Decreasing trend of sediment transfer function of the Upper Yellow River, China, in response to human activity and climate change

Abstract

An index (F_s) for sediment transfer function is introduced, based on the sediment budget at the channel scale. The purpose of this study is two-fold: to gain a deeper insight into how F_s is influenced by natural and human factors, and to provide some new knowledge for decision making in the management of the Upper Yellow River, China. Since 1960, the F_s of the Lanzhou to Toudaoguai reach of the Upper Yellow River shows a decreasing trend. At the drainage basin level, the decreased F_s can be explained by changes in precipitation and air temperature, as well as by a number of variables describing human activity, such as reservoir regulation, water diversion, and soil and water conservation. The higher temperature reduces the transfer function, while the larger runoff coefficient increases it. At the channel level, the decreased F_s can be explained by a number of variables of flow and sediment input. Three countermeasures for restoration of the F_s are suggested.

Editor Z.W. Kundzewicz

Résumé

Un indice F_s du transfert de sédiments a été défini, basé sur le bilan des sédiments à l’échelle du chenal d’écoulement. L’objectif de cette étude recouvre deux aspects : développer une connaissance plus approfondie de la façon dont l’indice F_s est influencé par des facteurs naturels et humains, et fournir de nouvelles connaissances pour la prise de décision dans la gestion de la partie supérieure du fleuve Jaune, en Chine. Depuis 1960, l’indice F_s du tronçon du fleuve Jaune amont compris entre Lanzhou et Toudaoguai, indique une tendance à la décroissance. A l’échelle du bassin versant, la diminution de l’indice F_s peut être expliquée par les modifications des précipitations et la température de l’air, ainsi que par un certain nombre de variables décrivant l’activité humaine, telles que la régularisation par des réservoirs, la dérivation de l’eau, et la préservation des sols et de l’eau. La température plus élevée réduit le transfert alors que le coefficient d’écoulement plus élevé l’augmente. Au niveau du chenal, la diminution de l’indice F_s peut s’expliquer par un certain nombre de variables d’entrée de débit et de sédiments. Nous proposons trois contre-mesures destinées à la restauration de l’indice F_s.

Key words:

• Upper Yellow River, China
• sediment transport
• human activity
• reservoirs
• changing hydrological regime

Mots clefs:

• cours supérieur du fleuve Jaune
• Chine
• transport des sédiments
• activité humaine
• réservoirs
• modification du régime hydrologique

Acknowledgements

All hydrometric data, including precipitation data for 300 raingauges in the study area, were provided by the Yellow River Water Conservancy Commission. The SSL data for relevant hydrometric stations was provided by the Yellow River Commission of Water Conservancy. The water storage capacity of reservoirs, soil and water conservation measures and annual amount of net water diversion data were provided by the Yellow Water Conservancy, and used in the present study with their permission. Data on flows and sediment concentrations in water diversions were provided by the Yellow River Institute of Hydraulic Engineering and Water Resources. Temperature data, from 52 county meteorological stations, were provided by the Chinese State Meteorological Bureau. I am also grateful to two anonymous reviewers, whose comments and suggestions were invaluable in improving the manuscript.

Additional information

Funding

The financial support from the National Major Basic Research Programme of China (Grant no. 2011CB403305), the Natural Science Foundation of China (Grant no. 41071016) and the Chinese Academy of Sciences is gratefully acknowledged.