Water consumption by levestock: how to calculate and optimize its use.Focus on Brazil
Résumé
Water scarcity is a risk for the planet, and agriculture’s contribution to water resource depletion is significant. It is thus important to implement methods to assess water use, especially by livestock. One method is the “water footprint”, based on calculations of blue water (from rivers and groundwater, consumed by and for livestock and to irrigate their feed crops), green water (evapotranspiration of crops fed to livestock), and gray water (a virtual amount needed to dilute water pollution). Separately, these 3 types of water are useful for managing water resources, but summing them may lead to misinterpretations; in addition, the sum is not related to wate r scarcity. Another method, life cycle assessment, generally considers only blue water but also includes off-site activities needed to produce inputs for animal production. A water stress index, a function of local water-depletion risk , is used to weigh water use to predict contribution of animal production on water scarcity. Regardless of the method, wide differences in water use exist depending upon country and type of livestock system. Attention is drawn to water resources and use in Brazil because of the importance of animal production there. Brazil has high regional heterogeneity in water resources, and water footprints can suggest ways to improve water use. Extensive recommendations are provided for reducing blue, green, and gray water use in livestock systems. Special focus is placed on ways to decrease crop irrigation. It is concluded that livestock water use needs to be analyzed in greater detail to improve water management, but that it should be done in a multicriteria approach, considering other environmental impacts at the same time
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