important and effective factors in the destruction of natural resources is the flood phenomenon, identification of this phenomenon and effective parameters in flood occurrence in natural resources and catchment areas is necessary. The purpose of this study was to determine the flooding of sub-basins in Jafarabad basin in Ilam province. In this research, the Jafarabad basin in Ilam Province is divided in to 12 sub-basins. For each sub-basin, 28 geometric, climatic, permeable and physiographic parameters such as area, environment, length and slope of main stream, length and slope of the basin, time of concentration, The coefficients of shape and variability of precipitation, vegetation cover, CN, discharge and ... have been calculated using GIS software. Factor analysis was used to determine the flood potential of the sub basins. The data of 28 sub-basin variables were analyzed by SPSS software and summarized in 5 main factors (shape, flow, slope, drainage and runoff). The results indicate that the factor of the form with a specific value of 11/30 is the most important factor in the flooding of the studied basin. Channel, slope, drainage and runoff factors with a specific value of 7.21,4.34,3.22 and 3.10 respectively Priority is in the next rank. Then, based on the factor scores of the study area, three large, medium and low flooding categories were mapped and a zoning map of the flood potential of the sub-basins was drawn in the GIS environment. Sub-basins (9,8,5,3) in the shape of the sub-basins (1,6,11) in the gradient factor, sub-basins (2, 7) in the drainage factor and in the runoff factor of the sub-basins (4,10,12 ) Have a lot of flood potential. In sub-basins, the similarity of flooding, erosion, vegetation, and human performance impacts is divided into 3 groups with high, medium and low flood potential. Sub-basins play a major role in the flooding of the basin, which affects the vast agricultural fields of the lower reaches.
Mrs Faranak Bahrami, Mr Abbas Ranjbar.s.a, Mr Ebrahim Fattahi,
Volume 18, Issue 50 (3-2018)
Abstract
Probable maximum precipitation (PMP), is the highest rainfall, which occurs at a given time in a basin. Hydrologist calculates the probable maximum flood for the design of overflow dams, by using the PMP, with two methods: statistical and synoptic. The purpose of this study is calculating PMP in the Ghomrood basin by using the synoptic method. For this purpose rain, meteorological data of the Iran’s Meteorological Organization were used. Also, the data on the 850 and 500 hPa levels were analyzed by the National Center for Environmental Prediction and the National Center for Atmospheric Research (NCEP-NCAR). In the following, the required synoptic maps produced and were studied. Iso rain maps were drawn, and depth-area-duration curves were determined. Eventually, PMP was estimated at 24, 48 and 72 hours. So that 24 hours PMP, by calculating 50 and 100 years return period of dew point estimated 51/75 and 54 mm respectively. Also for 48 hours PMP 128/25 and 132/05 mm, and for 72 hours PMP 97/9 and 101/75 estimated.
Mr Asdollah Hejazi, Mrs Fatemeh Khodaie Geshlag, Mrs Leila Khodaie Geshlag,
Volume 19, Issue 53 (6-2019)
Abstract
Varkesh
-Chai River with approximately 69 kilometer and north-south trend, in one of the main and permanent rivers of Tabriz city, That 10 villages with worn out texture have established in its main bed. Field studies show that, villages’development has been without knowing the rules governing hydraulic behavior, prediction of river hydrological behavior, and no respecting the main bed of river, it has been conserved to the agricultural land or garden. Lack of knowledge and attention to the above-mentioned cases and river bed manipulation has increased the vulnerability of villages, agricultural land or other human facilities of the flood risk in the catchment area. Therefore, it is necessary to study the areas potential to the flood occurrence and to prepare floodplain maps in district. In present study, flood levels were determined along the main river, during the return periods of 25 and 50 years. For this purpose, geography information systems (GIS) and HEC_RAS model and HEC_GEO_RASextension were usedto simulate earth geometry, river plans, left and right rivers shores, and flow rate obtained then, the villages exposed to flood with these return peaks were identified and then, hydraulic behavior of the river was simulated. Finally, solution to reduce the damages caused by flood along the main river were identified.
