ILSI Europe Report Series. 2011:1-38
Many parts of the world are considered to be water stressed through a combination of decreasing reliability in rainfall and growing population. Agriculture is one of the biggest users of water and it is important to ensure that water for food production is used efficiently and sustainably.
Most work on agricultural water use has focussed on cereal crops such as wheat, rice and maize but there is a need to consider how other crops can be sustainably sourced. Vegetable oil crops are an important agricultural commodity and were chosen as a model for assessing how to judge water sustainability for internationally sourced crops and vegetable products. The main aim of this expert group was to evaluate globally grown oil crops in terms of rain and irrigated water use.
Several data sources and models were used to determine the water status for production of sunflower, rapeseed, groundnut, soybean and palm oil. The concept of green water (rainfall) and blue water (water from rivers and groundwater) was incorporated in order to make the distinction between rainfed production, production relying on irrigation and production that is a combination of the two. Data were available for all of the crops except palm oil.
The approach used was based on quantifying the effect of water limitation on crop yield by estimating soil water availability, crop water use and crop water requirements. Water availability was conceived as the amount originating from rainfall and stored in the rooted soil. The objective of the study was to estimate crop water requirements and actual water use in relation to crop yield for the selected oil crops.
The results of this study show that there are considerable differences in the green and blue water requirements of the different oil crops for different regions. The differences were the highest for soybean where in some countries twice as much water per unit of crop area is used compared to the lowest water using countries, while in terms of water productivity the differences are even larger. The differences in water use are mostly due to differences in the local climate. In warm and dry climates the blue water use is much higher than in temperate climates with high rainfall.
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