Yukon River

Physical Geography

The Yukon River is situated in an area that has been the location for mining operations throughout the past few hundred years with large gold mining operations found in this region as a result of the setting of this region and how it was formed. The Yukon itself spans an area of 832,700 km² containing a portion of British Columbia, Canada where its source is located in Atlin Lake, and Alaska. The Yukon flows for 3,190 km through the bitter wilderness of an Arctic Tundra with long cold winter periods punctuated with minor warm summers. Below the Yukon River and its catchment will be broken down to develop an understanding of the overall physical setting of this unique river system.

Formation/Geology

The source of the Yukon is located in Atlin Lake, Canada, this lake is maintained by the Llewellyn glacier, the second largest glacier of the Juneau Icefield that is currently undergoing rapid retreat. Following on from Atlin lake the water of the Yukon flows to two more lakes Tagish Lake and Marsh lake respectively, it is within Marsh Lake that the course of the Yukon River itself begins. The Yukon River begins to flow westward where north of Whitehorse, the capital and only city within the Yukon, the river’s course begins to widen at this point incorporating the many of the Lakes of the interconnected Yukon fluvial system including Lake Bamberge. The river continues its journey westward where the Five Finger Rapids were the braided pattern of the river meanders around four islands within the channel creating almost impassable courses in all but one of the five channels. Following this point the Yukon continues its journey heading northwest into Alaska passing through inhabited areas such as Eagle and Fort Yukon where the course begins to flow Southwest following the confluence with Porcupine river. The river continued along this heading until Tanana where the yukon is joined by the Tanana River where the course follows a westward course until its confluence with the Koyukuk River. Following the confluence with the Koyukuk River the Yukon begins to flow in a South-southwest direction before it reaches Mountain Village, where the channel begins to braid into much smaller channels onto the Yukon-Kuskokwim Delta.

The Yukon region is also known for the rich gold deposits that are found in the region with mining occurring since the american gold rush, with larger industrial efforts continuing to this date. The gold deposits were formed as a result of the volcanic processes that formed the Earth’s crust and later from erosion by the rivers and streams within the Yukon basin. The gold deposits throughout the basin with some lying 5-10 m beneath riverbeds along the bedrock while other gold can be found along ancient riverbeds, with deposits found along hilltops. As a result of the rich gold deposits of the region, the area amongst the Yukon is still highly coveted today by larger mining operations that seek to collect the gold, which was not accessible during the initial gold rush, with modern mining technologies.

Climate

The climate of the Yukon river basin can be described as a Subarctic climate with relatively warm summers that have a short duration, while winters are long and cold. Climate stations in this region are few and far between therefore exact climatic values that reflect the entirety of the basin are hard to comeby. From available climatic information the average temperature of the yukon varies from 30°C in the summer while in the winter temperatures can reach -40°C. The average annual precipitation across the entire basin is approximately 480 mm with the types of precipitation ranging from rainfall to snow and snowfall. Most of the precipitation occurs in the summer when evaporation levels are higher, allowing for more moisture in the air, while during the winter months the region is frozen. The dominant air masses of the region are mainly the siberian and arctic air masses with some influence from the paciffic air mass being seen during the short summer period introducing warmer air to the region.

Human Geography

Many of the inhabitants of the Yukon Basin, spanning Canada and Alaska, belong to First Nation communities with multiple nations including the Dene, Tlingit, Inuit and Métis nations occupying the region including as many as 9000 people before the European settlement of the region. The number of First Nation inhabitants of the Yukon basin has however decreased over time with many early losses occurring as a result of European settlers introducing new diseases to the region or through conflict.

Throughout the 1800s the European settlers created trade links for furs and other products, however, are the advent of the gold rush in 1896 with the influx of many more Europeans searching for gold, with an estimated 100,000 prospectors moving into the Klondike region of the Yukon basin. As a result of the massive influx of people intensive gold mining operations began throughout the basin from 1896 to 1899, creating the groundwork for environmental damage that continued to impact the region to this day.

Catchment Management

The Yukon Basin is an extremely vital region for many First Nation communities, sustaining their lifestyle through the provision of water resources and as a source of food, with the many fish species within the river course. As such, in an effort to maintain the water quality of the region and the resources that it provides a cooperative of 70 First Nations and tribes from both Canada and Alaska have formed with the goal of making the Yukon and its tributaries a safe source of drinking water, known as the Yukon River Inter-Tribal Watershed Council (YRITWC) (Duffy et al., 2018).

Pollution

The Yukon river has a long standing history of pollution from mining, military installations, dumps and wastewater discharge within the basin. This legacy of pollution remains across the Yukon basin, while governmental organisations including the US Environmental Protection Agency (EPA) have classified the region as an unimpaired watershed (Duffy et al., 2018). The extraction of natural resources ranging from metal mining and coal to natural gas has led to an increase in the risk of environmental deterioration as a result of the release of contaminants into the natural environment. However, it can be seen that pollution within the basin is mainly sourced from external locations with environmentally persistent organic compounds and metal being identified within the basin sourcing external pollution from newly industrialising countries across Asia (Duffy et al., 2018).

Climate Change

Climate change is a major threat to the Yukon region with changes in climate patterns leading to an increase in the temperature of the region threatening the river system fed by meltwater as well as leading to the permafrost of the region melting releasing further greenhouse gasses into the environment. Climate change also poses a risk for the region with changes in precipitation patterns from snowfall to rainfall meaning that the glaciers that support the Yukon river will begin to retreat as there is a reduced amount of accumulation while ablation continues to occur leading to glacier recession. This retreat of the glacier could drastically affect the supply of water resources to the Yukon leading to environmental deterioration for the entire basin. Another potential threat to the Yukon river basin is sea-level rise, with most of the Yukon-Kuskokwim delta being situated at less than 30m above sea level, the low lying coastal region that many migratory birds and waterfowl use to support themselves has the potential to be inundated by the Bering Sea leading to environmental loss across the region (Duffy et al., 2018).