The amount of water in the Rhine is not always the same. The phrase used to describe the height of the water is ‘water level’. There have always been high water levels in the past, and this will continue in the future. Low water levels are also quite natural for a river! But though they are natural, they can cause problems.
Sometimes the water level in the river is higher than normal. This can be because of melting snow in the Alps or heavy rainfall, for example. High water is defined as water levels being higher than normal for eight days in a row.
Or there can be little or no rainfall for a long time, and then there is less water than normal in the river. This is called low water.
The Rhine is the most heavily used river in Europe for shipping. Many cargo ships use it to transport goods from one place to another. These goods are sometimes poisonous for plants, animals and people, so they must be kept out of the Rhine. If the water gets very high, shipping has to be suspended for safety. So high water can be bad for transport.
Too little water also sometimes stops ships travelling on the Rhine, for instance if the navigation channel is too shallow.
If there is not enough water in the Rhine, this can also mean that there is not enough to produce drinking water. Farmers also need water to irrigate their crops.
Most animals in the Rhine have no problems with high water. Migrating fish can even cross (small) weirs more easily if the Rhine is carrying a lot of water.
At low water, creatures that live near the surface of the water will have to go lower down. There is less space in the river, which means that they have to live closer together. Sickness can break out if there are too many animals living in a small area. Eels are particularly vulnerable to this. Most animals are able to survive during periods of low water, by laying more eggs for example.
Water plants do best if the water level does not vary too much within a year. Although some water plants disappear from some places for a time, most of them always return after a period of high water or low water.
Sometimes the water in the river gets so high that the surrounding area is under water. This is called a flood. The water floods over the banks or the dike, and then flows into the area behind the dike.
If a lot of people live and work in the flooded area, the water can cause a lot of damage. Imagine water coming up to your waist in your living room! In the most serious cases people can drown during a flood.