Water footprinting of agricultural products: a hydrological assessment for the water footprint of New Zealand's wines

Agriculture plays a key role in relation to global water stresses. Increasingly, water footprints (WF) are being used to indicate the impacts of the water use by production systems. International standards for WF are being developed and this paper contributes to these from a hydrological perspective. The impacts of water use through the life cycle of grape-wine production on water resources were assessed for two regions in New Zealand: Marlborough and Gisborne. The functional unit (FU) was a 750-mL bottle of wine at the winery gate. The WF was assessed using a full water-balance calculated by subtracting inflows from outflows. The net usage from groundwater and soil moisture storage was quantified as blue and green water footprints. We found a large variability of blue-WF even within a region. For the grape-growing stage, the average blue-WF was negative, at -81 L/FU and -415 LIFU for Marlborough and Gisborne indicating the water resources are being recharged on an annual timescale. The green-WF was negligible. The grey-WF, water required to dilute NO3-N leached in the vineyard phase, was 40 and 188 L/FU for Marlborough and Gisborne. However, the average concentration of NO3-N in the leachate was well within the drinking water standard of 11.3 mg/L (5.01 mg/L and 8.7 mg/L for Marlborough and Gisborne). The impacts of the winery phase were very small compared with that of the vineyard. The variability we have found indicates the importance of considering water issues at the local scale. Locale is the essence of terroir for wine. (C) 2012 Elsevier Ltd. All rights reserved.