Dangers to water quality

Why is water quality not the same all the time? The water is so dirty because waste water from homes and factories used to be discharged into the Rhine without being cleaned first. We no longer do that, but the water in the Rhine is still not clean enough.

Waste water

We all produce waste water every day, whether we use water for cooking, washing, flushing the toilet or watering the garden. Every person living in the Rhine catchment area uses on average 130 litres of water a day.

Farms and factories also produce waste water. Almost everything you buy uses water during its production.

‘Waste water’ is how we describe all the water that people use and that is discharged after use in one way or another. There are many ways of discharging waste water, for example via the toilet or as discharge from a factory. But also rainwater that falls in populated areas, as it picks up all kinds of substances from the soil on the way.


Chemical industry at Ludwigshafen (DE) Photo: BASF

Chemical industry at Ludwigshafen (DE) Photo: BASF

Almost all waste water is sent to a water purification plant before being released back into the environment. That wasn’t always the case. In the past, waste water was simply discharged into the Rhine, which was also called an ‘open sewer’ as a result. It could really stink!

Over 80 billion euros has been spent building water purification plants in the Rhine catchment area over the past 30 years. But this has certainly made the water much cleaner.

We inspect most of the water very thoroughly and are able to clean it. Waste water from homes contains bacteria, detergents, cleaning products, dirt and food residue. These substances can easily be broken down, but we still can’t get all the water clean enough. Medicines and pesticides can’t always be filtered out of the water.

Waste water from factories is carried through pipes to purification plants in towns. Some factors also clean their waste water themselves and then discharge it into streams, ditches and the Rhine. Industrial firms often use very particular waste water purification methods. So the water they discharge is almost always clean enough. The water can get too hot, and that’s another thing that needs to be controlled!

If waste water is not properly purified, water quality will fall. The purification process is pretty good, but we can still do better.

Climate change

The water in the Rhine is heating up. Between 1978 and 2011 the water temperature rose by 1 to 1.5°C on average, partly due to power plants. Power plants generate energy, and use water to cool their machinery. This water gets hot, and is then discharged back into the Rhine. These warm water discharges are the main cause of hotter water at those points.

Climate change is causing the water throughout the Rhine to become hotter. The heat reduces oxygen levels in the water, which is a real problem. This is because animals in the Rhine become weaker if there is not enough oxygen in the water. Weak animals get sick faster and more easily. High water temperatures can in some places even kill fish and shellfish.

Briefly, climate change makes the water hotter and so reduces its quality.

Read more about climate change.



Groundwater is all the water below ground, in soil and rocks. It is a hidden treasure that is connected day and night to rivers and lakes. Groundwater is the most important source of our drinking water, but it is very sensitive to pollution. Substances that have ever ended up in it are broken down very slowly or not at all.

Some of the groundwater is polluted almost everywhere in the Rhine catchment area. The most harmful substances and nutrients end up in groundwater as a result of agriculture.



Nutrients can also be a problem if their levels in the water are too high. Pesticides and nutrients pass through the soil from farming areas, and are carried by the groundwater into ditches, streams and eventually the Rhine. Precipitation also carries substances from other areas to the Rhine in the same way.

Polluted groundwater reaches the Rhine after a short time, and makes the water quality worse.

But that is not all. All kinds of things end up in the water via the air as well. This is because things are floating about in the air all the time. Nutrients and metals in particular end up in the Rhine in this way.