| Summary: | Mineral earth hummocks are one of the most widely distributed forms of patterned ground in the permafrost areas of the world, yet little is known of their hydrological role in the drainage of hillslopes. The impact of earth hummocks on subsurface drainage was studied at three hillslope plots during the snow-free periods of 1993 and 1994 at a small hummock-covered Arctic tundra watershed (Siksik Creek) in north-western Canada. Subsurface drainage occurs preferentially through the unfrozen saturated layer of the inter-hummock area, owing to its relatively high permeability and connected nature. The inter-hummock area is composed of primary channels, oriented in the downslope direction, and secondary channels, obstructed from conducting water directly downslope. Because of their very low hydraulic conductivity, earth hummocks obstruct hillslope drainage. As a result, the spatial distribution of earth hummocks on a hillslope influences the average tortuosity of the individual inter-hummock channels that comprise the hillslope drainage network. The time required for runo water to reach the streambank increases with increasing tortuosity of inter-hummock channels. Earth hummocks attenuate subsurface flows owing to seepage between the hummocks and the inter-hummock area. Hummocks also
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