This chapter documents the efforts of building the Regional Initiative for Hydrological Monitoring of Andean Ecosystems. It explains the background and motivations that led to the formation of a diverse consortium of institutions with a joint interest. The chapter presents the methodological approach that the monitoring network has adopted. It discusses in brief the main results, the most relevant milestones and breakthroughs, and the major challenges remaining and perspectives in the scientific, technological and social domains. The chapter argues that the correct use of the generated knowledge, from community level to national governance entities, proves crucial to increase catchment intervention efficiency and improve water resources management. It also presents the methodological guidelines for a participatory hydrological monitoring of Andean ecosystems. The objectives of this hydrological monitoring system are to ensure that the observatories in each watershed will generate standardized data that can be used in future studies and assessments of ecosystem services.