Water consumption is an impact category in Life Cycle Assessment that quantifies the use of freshwater resources by a product system throughout its life cycle. This category measures the volume of water consumed rather than simply withdrawn, focusing on water that is removed from its source and made unavailable for other users and ecosystem functions within the same drainage basin during the same time period.
ISO 14046 provides guidance on water footprint assessment as part of LCA, distinguishing between water withdrawal and water consumption. Whilst withdrawal refers to the total volume of water taken from a source, consumption specifically accounts for water that is evaporated, incorporated into products, transferred to another drainage basin, or otherwise made unavailable for immediate reuse in the local watershed. This distinction is crucial for understanding actual water resource depletion rather than temporary water use.
Water scarcity weighting represents an important methodological advancement within this impact category. Rather than treating all water consumption equally, water scarcity methods account for the regional availability and stress level of water resources. Areas with abundant water resources have lower characterisation factors, whilst regions experiencing water stress or scarcity have higher factors, reflecting the greater environmental significance of consuming water in water-scarce locations. This spatially differentiated approach provides a more accurate representation of potential environmental impacts.
Different LCIA methods approach water consumption with varying levels of sophistication. Basic methods may simply quantify the volume of freshwater consumed. More advanced approaches, such as the AWARE method recommended by UNEP, incorporate water availability indices that reflect both the scarcity of water in a region and the demand from human activities and ecosystems, providing characterisation factors that vary by location and time period.
