On the African continent and the Middle East, the supply of fresh water is a major problem. But also in Germany there is a contamination of rivers and groundwater by municipalities, agriculture and, most of all, industry. The sewage is contaminated with various pollutants. But in particular, industrial wastewater often contains large amounts of different salts.

The Werra, a German river, is considered one of the dirtiest river in Central Europe. The reason for this is an extremely high salt load. The value for chloride is about 5000% higher than that of a comparable flow without an extreme introduction of sewage. The amounts of magnesium and potassium are also far above the normal value.

The reason for the load is the introduction of lye from the mining industry. At the Werra, potash salts are extracted, which are exported for fertilizer production worldwide. A waste product of this potash salt recovery is sodium chloride, but also magnesium salts and others. These waste products are either disposed of on huge hills, pressed into the ground or led into the Werra as the already mentioned lye.

Nowadays the water is dominated by only one species. The boosted river cancer, a brackish water species from North America is a Neozoe (unnaturally introduced species) and became the dominant living being. In addition, the New Zealand dwarf snail, also a Neozoe, occurs frequently. There is only a small amount of mosquito and fly larvae and some other species from the originally occurring species in the body of water with an extremely small share of the individual species of the ecosystem.