Spatial Patterns and Drivers of Nonperennial Flow Regimes in the Contiguous United States
Spatial Patterns and Drivers of Nonperennial Flow Regimes in the Contiguous United States
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DOI：
10.1029/2020gl090794
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发表时间：
2021-01-28
影响因子：
5.2
通讯作者：
Allen, Daniel C.
中科院分区：
文献类型：
--
作者：
Hammond, John C.;Zimmer, Margaret;Allen, Daniel C.
全球超过一半的河流和溪流缺乏常年流动，了解其流动状态的分布和驱动因素对于理解其水文、生物地球化学和生态功能至关重要。我们分析了1979年至2018年美国连续地区的540个美国地质调查局流域的非多年生水流状况。多变量分析揭示了无流率、首次无流日期和干枯期持续时间的区域差异，自然和人为改变的流域之间存在进一步的差异。在大陆尺度上，干旱是无流指标的主要驱动因素，而在区域尺度上，气候、地理和人为驱动因素的独特组合出现。干干持续时间与非气候驱动因素的相关性较强。尽管非多年生尺度的稀疏分布限制了我们对这些河流的理解，但这里研究的流域表明，干旱和土地覆盖变化在调节未来河流干燥方面发挥了重要作用。全球大多数河流都是非多年生的，只在一年中部分时间流动，对维持下游的流动至关重要，为许多生物提供栖息地，并调节化学和生物过程。利用美国地质调查局（U.S. Geological Survey）对美国540个流域的长期测量数据，我们绘制了无流量比例的分布图，并研究了无流量比例的原因、每个气候年无流量的比例、无流量时间、首次记录无流量发生的气候年日期、干枯期的长度、从当地日流量峰值到首次出现无流量的平均天数。我们发现不同地区之间的无流特征模式存在差异，美国西部的无流分数较高，时间较早，干干持续时间较短。自然流域的无流分数较大，变化较小，而人工改造流域的无流时间较早，干落时间较短。在美国，干旱对间歇性的影响最大，但气候、生物物理和人类影响的独特组合在不同地区也很重要。与多年生河流相比，测量非多年生河流流量的仪表数量较少，需要增加监测以更好地了解干燥行为。要点。三个指标揭示了区域和人类驱动的非多年生水流模式：无流比例、首次无流天数和干流持续时间。人类改造的河流通常比未改造的河流干得更快，特别是在加利福尼亚和南部大平原。气候强烈影响无流比例和时间，但地理变量对干流持续时间更重要
Over half of global rivers and streams lack perennial flow, and understanding the distribution and drivers of their flow regimes is critical for understanding their hydrologic, biogeochemical, and ecological functions. We analyzed nonperennial flow regimes using 540 U.S. Geological Survey watersheds across the contiguous United States from 1979 to 2018. Multivariate analyses revealed regional differences in no-flow fraction, date of first no flow, and duration of the dry-down period, with further divergence between natural and human-altered watersheds. Aridity was a primary driver of no-flow metrics at the continental scale, while unique combinations of climatic, physiographic and anthropogenic drivers emerged at regional scales. Dry-down duration showed stronger associations with nonclimate drivers compared to no-flow fraction and timing. Although the sparse distribution of nonperennial gages limits our understanding of such streams, the watersheds examined here suggest the important role of aridity and land cover change in modulating future stream drying.Plain Language Summary A majority of global streams are nonperennial, flowing only part of the year, and are critical for sustaining flow downstream, providing habitat for many organisms, and regulating chemical and biological processes. Using long-term U.S. Geological Survey measurements for 540 watersheds across the contiguous United States, we mapped patterns and examined the causes of no-flow fraction, the fraction of each climate year with no flow, no-flow timing, the date of the climate year on which the first recorded no flow takes place, and length of the dry-down period, the average number of days from a local peak in daily flow to the first occurrence of no flow. We found differences in patterns of no-flow characteristics between regions, with higher no-flow fraction, earlier timing, and shorter dry-down duration in the western United States. No-flow fractions were greater and less variable in natural watersheds, while no-flow timing was earlier and dry-down duration was shorter in human-modified watersheds. Aridity had the greatest effect on intermittence across the United States, but unique combinations of climate, biophysical, and human impacts were important in different regions. The number of gages measuring streamflow in nonperennial streams is small compared to perennial streams, and increased monitoring is needed to better understand drying behavior.Key Points.Three metrics reveal regional and human-driven patterns of nonperennial flow: no-flow fraction, day of first no flow, and dry-down durationStreams with human modifications generally dry more quickly than unmodified streams, especially in California and the Southern Great PlainsClimate strongly influences no-flow fraction and timing, but physiographic variables are more important for the duration of dry down