Trace Element Export From the Critical Zone Triggered by Snowmelt Runoff in a Montane Watershed, Provo River, Utah, USA

Strontium isotope dynamics reveal streamflow contributions from shallow flow paths during snowmelt in a montane watershed, Provo River, Utah, USA

“…Flushed soil water contributes up to 75% of total discharge at Soapstone during snowmelt, with maximum amounts during May and June, resulting in the lowest 87 Sr/ 86 Sr ratios and dramatically altering water chemistry. The importance of flushed soil water for controlling water chemistry in the upper Provo River was also described in other papers using positive C–Q slopes for trace metals and rare earth elements (Checketts et al, 2020) as well as Hg and dissolved organic matter (Packer et al, 2020). Using 87 Sr/ 86 Sr ratios to track flow paths provides a step forward in quantifying contributions from direct snowmelt, flushed soil water and groundwater in montane streams like the Provo River.…”

“…The large differences in 87 Sr/ 86 Sr ratios in soil and bedrock, with corresponding differences in soil water and springs (Figure 3), permit the use of 87 Sr/ 86 Sr ratios in water as a solute tracer, particularly for Sr and Ca. Flushed soil water contributes up to 75% of total discharge at Soapstone during snowmelt, with maximum amounts during May and June, resulting in the lowest 87 Sr/ 86 Sr T A B L E 1 Annual and seasonal solute load and discharge at soapstone, woodland and hailstone River was also described in other papers using positive C-Q slopes for trace metals and rare earth elements (Checketts et al, 2020) as well as Hg and dissolved organic matter (Packer et al, 2020). Using Hailstone, all sample points plot near the mixing curve, suggesting that at larger scales the direct snowmelt component is not as important.…”

“…Discharge data were obtained from US Geological Survey (USGS) gauging stations at Woodland (USGS 10154200) and Hailstone (USGS 10155000). For the Soapstone site, discharge data were obtained from the iUTAH (innovative Urban Transitions and Arid region Hydro‐sustainability) project, with missing values interpolated by linear regression on Woodland discharge data (Checketts et al, 2020).…”

“…River sampling locations were selected to capture transitions between source waters from upper elevation siliciclastic rocks (S), mid‐elevation carbonate rocks (W) and lower elevation volcanic rocks (H). Modified after Packer et al (2020) and Checketts et al (2020)…”

“…The ephemeral stream samples represent a broad range of residence times and source areas, with a mixture of snowmelt and varying amounts of soil water and shallow groundwater. Sampling methods and frequency are described in Checketts et al (2020).…”