Increasing pressures on ecosystems in the Latin American region, as well as the adoption of multilateral conservation commitments, have led to the implementation of instruments that are economic in nature but oriented towards the recovery, conservation, and functioning of ecosystems such as Payment for Ecosystem Services (PES). In the Peruvian Andes, hydro-climatic factors and land-use changes are affecting the capacity of the ecosystems of the glaciated Cordillera Blanca to provide water services, in terms of both quality and quantity, to the main users of the Santa River basin. Thus, this study analyses how the socio-ecological interactions affect, and are affected by, the planned introduction of water-related PES in the Quillcay sub-basin, the most populated sub-basins along the Santa River basin. We use a conceptual model based on the current evolution of the water metabolism approac...