A two‐component hydrograph separation for three high‐elevation catchments in the Sierra Nevada, California

Abstract

Abstract:Two-component hydrograph separations were performed for three, nested, snowmelt-dominated catchments in Sequoia National Park. The purpose of the hydrograph separations was to: (i) differentiate between the old and new water contributions to discharge during snowmelt using υ 18 O signatures; (ii) identify the fraction of snowmelt that travelled through the subsurface (reactive) compartment during the snowmelt period using silica or sodium; and (iii) investigate the impact of changing end-member signatures on the separations. 'Old' water refers to water that was stored in the watershed during the previous year, whereas 'new' water is current snowmelt. Hydrograph separations were performed for both a high-accumulation (1998, annual precipitation 2Ð4 m) and an average year (1999, 1Ð3 m). The proportion of old water contribution to discharge during the rising limb of the hydrograph was 10-20%, with 80-100% of snowmelt being reactive, i.e. passing through soil and talus. Estimates of old and new soil water and direct snowmelt entering the stream varied among the catchments in 1999. Differences between these components were minimal in 1998, regardless of varying topography and differing proportions of soil, rock and talus. Using time-dependent rather than constant υ 18 O meltwater and silica soil-water signatures made a meaningful impact on both new and old water, and reactive and unreactive, estimates.

The importance of snowmelt spatiotemporal variability for isotope-based hydrograph separation in a high-elevation catchment

“…These studies showed a large pre-event water fraction (> 50 %) of streamflow that changed the understanding of the processes in catchment hydrology fundamentally (Klaus and McDonnell, 2013;Sklash and Farvolden, 1979) and forced a paradigm shift, especially for humid temperate catchments. However, other snowmelt-based studies in permafrost or high-elevation catchments (Huth et al, 2004;Liu et al, 2004;Williams et al, 2009) revealed a large contribution of event water (> 70 %), depending on the system state (e.g., frost layer thickness and snow depth), catchment characteristics, and runoff generation mechanisms. Klaus and McDonnell (2013) highlighted the need to quantify and account for the spatial variability of the isotope signal of event water, which is still a vast uncertainty in snowmelt-based IHS.…”

Sources and pathways of stream generation in tropical proglacial valleys of the Cordillera Blanca, Peru

“…Using hydrograph separation or end-member mixing analyses, several studies (Brown et al, 2006;Huth et al, 2004;Liu et al, 2004;Sueker et al, 2000) have estimated a wide range for the percent contribution of alpine groundwater to streamflow at the catchment scale. At a more detailed scale, Caballero et al (2002) investigated the hydrologic behavior of talus slopes and lateral moraines using salt tracer breakthrough curves in the Cordillera Real, Bolivia.…”

Identifying streamflow sources during spring snowmelt using water chemistry and isotopic composition in semi-arid mountain streams

“…The temporary storage of precipitation in snowpack, and its subsequent melting, controls the largest variability in solute and isotopic compositions of streamwater (Kendall and McDonnell, 1998). A snowmelt-driven water cycle presents unique challenges as well as opportunities to study hydrologic processes (Buttle and Sami, 1992;Huth et al, 2004;Jeelani et al, 2010;Laudon et al, 2002;Liu et al, 2004;Wels et al, 1991a). One challenge is characterizing the temporal and spatial heterogeneity of the isotopic compositions of event endmembers.…”