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Modelling the impacts of reservoir operation on river floods: a case study of Cauvery basin in India

  • Yeditha, Pavan Kumar
Publication Date
Oct 06, 2022
University of Ljubljana
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Floods are one of the most devastating natural disasters, affecting millions of people around the world. Extreme events have increased considerably due to climate change, which has increased the occurrence of floods in many major river basins around the world. India is a country with multiple monsoon-based rivers and extreme weather events. The occurrence of large-scale floods has increased noticeably. The socioeconomic impact of these floods is immense since they occur in such short periods. The Cauvery River basin is one of the key river basins identified as prone to flooding each year. There are numerous dams and barrages in the basin. The prevalence of floods in this basin is attributed to the basin's severe short-term and flashy rainfall pattern, according to reports and news stories. Furthermore, considering their primary aim of agriculture and drinking water supply, the dams do not appear to consider flood management. To better understand the occurrence of floods and the impact of dams on floods in the basin, comprehensive research was conducted utilizing process-based numerical modelling methods in conjunction with data analysis, emphasising the 2018 flood event. Following the knowledge of the processes in the basin connected to the occurrence of floods and dam operation, one-dimensional (1D) process-based hydrodynamic models (Delft3D-FM) paired with a Real-Time Control (RTC) tool for dam operation were built for the main Cauvery river, including some major branches including Kabini and Bhavani. Based on observable data, the model was initially calibrated and validated. It was then used to simulate the real-world system and understand the propagation of the 2018 flood. According to the results study, the dams in the basin did not produce any additional floods to the river other than passing through the arriving flood peaks. However, the dams may be utilised to mitigate the consequences of the flood. As a result, several dam operation scenarios were explored to determine whether the existing dams are suitable for flood management. To that end, a series of model simulation scenarios were created and tested to determine whether dams can be utilized to collect flood peaks and under what conditions they can be used for flood management. Based on an understanding of the flooded areas, the Mettur reservoir in the main Cauvery river was used for scenario simulations to assess the effects of the reservoir operation. Based on the reservoir analysis, it was found that the reservoir is not capable of capturing floods with its current specifications. To capture the impending flood peaks, two main scenarios were simulated: lowering the spillway crest level (i.e. increasing flow capacity) and raising the dam height (i.e. increasing reservoir storage). The findings of the simulation and analysis demonstrated that the reservoirs could capture the flood peaks in both scenarios. Even though these scenarios appear to help improve the flood management functions of the Mettur reservoir, other technical, economic, social, and environmental factors must be addressed when picking solutions for the real-world situation. This study successfully replicates and reveals some essential features linked to the consequences of dams on flood propagation in the Cauvery river, as well as the importance of reservoir storage and spillage capacity in conjunction with an efficient reservoir operation strategy.

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