近50年金沙江干热河谷区泥沙变化及影响因素分析——以云南省元谋县为例

 以金沙江干热河谷典型区域元谋县为例,通过对该区龙川江小黄瓜园水文站20世纪50年代以来输沙量的变化分析,结果表明,河流输沙量有增加的趋势,特别是80年代末至2000年,年均输沙量由400万t(1971—1980年)增加至750万t(1991—2000年)。为研究输沙量变化的原因,为当地生态环境建设提供理论指导,采用统计分析等方法对输沙量增加的影响因素进行分析,结果表明:50年来局地气候变化,特别是降雨量及降雨强度的增加使地表侵蚀加速,进入河道泥沙增多。同时,由于受牲畜数量快速增加、人口的迅速膨胀、生产方式的落后及农作物市场价格等因素影响,土地覆被及结构变化明显,即覆被盖度减小,坡耕地增加,灌草地等蓄水保土作用好的地类面积迅速减少,进而导致生态极为脆弱的元谋干热河谷区土壤侵蚀加剧,河道泥沙含量增加。此外,元谋县强烈的冲沟侵蚀也是龙川江输沙量增加的重要原因之一。

Sediment yields and impact factors in xerothermic valley in Jinsha River in the last 50 years: A Case study in Yuanmou County, Yunnan Province

The sediment yields of Jinsha River basin has shown a significantly in-creased trend in recent years.This research focuses on the Yuanmou County which is a typical xerothermic valley of Jinsha River basin.The sediment yields variation in Long Chuan River（Xiaohuangguayuan）,a river passing through this region during the period of 1956—2000 were analyzed.The annual sediment yield of the Long Chuan River has an increase tendency since 1950s.particularly,in 1990s.The mean annual sediment yield increased from 400×10⁴t（1971—1980） to 750×10⁴t（1991—2000）.By analysing the impact factors on sediment yields based on statistic analysis methods,it is shown that regional climate change,especially the increase in the quantity and intensity of rainfall,is the main reason accelerating the surface erosion and increasing the sediment yields of the river.At the same time,due to the rapid increase in the amount of livestock,rapid population expansion,lagged production methods and influence of crop market price, the land cover and the structure of land use have obviously changed during the recent 50 years.The decrease of land covered area,the increase of slope farmland and the decline of the area of shrub and grass,which have high values in soil and water conservation but relative low values in economic profit per unit,have heavily aggravated soil erosion and increased river sediments which extremely undermined the fragile ecology of xerothermic valley in Yuanmou County.Furthermore,the intensive gully erosion is another important inducement of the increase of sediment yields in Longchuan River.