ABSTRACT
Water is a key component in food production, deeply involved in the photosynthesis process. Water also carries nutrients through the plant from the roots to the leaf surfaces where it gets lost when stomata open to take in carbon dioxide from the air. Although agriculture is often referred to as the largest water-consuming activity, this generally refers to irrigation (70 percent of total withdrawals) and consumptive blue water use only. In reality, water use for food production is more complex, including also the green water resource (soil moisture from infiltrated rainfall). When including green water, the consumptive water usage is in the order of three and a half times more than generally stated. On the other hand, agricultural water usage as a whole – some 7,000 km3/yr – corresponds to only 6 percent of the 110,000 km3/yr of continental precipitation.
