The sensitivity of runoff generation to spatial snowpack uniformity in an alpine watershed: Green Lakes Valley, Niwot Ridge Long-Term Ecological Research station,Hydrological Processes

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The sensitivity of runoff generation to spatial snowpack uniformity in an alpine watershed: Green Lakes Valley, Niwot Ridge Long-Term Ecological Research station
Hydrological Processes ( IF 2.8 ) Pub Date : 2021-08-03 , DOI: 10.1002/hyp.14331
A. M. Badger _{1,

2} , N. Bjarke ₃ , N. P. Molotch _{4,

5,

6} , B. Livneh _{3,

7}

Affiliation

Seasonal water storage in high-elevation alpine catchments are critical sources of water for mountainous regions like the western U.S. The spatial distribution of snow in these topographically complex catchments is primarily governed by orography, solar radiation, and wind redistribution. While the effect of solar shading is relatively consistent from year-to-year, the redistribution of snow due to wind is more variable – capable of producing snowpacks that have varying degrees of uniformity across these hydrologically-important catchments. A reasonable hypothesis is that a warmer climate will cause snowfall to become more dense (i.e. wetter and heavier), possibly leading to less wind redistribution and thus produce a more uniformly distributed snowpack across the landscape. In this study, we investigate the role of increasingly uniform spatial snowpack distributions on streamflow generation in the Green Lakes Valley Niwot Ridge Long Term Ecological Research station, within the headwaters of the Boulder Creek watershed in Colorado. A set of idealized hydrologic simulation experiments driven by reconstructed snowpacks spanning 2001–2014 show that more a more uniform spatial snowpack distribution leads to an earlier melt-out of 31 days on average and tends to produce less total streamflow, with maximum decreases as large as 7.5%. Isolating the role of snowpack heterogeneity from melt-season precipitation, we find that snowpack uniformity reduces total streamflow by as much as 13.2%. Reductions in streamflow are largely explained by greater exposure to solar radiation in the uniformly distributed case relative to a more heterogeneous snowpack, with this exposure driving shifts towards earlier snowmelt and changes in soil water storage. Overall, we find that the runoff efficiency from shallower snowpacks is more sensitive to the effects of uniformity than deeper snowpacks, which has potential implications for a warming climate where shallower snowpacks and enhanced sensitivities may be present.

中文翻译：

高山流域径流生成对空间积雪均匀性的敏感性：格林湖谷，尼沃特岭长期生态研究站

高海拔高山集水区的季节性蓄水是美国西部等山区的重要水源。这些地形复杂的集水区雪的空间分布主要受地形、太阳辐射和风的重新分布控制。虽然遮阳的影响每年都相对一致，但风引起的雪的重新分布变化更大——能够在这些具有重要水文意义的集水区产生具有不同程度均匀性的积雪。一个合理的假设是，气候变暖会导致降雪变得更密集（即更湿和更重），可能导致风的再分布减少，从而在整个景观中产生更均匀分布的积雪。在这项研究中，我们调查了在科罗拉多州博尔德溪流域源头内的 Green Lakes Valley Niwot Ridge 长期生态研究站中，越来越均匀的空间积雪分布对水流生成的作用。一组由 2001 年至 2014 年重建积雪驱动的理想化水文模拟实验表明，空间积雪分布越均匀，平均融化时间越早，平均为 31 天，并且倾向于产生较少的总流量，最大降幅为7.5%。将积雪异质性与融化季节降水的作用隔离开来，我们发现积雪均匀性使总流量减少了 13.2%。流量减少的主要原因是在均匀分布的情况下，相对于更不均匀的积雪，更多地暴露于太阳辐射，这种暴露推动了更早的融雪和土壤储水量的变化。总体而言，我们发现较浅的积雪的径流效率对均匀性的影响比较深的积雪更敏感，这对可能存在较浅积雪和敏感性增强的气候变暖具有潜在影响。

更新日期：2021-09-17

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