Resolution, fractal characterization and the simulated hydrologic response of a Costa Rican watershed

Two objectives were pursued in this dissertation. The first was to develop a geographic information system (GIS) database, and an improved methodology for characterizing watersheds to provide parameters for use in a hydrologic model. The second was to utilize the database and model to determine the optimum range of resolutions at which to represent hydrologic response units (HRU) to simulate runoff in a Costa Rican watershed.;To attain the first objective, a GIS database of watershed characteristics was created for the Navarro watershed in Costa Rica. The database included land cover classifications derived from Landsat Thematic Mapper digital satellite imagery. To improve the land cover classifications, topographic normalization routines developed in a temperate region were tested in the tropical environment of central Costa Rica.;The GIS database was then utilized to develop an improved methodology for delineating HRUs which provide parameters for the U.S. Geological Survey's Precipitation Runoff Modeling System (PRMS). HRUs are units of a watershed partitioned on the basis of characteristics such as vegetation type, precipitation distribution, slope, aspect, and soil type (Leavesley et al. 1983).;To accomplish the second objective simulation of runoff from the Navarro watershed was undertaken using the GIS database of watershed characteristics, and the improved methodology for delineating HRUs. The accuracy of the simulated hydrologic response of the Navarro watershed was sufficient to warrant further analysis.;Simulations were then carried out using a series of 14 HRU resolutions from 20m to 1260m, in order to determine the range through which hydrologic response could be accurately modeled. Fractal characterization, a method to measure the relationship of the HRU patterns (based primarily on land cover) at different resolutions was also carried out. The range of self-similarity of the HRU patterns, as determined by fractal characterization, was compared to the range of resolutions through which accurate hydrologic simulations were achieved.;The results from the dissertation revealed a strong correspondence between the two ranges, and the research provided contributions in several areas.