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Abstract Intermittent streams currently constitute >50% of the global river network, and the number of intermittent streams is expected to increase due to changes in land use and climate. Surface flows are known to expand and contract within the headwater channel network due to changes in the water table driven by climate, often changing seasonally. However, the underlying causes of disconnections and reconnections throughout the stream network remain poorly understood and may reflect subsurface flow capacity. We assess how 3D subsurface flowpaths control local surface flows at Gibson Jack Creek in the Rocky Mountains, Idaho, USA. Water table dynamics, hydraulic gradients, and hyporheic exchange were monitored along a 200‐m section of the stream throughout the seasonal recession in WY2018. Shallow lateral hillslope‐riparian‐stream connectivity was more frequent in transects spanning perennially flowing stream reaches than intermittent reaches. During low‐flow periods, larger losing vertical hydraulic gradients were observed in paired piezometers in intermittent reaches than in adjacent perennial reaches. Contrary to dominant conceptual models, longitudinal measurements of hydrologic exchange in both intermittent and perennial reaches were seasonally variable except for one perennial reach that showed consistent significant gains. Observed drying dynamics, as well as subsurface pathways, were highly variable even over short distances (30 m). Flow probability and subsurface flow capacity at upstream locations can be assessed with an outlet hydrograph and upstream flow measurements. Accurate characterization of subsurface storage, discharge, and connection is critical to understanding the drivers of drying cycles in intermittent streams and their likely responses to future change.
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Assessing the Influence of Zero‐Flow Threshold Choice for Characterising Intermittent Stream Hydrology
ABSTRACT Zero‐flow recordings in gauged streamflow data are critically important for intermittent stream research. Acknowledging the high uncertainty in zero‐flow recordings, many studies pick a small number as zero‐flow threshold, below which the flow is considered to be zero. The choice of zero‐flow threshold is often arbitrary or unjustified, which leads us to wonder: would selecting a slightly different threshold change analysis result significantly? Here, we used a simple sensitivity analysis to assess how the choice of zero‐flow threshold impacts the calculated values of relevant metrics to intermittent stream research. Results show that these metrics tended to be more sensitive to lower zero‐flow thresholds, suggesting that even choosing a slightly different threshold could lead to meaningfully different results from the management perspective. This study highlights the need for reasonable justification of the choice of zero‐flow threshold and concludes with potential ways to reduce uncertainty in zero‐flow measurement.
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- PAR ID:
- 10550409
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Hydrological Processes
- Volume:
- 38
- Issue:
- 10
- ISSN:
- 0885-6087
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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