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Abstract Many headwater wetlands are integrated into flowpath networks and can serve as sources of streamflow for downgradient waters. We demonstrate this with five years of data in vernal pool, swale, and headwater stream complexes in the Central Valley, California. Long-term United States Geological Survey data suggest that the mean flow duration from the smallest watersheds in this region, including those with vernal pool, swale, and headwater stream complexes, is ~ 85 days per year. Our data concur, indicating that the annual days of flow per year from our vernal pool, swale, and headwater stream complexes ranges from ~ 20–200, but is ~ 85 when annual precipitation is 100% of normal. Peak stages are evident first in vernal pools which then propagate sequentially downstream through swales, headwater streams, and to the Sacramento River at celerities of ~ 1-1.5 m/s, consistent with expected flood wave velocities. Geospatial analyses show that these vernal pool, swale, and headwater stream features cover > 4% of the study area. Our results suggest these systems can be significant sources of streamflow, and therefore play an important role in maintaining the chemical, physical, and biological integrity of downstream waters, which has important implications for the definition of waters of the United States subject to regulation under the Clean Water Act.
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The Budyko shape parameter as a descriptive index for streamflow loss
Increases in evapotranspiration (ET) from global warming are decreasing streamflow in headwater basins worldwide. However, these streamflow losses do not occur uniformly due to complex topography. To better understand the heterogeneity of streamflow loss, we use the Budyko shape parameter (ω) as a diagnostic tool. We fit ω to 37-year of hydrologic simulation output in the Upper Colorado River Basin (UCRB), an important headwater basin in the US. We split the UCRB into two categories: peak watersheds with high elevation and steep slopes, and valley watersheds with lower elevation and gradual slopes. Our results demonstrate a relationship between streamflow loss and ω. The valley watersheds with greater streamflow loss have ω higher than 3.1, while the peak watersheds with less streamflow loss have an average ω of 1.3. This work highlights the use of ω as an indicator of streamflow loss and could be generalized to other headwater basin systems.
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- PAR ID:
- 10473645
- Publisher / Repository:
- Frontiers
- Date Published:
- Journal Name:
- Frontiers in Water
- Volume:
- 5
- ISSN:
- 2624-9375
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/frwa.2023.1258367
