The water footprint and virtual water exports of Spanish tomatoes

6 THE WATER FOOTPRINT OF TOMATO PRODUCTIONare notable (open-air - rainfed or irrigated- versus greenhouse).Rainfed open-air tomato production has by far thehighest water footprint with 966 l/kg, of which 84% is greywater footprint. The grey footprint of irrigated systems is,in comparison to that of rainfed systems, much lower, mainlydue to the higher yields of these production systems. Themajor producing provinces in Spain have in general low waterfootprints in terms of l/kg compared to the average ofthe rest of the provinces, but a much higher total water footprintin absolute terms (hm 3 ). This is because theseprovinces produce overwhelmingly the most part of the nationalproduction. The green and blue water apparent productivityof the tomato production ranged from 2.1 €/m 3 forrainfed systems to 3.1 €/m 3 of open-air irrigated systemsand 7.8 €/ m 3 for greenhouse production. By season, tomatoproduced in the middle season (June to September) renderedthe lowest apparent water productivity with 2.7 €/m 3 .By contrast, tomatoes produced in early (January to May)or late season (September to December) rendered higher apparentwater productivities, 7.5 and 9.5 €/l respectively. Inrelation to the origin of water, groundwater production presenteda higher blue water apparent productivity than thatof open-air irrigated production, around 7 €/m 3 compared to3 €/m 3 . When analysing the exports of tomato the yearlyamount of virtual water exported through the tomato exportsis 4, 88 and 134 hm 3 of green, blue and grey water respectively,with an average water apparent productivity of8.81 €/m 3 .1. INTRODUCTIONIn a context where water resources are unevenly distributedand, in regions where flooding and drought risks maybecome more severe, enhanced water management is a majorchallenge not only to water users and managers but also