alfalfa acreage is converted to corn, but increase if cotton or sorghum is converted (R.Allen, Univ. of Idaho, written commun., July 12, 2007. Data from Durwood et al. ).
Given the regional differences in rainfall and groundwater storage, the feasibility and sustainability of biofuel crop production as a function of water availability may vary significantly by region. Figure 2-2 shows the state-by-state water requirement of irrigated corn in the continental United States. It demonstrates that the amount of rainfall and other hydroclimate conditions in a given area causes significant (10-fold) variations in the water requirement for the same crop. Clearly there will be geographic limits on certain kinds of biofuels feedstock simply based on their water require-