Mehdi Vafakhah; Mostafa Zabihi Silabi; Sedigheh Modarresi Tabatabaei; Hossein Sarvi Sadrabad; Arezoo Shafiei Bafti; Negin Ghaderi Dehkordi; Mohammadreza Riahi; Seid Saeid Ghiasi
Abstract
Extended abstractIntroductionInvestigating the climatic condition over watersheds has a decisive role in water resource management planning. Meanwhile, changes in temperature and precipitation have a great effect on the discharge of rivers, soil erosion, and fluctuations in the level of ground water, ...
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Extended abstractIntroductionInvestigating the climatic condition over watersheds has a decisive role in water resource management planning. Meanwhile, changes in temperature and precipitation have a great effect on the discharge of rivers, soil erosion, and fluctuations in the level of ground water, and the occurrence of floods. It is very necessary to carry out research related to climate change in order to prepare as much as possible to deal with the harmful costs caused by this change. The review of the studies conducted in Iran also shows that the scale of the study is in most cases at the local level and the study of the mean annual discharge trend and its magnitude has not been studied especially over Iran country. Therefore, the current research was planned with the aim of determining the mean annual discharge trend and magnitude over Iran. Materials and methodsIn the present study, the trend of mean annual discharge in Iran was determined by considering the effect of dams using Mann-Kendall and Sen’s slope methods. First, the statistics of all the hydrometric stations located in the Iran six major drainage watersheds were obtained from Iran Water Resources Management Company. Finally, 139 hydrometric stations with a statistical period of 17 to 65 years were selected in this study. The statistics of these stations were compared with the data available in nearby stations and suspicious values were also controlled. The homogeneity of the data and reconstructing the missing data was carried out using the run test and linear regression through the station with the highest correlation coefficient for each station with incomplete station, respectively. In the next step, non-parametric Mann-Kendall and Sen’s slope estimator tests were carried out within XLSTAT software in order to evaluate the trend and its magnitude analyses. After determining the trend of the study hydrometric stations, the spatial distribution map of the mean annual discharge trend in Iran six major drainage watersheds were prepared within Arc/GIS 10.2 software. Results and discussionThe results showed that 14 hydrometric stations were affected by the dam. However, in the hydrometric stations without dam, 84, six and 35 hydrometric stations have a decreasing trend (60%), an increasing trend (5%), and no trend at the 95% confidence level, respectively. Examining the trend of the time series of mean annual discharge in each of Iran six major drainage watersheds also showed that 80% of the study stations in the Persian Gulf and Oman Sea watershed have a decreasing trend, while no trend were detected in 20%, 10% and 9% of the total study stations in the Caspian Sea, the Central Plateau, and the Persian Gulf and Oman Sea watersheds, respectively as well as all the stations of the eastern watershed (Hammon). In the meantime, all study hydrometric stations in Urmia Lake and Sarakhs watersheds and 68% of the study hydrometric stations in the Caspian Sea watershed have a decreasing trend. ConclusionThe results obtained from this research showed that the decreasing trend was detected in most of the hydrometric stations (84 hydrometric stations). Therefore, the decreasing trend of hydrometric stations in Iran can be related to the decrease in rainfall, increase in temperature and the emergence of excruciating droughts caused by climate changes and also human interference, including the excessive increase in the construction of dams and the change of unprincipled land use. However, one of the limitations of the current research is not taking into account climate changes and land use changes and determining the contribution of each of the mentioned factors in the decreasing and increasing trend of the mentioned stations. The results of the present research can be very useful and important for water planners and politicians in order to manage water resources.
Reza Chamani; Mehdi Vafakhah; Seyyed hamid reza Sadeghi
Abstract
Today, drought has become one of the hot topics of global concern, but its impact on the provision of services and functional health of watersheds in the face of this natural disaster has been less evaluated. Accordingly, in this study, the effect of drought on the Efin Watershed health has been evaluated ...
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Today, drought has become one of the hot topics of global concern, but its impact on the provision of services and functional health of watersheds in the face of this natural disaster has been less evaluated. Accordingly, in this study, the effect of drought on the Efin Watershed health has been evaluated based on changes in Reliability (Rel), Resilience (Res) and Vulnerability (Vul) indicators in the period 2005-2019. Based on this, the rainfall data of three rain gauge stations were interpolated using Inverse Distance Weighting (IDW) for the watershed and sub-watersheds. Standardized Precipitation Index (SPI) was then determined based on the mean and standard deviation of monthly data and was used to calculate the Rel, Res and Vul indicators. Finally, the overall health status of the watershed was determined by calculating the geometric mean of these indicators. The annual results showed that Efin Watershed in terms of Rel, Res and Vul indicators extends between 0.83-0.92, 0.17-0.33 and 0.24-0.54, respectively. The RelResVul index also has values between 0.37-0.53. The average watershed health indicator in this period was also calculated to be 0.42, which indicates mean watershed health condition. Spatial variations of watershed health also showed that Rel, Res and Vul indicators fluctuated between 0.85-0.86, 0.21-0.24 and 0.76-0.78 in different sub-watersheds. The results of rainfall analysis of the region, indicate that due to the relative stability of rainfall, the impact of human intervention and intensification of watershed health threatening factors, more than ever effect on the current situation and if not addressed will have harmful effects.
Reza Chamani; Seyed Hamidreza Sadeghi; Mehdi Vafakhah; Maryam Naghdi
Abstract
Drought is one of the natural disasters related to climate and one of the most important threats to human survival leading to adverse effects on social, economic, and environmental sustainability. In this study, it has been tried to evaluate the changes in reliability, resilience, and vulnerability of ...
