ABSTRACT
In the face of stable or even diminishing water supplies in some areas, how can agricultural systems produce more food? Exploring answers to this question forms the basis of this chapter. Most human food is derived from primary production processes that take place in agricultural ecosystems. Plant production is directly associated with water consumption through the transport of water by plants from the soil to the atmosphere, a process called transpiration. Thus, for each unit of biomass production, there is always some water that evaporates into the atmosphere. We define here water productivity (WP) as the ratio of crop production to water consumption (quantified in physical terms as kg/m3, or as $/m3 in economic terms). Before engaging in the assessment of how to improve WP in food production, it seems instructive to first examine the current state and productivity levels of agricultural systems.
