Be careful what you pour on the ground. It may come back to haunt you.
Groundwater is known to be important in areas where there are not vast reservoirs of surface water. Many municipalities use groundwater as drinking water. In the Great Lakes region, however, with our abundant surface water, we are inclined to think groundwater is not important. We could not be more wrong.
A recent study has found groundwater is more important in the Great Lakes region than we thought. This report finds groundwater is the most important source of recharge water for the Great Lakes, contributing more than half the water that refills the Great Lakes each year. Most communities around the Great Lakes get their drinking water from the lakes, therefore, it is very important that we protect both the quantity and quality of water in these lakes.
Groundwater is water that is found under the ground surface. It flows beneath our feet in the pore spaces of soil and in fractures in rocks. The depth at which soil becomes saturated with groundwater is known as the water table. Thus, a high water table means groundwater is not far from the ground surface. Water tables can fluctuate over time.
Wells are holes drilled into the ground that fill with groundwater. As water is drawn out of the well, groundwater flow replenishes the well. Or, at least, that is the idea.
Since groundwater flows beneath the ground, there is, I think, a tendency to think it is limitless and will always be there, but it is a finite resource just like everything else. If groundwater is pumped out in large quantities by municipalities or industries, it is, then, no longer in the ground. This may seem obvious, but do we act in a way that suggests we know this? So, groundwater is being removed from the ground and groundwater is the most important element in recharging the Great Lakes. Therefore, every litre of groundwater removed from the ground is potentially a litre of water lost to the lakes. In these days of falling water levels, that is worth thinking about.
Just as water quantity is affected by removal, water quality is affected by water (or other liquids) poured onto the ground, which will infiltrate to groundwater. This means gasoline and fuel oils spilled at gas stations or leaking from underground storage tanks get into the groundwater. Irrigation water used for agriculture can also get into the groundwater and will take with it fertilizers and pesticides sprayed onto those fields. Because groundwater flows underneath the ground, chemicals that would be destroyed by light or degraded if oxygen were present often are not broken down and stick around in the groundwater.
So, what can we do to protect groundwater resources? We can dispose of chemicals (paint and thinner, antifreeze, herbicides, pesticides, etc.) by taking them to a hazardous waste drop-off centre, recycle used motor oil, limit fertilizer use, and, of course, try not to waste water (tips courtesy of groundwater.org).
And we can hope, for groundwater, out of sight does not always mean out of mind.
Andrew Laursen is an assistant professor at Ryerson University, studying ecosystem ecology. Sophia Dore is an environmental scientist with Conestoga-Rovers & Associates, an environmental consulting company.
