The water footprint and virtual water exports of Spanish tomatoes

28 THE WATER FOOTPRINT OF TOMATO PRODUCTIONIn all cases the green water footprint is practically negligible.It should also be noticed that the grey water footprintof both Badajoz and Almería is similar, even if theproduction is greater in Badajoz. This is related to the higherexcess of Nitrogen in Almería, 139 kg N/ha as comparedto 68 kg/ha of Badajoz (MARM, 2008) (Appendix IV).However, different green, blue and grey water footprintproportions are found across production regions. In this regard,we see that the main component of the water footprintin Badajoz is the blue one (of the open-air irrigated production)whereas in Almería it is the grey one. Something similarhappens in the rest of the provinces.If the water footprint is an indicator of the water appropriationof a product (Hoekstra et al., 2009), its compositionmay help us identify the main areas of impact of its production.The main primary impact of the tomato productionin Badajoz, (also in Cáceres or Sevilla) would be the highvolume of blue water consumed, whereas in Almería (andMurcia, Navarra or Granada) would be the pollution of waterresources. It is through this type of analysis where thewater footprint reveals itself as a powerful indicator.4. APPARENT WATER PRODUCTIVITY AND VIRTUAL WATEREXPORTS OF TOMATO PRODUCTION4.1. Water apparent productivity of tomatoproductionThe apparent water productivity (WAP) is an indicator ofthe economic performance of the water use. As shown in Tables4 and 5 the water apparent productivity of tomato productionvaried from 0.025 to 36 €/m 3 , depending on the productionsystem, type of water (green or blue) and on the