watershed
Razieh Izanloo; Ebrahim Omidvar
Abstract
The damming can cause changes in the hydrological regime of the river. There is a crucial need to understand the potential impacts of water structures on river hydrologic regimes in order to set managed environmental flows. In this study, the statistics of Tang Esferjan hydrometric station at the outlet ...
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The damming can cause changes in the hydrological regime of the river. There is a crucial need to understand the potential impacts of water structures on river hydrologic regimes in order to set managed environmental flows. In this study, the statistics of Tang Esferjan hydrometric station at the outlet of Hoonejan watershed (Isfahan province) were used to investigate the monthly average discharge and flow duration curve alteration using IHA software (version 7.1). The amount of monthly flow has decreased in the post impact compared to the pre impact period. The flow duration curve is higher in all seasons before the construction of check-dams than after construction. The interpretation of flow duration curves shows the reducing effect of correction clauses in all types of flow. The hydrological indicators of the stream (normal discharge index in the high flow condition, normal discharge index in the low flow condition and normal discharge index) have decreased in the post-impact period compared to the pre-impact period. In all months of the year, except for February, March and April, the rate of decrease of the normal discharge index in the low flow condition (Q75) was higher than the normal discharge index in the high flow condition (Q25). The normal discharge index in the high flow condition has decreased more in the spring season than in other seasons after damming. The normal discharge index in the low flow condition in winter, autumn (91%) and summer (90%) has decreased more than in spring.
daniyal sayyad; Ebrahim Omidvar
Abstract
1-Introduction Runoff is one of the most important components of the hydrologic cycle. Since there are no observational data in basins lacking statistics, the process of calibration and validation of hydrologic models seems impossible in these basins. On the other hand, predicting runoffs in basins lacking ...
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1-Introduction Runoff is one of the most important components of the hydrologic cycle. Since there are no observational data in basins lacking statistics, the process of calibration and validation of hydrologic models seems impossible in these basins. On the other hand, predicting runoffs in basins lacking statistics is essential for planning and management of the basin (runoff estimation, ecosystem services, flood control) (Beck et al., 2016). However, predicting the runoff in basins lacking statistics has been comprehensively discussed using the calibrated hydrologic model in basins having observational statistics through the zoning approach (Yang et al., 2019:67). The zoning approach has been identified as the cheapest and most prevalent solution for solving the prediction problem of flows in basins lacking statistics (Cislaghi et al., 2020:348). According to the definition of the zoning approach, predicting runoff in basins lacking statistics is done using data transfer from basins having statistics to the basins lacking statistics (Rojas et al., 2016). 2- Methodology To conduct this study, firstly SWAT model was calibrated and validated in the watershed basin having statistics; then, the calibrated parameters were transferred to Sukcham basin which lacked statistics, to simulate and analyze the flow using hydro office-FDC software. To analyze the sensitivity of parameters in the zoning approach and for simplifying the complex structure of hydrologic models like SWAT, minimizing the number of parameters in the modeling phases was a necessity. To this end, firstly, a sensitivity analysis was done for the basin having statistics using 14 sensitivity parameters affecting the flow. According to the global sensitivity analysis, the parameters were ranked in SWAT CUP-SUFI-2 based on the sensitivity level and considering two P-value and T-stat factors. Later, 14 parameters having high sensitivity in the basin having statistics were calibrated and transferred to the basin lacking statistics (Sukcham) using zoning and physical approaches. 3-Results and Discussion According to the obtained results from sensitivity analysis of 14 sensitive parameters in the flow simulation, SLSOIL, HRU-SLP, CH-S1, CANMX, SOL-AWC parameters were recognized as the most sensitive parameters of the region. The performance evaluation criteria of NSE, R2, and PBIAS models, respectively, for the calibration periods, were 0.6, 0.65, and 10.7 and for the validation, periods were 0.47, 0.63, and 11.88, showing the acceptable accuracy of daily discharge simulation in the daily scale. After calibration and validation of SWAT model in the basin having statistics and the basin lacking statistics (Sukcham), the daily time step was applied for the 2008-2015 period, and the calibrated parameters of the basin having statistics were transferred to the basin lacking statistics through zoning approach and using physical characteristics. Considering Table (9), the average daily outlet runoff, as well as the average volume of annual outlet runoff for the basin lacking statistics (Sukcham), were estimated. The estimation of such information from basins lacking statistics can present managerial views toward controlling the flood and preventing the occurrence of devastative floods as well as providing the required water sources for filling the aquifers and agriculture in dry regions. Considering Figure (9), the moisture indexes (Q10-Q20) were respectively 0.12 and 0.16 m2/s (10 and 20 percent of the days in a year (33 and 73 days)), discharges were 0.12 and 0.16 m2/s or more. Considering the average extracted index from the curve, flow duration was obtained, respectively, 0.115 (30% of days in a year (110 days)), 0.111 (40% of days in a year (146 days)), 0.094 (50% of days in a year (183 days)), 0.081(60% of days in a year (219 days)) m2/s. Moreover, the scope of low flow index (Q70 toQ95) for 256 and 347 days of a year was obtained 0.058 and 0.024, respectively. In addition, the flood index (Q5) was 0.28 m2/s (5% of days in a year (18 days)), for which the flood discharge equaled 0.28 or more. 4-Conclusions Considering the performance evaluation criteria, the performance of SWAT in dry basins having statistics was good and satisfactory in the daily scale of calibration and validation phase. According to the results of administering the SWAT model in the basin lacking Sukcham statistics, the average daily runoff flow (0.107 m2/s) and the average volume of total annual outlet runoff (million m2) of this basin have been estimated. Then, the flow duration curve was drawn for the Sukcham River in the hydro office-FDC software. Considering the results of the flow duration curve of the Sukcham River, it could be concluded that the scope of moisture, moderate and low flow indexes were respectively, (0.12-0.16), (0.081-0.115), and (0.024-0.058) m2/s. Moreover, the flood index (Q5) was obtained 0.28 m2/s for Sukcham River; which meant that regarding 5 % of the days in a year (18 days), the flood discharge equaled 0.28 m2/s or more. The extraction of these results may help in better recognition of hydrologic behavior of basins lacking statistics for planning and management purposes of water sources such as controlling sudden floods and providing drinkable water and agriculture.
