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 Tribunal’s 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.

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.

#) 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.