How do we know all this? How do we know whether water is dirty? And how do we know what is bad for water quality and what isn’t?
You have to test water to answer these questions. You have to take measurements to find out what substances are in the water, and how much. And that is what is done. Lots of tests are carried out regularly at many places in different countries in the catchment area. The quality of the water in the Rhine is monitored from Switzerland through to the Netherlands. The measuring points are shown on the map of the Rhine catchment areas. These are called measuring stations, and are the places where the quality of the water is measured.
We are now able to measure very accurately what substances are in the water and how much.
And the techniques used to perform these measurements is improving all the time. This means that we are able to measure even more substances, even tiny substances that were impossible to measure in the past, like residues of make-up and medicines.
Scientists also try to find out where the substances came from. For example, were they discharged from a factory, or did they come from a ship? If they know where the substances come from, something can be done about it.
Scientists don’t just measure substances in the water. They also examine algae, plants, fish and other creatures to find out how healthy they are or how many of them there are. You can find out whether water quality is good by seeing whether plants or animals are healthy.