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.
