The study delineated the watershed of Nangalisan River, which is located in Villaverde, Nueva Vizcaya using different data sources. Selected watershed morphometric parameters were derived from six data sources; namely: Shuttle Radar Topography Mission (SRTM) 90-meter digital elevation model (DEM), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) 30-meter DEM, Interferometric Synthetic Aperture Radar (IFSAR) 10-meter DEM, elevation data extracted from Google Earth using TCX Converter (GE-TCX), National Mapping and Resource Information Authority (NAMRIA) 20-meter contour interval topographic map (DMA-TOPO), and ground point elevation data survey (GPES). All three non-DEM data were transformed into DEM and thresholds, or the number of cells that define a stream, were manually iterated to more or less get similar number of streams. In general, the watershed shape, size, centroid, stream length, number of streams, stream order, and watershed relief parameters varied considerably between data. IFSAR translated into highest watershed morphometric details.

Root Mean Square Error (RMSE) was calculated to compare the elevation values taken with GPS with elevation values extracted from all six data sources. ASTER data had the lowest RMSE while DMA-TOPO got the highest.

Raster resolution appeared to have great impact on the similarity of watershed parameter outputs. It was found out that high resolution DEM yields better representation of actual condition and results are more robust for analysis. GPES appeared to be useful only for detailed topographic survey of small areas with careful attention to critical elevation points or slope breaks.

Use of high resolution DEM data to generate different watershed morphometric parameters appeared to be more reliable than use of conventional sources such as ground point survey and old topographic data in terms of consistency of results and level of details.

Keywords: Watershed, Digital Elevation Model, Morphometric Data, Nangalisan River

Thesis (Master of Science in Forestry - Forest Resource Management)

Includes appendices and bibliographical references