Figure 1

Samuel Miller

and 2 more

In this study, we characterize the snowmelt hydrological response of nine nested headwater watersheds in southeast Wyoming by separating streamflow into three components using a combination of tracer and graphical approaches. First, continuous records of specific conductance (SC) from 2016 to 2018 were used to separate streamflow into direct runoff and baseflow components. Then, diurnal streamflow cycles occurring during the snowmelt season were used to graphically separate direct runoff into quickflow, representing water with the shortest residence time, and throughflow, representing water with longer residence time in the soil column and/or regolith layers before becoming streamflow. On average, annual streamflow was comprised of between 22% to 46% baseflow, 7% to 14% quickflow, and 46% to 55% throughflow across the watersheds. We then quantified hysteresis at both annual and daily timescales by plotting SC versus discharge. Annually, most watersheds showed negative, concave, anti-clockwise hysteretic direction suggesting faster flow pathways dominate streamflow on the rising limb of the annual hydrograph relative to the falling limb. At the daily timescale during snowmelt-induced diurnal streamflow cycles, hysteresis was negative, but with a clockwise direction implying that quickflow peaks generated from the concurrent daily snowmelt, with shorter residence times and lower specific conductance, arrive after throughflow peaks and preferentially contribute on the falling limb of diurnal cycles. Slope aspect and surficial geology were highly correlated with the partitioning of streamflow components. South-facing watersheds were more susceptible to early season snowmelt at slower rates, resulting in less direct runoff and more baseflow contribution. Conversely, north-facing watersheds had longer snow persistence and larger proportions of direct runoff and quickflow. Watersheds with surficial and bedrock geologies dominated by glacial deposits had a lower proportion of quickflow compared to watersheds with large percentages of metasedimentary rocks and glaciated bedrock.