多时间尺度下黄河上游径流复杂度变化特征研究

研究黄河上游径流复杂度变化特征，对揭示区域径流演化规律具有重要意义。同时采用灵活样本熵和多尺度熵对该区域干、支流12个水文站1956-2015年的年、汛期及非汛期径流复杂性进行测度，分析不同时间尺度下径流复杂度变化特征。结果表明：黄河上游干流的年径流呈不显著减小趋势，汛期径流减小的同时非汛期径流增大。支流除湟水民和站外，其他站年、汛期及非汛期径流均呈显著减小趋势。在不同时间尺度下，黄河上游干流贵德站至兰州站、支流湟水民和站的年、汛期和非汛期径流复杂度差异明显，径流复杂度变化具有指示人类活动影响的作用。人类活动在单一时间尺度下对年和非汛期径流的影响作用强于汛期，在多时间尺度下对汛期径流的影响作用强于年和非汛期，而对湟水民和站径流的影响在不同时间尺度和不同时段下差异较大。同时使用灵活样本熵和多尺度熵能详尽测度径流复杂度的变化特征，识别人类活动影响强度的差异。基流对黄河上游年径流和非汛期径流的补给比例大于全流域，其变化对年径流有重要影响。

Change characteristics of runoff complexity in the upper reaches of the Yellow River under multiple time scales

Studying the change characteristics of the runoff complexity in the upper reaches of the Yellow River has great significance to the understanding of regional runoff evolution. Here, both flexible sample entropy and multiscale entropy were used to measure the annual, flood and non flood season runoff complexity of 12 hydrological stations located in the main stream and tributaries of this region from 1956 to 2015, based on which the change characteristics of runoff complexity under different time scales was analyzed. The results showed that the annual runoff of the upper reaches of the Yellow River showed an insignificant downward trend, and the runoff decreased during the flood season but increased during the non flood season. Except for the Minhe Station of Huangshui River, all the other stations in the tributaries showed a significant downward trend in runoff including annual, flood season and non flood season runoff. Under different time scales, the runoff complexity of annual, flood and non flood season from Guide Station to Lanzhou Station in the main stream was greatly differentiated from that of Minhe Station of Huangshui River in the upper reaches of the Yellow River. The changes in runoff complexity also reflected the impacts of human activities. On a single time scale, the impacts of human activities on annual and non flood season runoff were stronger than that on flood season runoff, whereas on multiple time scales, it was the opposite. But, regarding to Minhe Station of Huangshui River, the impacts of human activities varied significantly at different time scales and different periods. Using the flexible sample entropy and multiscale entropy at the same time can help obtain detailed runoff complexity change characteristics, and identify the intensity difference of the impacts of the human activities. The recharge ratio of base flow to annual runoff and non flood season runoff in the upper reaches of the Yellow River was higher than that of the whole basin, and the change of base flow had a significat impact on annual runoff.