The Yukon is a land of numerous fast-flowing rivers and streams, but when Yukoners turn on their taps, it is almost always groundwater that flows out.

Groundwater is found beneath the surface of the land. It can seep naturally from the ground or flow out through springs, and it can also be pumped out from wells.

"More than 99 percent of Yukoners depend upon groundwater for their water supply at least a portion of the time," says Rick Janowicz, a hydrologist with the Department of Indian Affairs and Northern Development. "That is higher than in any other jurisdiction of the country."

But even though most Yukoners use groundwater every day for drinking, cooking and washing, we know very little about the state of this resource. DIAND collected some information in the early 1990s, but in general neither the quantity nor the quality of our groundwater is well known.

DIAND Water Resources, along with YTG Engineering and Development and City of Whitehorse Municipal Services, is now taking a closer look at both surface water and groundwater in the territory. The study is focussed on the Upper Yukon River watershed, as it is home to almost three-quarters of all Yukoners.

A pilot project looked at groundwater in the Wolf Creek and Pineridge subdivisions as 85 percent of the homes there depend on well water, a higher rate than in any other part of Whitehorse. Also more people and businesses are moving into the surrounding area, increasing the demands on groundwater.

The first step was setting up a database for wells in the area, recording information such as the location and depth of the wells, and the basic geology of the area where they were drilled. In most parts of the country this information could be tracked through drill logs, which are submitted to a central registry.

In the Yukon drill logs are not submitted to the government so a questionnaire was sent out to all homeowners in the area, asking for information on their wells. The high response rate -- 122 of the 154 surveys were returned -- indicates that homeowners also have a more than passing interest in this matter.

The pilot project also looked at how water moves into and out of the Wolf Creek aquifer, and a key question was whether wells in the area were already depleting water in the aquifer. A few homeowners in Wolf Creek, one of the oldest rural residential subdivision in Whitehorse, had already reported problems with their wells and three had drilled new ones.

Almost all of the 266 millimetres of precipitation that falls on the area every year either evaporates away or transpires back into the atmosphere as plants lose moisture. Only 25 mm is leftover as a surplus, and most of that runs off into streams such as Wolf Creek.

Only a tiny amount of water soaks into the ground every year, recharging the groundwater in the aquifer. This recharge occurs mainly during April when evapotranspiration is low and the snowpack is melting.

"The rest of the year the aquifer is not being recharged at all, so depletion is occuring," says Janowicz.

This means that the water table could rise and fall over the year, which could explain why some people have problems with their wells in summer when they usually use more water.

"People will often only drill until they get to the water table, says Forest Pearson, an engineering geologist with Gartner Lee Limited who was the main consultant for the project.

"If the water table fluctuates over the year, their well could go dry when the demand is high. They might have to drill a couple of feet deeper."

It is estimated that homes on wells only use about one percent of the total annual precipitation for the area. That might not sound like much, but it amounts to 20 percent of the water available for recharging the aquifer every year.

But groundwater is also renewed by the water filtering out of septic systems. The study has shown that 20 percent of the water that recharges the aquifer comes from septic tile fields.

If the water from septic fields is not filtered well enough, too many nutrients could end up in the groundwater. The pilot project did not look at water quality, but phase two -- which is already underway -- will provide that information.

In February the Yukon's first well for monitoring groundwater was drilled next to the playground in the Wolf Creek subdivision. Water samples will be taken regularly to monitor water quality, and a data logger will continuously monitor water flow.

Janowicz hopes that this pilot project will just be the start of the effort to learn more about groundwater in the territory. The Wolf Creek aquifer is one of 30 watersheds identified in the Upper Yukon River area, and the eventual aim is to have every well in the Yukon listed in the groundwater database, making it much easier to monitor the resource so essential to so many Yukoners.

For more information contact DIAND Water Resources at 667-3145.