Modified passive capillary samplers for collecting samples of snowmelt infiltration for stable isotope analysis in remote, seasonally inaccessible watersheds 2: field evaluation

Abstract

Abstract:Twelve modified passive capillary samplers (M-PCAPS) were installed in remote locations within a large, alpine watershed located in the southern Rocky Mountains of Colorado to collect samples of infiltration during the snowmelt and summer rainfall seasons. These samples were collected in order to provide better constraints on the isotopic composition of soil-water endmembers in the watershed. The seasonally integrated stable isotope composition (υ 18 O and υ 2 H) of soil-meltwater collected with M-PCAPS installed at shallow soil depths <10 cm was similar to the seasonally integrated isotopic composition of bulk snow taken at the soil surface. However, meltwater which infiltrated to depths >20 cm evolved along an isotopic enrichment line similar to the trendline described by the evolution of fresh snow to surface runoff from snowmelt in the watershed. Coincident changes in geochemistry were also observed at depth suggesting that the isotopic and geochemical composition of deep infiltration may be very different from that obtained by surface and/or shallow-subsurface measurements. The M-PCAPS design was also used to estimate downward fluxes of meltwater during the snowmelt season. Shallow and deep infiltration averaged 8Ð4 and 4Ð7 cm of event water or 54 and 33% of the measured snow water equivalent (SWE), respectively. Finally, dominant shallow-subsurface runoff processes occurring during snowmelt could be identified using geochemical data obtained with the M-PCAPS design. One soil regime was dominated by a combination of slow matrix flow in the shallow soil profile and fast preferential flow at depth through a layer of platy, volcanic rocks. The other soil regime lacked the rock layer and was dominated by slow matrix flow. Based on these results, the M-PCAPS design appears to be a useful, robust methodology to quantify soil-water fluxes during the snowmelt season and to sample the stable isotopic and geochemical composition of soil-meltwater endmembers in remote watersheds.

Hydrogeology of desert springs in the Panamint Range, California, USA: Identifying the sources and amount of recharge that support spring flow

“…To collect precipitation in the Panamint Range, we deployed two precipitation collectors in 14 October 2017 using the design described in Earman, Campbell, Phillips, and Newman (2006) (Earman et al, 2006;Friedman, Smith, Gleason, Wardern, & Harris, 1992;Frisbee et al, 2010;Scholl, 2006).…”

Streamflow generation in a large, alpine watershed in the southern Rocky Mountains of Colorado: Is streamflow generation simply the aggregation of hillslope runoff responses?

“…[2006] and Frisbee et al [2010a]. These collectors were installed in October 2007 at remote, high-elevation sites in the watershed prior to the onset of snowpack accumulation during October 2007 [Frisbee et al, 2010a].…”

“…Geochemical transformations were quite rapid in the soil, and lengthy residence times were not always needed to obtain significant geochemical evolution in the soil [Davis, 1964;Kennedy, 1970;Campbell et al, 1995;Frisbee et al, 2010a]. We monitored soil water using soil cores and modified passive capillary samplers (M-PCAPS) to constrain the geochemistry of the shallow subsurface runoff component.…”

“…We monitored soil water using soil cores and modified passive capillary samplers (M-PCAPS) to constrain the geochemistry of the shallow subsurface runoff component. M-PCAPS were installed at remote, high-elevation locations in the watershed to obtain samples of infiltrating meltwater during snowmelt and infiltrating rainwater during summer precipitation [Frisbee et al, 2010a[Frisbee et al, , 2010b. Soil cores were collected near the M-PCAPS, and soil water was distilled from these cores for stable isotopic analysis.…”

“…[25] The geochemical evolution of postinfiltration water in the Saguache Creek watershed appears to be controlled first by relatively rapid geochemical transformations in the soil [Frisbee et al, 2010a] and then by much slower geochemical transformations in the bedrock aquifer [Frisbee, 2010]. Results from a weathering study in the watershed indicate that the chemical weathering of bedrock minerals, namely, sodium-and calcium-rich feldspars, potassium feldspar, biotite, quartz, and hornblende, is the primary source of solute release to groundwater, streamflow, and spring flow [Frisbee, 2010].…”