Hydrological modeling in the Andean highlands: climate change scenarios in Chingaza páramo, Colombia

Abstract:

The páramos provide multiple ecosystem services to large cities, especially water supply. They are considered highly vulnerable ecosystems to changes in environmental conditions, including climate change. Despite its importance, In Colombia few modelling efforts have been made relating with its ecohydrologic functioning. In this research, TOPMODEL was applied in The Chucua basin with the aim of understanding the hydrological functioning on the páramo, and to forecast the effects caused by hypothetical scenarios of climatic change. Calibration and validation was performed with a number of data flows (2008-2009), and a maximum value of 0.76 efficiency model was obtained (Nash-Sutcliffe) suitable to represent the hydrological behavior of the páramo. Climate change scenarios for 2030 were tested using an assembly of parameters which presented a physical meaning, smaller value of infiltration excess overland flow, and a high Nash-Sutcliffe index. Simulation results exhibited low values of infiltration excess overland flow. This indicates high buffering capacity of the soil, and coincides with the predominance of subsurface runoff, given to the presence of special characteristics on soils, which present exceptional hydric behavior in these ecosystems. Future climate change scenarios revealed significant effects in simulated volumes (reduced up to 10%), especially when the precipitation was considered, in comparison with the role of increasing temperature on the runoff. The páramo seems to be adapted to drastic variations in temperature due to the characteristics of vegetation; although that is not the only variable that influences the potential evapotranspiration. On the other hand, there is a significant effect of the amount of available water on the water yield in the basin. The ecohydrological knowledge of the páramos in Colombia could be extended using TOPMODEL as a useful tool to understand the hydrodynamics of strategic ecosystems for water supply, under projected scenarios of climate change.