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首页> 外文期刊>Journal of Hydrology >Relative influence of upland and lowland headwaters on the isotope hydrology and transit times of larger catchments
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Relative influence of upland and lowland headwaters on the isotope hydrology and transit times of larger catchments

机译：高地和低地源水对较大流域同位素水文学和过渡时间的相对影响

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Weekly variation of δ~(18)O was measured over 2years in precipitation and river water in four relatively large catchments in north east Scotland. The River Dee (1712km~2) is predominantly upland, with impermeable geology and hydrologically responsive soils. The headwaters of the River North Esk (732km~2) are similar, but the lower third of the catchment is underlain by a major sandstone aquifer and is lowland (i.e. <300m altitude) in nature. The upper 20% of the River Don catchment (1273km~2) is upland, but the remainder is lowland with freely draining soils recharging significant groundwater reservoirs in superficial drifts. The River Ythan catchment (662km~2) is entirely lowland and similar to the lower Don. The hydrological responsiveness of the catchments was directly related to their upland area, with the Dee and the North Esk generating the highest specific discharges during high flow events. Conversely, the Don and Ythan had more subdued hydrological regimes, but higher specific discharge under baseflows. Despite broadly similar δ~(18)O variation in precipitation inputs, the variability of stream waters was increasingly damped in the order Ythan>Don>North Esk>Dee. Convolution integral models were used to estimate Mean Transit Times (MTTs) for the four catchments from the isotope data. These were reasonably well-constrained at around 2years for the Dee and 3years for the North Esk. Estimates for the Don and Ythan were poorly constrained and therefore highly uncertain, but are both likely to exceed 10years. MTTs in upland catchments in the Scottish Highlands are relatively short (ca. 2months-4years) and have been shown to be strongly correlated with soil hydrology, topographic indices and precipitation intensity. However, these relationships change in lowland areas as catchments become less surface water dominated and greater groundwater storage and deeper mixing processes result in much higher MTTs. Nevertheless, a close correlation between soil cover and MTT remains.
机译：在苏格兰东北部四个相对较大的流域，降水和河水在2年内测量了δ〜（18）O的每周变化。迪河（1712km〜2）主要为高地，具有不可渗透的地质和对水文敏感的土壤。北埃斯克河（732km〜2）的上游水源相似，但流域的下三分之一位于主要的砂岩含水层之下，自然界处于低地（即海拔<300m）。唐河集水区（1273km〜2）的上部20％为高地，其余为低地，土壤自由排水，在表层漂移中为大量地下水蓄积。伊丹河流域（662 km〜2）完全为低地，与唐河下游相似。流域的水文响应能力直接与它们的高地面积有关，在高流量事件中，迪伊河和北埃斯河的最高比排放量。相反，Don和Ythan的水文状况较弱，但在基流下的比水流量较高。尽管降水输入中的δ〜（18）O变化大致相似，但溪流水的变化性按Ythan> Don> North Esk> Dee的顺序逐渐衰减。卷积积分模型用于根据同位素数据估算四个流域的平均运输时间（MTT）。在Dee的2年左右和North Esk的3年左右，这些约束受到了很好的约束。 Don和Ythan的估计值约束有限，因此高度不确定，但都可能超过10年。苏格兰高地集水区的MTTs相对较短（约2个月至4年），并已证明与土壤水文学，地形指数和降水强度密切相关。但是，随着流域变得越来越少的地表水占主导地位以及更大的地下水存储量和更深的混合过程导致更高的MTT，这些关系在低地地区发生了变化。然而，土壤覆盖率和MTT之间仍然存在密切的相关性。

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