Agricultural Water Management 97 (2010) 1617–1627 Contents lists available at ScienceDirect Agricultural Water Management journal homepage: www.elsevier.com/locate/agwat A global benchmark map of water productivity for rainfed and irrigated wheat Sander J. Zwart a,b,d,∗ , Wim G.M. Bastiaanssen a,b , Charlotte de Fraiture c , David J. Molden c a WaterWatch, Generaal Foulkesweg 28, 6703 BS Wageningen, The Netherlands b Delft University of Technology, Department of Water Management, P.O. Box 5048, 2600 GA Delft, The Netherlands c International Water Management Institute, P.O. Box 2075, Colombo, Sri Lanka d Africa Rice Center, 01 B.P. 2031, Cotonou, Benin article info Article history: Received 18 December 2009 Accepted 21 May 2010 Available online 16 June 2010 Keywords: Water productivity Global modelling Wheat Remote sensing Benchmarking abstract The growing pressure on fresh water resources demands that agriculture becomes more productive with its current water use. Increasing water productivity is an often cited solution, though the current levels of water productivity are not systematically mapped. A global map of water productivity helps to identify where water resources are productively used, and identifies places where improvements are possible. The WATPRO water productivity model for wheat, using remote sensing data products as input, was applied at a global scale with global data sets of the NDVI and surface albedo to benchmark water productivity of wheat for the beginning of this millennium. Time profiles of the NDVI were used to determine the time frame from crop establishment to harvest on a pixel basis, which was considered the modelling period. It was found that water productivity varies from approximately 0.2 to 1.8 kg of harvestable wheat per cubic metre of water consumed. From the 10 largest producers of wheat, France and Germany score the highest country average water productivity of 1.42 and 1.35 kg m -3 , respectively. The results were compared with modelling information by Liu et al. (2007) who applied the GEPIC model at a global scale to map water productivity, and by Chapagain and Hoekstra (2004) who used FAO statistics to determine water productivity per country. A comparison with Liu et al. showed a good correlation for most countries, but the correlation with the results by Chapagain and Hoekstra was less obvious. The global patterns of the water productivity map were compared with global data sets of precipitation and reference evapotranspiration to determine the impact of climate and of water availability reflected by precipitation. It appears that the highest levels of water productivity are to be expected in temperate climates with high precipitation. Due to its non-linear relationship with precipitation, it is expected that large gains in water productivity can be made with in situ rain water harvesting or supplemental irrigation in dry areas with low seasonal precipitation. A full understanding of the spatial patterns by country or river basin will support decisions on where to invest and what measures to take to make agriculture more water productive. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Ensuring food security for a growing population in a world with a changing climate is a major challenge for the coming decades. Reducing malnutrition and meeting the food requirements for the projected additional 2–3 billion people, a growth mainly tak- ing place in developing countries, demands major investments in agriculture. Alongside with food security comes the challenge to provide agriculture with sufficient water resources which are required for the advocated increase in production (Molden et al., 2007). It is estimated that by 2050 an additional 5600 km 3 of evapotranspired water per year is required to meet the food ∗ Corresponding author at : WaterWatch, Generaal Foulkesweg 28, 6703 BS Wageningen, The Netherlands. Tel.: +31 317 423 602. E-mail addresses: s.zwart@cgiar.org, sjzwart@yahoo.com (S.J. Zwart). demands, if no gains in water productivity are made (Falkenmark and Rockstrom, 2004). Water consumption is defined here as the vapour flow, or evapotranspiration, that is associated with plant production and that diffuses into the atmosphere. The physical water productivity, defined as the crop yield divided by the total water consumption through evapotranspiration, is a performance indicator to determine whether systems use their resources effi- ciently or not (Molden and Sakthivadivel, 1999; Bastiaanssen et al., 1999). In farmer’s fields, the level of water productivity obtained is determined by many factors which include management of irri- gation water (Zhang et al., 1998a; Geerts and Raes, 2009) and fertilizers (Caviglia and Sadras, 2001), selection of crop variety (Siddique et al., 1990), soil tillage (Mrabet, 2002), mulching (Huang et al., 2005), planting pattern (Giunta and Motzo, 2004), and environmental conditions which include soil type, water quality (Nangia et al., 2008) and weather conditions (Sadras and Angus, 0378-3774/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2010.05.018