关键词: 山区河流; 大比降; 水温; 摩擦内能; 一维水温数学模型; 雅鲁藏布江;

Abstract: The energy conversion of water flow in process of overcoming resistance is an important factor influencing the water temperature variation in mountainous rivers of high gradient ratio.This paper took the Dahewan reach of the Yarlung Zangbo River in Tibet as the research object, and used mathematical models to explore the contribution of frictional internal energy caused by the drop to the temperature rise along the reach.The results showed that:(1) The total length of the river from Paizhen to Jiefangqiao in the Dahewan reach of the Yarlung Zangbo River is 250km.The measured water temperature changed significantly along the main stream from June to November, and the temperature rise reached 1.0～4.3℃.The monthly average temperature increase rate along the main stream ranged from 1.9 to 2.1℃/100km, and the heat source was relatively stable;(2) The transformation coefficient was 0.7 by calibrating the longitudinal one-dimensional water temperature mathematical model that took into account the transformation internal energy of the drop, and the model can invert the water temperature change process of the river section;(3) Friction internal energy and water-air heat exchange were the main reasons for the temperature rise of the Dahewan reach of the Yarlung Zangbo River, the water temperature increased 3.7℃ due to the drop with a contribution to temperature rise up to 90%.The research results can provide theoretical and data references for the research on water temperature of mountainous rivers of high gradient ratio.

Key words: mountainous rivers; high gradient ratio; water temperature; frictional energy; one-dimensional water temperature mathematical model; Yarlung Zangbo River;