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Grad student seminar: Runoff generation and land cover in the Panama Canal watershed

Thursday, February 20, 2020, 12:30PM - 1:30PM


Andrew Birch



The humid tropics are experiencing land use change at a pace which is often much more rapid than in many other parts of the world. While in many areas, forest clearing for pastoral grazing is ongoing, in others, increasing urbanization has led to the abandonment of pastoral land to forest succession. While the humid tropics receive vast amounts of rainfall, this rainfall is highly seasonal, with most occurring during only a small portion of the year. The effects of these common land use/land cover changes on the storage and movement of this seasonal water supply through the landscape are at present poorly understood, leading to poorly informed land use and water resource decision making. The purpose of this research is to address this knowledge gap, and develop a better quantitative understanding of how these common tropical land use/land covers influence hydrologic behavior. Our approach incorporated a combination of hillslope hydrometric data and various methods of geochemical end member mixing analysis from small catchments of varying land cover and land use history in the economically vital Panama Canal Watershed (PCW). Presented here are the results of our analyses, showing that changes to land use lead to dramatic differences in the seasonal water balance and storage dynamics between catchments of varying land cover. Using and end member mixing analysis (EMMA) approach, we attribute these differences to changes in the hydrologic flowpath networks activated during wet season rainfall events. While these varying hydrologic flowpath networks are dictated by minute changes to surficial soil structure following land use conversion, the resulting changes to seasonal water dynamics have major implications for any humid tropical region where a seasonal water supply must be managed in the face of environmental change.