The Kobuk River (Iñupiaq: Kuuvak; Koyukon: Hʉlghaatno), also known by the names Kooak, Kowak, Kubuk, Kuvuk, and Putnam, is a river located in the Arctic region of northwestern Alaska in the United States. It is approximately long. the Kobuk River is among the largest rivers in northwest Alaska, with widths of up to 1,500 feet (460 m) and flows reaching speeds of 3–5 miles per hour (5–8 km per hour) in its lower and middle reaches. The elevation of the Kobuk River Basin is on average , ranging from sea level at its mouth on the Bering Sea to on the summit of Mount Igikpak.
Topography along the river includes low, rolling mountains, plains and lowlands, moderately high rugged mountainous land, and some gently sloped plateaus and highlands. The river contains an exceptional population of sheefish (Stenodus Nelma), a large predatory whitefish within the salmon family, which spawns in the river's upper reaches during the autumn. A portion of the vast Western Arctic caribou herd utilize the Kobuk River valley as winter range.
Course
It is commonly assumed that the Kobuk River issues from Walker Lake, but the headwaters of the river are actually to the east of Walker Lake in the Endicott Mountains within Gates of the Arctic National Park and Preserve, just north of the Arctic Circle. The river flows briefly south, descending from the mountains through two spectacular canyons (Upper and Lower Kobuk Canyon), then generally west along the southern flank of the western Brooks Range in a broad wetlands valley. In the valley it passes a connected community of inland native villages, including Kobuk, Shungnak, and Ambler, where it receives the Ambler River.
In the river's lower reaches, where it passes between the Baird Mountains and Waring Mountains, it traverses Kobuk Valley National Park, the location of the Kobuk Sand Dunes. It then passes Kiana, entering its broad delta approximately 10 miles (16 km) southwest of town. The Kobuk empties into the Hotham Inlet of Kotzebue Sound approximately 30 miles (48 km) southeast of the city of Kotzebue.
History
The Kobuk's Inuit name, Kuuvak, means "great river". It was first transcribed by John Simpson in 1850 as "Kowuk". The river was explored by Lt. G. M. Stoney, USN, in 1883–1886, who wrote the name "Ku-buck" but proposed that it be called "Putnam" in honor of Master Charles Putnam, USN, an officer of the , who was carried to sea on the ice and lost in 1882. Lt. J. C. Cantwell, USRCS, also explored the river in 1884 and 1885 and spelled the name "Koowak" on his map and "Kowak" in his text. Ivan Petroff spelled the river name "Kooak" in 1880, and W. H. Dall spelled it "Kowk" in 1870. Lt. H. T. Allen, US Army, transcribed the Koyukon Indian name for the river in 1885, which he spelled "Holooatna" and "Holoatna." An average of 21 inches (53 cm) of precipitation falls in the basin. However, actual precipitation can range from 15 to 40 inches (40–100 cm), with greater amounts falling in the upper reaches of the river basin.
The Kobuk River Basin is very sensitive to changes in climate. Arctic climates have warmed at approximately twice the global rate in the last several decades. Records of air temperature from 1961 to 1990 logged at the latitudes of the Kobuk River show a warming trend of about 1.4 °F (0.78 °C) per decade. The warming has been strongest in the winter and spring months.
As a specific example, climate change will cause widespread thawing of permafrost in the discontinuous zone and significant changes in the continuous zone. Thawing permafrost can lead to a landscape of irregular depressions (thermokarst) due to subsiding soils. This can alter drainage patterns and even change the course of streams, whereas other areas could become swamp-like. In addition, slope stability will decrease and permafrost degradation could lead to erosion of river banks resulting in an increase in sediment transport by the rivers. These physical changes will impact nutrient cycling and biological processes within the basin as well.
Geology and soils
center|[[Permafrost regions along the Kobuk River
After the first stage of aggradation and sediment transport, the Kobuk began a new phase of erosion and landform development. The river exhausted its supply of easily erodible sediment upstream, thus decreasing its sediment load and increasing its load carrying capacity downstream. With more capacity downstream, the river began to incise into the alluvial fan it previously created, moving sediment stored for a long time on its original floodplains to newer floodplains even further downstream. In moister climates, the river has more water and thus more power, and cuts down through a sandy bed. In times of drier climate, wind dominates and blows a lot of sediment into a weaker fluvial system, leading to aggradation and floodplain re-distribution.
Currently, the Kobuk River in its middle and lower reaches is an anastomosing stream, with several braided channels in places, wide migrating meander bends, and oxbow lakes. It is controlled by yearly cycles of freeze and thaw, much like its surrounding landscape. For six months of the year, the river is largely still, frozen on top by a thick layer of ice. Within Kobuk Valley National Park are the Kallarichuk, Kaliguricheark, and Adillik rivers. All of their headwaters are in the Baird Mountains. Other surface water features within the basin include Lake Selby, Nutuvukti Lake, and Norutak Lake.