Water Yield Variation due to Forestry Change in the Head-Water Area of Heihe River Basin, Northwest China

Understanding the effects of forestation on the hydrological process is crucial to protecting water resources. In this study, the upstream Heihe River Basin is selected as the study area, which is the water source area of the whole basin. The grassland and forest are the main land use types, the proportion of which in the total land area is 21% and 50%, respectively. Firstly, a scenario of forestation was designed with the actual land cover data in 1980. Then a scenario with simulated land cover data in 1980 was established, in which the forest area increases by 12%. Thereafter a hydrological simulation was carried out with the actual and simulated land cover maps and the climate observation data during 1980-2010. The results suggested that the total water yield increased by 12.57 mm under the scenario with land use change during 1980-2010 compared with the simulation with the actual land cover in 1980. However, the results also indicated that the surface runoff reduced by 22.17 mm during the same period, indicating the forest land has "sponge" effects on the water resource in the mountainous watershed. These results may provide important information that supports operational practices, such as forest regeneration programs and watershed restoration