北川河流域降水与NDVI变化特征及其对径流的影响

Variation of Precipitation and Vegetation NDVI and their Effects on Streamflow in the Beichuan River Basin

采用Mann-Kendall检验等方法,对1961—2013年青海省西宁市北川河流域的降水、径流、NDVI指数进行趋势与突变点分析,采用小波Morlet函数分析方法,对降水、径流数据进行长时间序列的周期性分析,探究降水与植被对径流的调节作用。结果表明：北川河流域53 a的平均降水以0.729 5 mm·a-1的速度增长,归一化植被指数的斜率以0.005呈不显著增长趋势,径流深以0.490 5 mm·a-1的速度呈下降趋势;降水与径流的周期变化在不同时间尺度范围有差异性,变化周期为5 a的显著周期和41 a的接近显著水平周期;径流量受降水与NDVI的共同影响,其中7—10月的降水与NDVI对径流的影响显著,径流变化受当月和前一月的降水与NDVI变化控制。

The Beichuan River is the main water resource of the area around Xining City. In recent years,there was a serious ecological environment degeneration in the Beichuan River Basin because of the influence of global climate change and human activity disturbance. In this study,the streamflow data and the precipitation data during the period of 1961-2013 were analyzed,and the Mann-Kendall test was employed to detect the long-term change of precipitation and runoff volume during the study period. The spatiotemporal distribution of hydrologic features was analyzed by the Mrolet wavelet analysis method. Moreover,the remote sensing images of the vegetation NDVI data during the period from 1982 to 2013 were interpreted by RS and GIS means. Furthermore,the relationships among precipitation,vegetation and streamflow in the Beichuan River Basin were analyzed. Results showed that precipitation and vegetation NDVI in the Beichuan River Basin increased during the period from 1982 to 2013. The average annual precipitation was 518 mm and increased by 0. 729 5 mm·a-1 during the period of 1961-2013. The average,highest and lowest values of vegetation NDVI were 0. 365,0. 385 and 0. 333 respectively. Streamflow decreased during the period of 1961-2013,the average streamflow of the Beichuan River was 269 mm and decreased by0. 490 5 mm·a-1. The periodic variation of precipitation and runoff volume was different at different time scale.There was a significant positive correlation between streamflow and precipitation,and also a positive correlation between precipitation and vegetation NDVI. Human activities affected the streamflow significantly.