drop by 17% (MAI 1979: Vol II:p102). A January 2, 1992 World Bank memorandum stated that irrigated area in the SSP would drop by 30% without the NSP (Morse and Berger 1992: 250).
A 17% lower flow in the Narmada combined with a 17-30% drop in the SSP irrigated area due to the absence of the Narmada Sagar Project could decrease the area irrigable by the SSP to as much as 58-69% of the original estimate, if the two factors are cumulative. But the story doesn't end here.Canal Efficiency
The area irrigable by the SSP becomes even more uncertain when we examine the efficiency of the canal system. In any canal irrigation system, water is lost due to seepage and evaporation from the main canal, its branches, and from the distribution system and field channels. Water is also lost during field application and in the overall operation of the system. The overall water use efficiency is estimated after accounting for all the losses. The SSP authorities have "deemed feasible" an overall water use efficiency of 60% (NPG 1983:12, SSNNL 1989:360) for irrigation and of 75% for drinking water supply (NPG 19.83:4). (Water use efficiency is determined as the ratio of water reaching the target to that released at the source: Thus, if 600ml reach the field for every litre released at the dam, efficiency is deemed to be 60%.) The figure of 60% canal efficiency is based on several very questionable and overly optimistic assumptions (SSNNL 1989:356).
The project planners have completely neglected evaporative losses in the canal system! Given that large parts of the canal system are to run through the arid parts of Kutch, Saurashtra and North Gujarat where substantial losses through evaporation can be expected, such an assumption seems foolhardy at best and wilful deception at worst.
Other dubious assumptions made by the SSP authorities relate to estimates of seepage rates, field application losses and operational losses. Values assumed by the project planners are shown in Table 5 along with values observed in different systems in India and values used by the World Bank for irrigation projects in India.