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Linear wetlands that occupy the valley bottoms in the Canadian Arctic Islands represent distinct ecological niches in the polar desert environment, but the hydrologic processes associated with such wetlands are poorly known. One such wetland, the Muskox Fen (area 3700 m(2)) in central Ellesmere Island, N.W.T., was studied during a relatively dry year (1993). Hydrologic processes were most active in the spring, with snowmelt providing most of the water supply to the fen. Water storage capacity was satisfied easily, guaranteeing wetland saturation despite a low snowfall winter. At this time, the wetland was a poor regulator of runoff, the valley bottom served merely as a conduit for the basin meltwater to pass through. During the dry period in summer, the wetland received little lateral inflow from its catchment, and vertical processes of rainfall and evaporation prevailed while the water storage gradually decreased. In the wet period, saturation was restored after only moderate rainfall. For most parts of the summer, a high water table was maintained because permafrost impeded deep seepage loss, thus preventing excessive drying of the wetland vegetation.