Sardar Sarovar Project: a technological marvel of innovation

Sardar Sarovar Project: a technological marvel of innovation

Sardar Sarovar Project on river Narmada is not just one more big dam. It is a wonder of modern technology. This terminal dam on 1312-km long river Narmada, its water distribution network and its powerhouses show the vision of the planners and are an excellent example of innovation.

The project for irrigation water and hydel power is one of the greatest engineering projects in the country. If we talk about the Dam only, Narmada Dam with 163 M height is the third highest Dam in the country after Bhakara (226M) and Lakhwar (192M). In terms of volume of concrete used for the gravity dam it is the second largest in the world with aggregate volume of 6.82 mcm. The first one was the Grand Coolie Dam in USA. It is now replaced by ' Three sorges' dam of China.

The dam has spillway discharging capacity of over 30 lakh cusecs which is the third highest in the world after Gazemba in China and Takri in Brazil.

It is not only that the dam is unique, the canal system and its two powerhouses add many unique features to the Sardar Sarovar Project. It is one of the largest water resources development projects in India.

World's largest lined irrigation canal

The 532 km long Narmada main canal is the world's largest lined irrigation canal with a capacity of 40,000 cusecs of water at the head. The 40 branch canals spanning across 86,000km form the water distribution network.

The fact that the entire canal is lined is very important. It saves distribution loss of water and thus makes the channel quite efficient. It also prevents problem like water logging through seepage. This makes sure that maximum water reaches till the end. The main canal is designed with gentle slope of 1: 15,000 mt. It operates through gates over pool of water.

The Narmada main canal will cross major rivers of Gujarat such as Mahi, Sabarmati, Rupen, Khari, Saraswati, Banas etc. It will not only irrigate a command area of over 18.0lakh ha of land in Gujarat, it shall also discharge water into these rivers thus becoming the forerunner for the National Inter-River Garlanding scheme.

Another important component of the project which is very important for the inter-linking of rivers is carrying water through falls and lifts for the command areas of Saurashtra and Kutch. The Saurashtra branch canal with 14500 cusecs (425 cumec) capacity and Kutch branch canal with 77700 cusecs (220 cumec) capacity would be crossing the depression between main land in Gujarat and the Saurashtra and Kutch regions on the other side. In Saurashtra Branch Canal, the water would be lifted in five stages up to total head of 72m. Pumping stations at the five lift points are under implementation with a battery of 65 concrete volute pumps of 20 m3/s each (plus 22 vertcal turbinepumps of 5 cumecs) through a consortium of Indian and Italian collaborators. These pumping stations will be the largest in the country.

The line has a capacity of 40,000 cusecs of water.

Full supply level (FSL) at H.R.: 91.44m (300')
Length up to Gujarat-Rajasthan border:458.00km
Length in Rajasthan: 74.00km
Base width in head reach: 73.01m
Full supply depth (FSD) in head reach: 7.60m
Designed discharge capacity
a) In head reach: 1133 cumecs
(40,000 cusecs)
b) At Gujarat Rajasthan border:71 cumecs
(2500 cusecs)

The canal in its journey up to Rajasthan border will traverse through regions having diverse agro-climatic and soil characteristics and crosses numerous streams and major rivers. In all, about 600 structures of various type viz. cross drainage works, canal crossings, regulating and control structures etc, are proposed to be constructed along the main canal.

The Sabarmati and Mahi aqueducts are some of the largest structures in the world and architectural marvels in themselves.

Made to live 300 years

The construction of dam has many distinct features. Generally, dams have life of 100 years. This dam has life of 300 years. This is because of treatment of the catchments area. This reduces rate of siltation and as a result the life of dam increases.

The life of dam means that the time for which the dam stores water to maximum capacity. Because of siltation water-storing capacity gradually reduces and ultimately dam becomes useless. The only solution is dredging operations. However, this is not possible because of technical limitations. The only way is to reduce siltation in the catchment area.

This is done through afforestation in the catchment area. A study of the area through remote sensing in 1985-86 and 1994 showed that closed forest and open forest area had increased by 3,273 ha and 3001 ha, respectively. The degraded forest area had decreased considerably from 12,746ha to 7019ha.

Dam Dimensions

The dam is a 1210 m (3970 feet) long wall of concrete across the valley. It is designed to impound a reservoir with a full level of 139 m (455 feet) above sea level (asl). The middle section of the dam is planned to reach a height of 146.5 m (481 feet) asl. The bed of the river at the dam site is at 17 m (56 feet) asl so the planned height of the dam above the river bed is 129.5 m (425 feet).

