[EN] Water indicators and indices are useful tools to assess river basin performance, that is, to measure whether the basin operates satisfactorily under a wide range of possible future demands and hydrological conditions. Spanish regulations assess the performance of water demands by using reliability indicators (RIs), established by law in 2008. This article raises the possibility of updating RIs by comparing them with sustainability indicators (SIs). SIs are widely used for the assessment of river basin performance and several policy scenarios. We applied a water allocation model to the Guadiana River basin in Spain to compare indicators under three scenarios. The study was framed within the science of socio-hydrology, combining the physical environment of a water system with its influence on social aspects. SIs gave better results than RIs when comparing future scenarios. We also propose the introduction of a vulnerability indicator into Spanish regulations. The authors thank the Spanish Research Agency (MINECO) for the financial support to the ERAS project [CTM2016-77804-P], including EU-FEDER funds. Additionally, we value the support provided by the European Community in financing the project IMPREX [H2020-WATER-2014-2015, 641811].