近70年来不同地貌和植被类型区水沙特征演变及其对生态恢复的响应

黄土高原水土流失治理和退耕还林(草)等生态环境建设，对不同植被类型区和治理度下的水沙过程均产生了深刻的影响。以北洛河流域为例，基于1952—2019年实测水文数据，采用水文统计法，对比分析了上、中、下游等不同地貌和植被类型区生态恢复对水沙数量、径流调节、影响因素贡献等的影响及其差异。结果显示：(1)上、中、下游年均径流深分别为30、23、21 mm,产沙量为0.6、0.05、-0.02亿t。中游年均产流量占流域总水量的51%,上游年均产沙量占流域总沙量的90%以上。(2)上、中、下游径流深极显著减少，减少率分别为-0.28、-0.16、-0.43 mm/a;上游产沙量以0.02亿t/a速度极显著降低，中、下游产沙量不显著减少。(3)上、中、下游的削洪、补枯程度逐年代增加，与20世纪60年代比，21世纪10年代洪水期流量(Q₅)分别减少了63%、45%、60%,上游枯水期流量(Q₉₅)增加了68%,中游20世纪80年代枯水期开始产流。(4)与20世纪60年代比，上、中、下游21世纪10年代人类活动对产流量减少的贡献率分别为94.7%、26.7%...

Hydrologic and sediment responses to ecological restoration in different geomorphological and vegetation type areas in past 70 years

The purpose of this study was to reveal the effects of ecological environment construction such as soil and water conservation and the Grain for Green Program on hydrological processes in different vegetation type areas on the Loess Plateau. This work took the Beiluo River Basin as an example to investigate the hydrological responses and the variety in the regions with various landforms and vegetation zones in the basin. The results showed that: (1) the average annual streamflow depth in the upper, middle, and lower reaches was 30, 23, and 21 mm, respectively, while the correspondingly average annual sediment was 60, 5, and -2 million tons from 1952 to 2019. The average annual streamflow volume of the middle reaches accounted for 51% of the total volume in the whole basin. However, the average annual sediment delivery in the upper reaches accounted for over 90% of the total sediment in the basin. (2) All the streamflow depths in the three regions showed a significantly decreasing trend with the changing rates of -0.28, -0.16 and -0.43 mm/a in past 70 years, respectively. While the sediment delivery of the upper reaches demonstrated a significant downward trend at a rate of 2 million t/a, and in the middle and lower reaches it was only a slight reduction. (3) The function of runoff regulation was more and more enhanced with the time. Compared with 1960s, the high flow (Q₅) decreased by 63%, 45% and 60% in the 2010s, respectively, in the three regions. While the low flow (Q₉₅) increased by 68% in the upper reaches, and in the middle reaches it began to increase in 1980s. (4) Compared with 1960s, human activities contributed the reduction of streamflow by 94.7%, 26.7%, and 60.7% in 2010s, respectively, which dominated the reduction of sediment delivery of over 85% in the three regions. The results suggest that in the upper reaches with low vegetation cover but high speedy conservation measures, human activities dominated the significant reduction of streamflow and sediment, with runoff highly regulated and soil erosion more and more concentrated in several rainstorms. In the middle reaches, which had high vegetation cover but low speedy conservation measures, climate change dominated the hydrology with the runoff evidently decreased and slightly regulated. It implied that the responses of streamflow and sediment not only controlled by vegetation cover but also the restoration speed. It was expected to be helpful in understanding the ecohydrological processes in the Loess Plateau.