This article proposes some considerations on the relationship between the water balance for five municipalities located in the basin of the Seco river, Alto Magdalena region, and the municipality of Beltrán, Cundinamarca, Colombia, and the risk factors for the sustainability of the water supply to which the communities are exposed. For this purpose, a statistical review was made of official sources that record the historical and current status of the minimum and maximum levels of the annual flows of the tributary, and the exponential growth of the population in the region. Risk factors were documented based on direct observation, focus groups and interviews with social and institutional actors. In some municipalities the balance is unfavorable due to factors such as extractivism and the urban explosion, while in others the sustainability of the supply depends on the construction of infrastructure to guarantee the supply in dry weather.