Subsurface Pore Water Contributions to Stream Concentration-Discharge Relations Across a Snowmelt Hydrograph

Abstract

This study investigated the concentration discharge (C-Q) patterns of selected elements transported to streams during spring snowmelt through an instrumented mixed-conifer forested catchment in rhyolitic terrain in the Jemez Mountains (NM, United States). High frequency, concurrent sampling of soil solution and gasses, groundwater, and surface water enabled identification and sourcing of five groups of solutes with distinct C-Q behavior. Non-hydrolyzing cations and strong acid anions, had mostly positive C-Q relations and a clockwise hysteresis pattern related to flushing of a limited reservoir of solutes accumulated in soils under snowpack. Rare earth elements (REEs) and dissolved organic carbon (DOC), demonstrated large positive C-Q relations and a clockwise hysteresis pattern, consistent with their co-transport as metal-ligand complexes, and signaling biologically induced weathering reactions in the soil. Silicon and dissolved inorganic carbon (DIC) exhibited chemostatic C-Q trends and an anticlockwise hysteresis pattern consistent with sourcing from deep groundwater. Hydrolyzing metals (Mn, Al, Ti, and Zr) with high coefficients of variance (CV) for concentration relative to CV values for stream discharge and with no significant C-Q pattern, were found to be transported mainly as filterable colloids. Fe C-Q behavior was similar to this hydrolyzing metals group, but complexation with DOC was also important for Fe during the initial stage of the snowmelt hydrograph. Investigation of time-series of solutes and gasses provided evidence for biologically induced silicate weathering reactions that initiated in the soil subsurface and propagated down through groundwater to streams.

Distinct stores and the routing of water in the deep critical zone of a snow-dominated volcanic catchment

“…Corrected ages were calculated using the δ 13 C mixing model of Eqs. (5) and (6) following Pearson (1965), Pearson and Hanshaw (1970), and Clark and Fritz (1997) using an assumed δ 13 C DIC of calcite of 0 ‰, a calculated value of the δ 13 C DIC value of the recharge water, and A 0 of 100 pmC.…”

Hysteretic Response of Solutes and Turbidity at the Event Scale Across Forested Tropical Montane Watersheds

“…High-frequency data are particularly useful for understanding the hysteretic behavior of storm events. Solutes and sediments often display "hysteresis-loops" and the width, magnitude, and direction of these loops provide insight into how reservoirs of solutes and sediments are stored within the hillslope and exported to fluvial networks (Gellis, 2013;Koenig et al, 2017;Vaughan et al, 2017;Olshansky et al, 2018;Rose et al, 2018). Hysteresis occurs when concentrations at a given discharge differ on the rising and falling limbs of the hydrograph.…”

Storage and routing of water in the deep critical zone of a snow dominated volcanic catchment

“…In the same headwater catchment in the JRB-CZO, Olshansky et al (2018) observed temporal changes in major ion concentrations of soil, surface, and ground water during spring snowmelt 2017 and found positive Si concentration pulses during the falling limb of surface water hydrographs that were hypothesized to result from increasing groundwater contributions during receding surface flows because surface water Si concentrations were similar to those of shallow groundwater (Well 2D). However, surface water concentrations of other major ions (Ca 2+ , Na + , Mg 2+ , Mn, and SO4 2-) did not coincidentally rise despite higher shallow groundwater concentrations of those ions compared to Si, which suggests, instead, a deeper source of groundwater to La Jara streams.…”

“…Other studies used carbon pool and rare earth elements and ytrrium (REY) as biogeochemical tracers of streamflow generation (Perdrial et al, 2014;Vazquez-Ortega et al, 2015, 2016 and estimated groundwater contributions using end member mixing analyses (Liu et al, 2008a(Liu et al, , 2008b. The most recent JRB-CZO studies explored concentration-discharge relationships to study seasonal shifts of hydrologic flow paths (McIntosh et al, 2017) and identify the hydrochemical processes governing the transport behavior of five distinct groups of solutes (Olshansky et al, 2018). Furthermore, studies agree that there is little overland flow contribution to streamflow in headwater catchments (Liu et al, 2008b;Perdrial et al, 2014;Zapata-Rios et al, 2015a) and subsurface flow is the primary contributor to streamflow (Liu et al, 2008a(Liu et al, , 2008bPerdrial et al, 2014;Vazquez-Ortega et al, 2015;Zapata-Rios et al, 2015a;McIntosh et al, 2017;Olshansky et al, 2018;Wlostowski et al, In Review).…”

“…Furthermore, the cubic shape of the rising water table in the perched aquifer, as well as the rapid rise after inflection point in well 2D is indicative of groundwater recharge (Sophocleous, 1988(Sophocleous, , 1991a(Sophocleous, , 1991b. Further analysis of the rates of increase before and after the well 2D hydrograph inflection point can be found in Olshansky et al (2018).…”