Modelling the impact of afforestation on average annual streamflow in the Loess Plateau, China

To prevent severe soil erosion and to ensure sustainable development, the Chinese Central Government mandated in 1999 that forest cover would be significantly increased in the Loess Plateau, China. It is important to assess the subsequent impact on streamflow and its spatial distribution in the region. The water balance model of Zhang et at. (2001) was used in this study, and the results showed that the model was able to accurately Simulate average annual evapotranspiration (ET), but not average annual streamflow when compared with streamflow measurements from 38 hydrologic stations in the coarse sandy hilly catchments (CSHC) in the Loess Plateau. The model was then calibrated using the measured streamflow, and the index of agreement increased from 0.21 to 0.63, the relative error and root mean square error decreased from 42.7 and 17.2 to 18.0% and 7.9 mm, respectively. Hierarchical cluster analysis and stepwise regression were employed to regionalize the optimized model parameter and relate it to the dryness index and forest cover. Once calibrated, the water balance model was used to assess the impacts of two plantation scenarios on streamflow. The two plantation scenarios assume nearly 5.8 and 10.1% of the study area can be planted with trees. It was predicted that streamflow from the region will decrease by 5.5 and 9.2% under the two plantation scenarios. The rate of streamflow reduction decreased from southeast to northwest mainly due to decreasing precipitation. Copyright (c) 2007 John Wiley & Sons, Ltd.