黄淮海流域植被覆盖变化对径流的影响

Analysis of the effects of vegetation changes on runoff in the Huang-Huai-Hai River basin under global change

植被是流域水循环过程的重要环境因子之一,植被变化对径流的影响是当前研究的国际前沿和热点问题。以全球变绿最突出的黄淮海流域为研究对象,基于1982—2016年水文气象观测资料及归一化植被指数(NDVI)数据,利用Mann-Kendall等趋势检验方法检测NDVI的时空变化特征。基于Budyko-Fu公式构建黄淮海流域水热耦合模拟模型,分析模拟径流对Budyko-Fu模型参数ω的敏感性;基于参数ω与气候、植被等要素的统计关系,建立利用气候季节性指数和NDVI计算参数ω的经验公式,利用弹性系数法,识别参数ω对NDVI变化的响应,利用复合函数链式求导法则研究NDVI变化对黄淮海流域径流的影响。结果表明:1982—2016年黄淮海流域NDVI呈显著增加趋势;NDVI增加会使模型参数ω增加,进而导致径流量减少;NDVI每增加10%,黄淮海流域径流量平均减少8.3%;植被变化对径流的影响具有显著的空间差异性,气候越干旱、植被条件越差地区的NDVI变化对径流影响越显著。

Vegetation is one of the critical environmental factors driving the hydrologic cycle.The impact of vegetation change on runoff is a hot issue.As a pronounced greening region,the Huang-Huai-Hai River basin(HHHRB)was selected as the studying area.Based on long-term(1982—2016)hydro-meteorological and Normalized Difference Vegetation Index(NDVI)datasets,the spatial and temporal change in NDVI was detected using Mann-Kendall′s test methodology.The relationship between NDVI and the parameterωof Budyko-Fu′s model was analyzed using an empirical formula and an elasticity method.Taking the parameterωas a link,the impact of NDVI change on runoff in HHHRB was investigated with the chain rule for derivatives of complex functions.Several new findings were investigated:①There was a statistically significant increasing trend in NDVI during the last 35 years over HHHRB.②An increase in NDVI would increase the model parameterω,thereby leading to a decrease in the runoff.③There might be an average reduction of 8.3%in runoff as a 10%increase in NDVI in the HHHRB.④The runoff was more sensitive to NDVI change under drier climate and sparser vegetation conditions.The results could improve the understanding of the mechanism of the water cycle in a changing environment and might provide scientific and technological support for water resources planning and vegetation management.