Spillways and Energy dissipators Division (SED) is engaged in carrying out studies related to spillways of dams. This division undertakes studies for evolving efficient,economical and safe hydraulic designs of spillways, energy dissipators, head race and tail race tunnels, power intake,water conductor systems, sediment bypass tunnels and desilting basin for various irrigation, hydropower and multipurpose projects in India and abroad. The studies carried out with the help of physical / numerical models, and desk studies or a combination of these.

Majority of the major dam projects in India are studied/optimized at the SED division Studies were carried out for the design of spillways and under sluices for the dams like Hirakud, Koyna, Bhakra, etc. During early eighties the focus of dam building activity shifted to the north and north eastern parts of the country i.e. tapping the Himalayan Rivers. The design of dam and its appurtenant structures in north and north eastern parts of the country is very challenging due to its fragile geology, topography of the site, GLOF and various other site constraints. SED Division has helped in the design of such complex structures by constantly innovating new designs of spillways and energy dissipators. Coastal reservoir is a paradigm shift in water resources development from storing water in inland dams to storing freshwater by the coast.The requirement of design of spillways and energy dissipators for coastal reservoirs are unique and is being studied for Kalpsar Project. More than 200 National and International projects have benefited from the safe , economical and efficient optimization of hydraulic structures carried out at SED division.

Scientists of SED, as members, have even contributed in finalising many IS codes under WRD (9), WRD (14) and WRD(29).

Broad areas of expertise

The major scope of studies include evolving hydraulically efficient and safe design for the following studies/parameters:

• Approach flow conditions upstream of the spillway
• Assessment of discharging capacity with full and partial gate openings
• Pressures over spillway surface and design of aerators
• Water profiles for design of training walls, divide walls and location of trunnion beam
• Performance of energy dissipating arrangement
• Scour downstream of energy dissipator and plunge pool design
• Construction stages of spillway
• Protection works near the spillway
• Assessment of prototype performance
• Transient analysis of the water conductor system
• Settling efficiency of desilting chambers and flushing efficacy of Silt flushing tunnel
• Performance of bypass tunnels for carrying excess discharge and high sediment concentrations

Significant Contributions

• SED Division conducted physical and numerical model studies for Subansiri Lower Hydroelectric Project Pradesh/Asaam, India’s largest hydel project having an installed capacity of 2000 MW. Based on the extensive studies carried out on physical and numerical models, the design of the spillway, energy dissipator and aeration system was finalized.
• Studies for the Indira sagar dam spillway, MP for revised energy dissipation system prove to be a classic example in model-proto conformity. The existing roller bucket-type energy dissipation arrangement system was damaged. CWPRS in consultation with CWC and NHDC suggested a ski-jump bucket as a revised energy dissipator. During the 2019 flood SED Division scientists witnessed the functioning of the spillway.
• Polavaram Irrigation Project, Andhra Pradesh is a national project being constructed on the river Godavari in Andhra Pradesh. Studies were carried out in CWPRS to optimize the designs of spillway, energy dissipator and layouts of approach channel, spill channel and guide bund. The Dam Design Review Panel (DDRP) recommended the adoption of all the layouts.
• In the upper reaches of mighty rivers like Brahmaputra, the river gorges are narrow and the discharges to be passed through spillway are high. Therefore, designing an orifice spillway becomes difficult. Multi-tier spillways have evolved to overcome this difficulty for Lower Siang Project, Arunachal Pradesh. The bottom orifice spillway is designed to take care of normal flood as well flushing of sediment and the upper spillways will cater excess flood to be passed through reservoir. Physical model studies conducted in the division became very much useful in visualizing and finalzing the complex design of spillway and energy dissipator for such unique problem..
• Salma dam spillway, Afghanistan was optimized through extensive model studies at SED division. CWPRS received the award of appreciation in recognition of the role played by CWPRS in partnering with WAPCOS for Model Studies, which contributed to the successful completion of the Project.
• Sardar Sarovar Dam Project,Gujrat is one of the biggest and most important projects in the country. Hydraulic model studies conducted at SED Division, CWPRS played a major role in designing the gigantic spillway and the appurtenant structures. Apart from conventional studies, some specialized studies like the studies for measurement of hydrodynamic bending moments on the divide walls in the stilling basin, pull-out forces on the right training wall, uplift forces on the stilling basin floor slab, design of aerators and design of low-level hump on the partly completed spillway were conducted. Some of these studies were unique in nature and were conducted for the first time in the country.
• Double lake tap studies forKoyana Dam, Maharashtra were carried out at SED Division. Model results confirmed well with the prototype observations.
• A unique site specific submersible weir type sediment exclusion arrangement for a dam footKol Dam H.E. Project, Himachal Pradesh was proposed and implemented as the provision of desilting basin was not practicable. Model tests revealed that the suggested weir type sediment exclusion arrangement is capable of preventing the entry of coarse sediment (size more than or equal to 250 microns) into the power intake.
• Optimization of length of desilting basin and modification in its other components for various hydroelectric projects in Himalyan region viz. Nathpa-Jhakri, Teesta, Parbati, Uri, Chamera in India and Kholongchhu, Punatsangchhu, Tala, Mangdechhu in Bhutan were carried out in SED Division.