Now that you know a little bit more about groundwater from our previous blog post, one thing that may be on your mind is that this type of water is dirty, because it is stored together with soil and rocks (and other things we may think of as unclean), but that is not actually the case! Groundwater is generally considered to be cleaner that the surface water you see in rivers and lakes. That is because the tightly packed soil particles can act as a sieve and filter out unwanted pollution.
Many people around the world, including more than 750,000 here in Ireland, use groundwater in their houses and in agriculture, which is collected via wells. The two most common types of wells are shown in Figure 1, these are hand-dug, which are shallower and wider, and drilled wells (or boreholes), which are quite narrow and much deeper (some can be more than 100 metres deep!). Well water is also commonly used for drinking, but extra care must be taken if that is the case. We did mention before that groundwater is generally cleaner than surface water, but even so contamination can still take place.
Figure 1: Pictures of a 3 metres deep hand-dug well (left) and a 43 metres deep borehole (right)
Contamination of wells can happen from the surface, entering the well from the top, or even via the soil, in cases where soil filtration is not enough or when the spaces between local soil particles is too big and can’t filter much (think of a sieve with holes that are too large). Not to worry, though, because hydrogeologists have identified the principal ways (or pathways) via which contaminants can enter groundwater wells and, based on that knowledge, many protective elements have been added to well construction. The addition of these elements helps to keep the well water clean and safe for our use (Figure 2).
Figure 2: Illustration of an ideal drilled well (also known as borehole) with its protective elements
It is also recommended by the Environmental Protection agency (EPA) that those that use their own well water for drinking get it tested at least once per year, preferably after rainfall periods, to ensure all protective elements are working as they should. Things to look for are microbes (such as Total Coliforms and Escherichia coli) and potentially harmful chemicals. Water treatment, like reverse osmosis and UV lights, can also be installed as an extra protective step.
Groundwater is one of the biggest sources of water in Ireland (and in the world!) and, as we have now learned, when extracted and treated with the appropriate care it can be used safely and reliably for all intended uses.
Reference: Environmental Protection Agency, 2020. Protecting Your Private Well. Viewed 21 October 2020 < https://www.epa.ie/water/dw/hhinfo/protprivwell/>