This paper by the Madras Institute for Development Studies presents estimates of the ‘consumptive use’ of water in crop production; the ratio of consumptive use to gross water utilization; and productivity per unit of consumptive use. This is done separately for different crop groups in irrigated and rain-fed lands, by states and agro-climatic regions and major river basins.
Estimates suggest that the total consumptive use of water by crops in the early nineties is around 660 bcm per annum. Irrigated crops comprise about 40 percent of total crop area, but they use much more water per unit area, they account for some 55 percent of total consumptive use. The large inter-regional variations in consumptive use rates reflect the combined effect of climate, extent of irrigation and crop patterns.
The ratio of consumptive use from irrigation to gross utilization of water from surface and ground water is around 38 percent for the selected basins taken as a whole. It is relatively less (26-27 percent) in the basins of east flowing peninsular rivers, 40 to 50 percent in Ganges and Indus basins; and 55 percent in basins of west flowing rivers (excluding the west coast rivers). Differences in the extent of groundwater use seem to account for these differences to some extent.
Significant changes in volume and sources of water use as well as technical efficiency of irrigation have taken place between the mid sixties and early nineties. Total consumptive use has increased by about 18 percent; consumptive use by un-irrigated crops has marginally declined and that of irrigated crops increased by some 90 percent overall. Consumptive use of irrigation water has nearly doubled. Rainfed crop patterns seem to have become on the average slightly more water intensive and those of irrigated crops slightly less water intensive over this period. The picture however varies across states.
The paper ends by highlighting the need and scope for more refined and detailed studies in terms of methodology and estimation methods.
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