A reconnaissance field survey was carried out in the study area.
Geological and topographic maps were used in combination
with aerial photographs of appropriate scale. Land use units
were delineated on the photographs and verified in the field.
Land use classifications, soil conservation practices and other
factors of each land use unit were recorded. Soils were mapped
by delineating units on the aerial photographs and subsequently
verified on the ground. Profile descriptions were recorded
according to the description manual for soil profiles. A total of
32 soil samples were taken with at least one set of soil sample
taken from each mapping unit. The physical and chemical
properties were determined using standard laboratory
procedures. Rainfall data from 1983 to 1996 were obtained
from the one meteorological station located within the
Taipingxi watershed (2614 ha). A 1:10,000 topographic map,
including the Taipingxi watershed, was input to the GIS by
manual digitization with TOSCA. An interpolation routine was
employed to derive the elevation surface from the rasterized
line data. The digital elevation map (DEM) was used as the
base for other topographic-related analyses. The soil, land use,
and other related attributes were input to the GIS by manual
digitization and keyboard entry. The polygons and their
attributes were connected with uniform code. These vector
maps were also converted into raster, which had the same
reference system and resolution as the DEM. The data sources
were integrated in the GIS with grid-cell format. Each defined