Mohammad Reza Jafari; Iraj Jabbari; Haji Karimi
Abstract
There are several stream channels in Musian Plain which change surface flow regularly as well as cause great damages to the basin’s residents. In order to prevent or reduce the risk of flow regime changes, surface flow dispersion on the permeable alluvial fans is controlled by implementation of ...
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There are several stream channels in Musian Plain which change surface flow regularly as well as cause great damages to the basin’s residents. In order to prevent or reduce the risk of flow regime changes, surface flow dispersion on the permeable alluvial fans is controlled by implementation of the biological and structural practices. Therefore, in this study, two objectives are followed: first, comparison of flow regime changes of Musian Plain on the flood spreading and adjacent areas (control area), where there have been no structural and biological practices; and then, evaluation of these changes impacts in the area’s dynamics and land use. For this purpose, satellite images of Landsat 7 and 8, TM, ETM, and ETM+ sensors in 1998, 2002 and 2014 were used. The relationships between morphological parameters in the control and spreading areas, before and after flood spreading were obtained. Then, the effects of flow regime changes, as well as, land use dynamics were assessed. Results showed that the structural and biological practices are the main factors which change the flow patterns in the study area. The relationships between morphological parameters before and after practices showed the changes of drainage density index from 1.5 to 1.09 (km/km2), as well as the bifurcation ratio from 3.11 to 11.45; respectively. It indicates the stable flow regime in flood spreading practices rather than the control area. Controling and reducing the vlume of flood, means 9.1 MCM annual recharge , decreasing trend of average permeability in spreading areas, compare to basic permeability as much as 13.57 and 17.95 (cm.h-1), respectively,reduction of sand particle and increasing of clay and silt in flood spreading area compared to the control area, development of cultivation area up to 2410 (ha), rising of forage production by 109 (kg/ha-1), the increasing of trees and wells as much as 254181 and 62 respectively. Also, floodwater spreading affects on the pattern of flow dynamic and land use of the Musian area.
Marzieh Hajimohammadi; Abolfazl Azizian; Bagher Ghermezcheshmeh
Abstract
Knowledge of climate variabilities and their behavior in future periods and their effects in various fields has great importance especially in strategic and macro planning in water resources. This study aims to evaluate the effect of climate change on hydrological condition of the Kan Watershed. For ...
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Knowledge of climate variabilities and their behavior in future periods and their effects in various fields has great importance especially in strategic and macro planning in water resources. This study aims to evaluate the effect of climate change on hydrological condition of the Kan Watershed. For this purpose the HadCM3model under the A2 emission scenario and also statistical downscaling model (SDSM) were applied for temperature and rain variables simulation. Then, SWAT model was used for monthly runoff simulation and SUFI-2 algorithm was used in SWAT-CUP software pack for calibrating and uncertainly analyzing. The performance of SDSM model was evaluated base on MBE and NRMSE parameters, the result indicated that temperature variable was simulated more accurate than of precipitation. The result of the predicting temperature in period (2011-2040) compare with the base period (1961-2001) showed the maximum and minimum temperature will increase by 1.3 and 0.8 °C, respectively. Also, the rainfall will decrease by 3-4 percent for all of selected stations. The most rainfall reduction will be for spring. While in some months of winter an increase of precipitation was predicted. The result of calibration and validation of SWAT model agreed well with the observed data, so that Nash-Sutcliff efficiency coefficient, as objective function, was 0.82 and 0.71, in calibration period (1983-1991) and validation period (1992-1996) respectively. Finally, results of runoff prediction showed an increase in winter and a decrease in other seasons based on climate scenarios. Overall, according to obtained results runoff will decrease by seven percent for future period.
Mohsen Tavakoli; Haji Karimi; Hadi Norollahi
Abstract
Climate change and global warming is one of the most important issues in the world that is discussed in public and professional meetings. Long term climate change forecasting has an important role on water resources planning and management, due to fragile climate of our country. The present study aimed ...
