Forest change: hydrological effects in the Upper Yangtze River valley

摘要

Forest change in the Upper Yangtze River valley can impact the hydrological features of the region. For 100 years, forest areas in the Yangtze River valley have been decreasing. At the end of 1970s, forest coverage reached to its lowest point. After 1980, great efforts have been made to construct a shelter- forest system in southwestern China. Vegetation has gradually recovered in the Upper Yangtze valley. Forest coverage ratio has risen from 13% in 1978, to the current 21% for the Sichuan Basin. Reforestation has improved ecological conditions. The low flow rate and regional water conservation index of the river have increased in the past ten years, and the runoff coefficient for all watersheds in the valley has risen. The low flow rate has shown an increase or has stabilized. Regional soil loss is now under control. The average content of suspended sediment in the stream flow for a key station on the Yangtze River has changed from 1.14 kg m~(-3) before 1989 to 1.05 kg m 3 after 1990. These results show that the hydrological conditions in the Upper Yangtze valley is improving and will benefit further from reforestation.