Spatio-temporal variability of streamflow in the Yellow River: possible causes and implications

Abstract

The water shortage in the Yellow River, China, has been aggravated by rapid population growth and global climate changes. To identify the characteristics of streamflow change in the Yellow River, approximately 50 years of natural and observed streamflow data from 23 hydrological stations were examined. The Mann-Kendall and Pettitt tests were used to detect trends and abrupt change points. The results show that both the natural and the observed streamflow in the Yellow River basin present downward trends from 1956 to 2008, and the decreasing rate of observed streamflow is generally faster than that of the natural streamflow. Larger drainage areas have higher declining rates, and the declining trends are intensified downstream within the mainstream. The possibility of abrupt changes in observed streamflow is higher than in natural streamflow, and streamflow series in the mainstream are more likely to change abruptly than those in the tributaries. In the mainstream, all the significant abrupt changes appear in the middle and latter half of the 1980s, but the abrupt changes occur somewhat earlier for observed streamflow than for natural streamflow. The significant abrupt change for the observed streamflow in the tributaries is almost isochronous with the natural streamflow and occurs from the 1970s to 1990s. It is implied that the slight reduction in precipitation is not the only direct reason for the streamflow variation. Other than the effects of climate change, land-use and land-cover changes are the main reasons for the natural streamflow change. Therefore, the increasing net water diversion by humans is responsible for the observed streamflow change. It is estimated that the influence of human activity on the declining streamflow is enhanced over time.Key words streamflow; trend; abrupt change; Yellow River, China Causes éventuelles et implications de la variabilité spatio-temporelle des débits du fleuve JauneRésumé La pénurie d'eau dans le fleuve Jaune, en Chine, a été aggravée par la croissance rapide de la population et les changements climatiques. Pour identifier les caractéristiques du changement des débits dans le fleuve Jaune, près de 50 ans de données sur les débits naturels et observés à partir de 23 stations hydrologiques ont été examinés. Les tests de Mann-Kendall et de Pettitt ont été utilisés pour détecter les tendances et les points de changement brusques. Les résultats montrent que tant l'écoulement naturel que l'écoulement observé dans le bassin du fleuve Jaune présentent des tendances à la baisse de 1956 à 2008, et que le taux de diminution du débit observé est généralement plus rapide que celui du débit naturel. Les grandes surfaces de drainage présentent des taux de diminution plus élevés, et les tendances à la baisse sont intensifiés en aval dans le bief principal. La probabilité de changements abrupts dans le débit observé est supérieure à celle de l'écoulement naturel, et la série des débits dans le bief principal est plus susceptible de changer brusquement que celles des affluents...

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