Abstract Oxbow lakes generated from meandering river cutoffs are an indispensable component of riparian ecosystem. This study aimed to examine whether predictable patterns in water properties arise relative to oxbow lake geometry and lake-channel connectivity. We selected 24 oxbow lakes along a meandering river belt in Zoige Basin, the Tibetan Plateau, to conduct field work at the beginning (May) and the end (September) of the flood season, 2019. Six parameters (pH, dissolved oxygen (DO), conductivity, total dissolved organic carbon, nitrogen and phosphorus) were measured to represent water property. Lake surface area, length, width, length/width ratio, distance to active channel, and curvature were measured to represent lake geometry. Shrinkage ratio, defined as current lake length/initial lake length, was measured to represent lake-channel connectivity between oxbow lakes and active channel. We found an environmental gradient relative to connectivity. As oxbow lakes aged and gradually disconnected from the channel, increased DO and nutrients drove the lakes towards eutrophication. This trend however was disturbed by (i) flood pulses that diluted nutrient concentrations in oxbow lakes and narrowed the differences among different types of lakes and the channel through altering lake-channel connectivity, and (ii) lateral meander migration passed through older lakes such that regulated water properties by reconnecting older lakes to newly formed lakes. Maintenance or restoration of connectivity thus should be of great importance to prevent oxbow lakes from eutrophication in meandering river belts in Zoige Basin.

中文翻译：

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青藏高原若尔盖盆地牛轭湖-曲流河连通性的环境梯度

摘要 蜿蜒河流截断形成的牛轭湖是河岸生态系统不可或缺的组成部分。本研究旨在检查与牛轭湖几何形状和湖-河道连通性相关的水特性的可预测模式是否出现。我们选取青藏高原若尔盖盆地蜿蜒河流带的 24 个牛轭湖，在 2019 年汛期开始（5 月）和结束（9 月）进行实地考察。 6 个参数（pH 值、溶解氧（DO）） )、电导率、总溶解有机碳、氮和磷) 来表示水的性质。测量湖泊表面积、长度、宽度、长宽比、到活动河道的距离和曲率以表示湖泊几何形状。收缩率，定义为当前湖泊长度/初始湖泊长度，被测量以代表牛轭湖和活动河道之间的湖-河道连通性。我们发现了与连通性相关的环境梯度。随着牛轭湖老化并逐渐与河道断开连接，溶解氧和营养物质的增加导致湖泊富营养化。然而，这一趋势受到以下因素的干扰：(i) 洪水脉冲稀释了牛轭湖中的养分浓度，并通过改变湖-河道连通性缩小了不同类型湖泊和河道之间的差异，以及 (ii) 横向曲流迁移穿过了较旧的湖泊，使得通过将旧湖泊重新连接到新形成的湖泊来调节水属性。因此，维护或恢复连通性对于防止若尔盖盆地曲流河带的牛轭湖富营养化具有重要意义。