On the hydrological difference between catchments above and below the intermittent‐persistent snow transition

Abstract

Because of the importance of snow for river discharge in mountain regions, hydrological research often focuses on seasonally snow-covered zones. However, in many basins the majority of the land surface area is intermittently snow-covered. Discharge monitoring in these areas is less common, so their contributions to downstream rivers remain largely unknown. We evaluated hydrological differences between three intermittently snow-covered (mean annual Jan 1-Jul 3 snow persistence <60%) and two seasonally snow-covered headwater catchments in the Colorado Front Range. We compared water balance variables to evaluate how and why discharge differs between the snow zones and estimated the relative contributions from each snow zone to regional river discharge. We focused on water years 2016-2019 and used a combination of in situ sensors and regional climate datasets. Annual discharge from the intermittent snow zone was low for all three catchments (10-77 mm), despite covering a wide range in annual snow persistence (25%-64%), whereas annual dis-

What drives Fyw variations with elevation in Alpine catchments?

“…In fact, the limited number of snowfall days and mid-winter melt reduce the snow accumulation in the lower elevation subclass of hybrid regimes. Such a snowpack does not protect the underlying soils from freezing (Harrison et al, 2021). Even for low elevation locations (< ≈1500 m asl.…”

“…Accordingly, the value of the classification proposed here is not to shed new light on streamflow dynamics but to objectively connect the streamflow regime shape to summer-to-winter streamflow ratios and to the mean snow cover extent. The new classification scheme can be applied outside Switzerland and the objective and explicative classifiers, on which it is based, allow the study of regime changes (e.g., from snow-dominated to hybrid) that will become increasingly more apparent 465 under climate change (Lucianetti et al, 2020;Harrison et al, 2021).…”

“…of hybrid catchments is increasingly influenced by the snowregime. Here, the building up of a persistent, deep snowpack can promote deep vertical infiltration by insulating the soil and thereby preventing freezing (Jasechko et al, 2016;Harrison et al, 2021). The resulting effect on water partitioning between the surface and the subsurface has however to be analyzed in light of the temporal concentration of water input 495 on the snowmelt period and remains largely unexplored to date (Rey et al, 2021).…”

“…The positive correlation between Fyw and Fqd in hybrid catchments can be explained by two mechanisms: i) high baseflow points towards system saturation being high, which favors connectivity and ii) ephemeral snowpacks can favor freezing phenomena inhibiting winter snowmelt infiltration and thereby favoring fast flow processes (Harrison et al, 2021). 535…”

The Role of Groundwater Flow in a Montane, Semi-Arid, Headwater Catchment

“…In the Colorado Front Range of the Southern Rocky Mountains in North America, groundwater-derived baseflow can account for more than 75% of streamflow during dry conditions (Clow et al, 2003) and more than 60% during the early snowmelt season (Liu et al, 2004). This store and release process offers a mechanism for providing a reliable source to maintain streamflow, even during warmer and drier months, which often coincide with the highest environmental and anthropogenic demands (Harrison et al, 2021;Wilson and Guan, 2004;Markovich et al 2019).…”