Hydraulic modelling for reservoir flushing of run-of-the-river Parbati-III hydroelectric project, Himachal Pradesh, India.

Neena Isaac, Eldho T.I.

Friday 3 july 2015

9:15 - 9:30h at South America (level 0)

Themes: (T) Sediment management and morphodynamics, (ST) Basin-wide sediment management

Parallel session: 14J. Sediment - Basin

Run-of-the-river hydropower projects are developed based on the concept of sustaining reservoir life by sediment management. The prime criteria for planning and design of run-of-the-river projects should be sediment management. Sediment removal and capacity restoration is achieved by hydraulic flushing / sluicing through low level outlets. The choice of the most efficient method depends on reservoir geometry, flow and sediment characteristics and reservoir operation schedule. Simulation with numerical and physical models is essential for optimizing the design and operation of such projects. In this paper, reservoir flushing studies carried out for the Parbati stage-III hydroelectric project (520MW) on river Sainj in Himachal Pradesh, India is presented. Project consists of 41m high dam and orifice type spillway bays with crest near river bed for passing sediment during flushing. Hydraulic flushing studies were conducted on 1:100 geometrically similar scale model of dam and reservoir. Experiments were conducted to estimate the quantity of sediment removed by flushing with discharges of 75, 150 and 300 m3/s and durations of 12, 24 and 36 hours equivalent to prototype with the objective to optimize the flushing discharge and duration. It was observed that the annual sedimentation could be flushed with peak discharge of 300 m3/s in 24 hr. duration. Flushing is effective with lower discharges from 150 m3/s also but with longer durations of flushing. The intake level remains clear of sediment deposition level for all the reservoir operating conditions.