SEDIMENT SOURCES OF TYPICAL SMALL WATERSHED IN GRANITE AREA OF THREE GORGES, YANGTZE RIVER

摘要

Once the hydro-junction engineering in the Three Gorges of Yangtze River is finished, sediment will be one of the important factors that endanger its safe operation. Research on the sediment sources in small watershed of Three gorges area can guarantee hydro-junction engineering's safe operation. In a selected typical small watershed, several soil profiles were dug, and the relationship between physical characteristics of soil under different types of land utilization and soil erosion was analyzed through the investigation of soil erosion, the observation of sediment and runoff in slope plot. The quantity of soil erosion in different slopes and gully under different types of land utilization was measured, and the proportion of soil erosion quantity to the total sediment yielded from watershed was calculated. The results show that the characteristics of soil grain under different types of land utilization are closely correlated to the extent of soil loss. With the increasing of soil loss, the sorting coefficient for soil particle diameter of A layer decrease in different types of land utilization. The symmetry of diameter groups is low in different types of land utilization. Sediment in granite area of Three-gorges mainly originates from soil erosion in slope. Sediment yielded from slope chiefly comes from arable land located at slope, and the quantity of sediment yielded from arable land located at the slope above 25 ° accounts for about 50% of the total sediment yielded from slope.