Human resources are one of the most important assets of water utilities (WUs), being responsible for assuring systems management and playing an important role in the tacit forms of organizational knowledge. In organizations with responsibility for managing extensive, diverse infrastructure with long life-cycles, with adequate service and acceptable risk levels, knowledge transfer between peers should be assured to maintain a stable human resources framework. In WUs, strategic asset management should include the long-term planning of human resources alongside urban water infrastructure assets, to ensure service sustainability. Based on these assumptions and driven by the legal obligations in developing infrastructure asset management plans, Administração e Gestão de Sistemas de Salubridade, S.A. (AGS) created and implemented a novel personnel aging index (PAI) with the main goal of evaluating the human resources framework, including employee ages and professional categories, and the remaining time needed to transfer knowledge to new members of staff. This paper describes AGS' approach to human resources management under the asset management policy and PAI's formulation. A case study with 10 AGS WUs is presented, aiming to evaluate their teams' maturity level and allowing comparison between WUs.