Water erosion is one of the main problems linked to tropical soils
management, being the surface runoff responsible for the most part of sediments
transported and deposited. This study has as objectives to determine total surface
runoff and peak discharge, and to generate concentrated semi-empirical
hydrological models, applying these models to soil losses model “Modified
Universal Soil Loss Equation – MUSLE”, on a watershed occupied by
eucalyptus plantations and native forest, in the Coastal Plain region, Aracruz
county, Espirito Santo state, Brazil. Yellow Argisol medium/clayey texture
(PA1), Yellow Argisol moderately rocky (PA8), and Haplic Plinthosol (FX) are
the main soil classes of the watershed. Hydrological data were monitored
between 1997 and 2004, with rainfall data being collected by automated weather
station for obtaining the hyetograms. Hydrographs were generated with
discharge data from precalibrated weir, with water-sensor level, installed on the
stream flow control section of the watershed. Soil moisture was monitored up to
1.6 m depth. CN-SCS method did not produce good accuracy, overestimating
the runoff and peak discharge for individual rainfall events. Semi-empirical
models, based on rainfall characteristics, showed good estimates, and can be
used for hydrological simulation. MUSLE model showed to be appropriated for
soil losses predictions on the watershed being recommended the “a” and “b”
coefficients equal to 14.96 and 0.59, respectively, with a topographical factor of
1.28. Soil use and management adopted on the watershed showed to be
conservative, and this can be confirmed by the low soil losses on the watershed
balance and on the stream flow control section.
