ISSN (Print) - 0012-9976 | ISSN (Online) - 2349-8846

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Redefining Irrigation Potential-Don t Damn the CV Alone

Redefining Irrigation Potential Don't Damn the CV Alone S M Vidwans MY critique (EPW, December 4, 1993) of the paper 'Redefining Gujarat's Irrigation Potential' (EPW. June 26, 1993) by D H Parikh, A J Vera and Y K Alagh (PVA for short) showed that PVA's paper failed in its objective of establishing variability of rainfall as the reason for redefining (i e, down-rating) Gujarat's irrigation potential. But, as the critique pointed out, rainfall variation obviously affects irrigation potential in terms of the volume of water stored in the reservoir the very reason why the dependability factor comes into play. If dependability is 75 per cent, in that much per cent of years over a long period full potential will be realised and in 25 per cent less than full. One can therefore think about an average potential that will be obtained over a long period, an average or (I) full potential in 75 per cent of years, and (2) less than full potential less by varying amounts in the remaining 25 per cent. The difference between the full and the average potential gives the extent of down-rating of the former that will be required because of rainfall variation. Thus, the maximum, though unlikely, extent of down-rating will be 25 per cent when dependability is 75 per cent, and 50 per cent when the latter is 50 per cent. It is therefore a truism that full irrigation potential requires to be down- rated on account of rainfall variation; it is surely not a discovery. The only point of interest perhaps is the extent of down-rating and its relationship with rainfall characteristics. Possibly a minor point, it becomes statistically interesting to pursue because PVA raised it and handled it rather unsuccessfully. That is the limited objective of this follow-up paper.

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