DOI: 10.5066/p13x4sxb
title: Modeled streamflow and associated data from 2021-2022 for ephemeral channels to the San Juan River, Four Corners Region, USA

description: 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)AR2/3S1/2
 
where Q is the peak streamflow (m3/s),  
n is the Manning roughness coefficient (s/m1/3, often omitted)  
A is the cross-sectional area (m2),  
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 data release contains three different files relating to pressure transducer data collected at six tributaries to the San Juan River. Pressure transducers were installed beginning on 3/4/2021 and collected data until 12/31/2022. The mean daily streamflow 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 were corrected for barometric pressure using pressure readings from the dataset that directly proceeds the event. The events-based file contains event-based stage and streamflow values derived using the same methods at a 15-minute resolution. Events were determined by visual analysis of hydrographs derived from pressure transducer stage values. The data were corrected for barometric pressure using pressure readings from the dataset that directly proceeded the event. The raw stage file contains raw stage (depth in feet of water) values computed by the pressure transducer. These data are not corrected for barometric pressure and do not represent actual depth of water in the respective tributaries. 

References 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/.