Figuring out what a Yukon stream is doing during the winter can be tricky.

For one thing, it's mostly out of sight under several layers of ice and snow. Checking the water level and rate of flow is no easy task. In the past, it usually required large tools like ice augers, a great deal of physical effort, and a certain amount of risk.

Using more modern tools brings up other problems – cold temperatures, ice forming on the instruments, equipment breakdowns, and the difficulty of reaching the instruments once winter conditions set in.

However, for a variety of economic and environmental reasons, it's important to know how streams and rivers behave in winter, says Stuart Hamilton, a Vancouver-based Environment Canada scientist.

Most Canadian streams are at their lowest flow levels in late winter, a critical period for aquatic habitat, particularly as it relates to fish mortality and reproductive success, he explains. People trying to manage fish habitat and populations need to know what's happening under the ice.

Winter stream flow also has major economic implications, Hamilton adds. For example, ice-jam floods alone cause more than $60 million damage in Canada every year.

"Winter flows are critical for effective reservoir management, and knowledge of winter flow is necessary to avoid or mitigate the risk from ice-jam flooding."

Hamilton is in charge of a research project designed to find better and more accurate ways to measure winter stream flow. The Wolf Creek Research Basin near Whitehorse is one of several locations where information is being collected. The Yukon part of the project also involves participants from Indian and Northern Affairs in Whitehorse and the Yukon Energy Corporation.

Wolf Creek is particularly interesting because it doesn't fit the expected pattern for Canadian rivers. The traditional assumption, Hamilton explains, is that the amount of water flowing in streams and rivers gradually declines through the winter, as the sources of water are locked up in ice and snow.

However, a study of the flow in Wolf Creek in the winter 1998-99 showed a different pattern. Instead of a gradual decline, stream flow stayed fairly constant until well on in January. Then it dropped dramatically, hitting extremely low levels in late March. And estimates of the flow in Wolf Creek, based on standard models, didn't match the patterns actually measured.

The flow pattern over that winter "is not explainable by any known mechanism," Hamilton says. Some of the factors that might be affecting it include late freeze-up in Wolf Creek because of the relatively warm groundwater that flows into it, possible ice blockage at the outlet of the small lake that feeds Wolf Creek, or even the time of day when the measurements are taken.

Hamilton hopes that the current research program will reveal more about the reasons behind the flow pattern and any implications it holds for monitoring small northern streams.

Over the winter of 2001-02, Hamilton and his colleagues are using a variety of methods, including an intensive automated monitoring program, to measure flow patterns in Wolf Creek and the Athabasca River. The information they collect will be used to develop, test, and evaluate methods of monitoring and predicting winter flow patterns.

Hamilton doesn't expect to come up with a monitoring method that suits all streams. However, he does hope the project will help researchers and water monitoring agencies make better decisions about which approach to use at a particular stream in order to produce accurate results reliably, safely, and efficiently.

For more information about hydrology research at the Wolf Creek Research Basin, contact Ric Janowicz at DIAND Yukon, (867) 667-3223.