March 22 marks UNESCO World Water Day. This is an annual opportunity to remind us of the importance of protecting our water. Water in all its forms: rivers, oceans, glaciers, groundwater. Yes, groundwater.
Posted yesterday at 12:00 p.m.
Groundwater is in a way the mirror of surface water, one being above and the other below. Both follow the same good old water cycle, invariably subject to gravity. Being deposited on the ground by the rain, these waters follow their course until their final destination which is the ocean. The difference between the two is simply the time scale. Fresh water passes through rivers and lakes in days, months, and years, while groundwater passes through soils in months, years, and sometimes tens of thousands of years. That being said, groundwater is beneficial to humans because, unlike surface water, it can be drunk without too many treatment steps thanks to the filtration capacity of the ground.
It is a very economical resource, which explains why 30% of the Canadian population depends on it as a source of drinking water.
Groundwater is therefore useful and important. However, protecting it comes with its own set of scientific challenges. The field of on-site sanitation is rich in examples of this kind, including that of antibiotic resistance. Antibiotic resistance arises from various organisms that have adapted to environments that contain antibiotics on a recurrent basis. In this sense, sewage sludge from wastewater treatment contains strains of microorganisms resistant to antibiotics, since it comes into contact with wastewater that contains antibiotics.
In cities, where domestic wastewater is collected in the sewers and then treated in factories, this sewage sludge is kept in the processes for no more than 30 days, which means 30 days of change. In isolated residences, where wastewater seeps into the ground and then joins groundwater, sewage sludge gradually forms in the ground. However, the lifespan of these systems is 30 years without changes, which amounts to saying that the microorganisms are left to mutate for 30 years!
To assess the risk posed by these systems, several questions must be asked. Will antibiotic resistance genes reach the aquifer? Does the soil excavated during the dismantling of the system represent a risk? Can antibiotic resistance genes spread through the environment during surgery?
Answer: I don’t know, but I admit that it worries me a little. It is for these reasons that our research team at Polytechnique Montréal is studying these questions.
In any case, it is not so simple to characterize the phenomenon, and it must be done over several years before arriving at a conclusion.
I believe that groundwater conservation requires a special effort in risk management. With groundwater, everything can be fine for a long time, and problems arise years later. It is then difficult, if not impossible, to rehabilitate the aquifer. Given the time scales involved, and the efforts required to study groundwater, it is necessary to waltz between scientific characterization programs, the precautionary principle and the long-term vision.
A vision that is all the more difficult to put forward politically when, as its name suggests, groundwater is underground and invisible. Therefore, it seems less interesting than surface water. Groundwater does not produce pretty landscapes and does not allow swimming or navigation.
I end on a more positive note by putting forward an initiative for groundwater conservation. In 2008, the Quebec government began funding groundwater knowledge acquisition projects. These projects, which are still in progress, have made it possible to document a host of parameters ranging from the direction of groundwater flow to the level of aquifer vulnerability, by region. This is very valuable information to lead to an integrated management of water resources.