Experiments, using warm seeding technique, on operational basis, were conducted during 2 summer monsoons of 1973 and 1974, over the 13,000 sq. km catchment area of the Rihand reservoir in the state of Uttar Pradesh, India. In the first year of operation, seeding was not done on many seedable days when flying could not be undertaken. Considering those not-seeded days as control days and nearly equal areas adjoining the eastern and western boundaries as control areas, the result was evaluated by using 24 hours rainfall data from the ordinary raingauges functioning in all the areas. In the second year of operation, seeding was not done, in general, on every fifth seedable day which was considered as control day. Seeded days, which were nearest to the control days, were considered as experimental days for evaluation. The result was evaluated by using 24 hours rainfall data from the ordinary raingauges and 5 hours rainfall data from the self-recording raingauges. The analysis suggested an increase in rainfall in the catchment area upward of 16 percent, which is statistically not significant. Microphysical measurements were made concurrently with the seeding operation. A summary of the measurements is presented.
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Kapoor et al. (1976) studied this question.