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Climate change and global warming is one of the most important issues in the world that is discussed in public and professional meetings. Long term climate change forecasting has an important role on water resources planning and management, due to fragile climate of our country. The present study aimed to investigate the effects of climate change on discharge changes in Golgol Watershed as one of the Ilam dam sub-watersheds. In this research, first, temperature, precipitation and potential evapotranspiration data were downscaled and then, hydrological condition of the watershed is simulated using SWAT hydrological model. Next, the results of downscaled HadCM3 data under two scenarios of A2 and B2 were downscaled using SDSM and in the next step stream flow of three period including 2010-2039 (2020s), 2040-2069 (2050s), 2070-2099 (2080s) and base period of 1990-1961 (Baseline), simulated using SWAT model. Finally, the effects of climate change assessed until the end of the century. The results indicated that annual discharge will decrease for 2020s, 2050s and 2080s under A2 scenario by 6.3, 16.9 and 24.1percent, and will decrease under B2 scenario by 10.9, 8.8 and 13.2 percent, respectively. Resualts demonstrated that climate change as one of the negative phenomena that affects on the amount of water in Ilam Dam should be considered by managers and planners.
Mohammad Rostami; Nima Rohani; Hamdi Reza Sheybani
Abstract
Login driftwoods into the river flow and their accumulation in the upstream of the bridge will decrease the flow carrying capacity of the bridge. Blockage may cause a strong reduction in the flow rate through the bridge and therefore a strong increase in upstream water level which may lead to flooding ...
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Login driftwoods into the river flow and their accumulation in the upstream of the bridge will decrease the flow carrying capacity of the bridge. Blockage may cause a strong reduction in the flow rate through the bridge and therefore a strong increase in upstream water level which may lead to flooding or nearby urbanized areas. Drift woods either accumulates at a single pier, or it spans between two or more piers or it gets blocked at the bridge deck. Since the evaluation of such a mechanism in nature and in flood time is very difficult and limited knowledge is currently available on the likelihood of bridge blocking by the driftwoods, therefore, it is necessary to evaluate experimentally the movement of the driftwoods through the river flow and the effect of bridge characteristics on driftwood accumulation and blockage. The main purpose of this experimental study is to analyze the driftwood blocking probability at bridge depending on drift dimensions, driftwood shape (single log and log with branches), flow characteristics, method of driftwood entry into the flow and bridge characteristics. Tests were carried out in an inclinable rectangular flume and a bridge with guard rails was installed into the flume. The tests were performed by different length of driftwood, smooth and with branches, the number of entering driftwood to the channel flow (individual or aggregate), in the presence and absence of bridge pier and with three levels of water flow in the upstream face of the bridge. Entering each case of driftwoods has been repeated 10 times and then bridge clogging probability has been determined. The results showed that in case of water level come to low cord of the bride's deck , the clogging probability a bridge with and without pier changed from 13% to 93% and 33% to 100 respectively. The results showed that lengthening and increasing the number of driftwood and trunk with branches, the presence of the pier, and finally the rising water flow will increases the clogging possibility.
Touraj Sabzevari; Mehdi Mokhberi; Sadegh Hosseini khotbehsara
Abstract
Catchments consist of a series of sloping pervious overland whose surface and subsurface runoffs are transmitted to their outlet through stream networks. In the catchments with high perviousness and good vegetation cover, the amount of subsurface gains more significance and it might have a considerable ...
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Catchments consist of a series of sloping pervious overland whose surface and subsurface runoffs are transmitted to their outlet through stream networks. In the catchments with high perviousness and good vegetation cover, the amount of subsurface gains more significance and it might have a considerable share in the direct runoff. In this study, a hydrologic rainfall simulator model with the length of 1.92 meter and width of one meter and depth of 0.35 meter has been used which its surface and subsurface amount of flow have been measured by means of two different weirs. The texture of soil in Estahban Watershed was loamy sand. The experiments were conducted under three slope angles of 0.1, 3, 6 and 9 degrees and under rainfall intensity of 31.73, 47.6 and 63.46 millimeter per hours. Based on the results, the slope changes from 0.1 to 3 degrees resulted in 50 percent decrease in the subsurface flow and 10 to 15 percent increase in the surface flow in different rainfalls, but, from the slope of 3 to 9 degrees, no significant change was observed in the two flows and in the slope change from 6 to 9 percent of subsurface flow and 2 percent of surface flow, there was surface flow observed. The increase in rainfall intensity causes rise in hydrograph amount of surface and subsurface flow. The proportion of surface to subsurface flow changed on average between 7.5 and 14.5 times the subsurface flow under three rainfalls for the loamy sand. With the increase in slope, the surface flow amount increases and infiltration decreases. In this study, two non-linear regression equations were presented for measuring surface and subsurface peaks which is a function of length, slope and rainfall intensity of the slope.
