Incorporating Virtual Water into Water Management: A British Columbia Example

Virtual water is the water required to produce food or a commodity, and includes rainwater in addition to irrigation and the water required to grow feed in livestock systems. Measuring virtual water is a useful concept in assessing water management as it permits the comparison of crops and livestock from the perspective of embedded water. To evaluate trade-offs in water allocation in countries like Canada with large regional variability in climate, virtual water should be calculated on a watershed scale. Two watersheds in Canada were selected representing wet and dry regions, and virtual water requirements for crop and livestock products were evaluated. For both the Lower Fraser Valley and the Okanagan basins, the results indicate that the most water demanding agricultural activities are livestock and fodder production. In the Lower Fraser basin, berry crops require 32 Mm(3) of virtual water per year and have a potential value of $95 million. In contrast, the major fruit crops in the Okanagan require 63 Mm(3) of virtual water per year and have a potential value of $68 million. Blueberries and grapes which have moderately high virtual water contents have been expanding in the Lower Fraser and Okanagan basins respectively. Water to grow feed dominates overall animal virtual water requirements. Livestock requires nearly 4.5 times more virtual water per year than crops in the Lower Fraser, poultry and dairy having the largest virtual water requirements. In the dry Okanagan basin the total virtual water requirements for crops and livestock are similar. To accommodate future growth, decisions on water management will need to be made, particularly in dry basins such as the Okanagan. Virtual water calculations provide information that can assist decision makers in the strategic choices of reallocation and conservation water use.