黄土丘陵区小流域土地覆被变化对径流产沙量的影响

为探讨黄土丘陵区小流域土地覆被变化特征及其对流域径流产沙量的影响,以黄土丘陵区吕二沟、罗玉沟及其嵌套流域(桥子沟)等3个小流域为研究对象,运用数理统计学、配对流域等方法定量分析了3个小流域不同研究时段内土地覆被变化对径流产沙量的影响.结果表明,1982~2004年间,林地面积以1.07%/a的速率快速递增是吕二沟流域土地覆被变化的最明显特征,而罗玉沟流域在国家坡改梯工程影响下,坡耕地面积大幅减少,1986~1995年间约73%坡耕地转化为梯田;结合配对流域法可知,土地覆被变化是导致流域径流和产沙减少的主要原因,在相同降雨条件下,径流深、泥沙量分别减少43.76%和35.23%.流域年径流模数与年降水量和流域森林覆被率均呈指数关系,流域森林覆被率增加5%,径流模数可减少18.43%~37.58%.

Effect of land cover change on runoff and sediment yield of small watershed in Loess Hilly-gully region

To explore the impacts of land cover change on runoff and sediment yield in Loess Hilly-gully region, Lvergou watershed, Luoyugou watershed and her son basins of Qiaozigou in the study region were selected as the research objects. Mathematical statistics method and paired catchments approach were applied to analyze the effect of land cover change on runoff and sediment yield. Brief conclusions can be drawn as follows: The rapid increase of forest land at the rate of 1.07% per year was the most obvious features of the land cover changes in Lvergou watershed during the period of 1982-2004. Moreover, under the influence of terracing sloping fields, about 73% of sloping farmland was converted to terraces in Luoyugou watershed during the period of 1986-2004. Combined with the paired catchments approach, land cover change was the strongest contributor to the reduction in annual runoff and sediment yield of watersheds, and the average reduction rate reached 43.76% and 35.23% under the same rainfall condition, respectively. Annual runoff modulus and precipitation and forest cover rate were significantly correlated, and showed an exponential relationship for each watershed during the study period. When the forest cover rate increased by 5%, the runoff modulus decreased by 18.43% to 37.58%.