Reza Ghazavi; Maysam Nadimi; Ebrahim Omidvar; Rasul Imani
Volume 5, Issue 15 , October 2018, , Pages 54-79
Abstract
Abstract
Introduction
Information about river flow change and subsequent changes in water quality characteristics can help to manage and plan water resources. The environmental and socio-economic impacts of river flow changes are very important in an environmental water management. Climate change is an ...
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Abstract
Introduction
Information about river flow change and subsequent changes in water quality characteristics can help to manage and plan water resources. The environmental and socio-economic impacts of river flow changes are very important in an environmental water management. Climate change is an important challenge that should influence different parts of human life on earth such as rivers and lakes. The Evaluation of the impact of climate change phenomenon on the hydrological processes of rivers can decrease the challenges of managers and planners of water resources in the next period. The selection of suitable models is important for evaluation and prediction of the effects of climate changes on rivers and watershed discharge. Several hydrological models were used to evaluate the effects of climate change on a hydrological cycle. The Soil and Water Assessment Tool (SWAT) has been extensively used, mainly by hydrologists for watershed hydrology related subjects, since 1993. SWAT model should include both a forecasting model and weather generating model. This means that the generated weather data of the future should be presented to SWAT model for forecasting future rainfall and temperature. This is a new possibility for future river and watershed hydrology studies. The main aim of this study was to evaluate the effect of the future climate change on river discharge of the Heruchay River in Ardebil using SWAT model.
Methodology
In this study SWAT2009 model was used to in investigate and predict the quantitative changes of the discharge of the Heruchay River. For the period of 2014-2041, the daily rainfall and temperature data were predicted under three scenarios of A2, B1, and A1B, using LARS_WG climate model. The simulated data was used as the entered information of SWAT model and the model was implemented for 2014-2041 period.
SWAT is a river basin scale model that should work on a daily time-step. It was developed to predict the effect of the management decisions and climate change on the water cycle. In this study, SWAT model was used for its ability to simulate and forecast stream flow and evaluate the effect of climate change on river discharge.
A topographical map (Digital Elevation Model), climate data (daily rainfall, Maximum and minimum temperature), and soil and land use maps were prepared using GIS and measured data. As the precipitation is an important key input that influences flow and mass transport of the rivers, 5 rainfall gauging stations and 2 weather stations located in the study watershed were used.
Result and Discussion
The results of this study showed that SWAT model had an acceptable performance for discharge simulation during calibration and validation periods with coefficients of variation of 0.81 and 0.8 respectively for calibration and validation. Based on the results of A2 and B1 scenarios, the flow rate of the study river increased, whereas a decrease in the flow rate was predicated based on the results of the A1B scenario. The results of the climatic model indicated that the pattern of the rainfall should change in the prediction periods as the rainfall decreases in the winter and spring, while it increases in the summer.
Conclusion
This study offered a methodology for flow simulation and forecasting of future discharge via SWAT model. The effects of future climate change on flow quantity were examined. In this study, SWAT model was used to predict the impact of the future climate changes on river discharge. Model evaluation was done via Nash and Sutcliffe (NS), coefficients of determination (R2), P-factor, and R-factor. After model calibration, the predicted data under several climatic scenario were presented to the model. The results showed that the average of discharge will increase based on the A2 and B1 scenarios, while it will decrease under the A1B scenario. Therefore, it can be concluded that SWAT is a suitable model for discharge simulation in semi-arid areas. The results of this study also indicated that the combination of the results of LARS-WG and SWAT model should lead to an acceptable prediction of hydrological behavior of the rivers. It is important to notice that in this study only the effects of climate change on river discharge was evaluated. For a sustainable management strategy, other aspects of the watershed such as population pattern changes, land use change, and industrial development should be considered. The impact of the climate and land use change on water quality and soil erosion should also be investigated in the future studies.
