Ecohydrologic considerations for modeling of stable water isotopes in a small intermittent watershed
Ecohydrologic considerations for modeling of stable water isotopes in a small intermittent watershed
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DOI：
10.1002/hyp.11194
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发表时间：
2017-06
影响因子：
3.2
通讯作者：
J. Knighton;S. Saia;C. Morris;Josephine A. Archiblad;M. Walter
中科院分区：
文献类型：
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作者：
J. Knighton;S. Saia;C. Morris;Josephine A. Archiblad;M. Walter
自然产生的稳定水同位素示踪剂为水文模型的建立和校准提供了有用的信息。现有的模型包括关于非饱和区渗流混合(优先流与基质流)和蒸散(ET)分配的各种方法。在模拟页岩山流域时，我们用一个相对简单的模型评估了非饱和区简化假设的影响。页岩山流域是美国宾夕法尼亚州彼得斯堡附近的一个小(7.9公顷)温带森林流域。研究发现，非饱和带渗流的不同模型结构/假设和参数设置对模拟和观测到的非饱和带水同位素特征的一致性有很大的影响。结果表明，冬季和春季，非饱和区渗流混合主要影响非饱和区δ18O和δ2H，渗流最好地表现为优先流和基质流的结合。我们评估了与ET分配为蒸发和蒸腾作用相关的重要性和含义，并证明了纳入ET分配的植物生长模型大大改善了春季非饱和带观测到的水文同位素模式的重现性。我们发现，非饱和区渗流混合和ET分配方法对δ18O和δ2H流没有实质性的影响，并得出结论，观测到的径流同位素数据并不总是强烈地预测流域内过程的模式性能。
Naturally occurring stable water isotope tracers provide useful information for hydrologic model development and calibration. Existing models include varied approaches concerning unsaturated zone percolation mixing (preferential versus matrix flow) and evapotranspiration (ET) partitioning. We assess the impact of unsaturated zone simplifying assumptions when simulating the Shale Hills Watershed, a small (7.9 ha), temperate, forested watershed near Petersburg, Pennsylvania, USA, with a relatively simple model. We found that different model structures/assumptions and parameterizations of unsaturated zone percolation had substantial impacts on the agreement between simulated and observed unsaturated‐zone water isotopic signatures. We show that unsaturated zone percolation mixing primarily affects the unsaturated zone δ18O and δ2H during winter and spring and that percolation was best represented as a combination of both preferential and matrix flow. We evaluate the importance and implications related to the partitioning of ET into evaporation and transpiration and demonstrated that incorporation of a plant growth model for ET partitioning substantially improved reproduction of observed hydrologic isotopic patterns of the unsaturated zone during the spring season. We show that unsaturated zone percolation mixing and ET partitioning approaches do not substantially influence stream δ18O and δ2H and conclude that observed streamflow isotopic data is not always a strong predictor of model performance with respect to intrawatershed processes.