无定河流域不同地貌区径流变化归因分析

分析了无定河流域干流与其支流(黄土丘陵区的大理河和风沙区的海流兔河)的年径流变化(1960—2012)及其成因,并预测了其径流的变化趋势。结果表明:无定河及其不同地貌区支流海流兔河和大理河流域1960—2012年径流量均显著下降,但年降水量未发生显著变化;无定河和海流兔河流域年蒸散量未发生显著变化,仅大理河流域年蒸散量在1990s年代后期显著增加。无定河流域径流变化突变点发生在1979年和1996年,海流兔河流域径流变化突变点在1971年和1990年,而大理河流域径流突变点发生在1971年。人类活动对大理河流域1972—2012年径流减少的贡献大约占50%,对海流兔河流域1972—1990年和1991—2012年两个时期径流减少的贡献率分别为44.4%和82.4%。未来,无定河及其支流年径流量均呈持续下降趋势。归因分析表明大规模的水土保持治理措施减少了大理河流域侵蚀产沙量的同时,也在一定程度上减少了大理河流域的径流量,而过度的农田灌溉引水是海流兔河径流量下降的主要原因。因此,未来在大理河流域要优化现有植被建设布局,减少流域蒸散发,减缓径流下降;在海流兔河流域要进一步退耕还林(草),适当控制农田灌溉面积,提高灌溉用水效率,在减少灌溉用水的同时提高流域水源涵养能力。

Runoff changes and attribution analysis in tributaries of different geomorphic regions in Wuding River basin

In this study, the runoff changes and their attribution from 1960 to 2012 for Wuding River basin and its two tributaries, Hailiutu River in the wind-sand region and Dali River in the Loess hilly region, were analyzed. The future trends in runoff changes in the three rivers were also predicted. The results revealed that runoff of the Wuding River, Hailiutu River, and Dali rivers decreased significantly during the period of 1960 to 2012, although the annual rainfall in the three river basins did not change significantly during this period. The annual evapotranspiration of the Wuding River and Hailiu River was nearly constant, while the annual evapotranspiration of Dali River has increased significantly since the late 1990s. Abrupt change points of runoff were detected in 1979 and 1996 of Wuding River, 1971 and 1990 of Hailiutu River, and 1971 of Dali Rive, respectively. Human activities accounted for approximately 50% of the runoff reduction in Dali River from 1972 to 2012 and 44.4% in Hailiutu River from 1972 to 1990, 82.4% from 1991 to 2012, respectively. In the future, the annual runoff of the Wuding River and its two tributaries, Dalihe River and Hailiutu River would continue to decline. Attribution analysis revealed that large-scale soil and water conservation measures are the main reasons for sediment and runoff reduction in Dali River. The water conservancy projects'' constructions and farmland irrigation are the main reasons for runoff reduction in Hailiutu River. Therefore, it is necessary to optimize the existing vegetation pattern to reduce evapotranspiration and decelerate the decrease rate of runoff in the Dali River basin. In the Hailiutu River basin, it is necessary to conduct "Grain to Green", to control the irrigation area of farmland, improve the efficiency of irrigation water, and reduce the amount of used irrigation water, at the same time to increase the water conservation capacity as well.