Event-Based Runoff Across Changing Land Covers in the Panama Canal Watershed: A Synthesis of Hydrophysical Measurements and Hydrochemical Tracers Using Hydrograph Separation

Tuesday, 16 December 2014
Guy Litt, University of Wyoming, Laramie, WY, United States, Chris Gardner, Ohio State University, Columbus, OH, United States, Fred L Ogden, Univ. of Wyoming - Dept 3295, Laramie, WY, United States and William B Lyons, Ohio State Univ, Columbus, OH, United States
Tropical hydrology is understudied relative to its temperate counterparts and thus presents challenges for understanding catchment runoff behavior undergoing land use change. Combining hydrometric and hydrochemical observations can shed light on potential differences in runoff processes under changing land covers. We compare event-based dual member hydrograph separations across humid tropical lowland forest (142 ha), mixed land use (176 ha) and pasture (36 ha) catchments following two years of monitoring during the seasonal dry to wet season transition. Stable water isotope and electrical conductivity tracer event water fraction estimations agree well during small runoff events, but exhibit different results during a large runoff event with a greater runoff coefficient. Geochemical tracers exhibit event water fraction maximums during hydrograph recessions and a seasonal transition in runoff behavior among all land uses. From these results we identify potential runoff mechanisms in these steep humid tropical catchments under varying land uses.