Topographic controls on the annual runoff coefficient and implications for landscape evolution across semiarid Qilian Mountains, NE Tibetan Plateau Topographic controls on the annual runoff coefficient and implications for landscape evolution across semiarid Qilian Mountains, NE Tibetan Plateau

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Vol17 No.2: 464-479

【Title】Topographic controls on the annual runoff coefficient and implications for landscape evolution across semiarid Qilian Mountains, NE Tibetan Plateau

Author】CAI Shun; GENG Hao-peng*; PAN Bao-tian; HONG Yang; CHEN Li-ping

Addresses】Key Laboratory of Western China's Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China

Corresponding author】GENG Hao-peng

Citation】Cai S, Geng HP, Pan BT, et al. (2020) Topographic controls on the annual runoff coefficient and implications for landscape evolution across semiarid Qilian Mountains, NE Tibetan Plateau. Journal of Mountain Science 17(2). https://doi.org/10.1007/s11629-019-5584-7

DOI】https://doi.org/10.1007/s11629-019-5584-7

Abstract】The combination of different topographic and climatic conditions results in varied precipitation-runoff relations, which in turn influences hillslope erosion, sediment transport and bedrock incision across mountainous landscapes. The runoff coefficient is a suitable tool to represent precipitation-runoff relations, but the spatial distribution of the runoff coefficient across tectonically active mountains in semi-arid environments has received little attention because of limited data availability. We calculated annual runoff coefficients over 22 years for 26 drainage basins across the semi-arid Qilian Mountains based on: (i) annual discharge records; and (ii) the China Meteorological Forcing Dataset to enhance our understanding of the precipitation-runoff processes. The mean annual runoff coefficients show no obvious spatial trends. When compared to potential controlling factors, mean annual runoff coefficients are highly correlated with mean slope rather than any climatic characteristics (e.g., mean annual precipitation and Normalized Difference Vegetation Index). The slope-dependent runoff coefficient could theoretically have enhanced the topographic control on erosion rates and dampen the influence of precipitation. The enhanced discharge for drainage basins with less precipitation but steep topography in the western Qilian Mountains will enable fluvial incision to keep pace with ongoing uplift caused by the northward growth of the Qilian Mountains. The geomorphic implications are that tectonic rather than climatic factors are more significant for long-term landscape evolution in arid and semi-arid contexts.

Keywords】Landscape evolution; Precipitation-runoff process; Qilian mountains; Semiarid environments