Temporal variations of streamflow in a mid-latitude Eurasian steppe watershed in the past half century

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Courtesy of IWA Publishing

Previous studies either did not identify abrupt change or identified such change but did not exclude it from the detection of trend in streamflow. As a result, an overall downward trend might be erroneously detected as an upward trend because of abrupt increase, while an overall upward trend could be faked as a downward trend due to abrupt decrease. The objectives of this study were to: (1) present a methodology to analyze trend in streamflow in the presence of abrupt change; and (2) use this methodology to detect trend and extreme occurrence of streamflow in the Upper Balagaer River watershed, a mid-latitude nearly pristine precipitation-fed Eurasian steppe watershed in north China. The results indicate that streamflow abruptly decreased around 1994 and exhibited no significant trend from 1960 to 1993 but a significant decrease trend since 1994 (in particular after 1999). In addition, the occurrence of days with a low streamflow was greater after 1994, whereas the occurrence of days with a high streamflow was smaller. Further, the inclusion of the abrupt change in the analysis could compound the detection of the pre-1994 trends but had minimal influences on the detection of the post-1994 trends. These results can be representative across the Eurasian steppe region beyond the study watershed.

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