This article highlights the economic and ecological value of the water resource systems of Ecuador's páramo and montane forest region and gives a description, based on a survey of recent literature, of the mechanisms controlling the rainfall–runoff process and how changes in land use alter the transformation. The review reveals that available understanding is partial, the result of individual and isolated research efforts, and is hindered by a lack of long-term complete and consistent data sets. Available knowledge does not yet permit up- and downscaling of findings. The article concludes by (1) citing some of the major gaps that impede hydrological understanding of the tropical Andean ecosystems and (2) proposing recommendations to speed up understanding and development of policies and measures to guarantee ecologically safe and sustainable development of the fragile water-based ecosystems of Ecuador's tropical Andean region.