Modelling for Desilting chamber of naitwar Mori Hydro Power Project

The paper describes in detail the physical model studies conducted for desilting arrangement of Naitwar-Mori Hydropower Project in Uttarakhand, under different operating conditions on a geometrically similar physical model built on a scale of 1:15 at Hydraulics Research Station, Bahadrabad. It has been planned to utilize the water of River Tons for power generation upto 60 MW on a run-of-the river type scheme harnessing a head of about 96.76m. Twin desilting chambers of length 130 m, width 25m and depth 13.50m have been provided in the project to remove particles of size bigger than 200micron.

The model studies were conducted for a desilting arrangement consisting of power channel with its x-section having side slope of 1:1.5 and a well designed transition connecting the desilting chamber. Though, the overall silt trapping efficiency in this case was found in the range of 92 to 94 % for a silt load ranging from 2000 to 4000 PPM, majority of the silt load got deposited in the power channel itself due to low velocity in the channel resulting into very low silt flushing efficiency (SFE) i.e. around 2.5 %, which is not desirable. In order to overcome this problem, it was proposed to modify the power channel in different stages by reducing the x-sectional area of u/s transition and making the side slope of channel steeper. It was found that modifying side slope of the channel is more instrumental in improving SFE. However it needs some more modifications in the transition portion so as to improve the silt flushing efficiency (SFE) to the desired extent.