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首页> 外文期刊>Hydrology and Earth System Sciences >Transit times from rainfall to baseflow in headwater catchments estimated using tritium: the Ovens River, Australia
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Transit times from rainfall to baseflow in headwater catchments estimated using tritium: the Ovens River, Australia

机译：用rainfall估算的从上游流域降雨到基流的过渡时间：澳大利亚奥克斯河

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摘要

Headwater streams contribute a significant proportion of the total flow to many river systems, especially during summer low-flow periods. However, despite their importance, the time taken for water to travel through headwater catchments and into the streams (the transit time) is poorly understood. Here, H-3 activities of stream water are used to define transit times of water contributing to streams from the upper reaches of the Ovens River in south-east Australia at varying flow conditions. H-3 activities of the stream water varied from 1.63 to 2.45 TU, which are below the average H-3 activity of modern local rainfall (2.85 to 2.99 TU). The highest H-3 activities were recorded following higher winter flows and the lowest H-3 activities were recorded at summer low-flow conditions. Variations of major ion concentrations and H-3 activities with streamflow imply that different stores of water from within the catchment (e.g. from the soil or regolith) are mobilised during rainfall events rather than there being simple dilution of an older groundwater component by event water. Mean transit times calculated using an exponential-piston flow model range from 4 to 30 years and are higher at summer low-flow conditions. Mean transit times calculated using other flow models (e.g. exponential flow or dispersion) are similar. There are broad correlations between H-3 activities and the percentage of rainfall exported from each catchment and between H-3 activities and Na and Cl concentrations that allow first-order estimates of mean transit times in adjacent catchments or at different times in these catchments to be made. Water from the upper Ovens River has similar mean transit times to the headwater streams implying there is no significant input of old water from the alluvial gravels. The observation that the water contributing to the headwater streams in the Ovens catchment has a mean transit time of years to decades implies that these streams are buffered against rainfall variations on timescales of a few years. However, impacts of any changes to land use in these catchments may take years to decades to manifest themselves in changes to streamflow or water quality.
机译：上游水源对许多河流系统的总流量贡献很大，特别是在夏季低流量时期。然而，尽管它们很重要，但人们对水流过上游水源汇入溪流所花费的时间（运输时间）知之甚少。在这里，溪流水的H-3活度用于定义在变化的流量条件下对来自澳大利亚东南部奥克斯河上游的溪流做出贡献的水的迁移时间。溪流水的H-3活性在1.63至2.45 TU之间变化，低于现代当地降雨的平均H-3活性（2.85至2.99 TU）。在冬季流量增加之后记录了最高的H-3活动，而在夏季低流量条件下记录了最低的H-3活动。主要离子浓度和H-3活度随流量的变化意味着在降雨事件期间动员了集水区内不同的水储量（例如来自土壤或重水石），而不是通过事件水简单地稀释了较旧的地下水成分。使用指数活塞流模型计算的平均运输时间为4到30年，并且在夏季低流量条件下会更长。使用其他流量模型（例如指数流量或弥散）计算的平均渡越时间相似。 H-3活动与每个流域输出的降雨百分比之间以及H-3活动与Na和Cl浓度之间存在广泛的相关性，可以对相邻流域或这些流域中不同流域的平均通过时间进行一阶估算。被制造。烤箱上游的水的平均通过时间与上游水流相似，这意味着冲积砾石没有大量的老水输入。观察结果表明，在烤箱集水区的上游水源中的水的平均传播时间为数年至数十年，这意味着这些水流可以缓冲几年时间范围内的降雨变化。但是，这些流域土地利用的任何变化所产生的影响可能要花费数年甚至数十年的时间才能体现在流量或水质的变化中。

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