Understanding blue and green water for feed production in animal agriculture

Abstract Text: Increasing demand for animal protein combined with concern about water scarcity demands thoughtful considerations of the water footprint of animal agriculture.  This water footprint can be discussed in the context of green water which is rainfall that does not become runoff, and blue water which is surface or groundwater that is consumed as a result of the animal production system.  Much of the green and blue water utilized by animal agriculture provides for the production of grain and forages. As such the type of feed utilized by specific animal production systems can dramatically influence the water footprint of the system.  Grazing systems will generally result in larger water footprints than grain based production systems because the higher quality grain based systems provide for more gain per unit of water used.  However, this reduced water footprint come with increased environmental impacts such as erosion and offsite nutrient losses from the grain production systems.  Furthermore, pasture based systems overwhelmingly utilize green water which would likely be consumed at similar rates if the pasture was used for meat production or wildlife habitat.  Lastly, regional differences in soil type, rainfall distribution and atmospheric water demand (evapotranspiration) also influence the water footprint of animal agriculture by impacting crop water use efficiency. 

Keywords: life cycle analysis, groundwater, feed production