Mohammadreza Goodarzi, Atiyeh Fatehifar,
Volume 19, Issue 53 (6-2019)
Abstract
In the present time, with the increase of industrial activities and the neglected environmental issues, the effects of climate change have become more evident and poses this phenomenon as a global difficult. Increasing the probability of occurrence of extreme climatic events such as flood and increasing the frequency and intensity of the effects of climate change. The northwest of the country is one of the most vulnerable areas of the country due to its semi-arid and mountainous climates and high rainfall variability. Therefore, zoning due to climate change is essential. Therefore, in this study, in order to investigate the risk of flood in the Azarshahr basin, due to climate change, using the CanESM2 general circulation model under RCP8.5 scenarios negativity according to the assessment report fifth IPCC, rainfall and temperature variables were down scaling by Statistical down scaling model (SDSM). Then,with hydrological model SWAT the daily runoff, the basin map and the lines of the canals are achieved. The results of the evaluation of the SDSM model with a coefficient of determination and Nash-Sutcliff 0.95 on average represent the good performance of the model in the down scaling of large scale data. The results show an increase of 0.23 ° C and 4.53% rainfall and maximum discharge. The basin is zoned with the combination of the maximum mean discharge map, the coefficient and distance from the river with the AHP approach. Due to the zoning they are 41.55% of the area of the basin, at very low and low risk, 27.23% at average risk and 31.2% at high and very high risk. Also, with the final map, it became clear that the mid-basin had a high risk due to its prerequisite conditions and that it needed to carry out managerial actions.
Mr Asadollah Mollazehi, Dr Mohammadreza Pudineh, Dr Mahmood Khosravi, Dr Mohsen Armesh, Mr Aliasghar Dehvari,
Volume 20, Issue 58 (9-2020)
Abstract
Today, due to climate change, natural hazards and how to deal with them are among the most important concerns of researchers in environmental planning and crisis management. The purpose of this study is the assessment of the potential flood risk in Sarbaz drainage basin. For this purpose, the databases including elevation, slope, geological characteristics, soil characteristics, precipitation, vegetation, land use, and vector layers of the main channel, streams and drainage densities of the basin were used. By using the questionnaire and experts' opinion as well as hierarchical analysis, the weight of influences of each layer was calculated in basin flooding. Each of these layers was classified based on the flood potential from low to high-risk scale and eventually merged with the weighted overlay model in Geographic Information System. The results showed that main streams, land use, and precipitation are the most important components in the flood risk of the Sarbaz river drainage basin. From the total area of the Sarbaz basin, only 0.5% has a high to extremely high flood potential, and the central areas of the basin have the highest potential for flood due to topography and special hydrographic conditions. In addition, the main river basin districts towards the outlet of the basin as well as parts of the margins of important sub-streams have the highest flood potential. Despite the limited area of the high-risk zone, due to population density and agricultural land, the importance of this area is very high in crisis management.
Dr. Sadegh Karami,
Volume 20, Issue 59 (12-2020)
Abstract
Importance of climate change is global. This issue to some extent has been out of human control. Human beings can only provide security and the community with knowledge and management against its negative consequences. On the basis of this research, the present paper analyzes the impact of climate change on Iran, on a small scale and applied to the central catchment area. The findings of the research indicate that climate change has shown the geographic region of Iran in terms of changing the rainfall pattern, decreasing precipitation and increasing its temperature. In the next step, these cases resulted in excessive withdrawal of groundwater aquifers and it has reduced the quality of underground water. This chain has led to the design of inter-basin water transmission projects, which is at least the result of the cycle of social tensions that has occurred in recent years. Considering the geographical extent of the basin and its belonging to one of the most frequent aspects of Iran's civilization, the set of consequences of climate change in the central catchment area, in addition to its impact on various social, political, economic and environmental layers, also has several scale effects. And its destructive effects go beyond national scale and to an extent beyond the scope of Iranian culture. In this regard, the research findings indicate that climate change in the central watershed is influential in many aspects of society and the country, so that if the current process continues, the current Iranian civilization will face a strategic challenge. To this end, at the end of the research, good water governance, as the best way to confront and control the negative consequences of climate change on the central catchment area, and Iran in general, has been argued.
