Modeling Hydrological Appraisal of Potential Land Cover Change and Vegetation Dynamics under Environmental Changes in a Forest Basin

An integrated multi-model approach to predict future land cover in the Da River Basin in Vietnam was developed to analyze future impacts of land cover change on streamflow and sediment load. The framework applied a land cover change model and an ecological model to forecast future land cover and leaf area index (LAI) based on the historical land cover change, and these data were then used in a calibrated distributed hydrological model and a new sediment rating curve model to assess hydrological changes and sediment load in the river basin. Results showed that deforestation would likely continue, and that forest area would decrease by up to 21.3% by 2050, while croplands and shrublands would replace forests and increase by over 11.7% and 10%, respectively. Streamflow and sediment load would generally increase due to deforestation in the Da River Basin in the 2050s, in both the wet and dry seasons, but especially in the wet season. In this case, the predicted annual sediment load was expected to increase by about 9.7% at the Lai Chau station. As deforestation increased, sediment load and reservoir siltation could likely shorten the lifespan of the recently constructed Son La Reservoir. The applied integrated modeling approach provides a comprehensive evaluation of land/forest cover change effects on the river discharge and sediment load, which is essential in understanding human impacts on the river environment and in designing watershed management policies.