Simulation of a Costa Rican watershed: Resolution effects and fractals

Simulation of runoff from the Navarro watershed in Costa Pica was undertake n using the U.S. Geological Survey's Precipitation Runoff Modeling System, developed and operated within the Modular Modeling System. A geographic inf ormation system (GIS) database of watershed characteristics, and GIS-based methodology for delineating modeling response units (MRU) were utilized to enhance the spatial representation of watershed features and physical proce sses. Simulations were carried out using a series of MRU resolutions (from 90 m(2) to 1,260 m(2)) in order to determine the range through which the hy drologic response could be accurately modeled. Fractal characterization pro vided a method to measure the relationship of the MRU patterns (based prima rily on land cover) at the different resolutions. The range of self-similar ity of the MRU patterns, as determined by fractal characterization, was com pared to the range of resolutions through which accurate hydrologic simulat ions were achieved. The results from this research revealed a strong corres pondence between the two ranges, and indicate that a range of data resoluti ons may be useful in representing tropical watershed characteristics for hy drologic modeling and watershed management.