Consensus building results on the new scarcity indicator from WULCA

Abstract

The need for consensus-developed and recommended methods for water use impact assessment is clear in order to perform a water scarcity footprint consistently with ISO 14046:2014 and for consistently assessing water consumption impacts in LCA. This challenge was undertaken by the WULCA working group, of the UNEP-SETAC Life Cycle Initiative in 2013. Including method developers and experts from different fields, the group developped a consensus-based indicator to assess impacts from water comsumption at the midpoint level, complying with the requirements of the ISO document. This work presents the recommended methodology for performing a water scarcity footprint including a case study application. The process started with the identification of the question to answer and three proposals which emerged from the three expert workshops held in Zurich, San Francisco and Tzukuba in 2014. The group then selected criteria used to evaluate the proposals which led to a preliminary recommendation presented in 2015. From this recommendation and the testing phase that followed, additional specific and influential modeling choices were identified, analyzed and adjusted accordingly, and sensitivity analysis were performed on the most uncertain aspects. These choices and analysis are presented, which include the span of the indicator, the different choices of spatio-temporal aggregation and their meaning when the native resolution of the indicator cannot be used, and the sensitivity of the environmental water requirement (EWR) parameter. The resulting and consensus-based single metric, covering the entire globe, modelled at various temporal and spatial scales for application in LCA, is presented in details along with the interpretation and application on the rice case study. The group is proposing the result of its work and new consensus-based indicator with the expectation that it will be adopted widely and hence decrease disparity and confusion when it comes to applying the new ISO standard on water footprinting, by providing an internationally approved, robust and simple indicator for assessment of potential impacts from water consumption.JRC.H.8-Sustainability Assessmen