Nutritional water productivity and diets

The increase in water productivity is likely to play a vital role in coping with the additional requirement for food production and the growth of the uses of water other than in agriculture in the coming century consistent with the shift from productivity per unit land to productivity per unit water, the nutritional productivity of water is calculated as energy, protein, calcium, fat, Vitamin A, iron output per unit water input. Nutritional productivity is estimated in the agricultural context of California for the main crops and food products. In general vegetal products are much more productive than animal products. Four crops emerge as highly productive for one or several key nutrients: potato, groundnut, onion and carrot. A balanced diet based on these four crops requires a consumption of water (evapotranspired) of 1000 l per capita per day, while the current needs for the diet in the USA is 5400 l, and 4000 l for developed countries. On the basis of nutritional productivity analysis it is further demonstrated that a signi®cant part of the additional water resource to produce food for the next century population can be generated by changes in food habits. A reduction of 25% of all animal products in the developed countries' diet generates approximately 22% of the additional water requirements expected by the year 2025. # 2000 Elsevier Science B.V. All rights reserved.