Answers to some very commonly and frequently asked questions related to the Sardar Sarovar Project are briefly presented here.   

Q.
Whether the assessment that at least of 28 Million Acre Feet (MAF) of water flow down the river was correct, whereas measurements of the actual flow between 1948 and 1993 showed that this has been only 22.75 MAF ?


The availability of water in Narmada river has been assessed in the most sophisticated and systematic manner in consultation with the Central Water Commission (CWC) - the highest expert technical body of the nation - by utilizing rainfall series from 1891 to 1992 and actual river flow series from 1948 to 1992. The actual rainfall series for 45 years is not adequate for planning mega project with a life of more than 100 years and a large catchment with co-efficient of annual flow variations of 0.35 which may need minimum 130 years data of both rainfall and river flows. Therefore combined actual and hind cast data available of about 100 years is used as per international standard practice. Based on this method, 75% dependable availability is 27.22 MAFT.

The Narmada Water Disputes Tribunal (NWDT) has adopted value of 28 (27.22 ) MAF based on an agreement reached between the Chief Ministers of the four party States in 1974. which formed the basis for apportioning of Narmada waters between the party States.

The water availability in the Narmada river at Garudeshwar was first estimated by Khosla Committee in 1965 by using the observed data from 1948-49 to 1962 along with hind cast data of run-off based on rainfall values from 1915 to 1947, as 28.72 Million Acre Feet (MAF) at 75% dependability. This figure of available run-off was accepted by Govt. of Gujarat. The Govt. of Madhya Pradesh and Maharashtra used longer series of hind cast data from 1891-1946-47 along with observed data from 1948-1962 and arrived at 75% dependable value of run-off as 27.14 and 27.17 MAF respectively. The method of hind-casting flow series employed in above analysis is as per the international practice. In Narmada river a minimum of 130 years of data of both rainfall and river flows are required considering coefficient of annual variation to be at 0.35. The Central Water Commission in 1993 had also endorsed the Tribunalís determination of 28 MAF using the above method of hind-casting the flow series. Therefore the availability of 28 MAF water arrived by standard scientific methods and practices was adopted.

Q. When the power actually produced by the SSP will be much less than the installed capacity, mainly because irrigation in the long run will be preferred over power generation. What are the safety measures to be adopted to avoid such scenario ?

Power generation from Sardar Sarovar Project is envisaged in two Power Houses - the River Bed Power House (RBPH) with an installation of six units of 200 MW each operating under a head range of 116.6 mtr. to 75 mtrs located in an Underground Power House, and, the Canal Head Power House (CHPH) with an installation of five units of 50 MW each operating under head range of 46.13 mtr. to 18.12 m located in a surface Power House at the off-take of the Narmada Main Canal.   

The power generation at CHPH would depend upon the releases for irrigation for Gujarat and Rajasthan as per the directions of the Tribunal and  power generation at RBPH would depend upon the water surplus arising after the irrigation requirement. The NWDT in its report considered the likely pace of irrigation development by the party states for utilisation of their allocated shares and indicated three stages of irrigation development in the basin, reckoned from the date of Gazette notification of the report.
  

Power benefits at SSP would depend upon the irrigation abstractions by the party States and is a complex exercise involving multipurpose river system of dynamic characteristics. The Central Electricity Authority together with the power beneficiary states of Madhya Pradesh, Maharashtra, Gujarat carried out different studies for evaluation of power benefits from SSP complex using multi reservoir simulation system. All the studies were taken into account while arriving at the power benefits. The power benefits effect of the three stages of irrigation development are given below.

Stage of Irrigation Development

Years

RBPH

CHPH

 

 

Firm

GWH

Seasonal

GWH

Total

GWH

Firm

GWH

Seasonal

GWH

Total

GWH

Stage-I #

00 - 10

3635

1431

5066

213

190

403

Stage-II @

10 - 30

517

1334

1851

676

111

787

Stage-III $

30 - 45

0

520

520

440

345

785

#) Partial development of irrigation in Gujarat and full in Rajasthan to utilise 3.05 MAF out of 9.5 MAF share of two States.
(@)
Irrigation development in Gujarat to increase from 3.05 to 9 MAF. However, use in M.P. to be only 13 MAF against 18 MAF allotted.
($) Full irrigation development in M.P. also.

Thus, it would be observed from the above that the firm energy from the River Bed Power House would vary from 3635 GWH (415 MW continuous) in the initial years to NIL in the final stages of irrigation development. To preserve the capacity value of this station and its continued utility as a peaking station throughout its life, pump turbine and generator motor sets are provided at this station. The machines at RBPH would thus run for about 6 hours daily during the period of peak demands, discharging water into the lower reservoir, created by constructing a tail pool dam at Garudeshwar 12 Km downstream of Sardar Sarovar Dam. During the off-peak periods the water from this lower reservoir would be pumped back into the main reservoir by drawing power from the grid thus making the water available in the upper reservoir for peaking operation of the next day. The power benefits from CHPH would increase from 213 GWH (24.3 MW continuos) to 440 GWH (50.2 MW continuous) in the initial stages of irrigation development. This project would also afford substantial secondary energy benefits. The above assessment of power benefits was based on the assumption that ISP would be completed and become operational concurrently or earlier than SSP.

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