Liard

Excerpt from Mackenzie River Basin: State of the Aquatic Ecosystem Report 2003 by the Mackenzie River Basin Board (p. 115-132). Full report available at http://www.mrbb.ca/information/34/index.html

 

The Liard River and its tributaries drain an area of approximately 275,000 square kilometers, making it Canada’s ninth largest watershed. The Liard River begins its journey in the Pelly Mountains of southeastern Yukon, flows through northeastern British Columbia, and then crosses into the Northwest Territories where it drains into the Makenzie River.

Much of the Liard sub-basin is covered by coniferous and mixed-wood forest. Intensive agriculture is limited to a small area near Fort Nelson in the southernmost part of the sub-basin. There are extensive mountainous areas, especially in the headwaters along the Yukon-Northwest Territories border and in the western part of the sub-basin. Heavy summer precipitation, melting permafrost, deforestation and disturbances to the land caused by the petroleum industry may cause landslides, which can have major effects on local water quality and quantity.

There were 8,500 people living in the Liard sub-basin in 2001. Most of the population is centered in Fort Nelson, BC and Watson Lake, Yukon. Fort Simpson, which lies at the confluence of the Liard and Mackenzie rivers is considered in the Mackenzie-Great Bear basin. First Nations people make up approximately 27% of the population. Not captured in the census is the large number of winter industrial workers that may come in from other communities.

Logging occurs primarily within the Fort Nelson Timber Supply Area, and area that encompasses much of the sub-basin that lies in British Columbia. The Liard sub-basin contains extensive oil and gas reserves. Currently only three mines are operating (tungsten, jade/nephrite), however historically, mining was an important industry. Tourism and outdoor recreation are growing contributions to the economy.

Natural conditions are the probable causes of water quality variations in the Liard River. In general, water quality in the Liard River was as good in 2002 as it was during the 1980s. The amount of treated sewage discharged in the Liard sub-basin is small, and sewage treatment is adequate for the major communities. In rural areas and on reserves, the extensive use of septic systems, subsurface fields and settling ponds means that local groundwater quality must be monitored to ensure that well water does not become contaminated by seepage from such structures.

Flow in the Liard River has declined slightly over the past few decades possibly as a result of changes in climate. This decline is consistent with a decline that was reported in the Smoky River. Whether the declines are due to climate change caused by human beings or whether they are part of a normal pattern of long-term fluctuations remains unknown. In addition, the ecological impacts of decreasing flows need to be better understood.

The timing of discharge in the Liard River has changed slightly in recent decades. The lower flows in summer and the higher flows from fall to early spring are consistent with predictions from climate change models, suggesting that a changing climate may be partially responsible for the observed changes. It is possible that these small changes are part of a normal pattern of long-term fluctuations.

Surface water in the Liard sub-basin is withdrawn for industrial and community needs, with the primary user being a microhydro facility in the Yukon. The total volume of water licensed for withdrawal is negligible in comparison to the flow of water in the Liard River.

Fish stocks in the sub-basin are used to some extent by commercial, subsistence, and sport fishers. Lake trout stocks have improved in Frances Lake, but have deteriorated in Watson Lake. Watson, Frances, and Simpson lakes have excellent northern pike fisheries and healthy fish communities. There are no other major concerns at this time, but the scarcity of information makes it difficult to determine the state of fish stocks or to identify changes in the use of this resource.

Observations made by some aboriginal inhabitants of the lower portion of the Liard sub-basin provide insight into the population trends, distribution, and health of certain wildlife species. Of particular concern are the deterioration in fish quality and the declined in populations of muskrat and certain species of waterfowl reported by some of the people.

There are nineteen aquatic and riparian wildlife species, including nine species of fish, considered to be at risk in the BC and Yukon portions of the sub-basin. While some species at risk are naturally rare and not under imminent treat from human activities, others are threatened by various human activities, particularly the fragmentation and loss of habitat due in part to the continued development of roads and seismic lines. In a global context, the Liard sub-basin has experienced a relatively low level of impact to its species and ecosystems.

Periodic flooding of the Liard River is a natural occurrence that is important for the health of the aquatic ecosystem. However, floods can damage communities along the lower reaches of the river and threaten human safety. Flood forecasting provides warning to the affected communities. There is no indication that the frequency or severity of floors has increased in the sub-basin.

Academic


Jennifer Fresque-Baxter, University of Waterloo