The conversion of natural grasslands to both pine plantations and cultivation was studied in the South American tropical alpine ecosystem called páramo. Hydrological and meteorological data were collected from four microcatchments, each with predominant vegetation,. The water balance was analysed in order to obtain the evapotranspiration of each catchment. The natural grasslands catchments had the lowest evapotranspiration. Evaporation in the cultivated catchment was about 20-40% higher, compared to 40-70% in the pine catchment. Flow duration curves were derived from the discharge time series and used to assess differences in the hydrological response of the catchments. The cultivated catchment is characterized by a significantly faster hydrological response than the natural catchment. The flow duration curves show higher peak flows and lower base flows. In the pine catchment, both peak and base flow are drastically lower because of higher local consumption. In the past, pine plantations have been widely considered as a viable method to improve the economic return of the páramo. In view of the importance of the páramo as a water supplier, these activities might need to be re-evaluated.