Index of Sustainability of Water Supply Systems (ISA): An Autonomous Framework for Urban Water Sustainability Assessment in Data-Scarce Settings

Urban Water utilities in low- and middle-income countries face systemic challenges, including data scarcity, institutional fragmentation, and aging infrastructure, that constrain the applicability of conventional benchmarking tools reliant on peer comparisons. This study introduces and validates the Index of Sustainability of Water Supply Systems (ISA), an autonomous diagnostic framework that evaluates sustainability without external references. The ISA integrates 49 indicators across economic, social, and environmental dimensions, transforming raw utility data into standardized quality scores through non-linear conversion functions and weighted aggregation. When applied to 14 urban water systems in southern Ecuador, the ISA revealed severe sustainability deficits: all scored between 25 and 43 on a 0–100 scale, with 71% classified as poor and 29% as deficient. Key weaknesses included inadequate cost recovery, network renewal below 0.2%/year, lack of wastewater treatment, limited watershed protection, intermittent supply under 12 h/day, and persistent water quality issues. A critical failure was an Infrastructure Leakage Index > 38 in 7 of 14 systems. The ISA’s autonomous design enabled identification of systemic vulnerabilities, including governance gaps and environmental deficits. These results confirm the ISA’s practical utility as an equitable, actionable diagnostic tool for utilities and regulators to prioritize interventions and advance SDG 6 in data-constrained settings.