Shila Hajehforosh, Amir Karam,
Volume 21, Issue 60 (3-2021)
Abstract
River management, including strategies that effectively have an effect on the behavior. Geomorphological management, is the study of shapes, nature, and origin, processes of emergence, development and use of human and material composition of the Earth. The assessment of river character and behavior in Stage 1 is based on analysis of the assemblage of geomorphic units (channel and floodplain landforms) along any reach. Arangeh River basin were identified in 1and 3 styles, including: Headwater, Gorge style in confined valley setting, planform controlled, floodplain bed, low sinuosity cobble, low sinuosity gravel, bedrock controlled sand, meandering gravel, unconfined low sinuosity cobble with Side stabilized, partly-confined low sinuosity cobble with Side stabilized, partly confined Asymmetric valley with cobble, , partly confined symmetric valley with cobble ,Artificial bed.Geomorphic conditions of each of the styles were evaluated in the two stage of river style framework. at this stage of adjustment of Each style is determined to the confusion of peak flow by using criteria such as channel characteristics (size, shape, morphology Bank and plants channels), channel plan form (sinuosity, lateral stability, geomorphic units into the channel and River flood plain and plants) and features bed . Two Style had good geomorphic conditions (floodplain bed bedrock controlled sand, unconfined low sinuosity cobble with Side stabilized) show the potential of a good adjustment, and the reach has a good of potential adjustments are more sensitive to changes . In the fourth stage of rehabilitation is carried out in reach scales, basins and river basin based on forecasts of possible changes in the future and potential of Geomorphic River Recovery. Each style is proposed management priorities in accordance with the geomorphic and recycling potential.
Aghail Madadi, Ebrahim Beheshti Javid, Nazfar Aghazadeh,
Volume 21, Issue 62 (9-2021)
Abstract
During the last years, following an increase in damages due to occurrence of landslides, human has decided to reduce such losses. Therefore, identifying regions susceptible to landslide and classifying them can partly help man to prevent from happening above phenomena. The current study aims to demonstrate factors contributing to occurrence of landslide in Candrigh Chay basin and then, flattening the basin regarding risks related to landslide event using one methods, Network Analysis Process. In this direction, as respects to basin morphology and also, findings of past researches , ten factors involved in occurring landslides in Candrigh Chay Basin were recognized and used : lithology , land use , rainfall , slope , slope aspect , road slide , sluice power index (SPI), sediment transfer index (STI).Network Analysis Process(ANP) Method was implemented to score and classify factors and scales. Was carried out in order to measure classes of each parameter. The final map showed that the basin has 4 classes considering landslide. Findings reveal flats with low risk and flats with high risk have the least area in Candrigh Chay basin. On the other hand, flats with medium risk and high risk allocate the most area of basin for themself. Comparing slid surfaces with flats facing risks indicates regions located at high and average risk class possess most areas of slide surfaces so that a flat involving very high risk and a flat with high risk devote 35 percent (79km²) and 32/6 (72km²) of landslides for themselves, respectively. In other words, more than 77 percent of landslides conform to flats covering very high and average risk. Moreover, petrology, slope, and, sluice slide were identified as the most effective agents in occurring land_slides. One models, Network Analysis Process (ANP) were utilized through this project
Mrs Elaheh Asgari, Dr Mohammad Baaghideh, Dr Majid Hosseini, Dr Alireza Entezari, Dr Asghar Kamyar,
Volume 21, Issue 63 (12-2021)
Abstract
Understanding the main components of the watershed water basin and analyzing their hydrologic behavior are among the key components of any planning and management procedures in the field of water resources engineering. Today, the need to use modern technologies in hydrological modeling of watersheds has been discussed more than before. The purpose of this study is the simulation of hydrological components in various land use categories in the catchment area of the Dez river basin. Since the tool used in the research is the SWAT model and the SUFI-2 algorithm, the database used include a range of input data. In order to determine the level of sensitivity of the model to the input parameters, global sensitivity analysis was performed. Then, by adjusting the selected parameters and using the observation current, the model was calibrated and validated for the periods 2007 - 1994 and 2013 - 2008, respectively. The coefficients of NS, R2, P-factor and R-factor confirmed the model's ability to simulate river flow in the studied basin. The results of the model showed that the areas with forest use share the highest contribution to aquifer nutrition, and the barren lands have the highest surface runoff. Surface runoff has the leading role in creating the main stream of the river and after that the main flow has been effective in this area. The forest use change to Agricultural lands and pasture will change the hydrological parameters of the basin, and the result of these changes will lead to the increase in the surface runoff, the reduction of nutrition of groundwater resources and the reduction of river basin water. The SWAT model can be used as a precursor model in watershed management studies.