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Drought is one of the natural disasters related to climate and one of the most important threats to human survival leading to adverse effects on social, economic, and environmental sustainability. In this study, it has been tried to evaluate the changes in reliability, resilience, and vulnerability of the Chalous Watershed under the influence of drought in the period of 1982-2017. In this vein, rainfall data of nine stations were interpolated using invers distance squared method to the whole watershed. The SPI drought index was then determined through determining the mean and standard deviation of the data. To calculate Rel, Res and Vul indices, the mean value of SPI Index was used. By calculating the geometric mean value of these indicators, the general health status of the watershed was determined and quantified. The results showed that the SPI Index in this period varied between -1.43 and 2.25. Drought index had a similar pattern to that of rainfall with an increasing trend at the end of the period. The watershed health assessment also showed that the indicators of reliability, resilience, and vulnerability were found 0.5, from 0.23 to 0.62 and from 0.06 to 1, respectively. The geometric mean of these indices was also ranged between 0.19 and 0.58. The overall health condition of the Chalous Watershed based on the dynamics of drought index with a mean index of 0.45 was classified as “moderate”. The findings of the current research will play an important role in explaining the methods of adaptive management of the watershed.
Mojtaba Rezaei; Mehdi Vafakhah; Bagher Ghermezcheshmeh
Abstract
Flood is a sudden happening and quick and destructive event that causes death and financial sensible and unsensiable damages in different parts on the world and Iran annually. Control or decreasing these destructive impositions needs precise and accurate studies. So, recognition of the places with runoff ...
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Flood is a sudden happening and quick and destructive event that causes death and financial sensible and unsensiable damages in different parts on the world and Iran annually. Control or decreasing these destructive impositions needs precise and accurate studies. So, recognition of the places with runoff generation potential is very important. In current study, two major aims of investigation of the application of distributed ModClark model in flood hydrograph simulation and determination of flood source area in distributed and sub-watershed condition were investigated in the Khanmirza watershed, Chaharmahal-e-Bakhtiari Province. For this reason, at first, inputs of model were extracted by ArcGIS 9.3 and then model was calibrated and validated. In next step, in order to determine flood source area for cell units and sub-watersheds, by applying "Unit Flood Response" method, at first, design rainfall with return periods of 25, 50, and 100 years at the Aloni station were extracted and then influence of each cell and sub-watershed on output hydrograph of the outlet watershed were obtained. The results of model based on comparison between equal-width discharges show that at validation step, the model was simulated the flood hydrograph with high precision with root mean square error, efficiency coefficient, and R2 of 1.53, 0.89, and 0.74, respectively. Also, according to the results of current study, based on the flood volume relative error, peak discharge, base time, and time to peak, ModClark model had lower error in predicting the flood volume and peak discharge. The final results showed that flood source area increases in sub-watersheds from downstream to upstream, while it doesn’t follow any distribution in cell units.
Soheyla Aghabeigi; Abdol Rasoul Telvari; Sayed Khalagh Mirnia; Sadat Feiznia; Mehdi Vafakhah
Abstract
Sediment concentration in rivers, especially in seasonal ones, is affected by flood situation due to changes of rainfall or snowmelt events. Due to the importance of flooding flows in inundation and the useful age of reservoirs built on seasonal rivers, the study and assessment of this issue seems to ...
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Sediment concentration in rivers, especially in seasonal ones, is affected by flood situation due to changes of rainfall or snowmelt events. Due to the importance of flooding flows in inundation and the useful age of reservoirs built on seasonal rivers, the study and assessment of this issue seems to be essential. In the present research, suspended sediment concentration variation in spring and autumn floods and runoff from snowmelt in spring, have been studied for Abshine River in Ekbatan Dam Watershed. Over the forecast period, three storms in autumn, two storms in spring and five snow melt events were selected and compared. Analyzing 226 suspended load samples showed its variability in the area. Sediment rating curves in different base times showed different trends. The correlation coefficient (r) were 0.79 and 0.50 for storms and snowmelts and 0.81 for all data, respectively. Also, coefficient and power value analysis of sediment rating curve, presented the same erodibility for hill slope in both seasons (spring and autumn). Separating falling and rising limbs of flow hydrograph and assessing their effect on discharge explains a better Q-sediment concentration relationship. The hysteretic shape of discharge and sediment concentration had clockwise and anticlockwise form and compound pattern of both forms that reflected the distribution of probable sediment sources throughout the catchment.
Hossein Isanloo; Mehdi Vafakhah
Abstract
Flood estimation with certain frequency is one of the fundamental factors for designing hydraulic structures, floodplain planning, river coastal stabling, and watershed management. The Kushkabad watershed is one of the main sub-basins of Kashafroud basin located in the north-east of Iran, with an area ...
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Flood estimation with certain frequency is one of the fundamental factors for designing hydraulic structures, floodplain planning, river coastal stabling, and watershed management. The Kushkabad watershed is one of the main sub-basins of Kashafroud basin located in the north-east of Iran, with an area of 87.45 km2, and 11 kilometers far from Mashhad, which has always been facing severe damages due to flash floods in special climates and topography. In this research, HEC-HMS, flood frequency analysis, Creager, Dicken and Fanning rainfall-runoff hydrological empirical methods were compared. The statistical index of relative percent error was used for comparison of different methods. The results showed that HEC-HMS model has little difference with observed data, and empirical methods have a reliable approach with HEC-HMS model. On the other hand, regional flood frequency analysis has more significant difference with reality.
