黄土高原藉河流域近50年输沙量变化及影响因素分析

Changes of sediment yield in Jihe watershed on Loess Plateau in past 50 years

根据黄土高原丘陵沟壑区藉河流域1962-2008年输沙量数据,对该流域输沙量变化进行了趋势分析及检验。结果表明:年输沙量呈显著下降趋势,并于1976年发生突变,其年内分配极不均匀,汛期输沙量占全年比例达98.8%;流域降雨量没有发生明显趋势性变化,对输沙量减少的影响不大。70年代中期后人类活动引起的地表覆被变化对输沙下降影响显著,主要原因是流域坡耕地明显减少而梯田大范围增加,表明水土保持工程措施等对流域径流输沙过程起着重要作用。

The sediment yield change in 1962 to 2008 in the Jihe watershed on the hilly Loess Plateau is ana- lyzed and tested. The results show that the annual sediment yield presented a distinct decline in the research period, and its change point appeared in 1976. The monthly distribution was extremely uneven, i. e. , the sediment yield in the flood season accounted for 98.8% of the whole year. The annual precipitation was not found to have significant change in the research period, indicating that it did not affect the sediment yield evi- dently. However, the land cover changes caused by human activities have produced marked effects on the re- duction of sediment yield since the middle of 1970s. The main reason was that the sloping farmland decreased rapidly while the terrace increased hugely, it indicated that soil and water conservation practices played an im- portant role in runoff and sediment process.