An advanced hydrological approach for the characterization of the Water Scarcity Footprint at the sub-basin level

ISO 14046:2014 is nowadays the international standard for measuring the Water Footprint (WF) of products, processes, and organizations, following a life cycle approach. The Available Water Remaining (AWARE) is an ISO 14046-compliant characterization model to measure the WF characterization factors (CFs) at national and sub-national levels considering only the quantity aspect of the impact, named Water Scarcity Footprint (WSF). Despite being established on international consensus, AWARE is calculated with global water balance models and does not entail data of hydrological dynamics at high spatial resolution. Thus, the resulting WSF values may be inaccurate for local studies. We calculate sub-regional CFs at hyper-resolution (sub-basin scale) to highlight water shortages that are not visible using current methods and improve the reliability of WSF of products and processes. Hydrological information (i.e., water availability) was retrieved from the Italian national water balance model with 1 km spatial resolution (BIGBANG 7.0), and water consumption time series (2012-2021) were obtained at the municipality level. Results show that the recalculated CF for Tuscany (= 41.8 m³_{world equiv.} m^-3) is ∼26% higher than the original AWARE's CF, suggesting that the method is not able to capture the variability of water dynamics at the sub-basin level. WSF results for three representative crops (tomato, apple and corn) are influenced by the new CFs, increasing between 50% and 100%. The proposed approach can improve the reliability of WSF assessments and can be extended to the entire Italian territory and other territories in the world.