The distributive water metric: A justice-sensitive diagnostic framework for water scarcity assessment

Water scarcity metrics, from the Falkenmark indicator to SDG target 6.4.2, shape what governments, donors, and international organisations see, and therefore what they govern. Yet despite their considerable governance effects, these metrics remain dominated by aggregate, single-number approaches that systematically obscure distributive inequalities, groundwater depletion, transboundary power asymmetries, virtual water trade, and supply-side bias. Existing scholarship has shown that water quantification is political and has called for integrating justice into environmental assessment. Household-level metrics have demonstrated that measuring intra-country variation is feasible. However, there is a need to translate these insights into an operational reform of the scarcity metrics that govern global adaptation finance and SDG monitoring. This paper addresses that gap by developing a diagnostic architecture that connects established aggregate measures to indicators of distributional outcomes, governance, power, and sustainability. First, the paper provides a systematic genealogy and critique of dominant water scarcity metrics. Second, it introduces the Distributive Water Metric (DWM), a diagnostic framework that supplements aggregate scarcity measures with indicators of distributional outcomes and governance, power and sustainability. Third, it discusses implications for SDG monitoring, donor finance, and environmental governance. The paper concludes that effective water governance requires metrics capable of rendering distributive outcomes visible, because what scarcity metrics fail to see, governance systems rarely address.