黄土小流域水沙输移过程对土地利用/覆被变化的响应

以甘肃定西安家沟小流域为典型研究区,基于TM、ALOS遥感影像解译和地面长期水文数据,深入分析了1997至2010年间流域土地利用变化特征及其产流产沙效应。结果显示,（1）14年间,流域林灌草面积分别增加160.23%、176.33%和80.75%;坡耕地、居民地、裸地和梯田面积分别减少25.57%、0.16%、48.45%和21.52%。以2005年为时间节点,发现前期灌草增加较多、裸地减少明显,后期则是乔木增加比例和坡耕地减少比例更为显著,彰显出不同历史阶段植被恢复的策略变化。（2）流域出口多年平均径流量和输沙量分别由前期的18 249 m3和6 383 kg锐减至后期的2 292 m3和2 267 kg,流域土地利用/覆被有效增加是其主要驱动。（3）春冬季节,由于降雨稀少、径流泥沙的本底值很低,前后两个阶段的水沙输移量差异较小,土地利用/覆被变化的影响相对尚不显著。但在夏秋季节,随着降雨事件增多,土地利用/覆被变化减水减沙的效应趋于显性化。

Response of runoff and sediment process to changes in land use/cover in a small loess hilly catchment

In this study, based on TM and ALOS image interpretation and hydrological data, effects of land use/cover change on runoff and sediment yield were estimated from 1997 to 2010 in Anjiagou catchment, a typical loess hilly area in Dingxi, Gansu Province. The results were as follows. First, forests, shrubs and grasses increased 160%, 176% and 81% during the 14 years, respectively. Whereas, sloping farmland, residential area, bare land and terrace land decreased 25.57%, 0.16%, 48.75% and 21.52%, respectively. Taking the year of 2005 as a time node, shrubs and grasses were found to increase more, and bare land decreased sharperly in the former period, while more forests increased and more sloping shrubs decreased in the latter period, which indicated that the strategies of induced plant selection changed over different historical periods. Second, mean annual runoff and sediment yield in the latter period sharply decreased from 18 249 m3 to 2 292 m3 and from 6 383 kg to 2 267 kg, respectively. This situation can be attributed to the optimization of land use pattem and increases in vegetation coverage in the watershed. Third, in the springs and winters, due to the decrease of rainfall, water and sediment loss, the difference between former and latter period is not notable, indicating the role of land use/cover change is indistinctive, he seasonal variation of runoff and sediment was dominated by rainfall, and had no closely relation with land use/cover change. In the summer and fall, the effects of land use/cover change on water erosion became more significant with rainfall increase.