Pristine tropical forests play a critical role in regional and global climate systems. For a better understanding of the eco‐hydrology of tropical “evergreen” vegetation, it is essential to know the partitioning of water into transpiration and evaporation, runoff and associated water ages. For this purpose, we evaluated how topography and vegetation influence water flux and age dynamics at high temporal (hourly) and spatial (10 m) resolution using the Spatially Distributed Tracer‐Aided Rainfall‐Runoff model for the tropics (STARRtropics). The model was applied in a tropical rainforest catchment (3.2 km²) where data were collected biweekly to monthly and during intensive monitoring campaigns from January 2013 to July 2018. The STARRtropics model was further developed, incorporating an isotope mass balance for evapotranspiration partitioning into transpiration and evaporation. Results exhibited a rapid streamflow response to rainfall inputs (water and isotopes) with limited mixing and a largely time‐invariant baseflow isotope composition. Simulated soil water storage showed a transient response to rainfall inputs with a seasonal component directly resembling the streamflow dynamics which was independently evaluated using soil water content measurements. High transpiration fluxes (max 7 mm/day) were linked to lower slope gradients, deeper soils and greater leaf area index. Overall water partitioning resulted in 65% of the actual evapotranspiration being driven by vegetation with high transpiration rates over the drier months compared to the wet season. Time scales of water age were highly variable, ranging from hours to a few years. Stream water ages were conceptualized as a mixture of younger soil water and slightly older, deeper soil water and shallow groundwater with a maximum age of roughly 2 years during drought conditions (722 days). The simulated soil water ages ranged from hours to 162 days and for shallow groundwater up to 1,200 days. Despite the model assumptions, experimental challenges and data limitation, this preliminary spatially distributed model study enhances knowledge about the water ages and overall young water dominance in a tropical rainforest with little influence of deeper and older groundwater.

中文翻译：

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模拟热带雨林中的非固定水年龄：初步的空间分布评估

原始的热带森林在区域和全球气候系统中发挥着关键作用。为了更好地了解热带“常绿”植被的生态水文学，必须了解水如何分配到蒸腾和蒸发，径流和相关的水龄。为此，我们使用热带地区的空间分布示踪辅助降雨径流模型（STARR热带地区），评估了地形和植被如何在高时间（小时）和空间（10 m）分辨率下影响水通量和年龄动态。该模型被应用于热带雨林流域（3.2 km ²），该区域每两周一次至每月一次以及在2013年1月至2018年7月的密集监测活动期间收集数据。STARR热带地区进一步开发了该模型，将同位素质量平衡用于蒸散分配为蒸腾和蒸发。结果显示出对降雨输入（水和同位素）的快速水流响应，混合受限，且底流同位素随时间变化很大。模拟的土壤水储量显示了对降雨输入的瞬态响应，其季节分量直接类似于水流动力学，该过程使用土壤含水量测量独立评估。高蒸腾通量（最大7毫米/天）与较低的坡度梯度，更深的土壤和更大的叶面积指数有关。与雨季相比，在较干燥的月份，总体水分分配导致实际蒸发蒸腾量的65％是由蒸腾速率高的植被驱动的。水龄的时间尺度变化很大，从几小时到几年不等。溪流水的年龄被概念化为较年轻的土壤水，稍旧的，较深的土壤水和浅层地下水的混合物，在干旱条件下（722天）的最大年龄约为2年。模拟的土壤水龄从数小时到162天不等，对于浅层地下水长达1200天。尽管存在模型假设，实验挑战和数据局限性，但这种初步的空间分布模型研究可增强对热带雨林中水龄和总体年轻水优势的了解，而对深层和较旧地下水的影响很小。更深的土壤水和浅层地下水，在干旱条件下（722天），最长年龄约为2年。模拟的土壤水龄从数小时到162天不等，对于浅层地下水长达1200天。尽管存在模型假设，实验挑战和数据局限性，但这种初步的空间分布模型研究可增强对热带雨林中水龄和总体年轻水优势的了解，而对深层和较旧地下水的影响很小。更深的土壤水和浅层地下水，在干旱条件下（722天），最长年龄约为2年。模拟的土壤水龄从数小时到162天不等，对于浅层地下水长达1200天。尽管存在模型假设，实验挑战和数据局限性，但这种初步的空间分布模型研究可增强对热带雨林中水龄和总体年轻水优势的了解，而对深层和较旧地下水的影响很小。