Hydrology
zohreh khorsandi Kouhanestani; Fatemeh Taatpour
Abstract
Rainfall-runoff processes are among the most complex and nonlinear phenomena in hydrology. In water resources management, runoff forecasting faces challenges in ungauged watersheds.In this study, the efficiency of lumped models and machine learning methods was investigated in the Kabkian watershed, that ...
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Rainfall-runoff processes are among the most complex and nonlinear phenomena in hydrology. In water resources management, runoff forecasting faces challenges in ungauged watersheds.In this study, the efficiency of lumped models and machine learning methods was investigated in the Kabkian watershed, that is one of the principal branches of the Karun River. AWBM, Sacramento, SIMHYD, TANK, and SMAR Also, some algorithms in decision trees, artificial neural networks, and support vector regression were applied to simulate daily and monthly runoff in the Kabkian watershed. Monthly and daily discharge, precipitation, and potential evapotranspiration for the period between 1972 and 2022 were used,. The accuracy and efficiency of the methods were examined using R², the Nash-Sutcliffe coefficient, and RMSE. Results showed that SMAR and AWBM, in comparison to other lumped models, have the best efficiency in the simulation of daily discharge in the Kabkian watershed. The Nash-Sutcliffe coefficients for them in the test stage are 0.79 and 0.78, respectively, showing that these models have good efficiency in daily discharge simulation. Also, the SMAR and AWBM models' Nash-Sutcliffe coefficients are 0.71 and 0.72, respectively, and the R2 for the two models is 0.79 in the monthly time series. These values show that these models have good efficiency. In machine learning methods, in the daily series, the random forest algorithm's R2 is 0.61 and has the best efficiency in comparison to other methods. Also, in the monthly series, the random forest's R2 is 0.93, which illustrates good discharge simulation efficiency.
Hydrology
Leyla Babaie; Hirad Abghari; Raoof Mostafazadeh
Abstract
The occurrence of low flow and high flow periods in watersheds is a part of a river's regime. In recent years, changes in river flow and its intensification have impacted the production and utilization of river flows as well as water management, making it an important area of study. Evaluating various ...
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The occurrence of low flow and high flow periods in watersheds is a part of a river's regime. In recent years, changes in river flow and its intensification have impacted the production and utilization of river flows as well as water management, making it an important area of study. Evaluating various characteristics of the flow regime of natural rivers can help understand how river discharge changes due to climatic. In this study, changes in high flow and low flow indices at the Bitas watershed, Mahabad-chai, which monitors a naturally flowing river upstream of Mahabad Dam, were assessed for the period from 1963 to 2020. The results indicated that the Number Spell index was 144 during high flow periods and 253 during low flow periods. The Single Longest index was 1,635 for low flow periods and 163 for high flow periods. The average peak flow and average duration of peak flow indices for high flow periods were 22.6, and for low flow periods, they were 0.33. Additionally, the mean duration was 29.6 for high flow and 54.82 for low flow. According to the results, the total duration index for high flow periods fluctuated between 3 and 163, while the total duration index for low flow was 241. The findings of this study can be used to better understand changes in the natural flow regime, variations in the timing and frequency of low and high flow events, and ultimately to optimize the management of inflow to Mahabad Dam.
Hydrology
Raoof Mostafazadeh; Javanshir Azizi Mobaser; Shahnaz Mirzaei
Abstract
The river flow regime can be influenced by various climatic and anthropogenic factors, including land use changes, dam construction, flow diversion, and water abstraction, leading to changes in available water and environmental flow allocation patterns. This study compares the changes in flow regime ...
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The river flow regime can be influenced by various climatic and anthropogenic factors, including land use changes, dam construction, flow diversion, and water abstraction, leading to changes in available water and environmental flow allocation patterns. This study compares the changes in flow regime components between two rivers, one natural and one regulated by a dam, in Ardabil Province. Using R programming, various charts, change point analysis, and significant temporal trends were derived for flow statistics, including high flow, low flow, and baseflow. The results indicate change points in all three flow components (annual maximum, Q10, Q25, low flow, and baseflow) in both natural and regulated rivers, with more pronounced changes occurring in the regulated river after dam construction. In the natural Khiavchai River, high flow and peak discharge showed no significant trends, whereas in the regulated Balikhlochai River, all flow components exhibited significant decreasing trends. Comparison of flow duration curves and violin plots revealed substantial reductions in minimum flows and baseflows in the regulated river, with monthly discharge distributions strongly influenced by dam regulation. Comprehensive evaluation of river regime changes and flow components enables prediction of trends and effective water management for environmental flow allocation.
