Measurement of slope runoff in a permafrost region

Abstract

Installations at a High Arctic experimental site that is underlain by continuous permafrost allowed the measurement of slope runoff. Surface flow was collected near the base of the slope and the water was led to a flume with a V-notch weir. The water level in the flume was recorded and subsequently converted to discharge measurements. Subsurface flow was intercepted by an impermeable flow barrier set in a trench dug down to the permafrost table and later back-filled by the excavated slope materials. Water draining from above the flow barrier was fed into another flume unit similar to that for surface runoff. During the operational period, regular inspection of the flumes was required to ensure the prevention of ice formation or evaporative losses from the water in the flumes. Keywords: surface flow, subsurface flow, slope hydrology, permafrost.

Permafrost hydrology in North America1

“…In Cornwallis Island, Steer and Woo (1983) found that the bulk of subsurface flow occurred during the melt season, but annual surface flow on the same slope was 2.5 times larger than subsurface flow. Both surface and subsurface flows responded rapidly to snowmelt and, to a lesser extent, rainfall events that are often of low magnitude.…”

“…Since the position of the frost-table can change daily, the storage capacity is not static, but is approximated by z{t)n where n is the mean porosity of the thawed zone (Woo and Steer, 1983).…”

“…This method has been used extensively in the Canadian Arctic and subarctic (e.g. Rouse and Stewart, 1972;Woo et al, 1983;Wright, 1981) though it requires a knowledge of a'. Studies suggest that a' can be a step function in lichen-covered areas or can vary nonlinearly with soil moisture content .…”

“…Woo and Steer (1983) showed that differential thawing on a slope can produce a lower frost-table beneath the topographic divide, allowing water to be diverted to an adjacent slope through subsurface flow. Differential thawing can also produce depressions in the frost-table along which subsurface flow is concentrated preferentially.…”

“…Such a water-table profile is reinforced by the disposition of the snow cover, which tends to be thicker and resides longer within the concavity. More meltwater is then supplied steadily to the shallower thaw strip downslope of the concavity (Woo and Steer, 1983). For many low-lying slopes in the High Arctic, these localized, wetter zones become favoured locations for tundra vegetation growth in an otherwise arid, barren landscape (Porsild, 1957).…”