植被恢复背景下黄河中游及6个典型流域蒸散发及其组分变化格局

植被变化可通过改变下垫面条件的方式,调节植被蒸腾与土壤蒸发的分配比例,进而影响区域乃至全球水循环过程。自20世纪90年代以来,我国开展了大规模的植被恢复工程,全国植被覆盖度得到了极大提高,其中尤以黄河中游最为显著。以黄河中游6个典型植被恢复流域为研究对象,利用PML_V2模型和水文气象数据,验证了该模型模拟植被快速变化环境下的蒸散性能,并分析了2003—2018年间植被恢复工程背景下,黄河中游蒸散发（ET）及其组分（植被蒸腾Ec,截留蒸发Ei,土壤蒸发Es）的时空变化格局。结果表明：（1）对比流域水量平衡ET与PML模型结果,发现该模型在黄河中游具有较好的适用性（NSE >0.6）。（2）Ec对ET的分布格局起着主导作用,蒸散发及其组分的空间格局由夏季风作用下的植被空间分布所控制。Ec与ET的空间分布格局较为相似,Es与其相反。ET、Ec、Ei均呈显著增加趋势,Es则呈显著减小趋势,尤以流域中下游最为明显。（3）植被恢复背景下,黄河中游典型流域的蒸散发及其组分发生了明显的变化。相较于所在流域,流域中植被恢复区ET、Ec、Es、Ei分别偏高2.20%、5.86%、0.86%、7.44%,速率分别偏高-0.51 mm/a、0.55 mm/a、-1.11 mm/a、0.05 mm/a。

Variation patterns of evapotranspiration and its components in the Middle Yellow River and six typical basins under the background of vegetation restoration

By changing the underlying surface conditions, vegetation change can regulate the distribution ratio of vegetation transpiration to soil evaporation, and then change the regional and even global water cycle process, and have a profound impact on the sustainable development and utilization of water resources. Since the 1990s, China has carried out a large-scale vegetation restoration project, which has greatly increased the vegetation coverage, especially in the middle reaches of the Yellow River. In this paper, six typical vegetation restoration watersheds in the middle reaches of the Yellow River Basin as the research object, using meteorological and hydrological data, verify the performance of the PML_V2 model, and analyze in the vegetation restoration project background, from 2003 to 2018, the evapotranspiration in the middle reaches of the Yellow River (ET) and its components (Ec vegetation transpiration, Ei intercept evaporation, Es soil evaporation) change pattern of space and time. (1) By comparing the results of ET and PML models, it is found that this model has good applicability in the middle reaches of the Yellow River (NSE >0.6). (2) Ec plays a leading role in the distribution pattern of ET, which is controlled by the spatial distribution of vegetation under the action of summer monsoon. The spatial distribution pattern of Ec and ET is similar, while that of Es is opposite. ET, Ec, Ei all showed a significant increasing trend, while Es showed a significant decreasing trend, especially in the middle and lower reaches of the basin. (3) In the context of vegetation restoration, ET and its components in the typical watershed of the middle reaches of the Yellow River change significantly. Compared with their located watersheds, ET, Ec, Es and Ei are 2.20%, 5.86%, 0.86% and 7.44% higher, respectively, and the rates are -0.51 mm/a, 0.55 mm/a, -1.11 mm/a and 0.05 mm/a higher, respectively.