Hydrology
fatemeh ghavidel; Majid R.Banafsheh; Gholam Hasan Mohammadi
Abstract
The purpose of this research is to investigate the temporal changes and spatial distribution of the total cloud cover of the sky in the Ormia Lake drainage basin. In order to achieve the goals of this research, observational data on total cloud cover of the sky at five selected meteorological stations ...
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The purpose of this research is to investigate the temporal changes and spatial distribution of the total cloud cover of the sky in the Ormia Lake drainage basin. In order to achieve the goals of this research, observational data on total cloud cover of the sky at five selected meteorological stations and the product of total cloud cover of the sky (CFFCM) from MODIS sensors (Tera and Aqua) were used. The observed cloudiness values according to the ICAO standard were classified into five classes: cloudless sky, slightly cloudy, partly cloudy, semi-cloudy, and full cloudy, and the sky cloudiness changes were investigated. Pearson's correlation test was also used in order to investigate the relationship between the total cloud cover of the sky and the elements of precipitation, temperature, evaporation, and sunshine hours.The findings of the research showed that in the study area, the sky is mostly clear (28.7%) and slightly cloudy (23.9%), and only about 30% of the cases are semi-cloudy and full cloudy.In the examination of the frequency of occurrence of each of the cloudy classes, it was found that, in most cases, there was an increasing trend in the clear and slightly cloudy classes and a decreasing trend in the semi-cloudy and full cloudy classes.The study of the correlation coefficients between the total cloud cover of the sky and climatic parameters showed that there is a direct and significant relationship between the cloudiness of the sky and annual precipitation and an inverse relationship with temperature, evaporation, and sunshine hours, which is weaker in the case of annual temperature than the rest of the parameters, and also that the relationships established with observational data are more logical than those established with those established with satellite data. Investigating the spatial distribution of average seasonal cloudiness showed that cloudiness in winter and autumn is different from spring and especially summer. The highest amount of winter (summer) cloudiness is observed in the southern (northern) half of the Ormia Lake drainage basin, and this arrangement is consistent with the seasonal synoptic currents and the distribution of altitudes.
Hydrology
Raoof Mostafazadeh; Mostafa Zabihi Silabi; Mohamad Kazemi
Abstract
The increasing human needs and changes in climate patterns have led to the construction of water storage structures to meet the water demand in many regions worldwide, including Iran. Consequently, the hydrological regimes of rivers in various parts of Iran, due to human activities such as dam construction, ...
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The increasing human needs and changes in climate patterns have led to the construction of water storage structures to meet the water demand in many regions worldwide, including Iran. Consequently, the hydrological regimes of rivers in various parts of Iran, due to human activities such as dam construction, have undergone alterations in recent decades. Understanding the effects of dams on river hydrological regimes is essential for river flow management and the preservation of river ecosystems. In this regard, the present study assesses the changes in the health of the Urmia's Shahrchai River flow during three periods: pre-dam construction, dam construction, and dam operation, from 1951 to 2017, through calculating different flow health related indices. The results indicate that the deviation of all hydrological health sub-indices in the post-dam construction period is higher than the pre-dam construction period. Moreover, the deviation of flow regime sub-indicators was predominantly low to moderate until 1998 and varied from low to very high after 1998. Additionally, the highest deviation of studied flow health-related indices occurred during the reference and dam operation periods for flood occurrence and minimum monthly flow, respectively, while during the dam construction period, it pertained to minimum monthly flow. Furthermore, the findings suggest that the hydrologic health of Shahrchai River flow decreased by approximately 16% and 45% during the dam construction/operation periods, respectively, compared to the reference period. The results of this study can be utilized in the understanding of flow alteration and the sustainable regulation of the Shahrchai River flow regime.
Hydrology
Mahnaz Rezaei; Somaiyeh Khaleghi; Mohammad Mahdi Hosseinzadeh
Abstract
Considering the importance of the subject, in this research, the factors affecting the hydrological changes of the Taleghan River have been investigated. Descriptive-analytical methods have been used in this research. The most important data of the research included Landsat 5 and 8 satellite images, ...
