Importance of on-line sediment monitoring for hydroelectric projects -A case study

Himalayan rivers carry heavy sediment load during snow melt and monsoon season. For a large hydroelectric plant, with a number of generating units, it takes considerable time to close the plant when planned shutdown is essential, on consideration of heavy sediment load, as Units have to be closed one by one to ensure system stability and a proper sequence of closing and opening of gates has also to be followed simultaneously. As manual measurement of sediment load takes considerable time, to avoid serious damages to the underwater parts of turbine and other structures with the likely passage of highly silted waters, need for on-line sediment monitoring system has been felt for Nathpa-Jhakri Hydroelectric Project and process for import of such a system has been initiated which is likely to be operational during the coming flood season. Principles on which this system works and the specifications of the system have been discussed in the paper.