In the Norte de Santander and Santander departments of north-eastern Colombia, the unique Santurbán Páramo mountain grasslands supply a rapidly changing population with critical water resources and ecosystem services. However, unsustainable land use practices, discharge of untreated wastewater, and illegal mining are affecting the ecological health of the páramo ecosystems and jeopardizing the crucial water-provisioning, purification, and regulation functions on which all downstream residents depend. To address these threats to water security, multiple actors in the region have joined together to adopt a water stewardship approach to protect local water resources. Taking immediate action also makes economic sense, especially for local businesses—delaying interventions such as water stewardship and conservation could result in significant ecosystem degradation, water contamination and water shortages, hurting local businesses and communities. To avoid these negative outcomes and address them collectively, local groups have formed a multi-stakeholder cooperation platform, the ‘Alianza BioCuenca.’ Within this partnership, the public, private, and civil sectors are working together to find solutions to ensure the region’s water security, for the benefit of the millions of people in the region and downstream.