Relationship between isotope ratios in precipitation and stream water across watersheds of the National Ecological Observation Network
Relationship between isotope ratios in precipitation and stream water across watersheds of the National Ecological Observation Network
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DOI：
10.1002/hyp.15018
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发表时间：
2023-11-01
影响因子：
3.2
通讯作者：
Hu，Huancui
中科院分区：
文献类型：
--
作者：
Butler，Zachariah;Good，Stephen;Hu，Huancui
与降水通过流域移动相关的时间尺度揭示了对理解许多水文系统至关重要的过程。环境稳定水同位素比值（δ 2 H和δ 18 O）的测量已被用作示踪剂，通过检查进入的降水示踪剂变成河流排放需要多长时间来研究水文时间尺度，但到目前为止，空间和时间上有限的测量限制了宏观尺度的评估。在这项针对国家生态观测网络（氖）内北美生物群系的观测驱动研究中，我们检查了26个共存地点的降水（δP）和溪流（δQ）中的δ 18 O和δ 2 H稳定水同位素。在2014-2022年期间，每个站点平均收集了54个降水样本和139个溪流样本，对当地大气水线和当地溪流水线的评估显示，北美各地存在地理差异。用δP和δQ的季节幅度比值计算年轻水含量（Fyw），Fyw的范围为1%~ 93%，多数站点Fyw小于20%。基于伽马卷积模型计算的平均通过时间（MTT）显示MTT范围为0.10至13.2年，一半的站点MTT估计值低于2年。之间的显着相关性被发现theFywand流域面积，最长的流长度，和最长的流长度/斜率。MTT与场地纬度、经度、坡度、粘粒含量、温度、降水量和降水频率呈显著相关。我们报告的水时间尺度指标和环境特征之间的显着相关性与以前的研究报告有一些相似之处，表明这些数量主要是由现场或区域特定因素驱动的。这里提出的同位素数据的分析提供了重要的限制同位素变化在北美生物群落和水运动的时间尺度通过氖研究地点。
The timescales associated with precipitation moving through watersheds reveal processes that are critical to understanding many hydrologic systems. Measurements of environmental stable water isotope ratios (δ2H and δ18O) have been used as tracers to study hydrologic timescales by examining how long it takes for incoming precipitation tracers become stream discharge, yet limited measurements both spatially and temporally have bounded macroscale evaluations so far. In this observation driven study across North American biomes within the National Ecological Observation Network (NEON), we examined δ18O and δ2H stable water isotope in precipitation (δP) and stream water (δQ) at 26 co‐located sites. With an average 54 precipitation samples and 139 stream water samples per site collected over 2014–2022, assessment of local meteoric water lines and local stream water lines showed geographic variation across North America. Taking the ratio of estimated seasonal amplitudes of δP and δQ to calculate young water fractions (Fyw), showed aFywrange from 1% to 93% with most sites havingFywbelow 20%. Calculated mean transit times (MTT) based on a gamma convolution model showed a MTT range from 0.10 to 13.2 years, with half of the sites having MTT estimates lower than 2 years. Significant correlations were found between theFywand watershed area, longest flow length, and the longest flow length/slope. Significant correlations were found between MTT and site latitude, longitude, slope, clay fraction, temperature, precipitation magnitude, and precipitation frequency. The significant correlations between water timescale metrics and the environmental characteristics we report share some similarities with those reported in prior studies, demonstrating that these quantities are primarily driven by site or area specific factors. The analysis of isotope data presented here provides important constraints on isotope variation in North American biomes and the timescales of water movement through NEON study sites.