汉江流域植被变化及对径流的影响

Vegetation variation in the Han River and its impact on runoff

基于汉江流域的气象水文和归一化植被指数(normalized difference vegetation index,I_(NDV))数据,采用多元线性回归分析方法定量计算不同因素对汉江流域植被变化的影响程度,然后采用修正后的Budyko方程和弹性系数法定量计算植被变化对径流变化的影响程度。结果表明:1982—2015年的年均I_(NDV)呈显著的波动增长趋势(p<0.01),且空间异质性较明显,植被增长明显地区主要分布在中下游区域;气候条件和人为因素对I_(NDV)增长具有积极作用,贡献率分别为99.56%和0.44%,但其贡献率的时空分布存在显著差异;下垫面参数(ω)和I_(NDV)之间有较强相关性,表明流域产流能力对植被变化具有高度敏感性;气候因素引起的植被变化和人为因素引起的植被变化对径流量的贡献率分别为28.28%和0.12%,表明气候因素导致植被增长是致使汉江流域水资源减少的重要因素之一,因此,应高度重视植被生长导致流域水资源减少这一问题。

Runoff is one of the most important water resources in the watershed and is critical to the natural ecosystem.The Han River basin,as an important representative basin of the national"Yangtze River Economic Belt",is one of the water sources of China's South-to-North Water Transfers Project in the upper reaches,and the middle and lower reaches of the Han River are also the main industrial and agricultural production concentration areas in China.Water resources,which constitute one of the demand conditions for industry and agriculture in the region and one of the major constraints on the scale of socio-economic development,are extremely important for regional economic development.Therefore,the impact of vegetation changes on runoff changes under the influence of human activities is conducive to the sustainable development of the Yangtze River basin economy and the protection of the ecological environment to provide a scientific reference basis for research.Based on the meteorological and hydrological data and normalized difference vegetation index(I_(NDV))data of the Han River basin,the impact degree of different factors on the vegetation change of the Han River basin were quantitatively computed using multiple linear regression analysis method,then the impact degree of vegetation variation on discharge change was quantitatively calculated by an adjusted Budyko equation and elastic coefficient method.The Pettitt mutation test identified the mutation year for runoff in the Han River basin in 1991.The amount of runoff change due to each type of driver was calculated separately by the values of annual mean P,ET0,I_(NDV)and coefficientωin the base and change periods,using the elasticity coefficients obtained.Comparing the baseline and mutation periods,it was found that the mean annual reference evapotranspiration in the mutation period increased by 53.59 mm,runoff depth decreased by 119.80 mm,precipitation decreased by 76.31 mm,the subsurface parameter increased by 0.27,and the I_(NDV)increased by 0.03 compared to the baseline period.It shows that the subsurface of the Han River basin has been affected by human activities and has undergone significant changes.The annual mean I_(NDV)in the Han River basin showed a significant fluctuating growth trend from 1982 to 2015(p<0.01).The spatial heterogeneity was relatively obvious,and the areas with significant vegetation growth were mainly dominated by the middle and lower reaches.Among them,climatic conditions and anthropogenic factors contributed positively to the increase of I_(NDV),with contribution rates of 99.56%and 0.44%,respectively,but the spatial and temporal distributions of the contribution rates of the two influencing factors were significantly different.In contrast,there is a strong correlation between the subsurface parameterωand I_(NDV)in the Han River basin,indicating that the flow production performance of the basin is highly sensitive to vegetation changes.The contribution rates of vegetation changes caused by climate factors and vegetation changes caused by human factors to runoff were 62.44%and 0.28%,respectively,indicating that vegetation growth caused by climate factors wae one of the important factors leading to the reduction of water resources in the Han River.Therefore,great importance should be attached to the problem of vegetation growth leading to the reduction of water resources in Han River basin.