SITE DESCRIPTION and METHODS
The upper Kuparuk River study site extends from its headwaters to five
km below its intersection with the Dalton Highway. The majority of
sampling takes place within five km of the road, approximately 190 km
south of the Arctic Ocean on the North Slope of Alaska (68°39’N,
-149°22’E; Fig. 1). The river upstream of the intensely monitored
reaches has a main channel length of 25 km, drains an area of 143
km2, and has an average channel slope of 3.13% (Kriet
et al., 1992). It is a clear-water, meandering, cobble-bottomed,
pool-riffle stream that is typically frozen from late September or early
October until late May. The Kuparuk River has a spring flood (freshet)
resulting from melting snow followed by lower flows in the summer.
Summer water temperatures may reach 20oC and average 8
to 13oC. The climate at the site is typical of Arctic
regions, with a mean annual air temperature of about -7°C, low
precipitation (45% of the 20-40 cm of precipitation falls as snow), and
extensive – though variable – snow cover for 7 to 9 months. During the
summer the daily average air temperature is 7-12°C with the sun
continuously above the horizon from mid-May to late July. Permafrost
underlies the site to a depth of nearly 200 m, with an active layer that
thaws each summer to a depth between 30 and 50 cm (Bowden et al., 2014).