Saeed Najafi; Seyed Hamidreza Sadeghi; Tobias Heckmann
Abstract
Comprehensive watershed management programs need to take into account the sediment and related process in sediment management paradigm. Whilst, the dominant processes on sediment yield has not been considered in watershed scale yet. Accordingly, sediment connectivity is an emerging concept in sediment ...
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Comprehensive watershed management programs need to take into account the sediment and related process in sediment management paradigm. Whilst, the dominant processes on sediment yield has not been considered in watershed scale yet. Accordingly, sediment connectivity is an emerging concept in sediment management that has been accounted in recent years to investigate the sediment transfer from different sections of watersheds. Sediment connectivity is defined as the integrated transfer of sediment across all possible sources to all potential sinks in a system over the continuum of detachment, transport and deposition processes. The structural connectivity is therefore a concept derived from sediment connectivity which investigates potential of sediment particles displacement across a watershed on the base of anatomy of watershed's system. Naturally, identifying sectors with similar sediment connectivity patterns support applying similar and integrated sediment control mitigation strategies. The present research was planned to investigate the structural sediment connectivity in Taham Watershed in Zanjan Province for year 2014. To calculate the structural sediment connectivity, the Digital Elevation Model (DEM) and C Factor layers were used and the results were assessed according to field observations and surveying in several times. The results of the validity of the structural sediment connectivity map showed there were acceptable agreement between Field Index of Connectivity (FIC) and Index of Connectivity (IC). In addition, IC map with respective max, min and mean values of 1.02, -8.24 and -5.95, showed 32 percent of the study area had a high structural sediment connectivity that generally have been dispersed in western parts of the study area. Regarding to rapid appraisal and being low cost of IC calculation as well as identification of primary sediment sources, the structural sediment connectivity is a very useful concept for sediment management of watersheds of Iran.
Mohammadreza Khazaei; Ahmad Sharafati; Hadis Khazaei
Abstract
One of the most important impacts of climate change is the change of snowfall regime, especially extreme snowfalls in the future. Extreme snowfalls will be affected by increasing in extreme rainfalls and temperature oppositely in the future climate while the trend of changes is not clear. In this paper, ...
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One of the most important impacts of climate change is the change of snowfall regime, especially extreme snowfalls in the future. Extreme snowfalls will be affected by increasing in extreme rainfalls and temperature oppositely in the future climate while the trend of changes is not clear. In this paper, climate change impact on extreme daily rainfalls in the Mehrabad station of Tehran is assessed. Future daily precipitation and temperature projections of the CGCM3 model under B1, A2, and A1B emission scenarios are downscaled using IWG stochastic model. Snowfall is simulated using temperature threshold criteria, and climate change impact is assessed on snowfall in 2036-65 period. Results of the validation tests showed that the IWG model have reproduced a broad range of the temperature and precipitation statistics. Also, snowfall statistics specially the annual maximum daily snowfall distribution are well reproduced. The climate change impact assessment results showed that under various emission scenarios, despite increasing in extreme precipitation in the future in the Tehran Mehrabad station, annual maxima daily snowfalls would greatly decrease. So that, maximum daily snowfall with return period of two years would decrease more than 50% under all considered scenarios.
Freidoon Soleimani; Aaollah Kavian; Karim Solaimani; Forod Sharifi; Kaka Shahedi
Abstract
The major issues that must be addressed in watersheds is correct estimating threshold from the rainfall events. According to the agricultural leveling land and irrigation and drainage network of study area is exposed to sourounding runoff destruction, so watershed management activities such as design ...
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The major issues that must be addressed in watersheds is correct estimating threshold from the rainfall events. According to the agricultural leveling land and irrigation and drainage network of study area is exposed to sourounding runoff destruction, so watershed management activities such as design of small-scale water structures, sediment control structures, implementing the management actions in vegetation, soil and land utilization is required to understand and estimate surface runoff threshold. The aim of this study was to determine the effect of soil conservation practices on runoff initiation time and runoff coefficient using rainfall simulator in the Arayez plain. For this purpose, a rain simulator with a metal plot that has a square meter area was used. The treatments consisted of natural soil (observed), polyacrylamide at two levels 3 and 6 grams per square meter (P3 and P6, respectively) and Parsian mulch (Pc) that were conducted in sandy clay loam and sandy loam soil with three replications. The rainfall intensities set up to be of 32 and 50 mm per hour in slopes 7.5 and 12.5 percent. For statistical comparison split split plot design was used. Least Significant Difference (LSD) method was used for comparison of means. Results indicated that the mean of runoff initiation time in observed treatment is higher than mulch treatments, it means which runoff begins later in observed treatment. Mulches of P6 and Pc have not significantly differences in runoff initiation time. Runoff initiation time in P3 mulch much earlier began than the other treatments. Also, results revealed that the mean of runoff coefficient in different treatments (observed, P3, P6 and Pc) have a significant differences, and belonged to separate group.
