A Panama Canal Watershed Experiment: The Agua Salud Project
Does reforestation result in more or less dry-season runoff in the seasonal tropics? The Agua Salud project, managed by the Smithsonian Tropical Research Institute (STRI), aims to answer this question. Our study is being undertaken within the Panama Canal watershed, on lands adjacent to the old regrowth Soberanía National Park, which is in the former U.S. Canal Zone. Over the past two years we have planted over 150,000 trees, both native timber species and teak, in catchments that were until recently grazed pastures. We have instrumented these plantation catchments as well as control catchments that consist of pasture, old re-growth forest, early secondary succession, and an invasive grass species Saccharum spontaneum. Instrumentation installed to date includes 16 on-stream weirs in catchments that range from 8 to 400 ha, a network of triple rain-gages, two eddy-covariance systems, a surface energy balance station, 10 shallow groundwater monitoring wells, and automated water quality samplers. Studies completed to date include throughfall studies and soil analysis, a 25-year chronosequence in 108 secondary succession plots, and LiDAR overflights. Work in progress includes above- and below-ground carbon analyses, monitoring of all hydrologic and meteorological variables, and tracer studies using both natural and introduced tracers, as well as observations of shallow subsurface flow using electrical resistivity tomography at the hillslope scale. We are also educating large numbers of undergraduate, graduate, and post-doctoral students in the important field of tropical hydrology, in collaboration with Panamanian universities. Data and observations will guide the development of conceptual and physics-based hydrologic models to enable predictions of the effect of reforestation on the water-balance at time scales ranging from single-events to annual. Models will be used to up-scale knowledge developed at the plantation and catchment scale to the entire Panama Canal watershed. Knowledge gained and models developed will help aid in land-use management decisions in Panama, the Caribbean basin, and much of the mountainous seasonal tropics. Our project is working in close cooperation with the Panama Canal Authority and the National Environmental Authority of Panama.