The virtual water metaphor: Measurement concerns and associated externalities

This research addresses the virtual water metaphor as it relates to a semi-arid, agricultural production intensive region. It is motivated by previous calculations of the water content of agricultural commodities which may be misleading in the way in which they inform water policy. The dissertation addresses this concern in two ways.

First, I show that the use of a representative measure of crop water requirements can be inaccurate across relatively homogenous producing regions as well as through time. The sensitivity of these measurements suggest that continued use of the virtual water metaphor to inform water policy should only be undertaken when significant attention has been given to the methodology employed in its calculation.

Second, the use of the virtual water concept to promote increased production of high water content/low value crops in relatively water rich locations ignores the potential transfer of externalities to the production region. I evaluate four potential externalities associated with the production of irrigated agriculture in the area of Texas overlying the Southern Ogallala aquifer, with particular attention paid to the optimal rate of extraction for the non-renewable water resource.