by Herb Martin, Sask Water, Moose Jaw, Saskatchewan
Where to drill to locate a groundwater supply can seem like a mystery. But with some basic water well information, the task ahead of you will seem clearer.
Groundwater can be found in large volumes throughout Western Canada and is simply surface water that has temporarily slipped below the ground surface. This water continues to move downward obeying the laws of gravity until it encounters an aquifer. In the water well industry, the term aquifer is used to describe a layer of sand, gravel, or occasionally coal that yields water to a well. Once the water encounters an aquifer, it then starts to move horizontally through the aquifer layer at a very slow rate.
Below the ground surface, water flow rates are dramatically reduced as compared to surface water flow. This is because groundwater must move through voids that exist between soil particles. If water is moving through soil particles that are coarse in nature (sands and gravel rather than clays and silts) larger voids exist and water flow increases. Groundwater movements are frequently measured in metres or tens of metres per year.
In Saskatchewan, aquifers fall into two general categories. Bedrock aquifers, those deposited prior to the ice ages and glacial aquifers, those deposited by glaciers.
Bedrock aquifers are usually very extensive deposits of fine sands interbedded with layers of very dense clays and/or silts with occasional coal seams. Because of the extensive nature of these aquifers, locations for potential wells can be predicted by checking the records of completed testholes from previous well attempts. Bedrock aquifers tend to be deeper than glacial aquifers so completing a well will be more expensive. However, one must consider that bedrock aquifers, because of their extent, are less dependant on annual recharge and therefore more drought proof than glacial aquifers. It also must be pointed out that water quality can be a problem as water in deep aquifers is in contact with soil minerals for longer periods of time.
Glacial aquifers are formed by sands and gravels that were deposited by the glaciers during the last ice age. These aquifers are quite variable in size, shape, and depth. For example, they can occur close to the surface or they may be more than 150 metres deep., Glacial aquifers may be so small that they are only capable of supplying water to a single farm. On the other hand, they can be large enough to yield municipal water supplies. These aquifers, due to their irregular shape, make it difficult to predict locations with precision.
In comparing these two types of aquifers, it can be said that shallow aquifers yield the best water but unfortunately they may be susceptible to drought.
Back to the original question of HOW DO WE FIND THESE AQUIFERS? Because the sand formations are deposited in layers, a pattern can be established by looking at the information from completed testholes in the immediate area. For example, if most wells in your area are150 feet deep, you will probably be assured of completing a well at 150 feet.
Provincial governments in the three prairie provinces maintain records of wells that have been drilled. In Saskatchewan, contact Sask Water; in Alberta, contact Alberta Environment; and in Manitoba, contact the Department of Natural Resources. PFRA offices in all three prairie provinces will assist in finding and interpreting well records. Any of these agencies will help you to determine the well potential at your site by providing information about: