A multimedia fate model for assessing water consumption impacts in life cycle assessment: Proof-of-concept toward full water balance accountability

Soil-stored rainwater used by plants through evapotranspiration, known as green water, has been largely overlooked in Life Cycle Assessment (LCA), which typically focuses on surface- and groundwater (blue water). Furthermore, proper and full hydrological balance integration is still missing. This drawback limits accurate evaluation of freshwater consumption in agriculture and fails to reflect differences in impacts depending on local water availability of each water source. This study addresses this gap by developing a novel method that (1) includes soil water consumption (life cycle inventory) and its associated impacts (life cycle impact assessment) in LCA; (2) integrate vertical and horizontal water balance components within a single LCA methodology; and (3) set up a pilot watershed to develop LCI data and fate factors (FFs). The approach relies on the Soil Water Assessment Tool (SWAT+) watershed model. New agricultural LCI datasets were developed for total, green, and blue water consumption (m 3 water t −1 crop yr −1 , m 3 water t −1 crop month −1 ), along with FFs (average months, average annuals) modeling water flows across five hydrological compartments. Average annual fate factors range from 0.01 to 188 months, with groundwater showing by far the longest residence time (188.2 months) and receiving 72–77% of outflows from other compartments. Monthly, the FF range varies, but the overall conclusions remain the same. Groundwater is therefore the compartment most affected by water abstraction, whereas the use of surface water or soil water results in lower impacts. The method was applied in a watershed in the NE of Spain.