Towards Sustainable Municipal Drinking-Water Services: Long-Term Efficiency, Management Models, and Spatial Interdependence in Andalusia, Spain

Sustainable municipal drinking-water provision requires not only reliable infrastructure and universal access but also the efficient use of financial and organisational resources within heterogeneous territorial contexts. This study examines operational and governance dimensions of sustainability in municipal drinking-water services in Andalusia, Spain. First, robust order-m panel-data frontiers estimate efficiency for 309 municipalities over 2014–2024, comparing direct public management, private management, and intermunicipal cooperation. Second, spatial-panel models examine territorial interdependence and efficiency determinants for 205 municipalities over 2019–2023. No management model achieves the highest mean metafrontier cost efficiency across all population groups. Intermunicipal cooperation leads in municipalities with fewer than 20,000 and more than 50,000 inhabitants, whereas direct public management leads in the 20,000–50,000 group. Private management has lower mean efficiency than intermunicipal cooperation in all groups but exceeds direct public management in the smallest group. Spatial dependence is positive but modest. Per capita income and municipal debt are negatively associated with efficiency, while citizen participation and political orientation moderate the effects of unemployment and debt. The findings highlight the relevance of management design, intermunicipal coordination, and local institutional conditions as relevant to sustainable drinking-water provision informing local governance strategies aligned with Sustainable Development Goal 6.