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Considering the importance of the subject, in this research, the factors affecting the hydrological changes of the Taleghan River have been investigated. Descriptive-analytical methods have been used in this research. The most important data of the research included Landsat 5 and 8 satellite images, the SRTM 30-meter height digital model, Taleghan synoptic station climate information, and regional discharge information. Also, the most important tools used in the research were ArcGIS, ENVI, and SPSS. According to the subject of the study, this research has been done in several stages. In the first stage, the evaluation of land use changes, in the second stage, the evaluation of changes in climatic elements, and in the third stage, using IHA indicators, has been paid to evaluate the hydrological changes of the Taleghan River. The results of this research have shown that during the years 2000-2017, the average temperature of the region has increased and the area covered by snow has decreased. Also, under the influence of population growth, the use of artificial areas has increased and the use of gardens and pastures has decreased. Also, the total results of this research have shown that the discharge of the Taleghan River under the influence of natural and human changes, in terms of all IHA indicators, has had a significant decreasing trend. Also, among the stations in the region, the Glink station, which is located downstream of other stations, has faced more changes, which can be considered as the result of human activities and climate changes.
Hydrology
Firooz Abdolalizadeh; ََAli Mohammad Khorshiddoust; Saeed Jahanbakhsh
Abstract
In the current research, to investigate the future climate of the Urmia Lake catchment, the maximum and minimum temperature, rainfall and drought in the basin were projected for the period of 2015-2099 using NorESM2-MM climate model under the scenarios of SSP. The downscaling output of the model was ...
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In the current research, to investigate the future climate of the Urmia Lake catchment, the maximum and minimum temperature, rainfall and drought in the basin were projected for the period of 2015-2099 using NorESM2-MM climate model under the scenarios of SSP. The downscaling output of the model was done using the quantile mapping method and their accuracy was evaluated in the simulation of the base period (1990-2014) using the monthly diagram and RMSE and NRMSE indicators. The evaluation of the results showed that: the minimum and maximum temperature of the basin under the pessimistic scenario (SSP5-8.5) until the end of the century and under the optimistic scenario (SSP1-2.6) until 2075 have an ascending trend and then a descending trend. Average maximum and minimum temperature of the basin in the near future (1.0 to 1.8) and (1.1 to 1.8) ℃ and in the far future (1.5 to 4.8) and (1.3 to 4.3) ℃ will increase. The annual rainfall in the future period does not have a significant trend, but the average rainfall of the basin in the optimistic scenario will increase by 16.5% in the near future and 8.9% in the far future and in the pessimistic scenario will increase by 1.8% in the near future and 7.2% in the far future. According to the SPEI index, in the future period, under the optimistic scenario, moderate drought will have an ascending trend, severe drought will have a descending trend, and under the pessimistic scenario, the drought will have a descending trend.
Hydrology
Mohammad AKBARINASAB; Faezeh Abbasi; Nadia Talebpour
Abstract
Floods play an important role in the flow of rivers, so their investigation and analysis are importance. Studying the dynamics of floods and the water discharged into the sea (plume) is very important in the fields of fisheries, sedimentation, transportation and environment. Babolrud-River originates ...
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Floods play an important role in the flow of rivers, so their investigation and analysis are importance. Studying the dynamics of floods and the water discharged into the sea (plume) is very important in the fields of fisheries, sedimentation, transportation and environment. Babolrud-River originates from the south of Babol city and flows into the Caspian-Sea after traveling about 67 kilometers. In this research, the expansion of the plume entering from the Babolrud-River to the Caspian Sea during the spring flood of 2018 has been investigated. For this purpose, firstly the images of Sentinel-2 satellite were taken, then the required pre-processing including geometric and radiometric correction was applied. According to the spectral behavior of muddy and clear waters, in the spectral range of wavelengths of 0.4 to 0.78 micrometers, this phenomenon can be distinguished. As a result, by using this feature and the optimal index factor (OIF), the best color combination with the largest information was detected. The combination bands of 3, 4 and 8, with the OIF of 0.19, was defined as the best band combination. In the next step, NDVI, NDFI, and MNDWI were applied, and thresholds were applied to the defined indices for better separation of muddy and clear waters. These thresholds were identified by drawing spectral profiles at the plume of river and checking their histograms. Finally, by building the decision tree with all these indicators and applying the thresholds, the amount of muddy water from the flood entering the Caspian Sea from the Babolrud-River was revealed.