Mansor Parvin,
Volume 22, Issue 64 (3-2022)
Abstract
Semi-arid watersheds are sensitive to soil erosion process and suffer considerable losses each year. Morphometric studies are an important method for identifying susceptible erosion zones and are a prerequisite for assessing erosion patterns in watersheds.The semi-arid Kamyaran basin is at risk of soil erosion due to lithological diversity, varied geomorphology, rugged topography and the nature-based livelihoods of its inhabitants and determination of soil erosion potential of this basin is essential for scientific management and sustainable development. The purpose of this study is to prioritize soil erosion potential in the Kamyaran basin. Methodologically, this research is based on WSA and averaging methods based on the calculation and ranking of morphometric parameters. The results showed that according to WSA methods and averaging 53.63% and 75.91% of Kamyaran catchment area, respectively, are located in areas with high soil erosion potential and require protection plans. The WSA method has better performance for prioritizing soil erosion studies due to different morphometric parameters and how to calculate it accurately. Sub-basins located in the northern areas of the Kamyaran Basin have high potential for soil erosion and sub-basins in the southern areas have low soil erosion potential. In general, the amount of soil erosion potential in Kamyaran basins is affected by the lithological and geomorphological conditions of the basins and the parameters related to infiltration have the most influence on the extent of soil erosion potential in the basins.
Fariba Sfandyary Darabad, Mansour Kheirizade, Masoud Rahimi,
Volume 22, Issue 66 (9-2022)
Abstract
Floods are one of the most abundant and destructive natural disasters that every year are caused heavy losses of life and property. Due to human activity in river systems and construction in rivers, flood damage has an upward trend. One of the most important actions to reduce flood damage is the provision of flood hazard zoning maps and their use in spatial planning. In this study, the risk of flood in the Nirchay River Basin that located Ardebil province was investigated. For this purpose, the HEC-HMS model was used to simulate rainfall-runoff and to identify flood zones and fuzzy logic in order to overlay the layers and prepare a flood hazard zoning map.The simulation results show the high performance of the HEC-HMS model in simulating rainfall-runoff of the Nirchay River Basin and estimating peak flood discharges. Rainfall conversion to runoff at the Nirchay River Basin controlled by slope and land-use.The most runoff height and peak flow in Nirchay River Basin are located in the upstream sub-basins. This is due to the steep, low permeability soil, frequency impervious surfaces and high CN. The combination of layers using fuzzy logic has shown that about 8.6% of the surface of the basin are located with a high risk of flooding. These zones are located mainly on the floodplain of the Nirchay Basin. Due to the Low valley width and low slope, these lands are always at flood risk. Most settlements in the study area are located at downstream of the basin. This has increased the risk of flooding.
Ms Elaheh Ghasemi Karakani, Mr Ebrahim Fattahi, Mrs Loabat Salehi Pak, Mr Hooshang Ghaemi,
Volume 23, Issue 69 (6-2023)
Abstract
During the rainfall, the intensity of precipitation varies. Changes in the amount of precipitation during an event of rainfall are effective in the resulting of flood and its intensity. Knowledge of how rainfall changes over time during rainfall is determined by temporal distribution pattern of rainfall. For this purpose, availability of short-term time scales rainfalls data are important that obtained by rain gauge stations. However, the low density of the rain gauge network and the lack of sufficient data from the time pattern of rainfall have always been a problem in determining storm patterns for executive plans. Therefore, the simulation of WRF numerical weather models can be used. The WRF model is one of the most responsive models for predicting precipitation, temperature and atmospheric elements that used in this study. In this paper, three great storm events on 15 December 2003, 24 - 26 December 2006 and 6-7 March 2007 have been selected in the Parsian dam basin and surrounding areas in south west of Iran. The result of WRF numerical weather prediction model for these great storms compared with data loggers. It showed that the WRF model was able to performance the heavy rainfall and simulates the rainfall pattern in these dates.
