黄土丘陵沟壑区典型流域土地利用/土地覆被变化对径流产沙的影响

该文以黄土丘陵沟壑区第三副区内的桥子东、西沟为例，分析不同土地利用/土地覆被变化对流域径流输沙的影响.研究结果表明，土地利用/土地覆被对年径流输沙有显著影响，治理流域比未治理流域在丰水年、平水年和枯水年的年输沙率分别减少约44%、75%和86%；流域在土地利用后期(1995—2004年)比前期(1986—1994年)在平水年和丰水年的输沙量减少较大.从年内径流输沙变化来看，治理流域比未治理流域的减沙效应在5月和9月更为显著；而对于治理流域的两期土地利用时期，各月降水越多，后期时的流域月均输沙量比前期减少越多.暴雨洪水过程线和输沙过程线分析表明，土地覆被对流域暴雨洪水过程和输沙过程具有较强的调控作用.降雨和洪水流量频率分析表明，治理流域在前后两期土地利用时期，若具有相同频率分布的雨强，则任一重现期下流域后期土地利用时期的洪水平均含沙量小于前期. 

Effects of landuse-landcover change on sediment production of runoff in typical watershed in the loess gully-hilly region of China

Landuse is found to play much more important role among the factors such as climate, soil properties, topographical feature, vegetation cover, human activities, etc., which affecting soil erosion and sediment production. In order to understand the effects of landuse changes on sediment production and provide the oretical basis for landuse plan and management and ecological restoration, this study taking the controlled Qiaozidong Watershed and uncontrolled Qiaozixi Watershed in the third subregion of the Loess Plateau as examples, had analyzed the effects of landuse landcover change (LUCC) on sediment discharge. The results showed that the impact of landuse landcover on annual sediment yield was significant. The sediment discharging rate of controlled watershed had decreased by 44%,75% and 86% respectively in wet, normal and dry years over the uncontrolled watershed. Comparing to the period of 1986-1994 for landuse in the controlled watershed, it was in period of 1995-2004 that sediment discharge reduced more. In addition, the impact of landuse landcover on sediment discharge demonstrated seasonal fluctuation characteristics.The effects of sediment reduction in the controlled watershed displayed more significance than that in the uncontrolled one in May and September. To the controlled Qiaozidong Watershed, the reduction effect consisted with rainfall distribution. Finally, the flood sediment discharge had closely correlated with the rainfall amount, rainfall intensity in 60 min and the flood volume, and had greater impact on flood sediment discharge in the uncontrolled watershed than that in the controlled watershed. Rainstorm runoff process and the rainstorm sediment discharging process demonstrate that landcover has strong regulation and control function on flood process and sediment discharge process in rainstorm. For the Qiaozidong Watershed, in the same precipitation frequency distribution, the mean sediment concentration in the latter landuse period (1995-2004) was fewer than that in the former landuse period (1986 -1994) under all recurrence periods.