Consensus building on the development of a stress-based indicator for LCA-based impact assessment of water consumption: outcome of the expert workshops

The WULCA consensus characterization model for water scarcity footprints: assessing impacts of water consumption based on available water remaining (AWARE)

“…In LCA, indicators aim at quantifying potential environmental impacts of human interventions (such as water use or consumption) ultimately affecting three areas of protection: human health, ecosystem quality, and resource depletion (Jolliet et al 2004). Preliminary discussions within this working group identified the relevant question from an LCA perspective regarding potential impacts of water consumption at the midpoint level to be BWhat is the potential to deprive another freshwater user (human or ecosystem) by consuming freshwater in this region?^ (Boulay et al 2015a). Note that potential deprivation from water degradation, as assessed in Boulay et al (2011d) was not included in this indicator in order to avoid risks of double counting with water quality indicators when applied systematically.…”

“…Hence, subsequently, methods based on water consumption-to-availability (CTA) ratio were developed, with the reasoning that water withdrawn from the environment and released in the same watershed (for cooling purposes for example) does not generally contribute to local water scarcity (Boulay et al 2011c;Hoekstra et al 2012;Berger et al 2014) (even if local impacts may occur between the withdrawal and release points (Loubet et al 2013)). Outcomes from expert discussions within WULCA (Boulay et al 2015a) first identified the need to transition from WTA and CTA towards a demand-to-availability ratio (DTA), in order to better answer the overarching question identified above (Boulay et al 2014) since both ecosystem water demand and human consumption are considered in Bdemand.^The proposal was accepted by a panel of 48 LCA experts from academia, industry, and governmental institutions (Boulay et al 2015a) with, however, one main limitation identified, in addition to the challenge associated with quantifying ecosystem water demand. The DTA ratio (similarly to CTA and WTA) fails to represent the absolute water availability (per unit of surface).…”

“…For example, a DTA ratio of 0.5 describes that half of the water is required by current users, but whether this amount of water is 10 or 1,000,000 m 3 for the same area is unknown. This sometimes leads to arid areas showing less scarcity than known water-abundant regions (Berger and Finkbeiner 2013) and the relevance of this for LCA application can be questionable (Boulay et al 2015a). Three proposals emerged during the workshops, as described in Boulay et al (2015a) that could overcome this limitation, called DTA A , DTAx, and 1/AMD.…”

“…This sometimes leads to arid areas showing less scarcity than known water-abundant regions (Berger and Finkbeiner 2013) and the relevance of this for LCA application can be questionable (Boulay et al 2015a). Three proposals emerged during the workshops, as described in Boulay et al (2015a) that could overcome this limitation, called DTA A , DTAx, and 1/AMD. DTA A is based on a demand-to-availability (DTA) ratio but includes a filter for arid regions.…”

“…However, to date, no consensus-based approach exists to assess water scarcity impact as illustrated by the technical report (ISO 14073 2016) accompanying the ISO 14046 standard (ISO 14046 2014). It presents a series of water scarcity footprint examples which are simply not directly comparable, because the characterization models have different scales and ranges, and are based on different modeling choices, with some more human health or ecosystem quality oriented (Boulay et al 2014). The need for a consensus-based method emerged from method developers and several environmental label and declaration initiatives wishing to use global metrics and ensure comparability (Galatola and Pant 2014;ISO 14046 2014;Boulay et al 2015b) and was identified as priority by the UNEP-SETAC Life Cycle Initiative (Jolliet et al 2014).…”