Sara Kiani, Dr. Amir Karam, Ms Nasrin Hoseinaei,
Volume 23, Issue 70 (9-2023)
Abstract
The Kan-Soleghan basin is located on the southern Hillside of the Alborz, which has affected the Alp-Himalayan active zone over time. In this respect, the evaluation of active tectonic processes and their effects on many human activities, such as the design and construction of cities, powerhouse, dams, and industrial facilities are of great importance. The passage of the Tehran-North Freeway Tunnel from the area increases the activity of the faults that contributed to the formation of the current morphology of the basin. In this research, morphotectonic indices including river asymmetry index (Af), basin shape (Bs), hypsometric integral (Hi), Stream length index (Sl), mountain front sinusity (Smf), valley width to valley height (Vf), topographic symmetry (Tp) was calculated. Finally, the mean of the results of the indices was calculated as the LAT index. In the present study, topographic Map 1:50000 and digital elevation (DEM) maps with 30 m spatial resolution (ASTER sensors), the boundary layer of the basin, were used to calculate morphometric indices. The Kan-Soleghan basin area is divided into three tectonic regions with slow, semi-active, active Tectonic, and the calculation of the relative active tectonic (LAT) index indicates that the studied area is in tectonic terms in active state. The tectonic structures, especially the faults of the region, have affected the asymmetry and shape of the basin. The main river Kan-Soleghan also shows asymmetry, which can be said due to the structural factors, especially the faults of the region, the basin has asymmetry and deviation to the left of the basin. Also, the construction of the Tehran-north freeway and the location of the Tunnel openings in the vicinity of the northern fault of Tehran, is one of the human factors influenced by the tectonic activity of the area, which requires tectonic activity.
Mrs Somayeh Naderi, Prof. Bohloul Alijani, Prof. Zahra Hedjazizadeh, Dr. Hasan Heidari, Dr. Karim Abbaspour,
Volume 24, Issue 73 (6-2024)
Abstract
Evidence suggests that climate change will create uncertain regional agricultural production stability in the coming decades. This research investigated the impact of climate change on hydrology and sugar beet yield as one of the main crops in the Urmia lake basin using the Soil and Water Assessment Tool (SWAT). To address this, a baseline SWAT model was setup for 1986-2014. Afterward, the output was calibrated (1989-2004) and validated (2005-2014) in the SWAT-CUP software using the SUFI2 algorithm to simulate streamflow of 23 gauging stations and crop yield. The Nash-Sutcliffe efficiency was 0.43 and 0.53 for calibration and validation periods, sequentially. The Percent Bias was 45% and 16% for calibration and validation periods, respectively. As well as the agreement indices of 0.71 and the little Percent Bias (-6% to 10%) for crop production, verified the model's efficiency. The next step was downscaling and bias-correction of the precipitation and temperature data received from 3 climate models, namely GFDL, HadGEM2, and IPSL under RCP4.5 and RCP8.5 using CCT program. Then, the downscaled data were fed to SWAT, and Finally, hydrological fluxes and sugar beet yield were estimated for 2021-2050. Despite a dispersion of precipitation changes ranging from -12% to +35% in most scenarios, results highlight the pivotal role that the warmer temperature (+2.7°C) increases evaporation, resulting in sharpened pressure on water resources and runoff, especially, at the beginning of crop growth season. Finally, the negative impacts on crop productivity (-45%) is not unexpected. This means that sugar beet may suffer from climate change impacts, and the production of this plant will change over the next period in this region.
Keywords: Climate Change, Sugar Beet, Urmia Lake Basin, Sensitivity Analysis, SWAT.
