Yukon Water Resources has had the responsibility to carry out the flood forecasting and monitoring for Yukon Territory . Because of the importance of river transportation in Yukon 's history, the majority of Yukon communities are situated on the floodplain, and as a result, there is a long history of flooding. The most common cause of flooding is spring snowmelt, which normally occurs in June, affecting a number of communities throughout Yukon . Spring ice jam floods normally occur in May, and are more significant in terms of impact.
Flood forecasting requires a strong data collection program. To provide the necessary input information, Water Resources operates hydrometric, meteorological and snow survey networks.
Water Resources operates its own hydrometric network of 15 stations, as well as maintaining a cost sharing agreement with Environment Canada's Water Survey of Canada, for the operation of an additional 45 stations. Because of significant funding reductions, it was necessary to reduce the network by 40 % during the 1990s, to its present level. In order to obtain the required saving it was necessary to eliminate all high cost stations, regardless of utility. This has resulted in the virtual elimination of hydrometric monitoring in northern Yukon . The hydrometric network in northern Yukon is presently not adequate in coverage for all hydrological purposes.
Water Resources operates 8 specialized meteorological stations in key watersheds, primarily for flood forecasting, but also for the assessment of industrial development projects and forest fire indexing. These stations monitor air temperature, precipitation, rainfall, snow depth, relative humidity, wind speed and direction, solar radiation, barometric pressure, soil temperature and soil moisture. Snow water equivalent is monitored directly, using snow pillows, at 5 of the stations. This data is accessible on a real time basis using satellite telemetry. In addition, 60 manual snow survey sites are monitored several times during the spring snowmelt season, for flood forecasting purposes.
The streamflow forecasting program operated by Yukon Water Resources has traditionally provided estimates of seasonal runoff volumes for water supply purposes, and, estimates of the magnitude and timing of flows and elevations for all Yukon locations. These include winter and summer low flows as well as average flow conditions, which may be a limiting factor in many water supply situations, including hydroelectric, mining, fishery, municipal water supply, agricultural and river navigation applications. Because of public safety concerns, an emphasis is placed on the determination of flood flows.
Water Resources has a model where winter temperature, and daily spring temperature and water level, are used to project the timing of river break-up. When break-up is imminent, daily flights are made of the river to monitor break-up. Satellite telemetry, using Radarsat images are being used on a pilot study basis, to improve our forecasting capability.
Water Resources uses a simple temperature index model, and a more sophisticated energy balance model (SSARR developed by the United States Corps of Engineers) for providing 5 day snowmelt-streamflow forecasts for a number of Yukon communities. Because of the lack of data in some areas, the simpler model provides better results. We are in the process of replacing these models with newer versions.
 back
|
