SOIL AND WATER CONSERVATION IN THE CHILEAN PATAGONIA: A WATERSHED MANAGEMENT PLAN BASED ON A WATER EROSION GIS APPLICATION

The use of water erosion models coupled to geographic information systems (GIS) has simplified the soil loss analysis at the watershed scale. Models such as the Geo-spatial interface for the Water Erosion Prediction Project model (GeoWEPP) are able to determine erosion, distributed spatially and temporally. This study presents an application of this model in the Serrano River basin, located in the southern Chilean Patagonia. The dominant land use of this watershed is native forest which requires a management plan to allow forest explotation. In order to produce a conservation plan for the basin, a biophysical model was built and implemented in GeoWEPP. The model represented at a high spatial resolution the soil and climatic conditions, topography and existing vegetation. For the development of the conservation plan two scenarios were modelled: the actual condition of the basin and a condition without vegetation. Additionally, hillslope simulations were also undertaken to evaluate slope effects. The results showed that the presence of vegetation cover was the main factor controlling soil loss in the watershed. Once vegetation was removed, the slope was the factor that controlled erosion. From these results priority areas for the protection of soils were identified and a map of the river basin management was built. The map provides a guide for protecting the soils in the study area and the procedure followed in this study can be used as an example for designing soil conservation plans at watershed scale.