A soil water balance model for monitoring soil erosion processes and effects on steep lands in the tropics

Abstract

Water erosion is the major threat to soil and water conservation in the steep lands of the tropics. Besides surface erosion on gentle to moderate slopes, mass movements are common on steep slopes. In addition to the negative effects on productivity and crop production risks, in many tropical regions, offsite effects of sedimentation, floodings and landslides are also rooted in accelerated soil erosion. The prediction of water erosion by direct measurements in erosion plots, or by using empirical models has not generally given satisfactory results in the tropics, specially when mass movements are the potential erosion processes. Modeling the surface soil hydrological processes, under the prevailing conditions of climate, use, management and cropping in two selected sites of Venezuela, resulted in fairly accurate simulations of both the soil surface and landslide erosion processes and their main effects. The model SOMORE, used for such simulation, is based on easily available climate and soil input parameters, and produces as the main output the soil moisture regime in a daily basis, including the average soil moisture at root depth, and the water losses by surface and subsurface runoff, and by internal drainage. The output of the model is used as the basis for the selection, with a probabilistic approach, of the best alternatives of use and management of soil and water resources for each combination of soils, climate and topography.