Department of Natural Resources and the Environment, University of Connecticut, Storrs, CT, USA.
Volunteer, U.S. Geological Survey, Earth Systems Processes Division, Hydrogeophysics Branch, Storrs, CT, USA.
Nat Commun. 2021 Mar 4;12(1):1450. doi: 10.1038/s41467-021-21651-0.
Groundwater discharge generates streamflow and influences stream thermal regimes. However, the water quality and thermal buffering capacity of groundwater depends on the aquifer source-depth. Here, we pair multi-year air and stream temperature signals to categorize 1729 sites across the continental United States as having major dam influence, shallow or deep groundwater signatures, or lack of pronounced groundwater (atmospheric) signatures. Approximately 40% of non-dam stream sites have substantial groundwater contributions as indicated by characteristic paired air and stream temperature signal metrics. Streams with shallow groundwater signatures account for half of all groundwater signature sites and show reduced baseflow and a higher proportion of warming trends compared to sites with deep groundwater signatures. These findings align with theory that shallow groundwater is more vulnerable to temperature increase and depletion. Streams with atmospheric signatures tend to drain watersheds with low slope and greater human disturbance, indicating reduced stream-groundwater connectivity in populated valley settings.
地下水排泄产生水流，并影响河流热状况。然而，地下水的水质和热缓冲能力取决于含水层的源深。在这里，我们将多年的空气和河流温度信号进行配对，将美国大陆的 1729 个站点分为主要受大坝影响、浅层或深层地下水特征或缺乏明显地下水（大气）特征的三类。大约 40%的非大坝河流站点具有显著的地下水贡献，这表明空气和河流温度信号特征存在显著相关性。具有浅层地下水特征的河流占所有具有地下水特征站点的一半，与具有深层地下水特征的站点相比，其基流量减少，升温趋势的比例更高。这些发现与浅层地下水更容易受到温度升高和枯竭影响的理论相一致。具有大气特征的河流往往流经坡度较低、人类干扰较大的流域，这表明在人口密集的山谷环境中，河流与地下水的连通性降低。
