Land use and climate change impacts on mountain watershed hydrology in data-poor humid tropics

Abstract:

The tropical low latitudes characterized by livelihood supporting multi-use landscapes are experiencing climate shifts more significant than elsewhere on the planet. In these regions, land use induced changes to soil matrix and macropore hydraulic conductivity affect the processes of percolation, lateral flow, and overland flow generation. This leads to altered watershed and stream hydrology. To distinguish the influences of climate and land use on stream hydrology, we used a distributed physical hydrology model to describe and predict watershed hydrology under variable land use and climate conditions. The GIS-based model can simulate the hydrological response to specified land use configurations in a watershed when limited precipitation and soil data are available. We simulated the rate that precipitation travels through three watersheds located in the central highlands of Costa Rica and explored how resilient this travel time is to different climate conditions and land use distributions. The model revealed abrupt changes in simulated stream hydrology resulting from land use conversion and increases in precipitation intensity. Our findings suggest that decreased soil storage capacity associated with deforestation leads to increased overland flow and peak flow magnitude, reducing the hydrologic resilience of watersheds to predicted increases in precipitation intensity associated with climate change. A sensitivity analysis of the model parameters showed that the impacts of land use more significantly alter watershed hydrology than climate parameters.