Trends in Virtual Water Export from the High Plains, 1950-2010

Water and land are both essential to humans in order to produce food. Over the last century the human population grew rapidly and with it the demand for food. One consequence is an amplified demand for water, which may cause an increase in water scarcity. A possible solution is to import virtual water, all water consumed by a product during production and processing. The United States is one of the major net exporters of virtual water because of the trade of agricultural products. The High Plains region in the central United States has experienced large land use change during the last 150 years, from grassland to one of the country’s main agricultural areas. One driver was water provided by the High Plains aquifer. The purpose of this thesis was to investigate the correlation between this land use change and virtual water exports from the area. This required quantification of the virtual water exports from the study area by volume and region for the selected commodities of wheat, corn, beef, and milk. Virtual water export is a product of the water footprint, and the export quantity and was estimated from 1950 to 2011. The water footprint was calculated using evapotranspiration estimated using the Soil Conservation Service Blaney-Criddle method and output quantity (yield, mass of product). The reported export data had limited temporal availability and limitations. Thus, a method was developed to estimate export data. Mexico was the largest importer of virtual water for corn, beef, and milk, while Egypt was the largest importer of virtual water for wheat. Further analysis showed an increase in virtual water export since 1950. The correlation between land use change and virtual water export was strong (R2 = 0.8). In conclusion, virtual water export is one driver for land use change in the High Plains. The projected increase of exports from the region will contribute to more land use change related to food production. This could increase the risk of water scarcity in the region. Therefore, importing countries have an impact on water and land use in the High Plains