GUWAHATI, Oct 26 - To mitigate the repeated flood devastation caused by the Ranganadi, Doyang, Kopili, Karbi Langpi and Kuri Chhu (Bhutan) hydel dams in their downstream areas, state-of-the-art technologies like the Piano Key Weir (PKW) technology should be adopted in these projects to provide them with adequate flood cushions.
Moreover, the rule curves for reservoir-operating schedules of the hydel projects also require modification, after structurally upgrading them for flood storage space.
These observations were made by noted river science engineer Prof Nayan Sarma, a former professor at IIT Roorkee and presently an honorary professor of river science with the University of Nottingham, UK, while delivering the second Prabodh Chandra Sarma Memorial Lecture at the Pan Bazar auditorium of the Assam Chapter of the Institution of Engineers (India) on sustainable development, hydropower-created flood and its remedies for the North East region. Guwahati Zone of the ASEB Pensioners� Association (GZASEBPA) organised the lecture.
�To provide for necessary Flood Cushion in the reservoir storage space for holding back excess floodwaters, it is advised to adopt Piano Key Weir (PKW) technology for the dams after carefully configuring PKW features with model tests.
�Similar PKW has been constructed by Electricite de France (EDF) on a number of much older dams in France in recent years for achieving enhanced hydraulic performance and increased reservoir storage volume. Reservoir operation Rule Curves should be upgraded appropriately using simulation and optimization techniques,� he said.
On the rule curves, he said the grim lesson to be learnt here is � Kerala received 12 billion cubic metres (BCMs) of water in three days of exceptionally heavy rainfall during August 15-17, 2018, which was more than double the capacity of its all 44 dam reservoirs at 5.8 BCMs. Significantly, all reservoirs of Kerala dams, including the multipurpose ones, cater only to hydel generation, irrigation, drinking water, without any earmarked space for flood storage.
This resulted in the massive flood deluge inflicting severe toll on lives and property, he asserted.
Prof Sarma also laid stress on putting in place state-of-the-art multi-satellite GPM precipitation based early warning system with maximum possible lead time. This will need to use high resolution digital elevation model (DEM) data of watershed areas and stream topography for operation of hydrological and hydraulic models for real time flow simulation of overland flow, flood flow propagation and flood forecasting, he said.
He regretted that the existing hydroelectric projects in the North East do not have any provision to control floods. Hydel dams are not meant for flood control, he said.
In this context, he referred to the Integrated Water Resources Management (IWRM) approach, which is a water resources planning approach with storage spaces in the projects for flood cushion, irrigation and ecology, besides generating hydroelectric power. He claimed that the European countries don�t think of a single-purpose dam.
Earlier, addressing the function, noted hydro expert and former Chairman of the North Eastern Electric Power Corporation (NEEPCO) SN Phukan, who was involved in the construction of hydel projects like Umtru, Umium and Kopili, said that hydel projects like Ranganadi and Kopili are to release the floodwaters since they don�t have the flood moderation provision.
The Ranganadi project is a run-of-the-river project, and is not designed for holding floodwater, the Kopili project earlier had no gate and hence, floodwater was to overflow the barrage of this project, Phukan said, adding that only recently, this project has been provided with gates.
The function, presided over by GZASEBPA president G Das, was also addressed by general secretary P Deka and late Prabodh Sarma�s brother Subodh Sarma on behalf of the family.