Associated Infrastructure

The main canal leading from the reservoir is scheduled to be 460 km (286 miles) long, eventually reaching the state of Rajasthan. It is 250 m (820 feet) wide at its head near the dam and planned to be 100 m (328 feet) wide at the Rajasthan border. A network of secondary canals totalling 75,000 km (46,600 miles) in length is planned to deliver the irrigation water to farmers. Large electric-powered pumping stations will need to be built to deliver water to the Saurashtra and Kutch branches of the canal system. A large powerhouse containing turbines and related machinery is being built at the dam and a smaller one at the head of the canal. A weir is to be built at Garudeshwar, around 16 kilometres downstream of the dam, with a capacity to store six hours of the maximum flow through the Sardar Sarovar turbines. This water can be pumped back into the reservoir at times of low daily electricity demand and then released through the turbines again to generate electricity at times of peak demand.

Will stand straight even at 8 R

After the devastating earthquake of Kutch, the question of damage to big structures like dam has come in sharp focus. Almost 30 years before this earthquake, the planners of the Narmada Dam had thought of this problem. They studied seismic activity data of past several decades and found that earthquakes were maximum around 7 degree on the Richter Scale. The entire structure of the Sardar Sarovar project is to withstand shocks and tremors upto 8 degree on the richter scale. A fact not known to many. Sophisticated seismology instruments have been installed for monitoring earth's acitivites. Studies are being done regularly to monitor and find solutions of problems that may arise from time to time.

World's second largest single cable ropeway

The length of the dam is 1210mt. Naturally, the entire construction along the length is a challenging task. To transport concrete and other construction material a long ropeway of 1260mt. has been set up. A trolley attached to the ropeway looks like a bucket from the ground. You know how much material it can transport? Three truck loads in a single trip!

The entire ropeway is on a pair of straight cables. This was the longest straight single cable pair in the world until China built a longer cable in 2003.

Construction material for the dam is mixed through computer-controlled mechanism. This gives the exact quantity of different material to be mixed before the material is used in the construction.

Iced concrete

A special ice plant has been set up at the dam site! Ice has a lot to do with the construction of the dam. Concrete is basically lime, which on interaction with water produces heat. To prevent this reaction, ice flakes are added to concrete. It is ensured that the temperature of the concrete remains at 12C. Then only the construction process is allowed.

Two powerhouses to make the most of Narmada water

The project has two powerhouses. Riverbed powerhouse of 1200 MW and canal head powerhouse of 250 MW. The two powerhouses have been planned to maximize the use of water. In the Canal head powerhouse, water going to main canal is used for generating power.

River Bed Power House ( RBPH)

River Bed Power House has the largest installed capacity among pumped storage schemes in India. Size of power generating units is also largest of this type in the country. It has six units each of 200 MW. Five units have already been installed and the sixth is in final stage of installation. This powerhouse has been fully commissioned in June 2006.

This is underground power station on right bank of the river located about 165mt downstream of the dam. It has Francis type reversible turbine generators.

Canal Head Power House (CHPH)

Canal Head Powerhouse is a surface powerhouse to accommodate 5 units of conventional Kalpan Type generator each of 50 MW capacity. It is located at the toe of Vadgam Saddle dam, which will house the intake arrangement for power. This powerhouse has also been commissioned.

Innovative water distribution

The most important feature of the water supply is that it is volumetric instead of area approach. The system would be fully computerized to ensure equitable flow in all areas. This would guard against the most common problem of over use of water by initial command blocks, leaving less supplies to the areas down the canal.

The system would be fully computerized and remotely operated up to the level of 300 cusecs capacity. Another important feature is that the irrigation water in the command area of SSP would be delivered to farmers' groups and not to individual farmers. The groups will have to manage distribution within their block called village service area.

The remotely controlled system would make automatic adjustments for stroking of gates in the main canal and branches. The response time is extremely important for timely deliveries of water to remote areas of Kutch, North Gujarat and Saurashtra. In case of SSP, the response time will be less than 24 hours, which conventionally would be several days.

The farmers associations are also required to operate system on rotational delivery principles within the village areas. This would ensure that entire flow within village systems is distributed proportionately without any manual intervention. Thus farmers have not to do any gate operation and have only to regulate the hours per ha of individual farmers.