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).