GROUND WATER WITHDRAWLS: HOW MUCH IS TOO MUCH IS A MATTER OF DYNAMICS
Alfonso Rivera, PhD, is the Chief Hydrogeologist of the Geological Survey of Canada and author of two books: Canadaís Groundwater Resources (2014) and Regional Strategy for the Assessment and Management of the Transboundary Aquifer Systems in the Americas (2015). In an article published on January 10, 2017 in Groundwater Canada, "The state of ground water in Canada", he enumerates the questions that frame the need for more ground water knowledge in Canada; among others, these include how much ground water do we have, where is it located, how much of it do we use and what are the interactions between ground water, surface water, aquatic ecosystems and land use.
Water today spoke with Dr. Rivera about the issues of groundwater and how they relate to the current moratorium on new or expanded bottling water withdrawals in Ontario.
WaterToday - With regards to the Ontario government's recent moratorium on bottled water operations, Harden Environmental Servicesí senior hydrologist Stan Denhoed said in in an article in the Wellington Examiner, that "he supported the need for increased understanding of regional groundwater flow systems but argued there is no scientific merit in a sector-specific moratorium". Do you agree with this?
Rivera - I guess I will say as a short answer yes I do. Personally, I would have invested in studying the area and evaluating scientifically what it really means.
WaterToday - Do you think that water withdrawals for bottled water in Southern Ontario, although bottlers say they take very little of the total amount of water available, represent a threat to the groundwater in the area?
Rivera - Scientifically speaking, whether the water withdrawals for bottlers will affect groundwater, is a matter of scale. Yes it will affect something that might be nearby, say a kilometre from where you are withrawing the water from the well but it will not affect something that is 10 kilometres away. Although another factor comes into play in Ontario, particularly in Southern Ontario, and that is that most of the aquifers in the area are shallow aquifers. As a consequence they are mostly in connection with surface water with rivers or, and/or with lakes. So okay you may pump the water out of one well or two wells or four wells, but because the wells are not very deep and because they might be connected to other sources, then depending on the amount that is withdrawn, it will affect those other sources.
WaterToday - How much of an effect can it have?
Rivera - It depends. How far are the sources? How big are they? How much are they taking? What type of use is it? So it all comes down to quantity. And what I mean by quantity is the volume extracted, as a fraction of time. You know it can be 20 litres per seconds or 100 litres per second or 1,000 litres per second, thatís what I mean by quantity?
There are also many remnants of the last glaciation in Southern Ontario, you know sediments like clay and sands and gravels, so there are many, many ecosystems that are depending on water. And if they are as shallow as the groundwater is, or if the rivers are connected to the aquifers that are located in that area then you may diminish the base flow of a river which in turn diminishes the water reaching ecosystems or wetlands if you prefer. So at the end it can have an impact, even if the amount is small.
WaterToday - Are you saying that it does have an impact then?
Rivera - Iím not saying it does, Iím saying it might have an impact. And this means that these have to be evaluated. Itís the interconnections and the dynamics of the area that have to be understood because you can't really conclude anything before you do. It's a complicated system.
WaterToday - According to the Canadian Beverage Association, in 2009, 2.2 billion litre of water per year were produced in Ontario. So is that a lot of water?
Rivera - Okay. Well you know what that means if you take, if you divide that by 1000 it gives you 2.2 million cubic meters, and 2.2 million cubic meters is a very small amount compared to the groundwater resources in Southern Ontario. Itís a very small amount indeed.
WaterToday - So the bottlers have a point because they say they donít take much?
Rivera - No they donít take much if that number is correct. I mean it seems like a lot because billions seems like a lot, but those are litres. If you divide, if you go down and divide by one million, which is 1 cubic meter, and then you divide it by another million to have it in cubic kilometers, you don't have much altogether. Do you know how much water we use in Canada every year? We use 45 cubic kilometres of water in Canada per year.
WaterToday - Wow! that much?
Rivera - 45 cubic kilometres. Three uses combined - industrial, domestic and agricultural. 45 cubic kilometres. Thatís a lot of water. Of the 45, 44 are coming from surface water, 1 cubic kilometre is coming from groundwater.
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