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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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Headwater streams contribute a significant proportion of the total flow tomany river systems, especially during summer low-flow periods. However,despite their importance, the time taken for water to travel throughheadwater catchments and into the streams (the transit time) is poorlyunderstood. Here, 3H activities of stream water are used to definetransit times of water contributing to streams from the upper reaches of theOvens River in south-east Australia at varying flow conditions. 3Hactivities of the stream water varied from 1.63 to 2.45 TU, which are belowthe average 3H activity of modern local rainfall (2.85 to 2.99 TU). Thehighest 3H activities were recorded following higher winter flows andthe lowest 3H activities were recorded at summer low-flow conditions.Variations of major ion concentrations and 3H activities withstreamflow imply that different stores of water from within the catchment(e.g. from the soil or regolith) are mobilised during rainfall events ratherthan there being simple dilution of an older groundwater component by eventwater. Mean transit times calculated using an exponential-piston flow modelrange from 4 to 30 years and are higher at summer low-flow conditions. Meantransit times calculated using other flow models (e.g. exponential flow ordispersion) are similar. There are broad correlations between 3Hactivities and the percentage of rainfall exported from each catchment andbetween 3H activities and Na and Cl concentrations that allowfirst-order estimates of mean transit times in adjacent catchments or atdifferent times in these catchments to be made. Water from the upper OvensRiver has similar mean transit times to the headwater streams implying thereis no significant input of old water from the alluvial gravels. Theobservation that the water contributing to the headwater streams in theOvens catchment has a mean transit time of years to decades implies thatthese streams are buffered against rainfall variations on timescales of afew years. However, impacts of any changes to land use in these catchmentsmay take years to decades to manifest themselves in changes to streamflow orwater quality.
机译：上游水源在许多河流系统的总流量中占很大比例，尤其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河流的时间（渡越时间）却知之甚少。在此，使用溪流水的 3 H活度来定义在变化的流量条件下对来自澳大利亚东南部奥恩斯河上游的溪流做出贡献的水的转运时间。溪流水的 3 活度在1.63至2.45 TU之间变化，低于现代局部降雨的平均 3 H活动（2.85至2.99 TU）。冬季流量增加后， 3 H活性最高，夏季低流量条件下 3 H活性最低。主要离子浓度和 3 H活动随水流流动意味着在降雨事件中动员了集水区内不同的水储量（例如，来自土壤或重水石），而不是由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更长。使用其他流模型（例如指数流或离散）计算的平均运输时间相似。 3 活度与每个流域出口降雨的百分比之间存在广泛的相关性， 3 H活度与Na和Cl浓度之间存在相关关系，从而可以对相邻区域的平均通过时间进行一阶估算集水区或这些集水区的不同时间。来自上烤箱河的水具有与上游水流相似的平均运输时间，这意味着冲积砾石没有大量的旧水输入。观察表明，导致集水区上游水源流的水的平均传播时间为数年至数十年，这意味着这些流在数年的时间尺度上可以抵御降雨的变化。但是，这些流域土地利用的任何变化所产生的影响可能需要数年甚至数十年的时间才能体现在水流或水质的变化中。

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