States with critically low groundwater reserves were responsible for 41%, or about 38.6 million tonnes of India's domestic cereal trade. This worked out to nearly 39% of India's total groundwater being used up in producing and trading cereal among States. Moreover, a further 21% (19.6 Mt) of domestically produced cereals were exported from six States with 'semicritical' to 'critical' groundwater status equivalent to 32% of groundwater, according to an analysis by scientists spanning multiple institutions in India and abroad. The study appears in the peer-reviewed Environmental Research Letters.
Cereals are the source of about half the energy that an average Indian gets from her diet. Within them, rice and wheat dominate cereal production and it's also known that they are intensely water-consumptive crops. For this study, the researchers relied on mathematical modelling and used data-sets from 2011-12—the most updated they say—that had information on interstate trade of cereals, domestic cereal production, cost of transportation by rail and road between states. From this the 'water footprint' of producing and transporting cereals were estimated.
Previous studies of embedded-water flow in agricultural production have usually focussed on international movements, for instance the amount of water that was lost when a country imported a food crop from another, whereas this focussed on domestic movements and incorporates the role of the public distribution system as well as international outflows, the authors note.
Trade patterns varied between PDS (Public Distribution System) and non-PDS cereals. The majority (58%; 58.0 Mt) of interstate cereal trade occurred through the PDS. The total volume of embedded water traded through PDS rice and wheat amounted to 54.3 cubic km of green water and 36.7 km3 of blue water. As the main PDS contributors, the States exporting the most water through the PDS were Punjab (20.9 km3), Andhra Pradesh (12.6 km3) and Madhya Pradesh (9.9 km3). In addition, 35.8 Mt of non-PDS cereals were traded between States, corresponding to 45.1 km3 of green water and 17.3 km3 of blue water.
'Green' and 'blue water' refer to the volume of precipitation water that is consumed during crop production, either from evapotranspiration, transpiration, or incorporated into the final crop product. The blue water is that withdrawn from ground- and surface-water sources and consumed during crop production, or incorporated into the final crop product.
“Our findings reiterate the substantial potential for balancing water resources through the trade of crops in India, either in addition to or in place of large-scale infrastructure projects,” say the authors. The institutions involved in the study were the Kalinga Institute of Technology, Bhubaneshwar; Ashoka Trust for Research in Ecology and the Environment, Bengaluru; London School of Hygeine and Tropical Medicine, University College London and Brandenburg University of Technology, Germany.
