Hydrological modelling with TOPMODEL of Chingaza páramo, Colombia

Abstract

Páramo ecosystems are located on the upper parts of the tropical mountains, below the snow line areas or in isolated areas where no glacier ecosystems occur. These ecosystems are considered important for their biodiversity, but mainly because they are permanent source of water for populations located at the upper and middle parts of the Andes. Recent studies indicate that ecosystems located at high altitudes, are more vulnerable to climate change and to changes in land use, which threatens the ecosystem services derived from them. There are very few studies in these ecosystems, within which, studies on the hydrological functioning are even scarcer, which seems to be related to their position in the top of the mountains and difficulties associated with the access to them. This implies that there is a need to create tools that allow us to study these ecosystems, overcoming the current difficulties. Hydrological TOPMODEL is used to investigate the hydrological functioning of the páramo of Chingaza, through a case study in La Chucua basin. For this, we calibrate and validate the model using two data sets of climate and the hydrology of the basin (climate and discharge from 2008 and 2009, respectively). Through the calibration procedure we obtain a high efficiency value of 0.76 model (coefficient Nash - Sutcliffe), which adequately represents the hydrological behavior of the páramo. Simulations with better adjustment between measured and predicted values of discharge, have low values of surface infiltration excess runoff, indicating high water storage capacity on the soils. This agrees with the predominance of subsurface flow in studied ecosystem, given the special characteristics of soils. Results also show the large influence of factors represented in the model (topography and soils), on water basin response to rainfall events. This is significant evidence of exceptional hydrological behavior of the páramos, mainly related to the presence of soil with high organic matter content. These results imply that TOPMODEL is a robust tool, able to represent in a precise manner the hydrological functioning of the basin La Chucua, and consequently it is expected that TOPMODEL can also represent hydrological conditions of Chingaza páramo.