Mechanisms of runoff generation in the humid tropics are poorly understood, particularly in the context of land‐use/land cover change. This study analyzed the results of 124 storm hydrographs from three humid tropical catchments of markedly different vegetation cover and land‐use history in central Panama during the 2017 wet season: actively grazed pasture, young secondary succession, and near‐mature forest. We used electrical conductivity to separate baseflow (old water) from storm‐event water (new‐water). In all three land covers, new‐water dominated storm runoff generation in 44% of the sampled storm events, indicating the dominance of fast shallow flow paths in the landscape. Activation of these flow paths was found to depend on a combination of maximum rainfall intensity and total storm rainfall, which, in turn, relates to markedly contrasting hydrograph separation results among land covers. Relationships between these rainfall characteristics and storm runoff generation were nonlinear, producing a threshold response with the exceedance of specific rainfall volumes and/or intensities. The pastoral catchment delivered order of magnitude more new‐water during storm events than the two forested catchments. Although new‐water contributed minimally (<10%) to total wet season runoff in the forested catchments, 43% of runoff generation in the pasture came from five large rainfall events where a threshold response produced substantial increases in total runoff and new‐runoff efficiency. Based on our results, we propose a conceptual model of hydrologic flow paths in humid tropical systems that can explain previously observed disparities in seasonal storage and runoff with respect to land use/land cover.

中文翻译：

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巴拿马中部三个湿润热带流域的降水特征和土地覆盖控制湿季径流来源及降雨分配

人们对湿润热带地区的径流产生机理了解甚少，尤其是在土地利用/土地覆盖变化的背景下。这项研究分析了2017年湿季中巴拿马中部三个植被覆盖率和土地使用历史明显不同的潮湿热带流域的124个风暴水位图的结果：活跃放牧的牧场，次生幼年演替和近乎成熟的森林。我们使用电导率将底流（旧水）与暴雨水（新水）分开。在所有这三个土地覆盖中，在44％的采样风暴事件中，以新水为主的暴雨径流生成，表明景观中快速浅流路径占主导地位。发现这些流径的激活取决于最大降雨强度和总暴雨的组合，而这又反过来，与土地覆盖物之间明显不同的水文分割结果有关。这些降雨特征与暴雨径流产生之间的关系是非线性的，产生超过特定降雨量和/或强度的阈值响应。与两个森林集水区相比，牧区集水区在暴风雨期间提供了更多的新水。尽管新水对森林集水区总湿季径流的贡献最小（<10％），但牧场中径流产生的43％来自五次大型降雨事件，其中阈值响应使总径流和新径流效率大大增加。根据我们的结果，