Hydrological cycle on the North Slope of Alaska

Sufficient hydrological data has been collected, since 1985 for Imnavait Creek and 1996 for Upper Kuparuk River, to perform water balance calculations on the North Slope of Alaska. Permafrost is continuous under these basins, and sub-freezing temperatures dominate through the annual cycle with the snow-covered season lasting 8-9 months. These two small headwater basins receive about one-third of their annual precipitation as snow and two-thirds as summer rain (occasionally mixed with snow). The snowmelt period is a significant hydrological event each year and often produces the highest annual runoff; the floods of record are rainfall or rain/snow mixed summer events. The highest runoff ratios occur in Imnavait Creek during snowmelt and in Upper Kuparuk River during the summer. The Upper Kuparuk River, besides being 60 times larger, has higher terrain, steeper slopes, extensive bedrock outcrops and a few lakes. Water fluxes leaving Imnavait Creek catchment are about equally split between evapotranspiration and runoff; for the Upper Kuparuk watershed, it is estimated that 64% left as runoff and 36% as evapotranspiration. The quality of the data in these basins is quite good, except during extreme events.