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- Title
Nonlinear Riparian Interactions Drive Changes in Headwater Streamflow.
- Authors
Newcomb, Sarah K.; Godsey, Sarah E.
- Abstract
As drought and wildfire frequency increase across the western United States, our ability to predict how water resources will respond to these disturbances depends on our understanding of the feedbacks that maintain watershed function and streamflow. Previous studies of non‐perennial headwater streams have ranked drivers of low‐flow conditions; however, there is a limited understanding of the interactions between these drivers and the processes through which these interactions affect streamflow. Here, we use stream water level, soil moisture, sap flow, and vapor pressure deficit data to investigate ecohydrological interactions along a mountainous headwater stream. Correlation and cross‐correlation analyses of these variables show that ecohydrological interactions are (a) nonlinear and (b) interconnected, suggesting that analyses assuming linearity and independence of each driver are inadequate for quantifying these interactions. To account for these issues and investigate causal linkages, we use convergent cross‐mapping (CCM) to characterize the feedbacks that influence non‐perennial streamflow. CCM is a nonlinear, dynamic method that has only recently been applied to hydrologic systems. CCM results reveal that atmospheric losses associated with local sap flow and vapor pressure deficit are driving changes in soil moisture and streamflow (p < 0.01) and that atmospheric losses influence stream water more directly than shallow soil moisture. These results also demonstrate that riparian processes continue to affect subsurface flows in the channel corridor even after stream drying. This study proposes a nonlinear framework for quantifying the ecohydrologic interactions that may determine how headwater streams respond to disturbance. Plain Language Summary: Across the western United States, many watersheds are experiencing more disturbances like drought and wildfire. How well these watersheds recover after these disturbances depends on the relationships between streamflow and other environmental conditions like soil moisture, vegetation, and how warm and dry the air is. In this study, we investigated how these environmental conditions are impacting mountain headwater streams. Our analyses found that the strength and direction of the interactions between air, plants, soil, and water change throughout the year. This variability means that methods assuming consistent behavior cannot capture these interactions. Furthermore, the results show that the main drivers of changes in stream water are how much water plants use and how dry the air is, and this holds true even after streams dry. These findings suggest that in order to predict how stream networks will respond to disturbances like drought, models need to account for the dynamic relationships between environmental conditions and stream water. Key Points: Hydro‐ecological feedbacks are nonlinear and interconnectedConvergent cross‐mapping reveals that atmospheric conditions drive changes in stream water levelRiparian processes continue to affect subsurface flow in the channel corridor of headwater systems after streams dry
- Subjects
UNITED States; STREAMFLOW; WEATHER; VAPOR pressure; SOIL moisture; CHANNEL flow; WATERSHED management; RIPARIAN areas
- Publication
Water Resources Research, 2023, Vol 59, Issue 10, p1
- ISSN
0043-1397
- Publication type
Article
- DOI
10.1029/2023WR034870