Dana Rahimi, Javad Khoshhal Dastjerdi, Dariush Rahimi,
Volume 24, Issue 74 (9-2024)
Abstract
Among natural disasters, floods have the highest human toll. The economic impacts of floods are greater in developing countries, including Iran, and are particularly severe in the colder months of the year in the west of the country. The purpose of the present study is to analyze the most severe historical synoptic floods that occurred in Karkheh Basin (1 April, 2019). Descriptive - analytical research method and its environmental approach into circulation. Analysis of synoptic systems of large floods such as the April 12, 2019 floods show that Western Europe's high-pressure systems, Black sea, East of the Caspian and low pressure north of the Red Sea, Eastern Mediterranean in harmony with the high-rise systems of Western Europe, Low Mediterranean East with a temperature drop of about 50 degrees Celsius(The temperature at sea level In the eastern Mediterranean and Red Sea about 25 degrees Celsius and in the middle of the atmosphere -25 degrees Celsius) also the climb Humidity from the Arabian Sea, North Indian Ocean, Red Sea, Oman Sea and Persian Gulf and Along with Mid-width cold air loss On the area and the establishment of the Polar jet stream) Core up to 70 m(And the establishment of the front jet stream And positive rotation area On the area shows the structure of the synoptic systems causing the flood in the area.
Mrs Mahnaz Saber, Dr Bromand Salahi, Dr Abbas Mofidi,
Volume 24, Issue 74 (9-2024)
Abstract
In this study, the spatiotemporal variations of evapotranspiration (ET) were investigated in the southern part of the Aras River catchment. For this purpose, the ET networked data of FLDAS Noah model with horizontal resolution of 0.1 * 0.1 degree were used for a period of 38 years (2019-1982). After validating the data, the average annual ET values for the region were determined first. Then the monthly and seasonal distribution of the parameter were analyzed spatially. Subsequently, ET variations and anomalies were evaluated year to year. Also, the spatial distribution of the occurrence frequency of ET was investigated by considering the absolute thresholds of 50, 80, 100 and 120 mm for the Aras basin. The results show that the annual ET in the east of the basin is higher than the west of the basin. In the seasonal scale, spring and summer have the highest ET values, respectively. In the monthly scale, Mayو June, April and March had the highest ET values, respectively. In contrast, the autumn and winter months have the lowest average ET values. Also, the whole basin during the study period has experienced three distinct periods of ET changes that in the eastern and western parts of the basin, despite the same behavior in the second and third periods, a significant difference was observed in the first period. The results also indicate the existence of positive anomalies after 2002 in the whole basin, the highest values occurred in 2018 in the west of the basin. The study of the frequency of occurrence of absolute ET thresholds on the basin shows the high frequency of ET occurrence at all thresholds in the east of the basin. A study of nearly 4 decades of ET values in the Aras River Basin shows an increase in ET values over the last two decades over the entire basin, which can be attributed to the occurrence of global warming.
Zeinab Mokhayeri, Ebrahim Fatahi, Reza Borna,
Volume 25, Issue 76 (3-2025)
Abstract
To conduct this research, first, the data of monthly observations of synoptic and hydrometric precipitation from the National Meteorological Organization and the Ministry of Energy during the 30-year period (2006-2005) were obtained. To examine the prospect of future rainfall changes, the historical data of the period (1976-2005) and the simulated climate data of the period (2050-2021) using two models of CM3), (CSIRO-Mk3.6 from the series) Models (CMIP5) and according to 4 scenarios RCP2.6, RCP4.5, RCP6 and RCP8.5) that are available with a spatial resolution of 0.5 x 0.5 with the BCSD method have been used.Mean-based (MB) strategy has been used to correct the bias in the output of these models. The results of the AOGCM models showed that the CSIRO-Mk3.6 error coefficient was less than the GFDL-CM3 model for simulating precipitation in the case of Large Karun.The average future rainfall (2021-2050) in the whole basin compared to the average observed rainfall during the statistical period of 1976-2005 shows, in both models and scenarios in both basins in terms of amount and area of precipitation is decreasing significantly.Heavy rains in the Greater Karun Basin have been concentrated in all scenarios and models east of the basin. The highest rainfall was in the central foothills. The lowest rainfall is in the southwest and southeast. The final results of the present study are expected to be 83-116 mm. Both models are expected to have the highest rainfall in the Greater Karun Basin, with two scenarios: rcp4.5 and rcp2.6.
