Snow drought reduces water transit times in headwater streams
Snow drought reduces water transit times in headwater streams
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DOI：
10.1002/hyp.14437
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发表时间：
2021-11
影响因子：
3.2
通讯作者：
Catalina Segura
中科院分区：
文献类型：
--
作者：
Catalina Segura
了解水在流域中的传递时间是了解水文和生物地球化学过程的基础。然而，它的预测仍然难以捉摸，特别是在地形和降雨量短距离变化的山区。此外，气候变化对过境时间的影响仍有待研究，因为它继续改变山区的降水形式。水同位素比率被用来评估2014-2018年期间俄勒冈州西部七个小山区流域的平均通过时间(MTT)和年轻水分数(Fyw*)，其中包括2015年的一次重大区域性雪旱。2015年所有流域的MTT值比其他任何一年都短，而Fyw*比其他任何一年都大。2015年观察到的过境时间较短可能与地表水和较老地下水之间的连通性较低有关，这导致所有被调查的流域的水文响应均一，尽管它们的地理位置不同。2016-2018年的MT值在所有流域之间差异很大，但在较小的高海拔流域尤其如此，这表明2015年雪旱对严重依赖融雪投入的系统的影响更大。在相对潮湿/寒冷的年份，流域的固有特征，如流域面积和地形粗糙度，解释了所有流域过境时间指标的一些差异。干旱期间较短的运输时间对水质和溶质浓度有影响，因为生物地球化学过程在一定程度上受水在地下停留和相互作用的时间控制。尽管2015年雪旱的影响似乎是短暂的，但考虑到随着美国西部气候变暖，预计区域积雪量将会下降，这些结果尤其重要。
Knowledge of water transit times through watersheds is fundamental to understand hydrological and biogeochemical processes. However, its prediction is still elusive, particularly in mountainous terrain where physiography and precipitation change over short distances. In addition, much remains to be studied about the impact of climate change on transit time as it continues to change precipitation form in mountainous terrain. Water isotopic ratios were used to evaluate mean transit time (MTT) and young water fractions ( Fyw* ) in seven small mountainous watersheds in western Oregon over the 2014–2018 period that included a major regional snow drought in 2015. The MTT was shorter in 2015 across all watersheds compared to any other year while the Fyw* was larger in 2015 than in any other year. The short transit times observed in 2015 could be related to low connectivity between surface water and older ground water which resulted in a homogenous hydrologic response across all the investigated watersheds despite their physiographical differences. The 2016–2018 MTT vary widely across all watersheds but especially within the smaller high elevation watersheds indicating that the impact of the 2015 snow drought was stronger for systems that depend heavily on snowmelt inputs. During relatively wet/cold years intrinsic watershed characteristics such as drainage area and terrain roughness explained some of the variability in transit time metrics across all watersheds. Shorter transit times during the drought have implications for water quality and solute concentrations as biogeochemical processes are controlled in part by the time water resides and interacts within the subsurface. Although the impact of the 2015 snow drought appears short‐lived these results are particularly critical considering the expected regional snowpack decline as the climate warms in the western United States.