Mean daily streamflow from ephemeral channels to the San Juan River, Four Corners Region, USA

Streamflow data are essential for measuring water quality, including calculating loads of metals. Streamflow can be estimated from stage values (water height above known datum) using stage-streamflow ratings. However, in ephemeral channels, direct measurements of streamflow are often impractical due to remote, short-duration flow events, warranting the use of rating curves to derive discharge values. Recent advances in photogrammetry and low-cost uncrewed aerial systems (UAS) have enabled the creation of high-fidelity terrain models. This study used photogrammetry-derived digital surface models to extract channel geometry and model stage-streamflow ratings in the Four Corners region (the general area where the U.S. states of Arizona, New Mexico, Colorado, and Utah boundaries converge), replacing survey of channel geometry using traditional surveying equipment. The slope-area method, using channel-geometry measurements derived from UAS generated terrain models, was used to create a rating for each site.Streamflow was simulated with USGS stage data and applying the empirical Manning equation (Dalrymple and Benson, 1967).
Q=(1/n)AR^2/3S^1/2
where Q is the peak streamflow (m^3/s), 
n is the Manning roughness coefficient (s/m^1/3, often omitted) 
A is the cross-sectional area (m^2), 
R is the hydraulic radius (m), 
and S is the water surface slope (m/m, dimensionless).
Discharge shows a high sensitivity to the roughness coefficient Manning's 'n.' Accurate selection of Manning's 'n', considering riparian vegetation and spatial variability is crucial. Modeling methodology and efficacy is discussed thoroughly in the associated publication (Brown et. al, 2024).
This metadata file contains mean daily stage and mean daily streamflow values derived from pressure transducer readings and streamflow modeled using slope-area computation graphical user interface (SACGUI; USGS, 2013). The data was corrected for barometric pressure using readings directly proceeding the event.
Reference Cited:
Brown, J. E., Bosch, K. E., Shephard, Z. M., Van Zante, C. A., Ball, G. P., Wickle, J., Blake, J. M., and DeBenedetto, J., 2024. Stage-streamflow modeling of ephemeral channels along the San Juan River using stage sensors and channel geometry derived from small uncrewed aircraft systems, Geochemistry: Exploration, Environment, Analysis, (full citation to be updated upon publication)
Dalrymple, T., and Benson, M. A. 1967. Measurement of peak discharge by the slope-area method: U.S. Geological Survey Techniques of Water-Resources Investigations, book 3, chap. A2, 12 p. (Also available at https://pubs.usgs.gov/twri/twri3-a2/).
United States Geological Survey [USGS], 2013. Water Resources of the United States: SAC and SACGUI (ver. 2.0, August, 2013), accessed June 6, 2024 at: https://water.usgs.gov/software/SAC/.

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