Maryam Hafezparast; Zohreh Pourkheirollah
Abstract
The effect of RCP scenarios that have recently been analyzed in Iran is the results of (AR5) Intergovernmental Committee climate change (IPCC) that indicated the amount of rainfall, temperature in the upcoming period compared to the base period. In this study, changes in precipitation and temperature ...
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The effect of RCP scenarios that have recently been analyzed in Iran is the results of (AR5) Intergovernmental Committee climate change (IPCC) that indicated the amount of rainfall, temperature in the upcoming period compared to the base period. In this study, changes in precipitation and temperature and the effect of these parameters on the amount of runoff in the period 2016-2044 Doiraj Dam is considered. The amount of monthly temperature and precipitation models ACCESS1-0, BCC-CSM1.1, CANESM2, BNU-ESM, and CSIROK3-5-0 under the scenario RCP8.5 was prepared for the region. Then, Change Factor method of spatial and temporal downscaling is used for the study area. The temperature, precipitation and discharge values were intered to IHACRES model and after calibration and validation, the future runoff was simulated in this period. For hydrological drought analysis, frequency analysis, SWSI, SDI, SRI and threshold indices were calculated. The results showed an increase of 1.29 degrees Celsius of temperature and 1.28 percent in precipitation in 2016-2044 compared to 1987-2015. River flow has also increased by 4.9 percent compared to the baseline. The frequency analysis of annual runoff is obtained in futhure with return periods of 50 and 100 years 13.90 and 15.06 m3s-1 , respectively. Quantitative analysis of drought indices showed that in years 1996, 1998 and 2004 there was no drought and in 2008, 2009, 2011 and 2012 there was drought occurance. Also, in future periods of 2024, 2025, 2033 and 2035 drought conditions are very poor and in years 2020, 2029, 2037 and 2041 drought is evident. Also, checking the volume threshold method with the Q70 threshold showed that in the years 2037-2038 and 2040-2041 significant hydrological drought will happen with the lack of 64.2 million m3.
Mitra Tanhapour; Mohammad Ebrahim Banihabib
Abstract
Prediction of the sediment load in water resources engineering projects such as flow diversion projects and dam construction is important factor for determining their service life. In this study, a model for estimation of daily sediment discharge was proposed using multilayer perceptron Artificial Neural ...
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Prediction of the sediment load in water resources engineering projects such as flow diversion projects and dam construction is important factor for determining their service life. In this study, a model for estimation of daily sediment discharge was proposed using multilayer perceptron Artificial Neural Network (ANN) model with back-propagation learning algorithm. For this purpose, current day’s discharge (Qt), precipitation, number of day in the year (DOY) and previous day’s discharge (Qt-1) data of Zoghal Bridge station (located on Chalus River) from 1990 to 2009 were used for training, verification and test. Results of testing different combinations of input data sets showed that effective parameters of the model performance are current discharge parameter, antecedent discharge, precipitation and DOY, respectively. This results has a relatively good agreement with standardized coefficients of regression model. Coefficient of determination (R2) and Root Mean Square Error (RMSE) were used to compare the different structures of ANN. Therefore, best network with 3-5-1 architecture and the amounts of R2=0.89 and RMSE=0.02 was obtained by elimination of DOY variable. The performance of ANN model in the prediction of sediment discharge was compared with Sediment Rating Curve (SRC) and Multiple Non-Linear Regression (MNLR) model. The results showed, in the training and test steps, SRC method and ANN model have the best performance, respectively. Furthermore, in the test step, the ANN model performed better results compared to two other methods by increasing R2 about 16%. Generally, the proposed ANN model can be estimated sediment discharge by less calculation time and cost and also with more accuracy.
