黄河中游径流可再生性对于人类活动和气候变化的响应

径流可再生性的变化是水循环研究中的重要科学问题,对于干旱、半干旱气候区水资源的可持续利用有重要意义.以黄河中游河口镇至龙门区间1950—2008 年间的水文、气象资料以及人类活动(如引水、水土保持)等资料为基础,运用统计方法研究了径流可再生性指标I_rr的变化及其成因.在59 a 的时间尺度上,I_rr在总体上具有明显的减小趋势,但具有次一级的波动,其变化可以分为4 个阶段.研究发现,3 个气候变量(年降水量P_m、年均气温T_m和夏季风强度指标SMI)与当年I_rr的相关程度均不高,但它们的滞后作用对于I_rr的影响十分明显,表明气候因子对于径流可再生性影响具有某种时间尺度效应.以I_rr与某一气候因子的N年滑动平均值的相关系数与N的关系曲线的峰值或拐点所对应的N值作为气候因子影响I_rr的特征时间尺度,确定了P_m、SMI和T_m影响径流可再生性的特征时间尺度分别为11、9 和4 a.I_rr与各项水土保持措施的面积及水土保持措施总面积之间均表现出显著的负相关.1998 年以后开展的以大规模退耕还林(草)为中心的生态环境建设使得径流可再生性指标进一步降低.建立了I_rr与气候暖干化指标和水土保持总面积之间的回归方程式,该方程表明,I_rr随气候暖干化程度的增加而减小,随水土保持措施面积的增大而减小.

Runoff Renewability in the Middle Yellow River in Response to Human Activity and Climate Change

Runoff renewability is an important topic in the study of water cycle, and the knowledge of it is important for sustainable utilization of water resources in arid and semi-arid climate areas. Based on hydrological and meteorological data and the information related with human activity including soil and water conservation and water diversion, and using statistical method, we have studied the temporal variation in runoff renewability (I_rr) and its formative cause in the middle Yellow River basin. We found that at the time scale of 59 year, I_rr shows a decreasing trend superposed by some secondary fluctuations, which divides the variation into four stages. Although the correlations of I_rr with three climate variables in the same year such as annual precipitation (P_m), air temperature (T_m) and summer monsoon intensity (SMI) are relatively low, we found significant time-lag effect of the variation in P_m, T_m and SMI on I_rr, based on which the characteristic length of time-scale (L_t) can be determined. The correlation coefficients of I_rr with N-year moving averages of a climate variable were calculated and then plotted with N. TheNassociating with the turning point is determined as L_t. We found that the L_t for the influence of P_m, T_m and SMI on I_rr are 11, 9 and 4 years respectively. There is close negative correlation between I_rr and the area of each type of soil and water conservation measures, and the total area. The large-scale implementation of ecological restoration centering on“conversion of degraded farm land into forest and grass land ”since 1998 has resulted in a further reduction in I_rr. A regression equation between I_rr and the index (I_wd,5m) of warming and dryness and the total area (A_sw) of soil and water conservation measures was established which indicates that I_rr decreases with I_wd and A_sw.