Waters in the Rhine watershed are polluted by different substances. Pollutants may have different origins: e.g. settlements, industry, mining or agriculture. Nutrients are largely discharged from agricultural acreage. Other organic substances may reach waters through municipal and industrial wastewater, e.g. from foodstuff production.
The construction of wastewater treatment plants in the Rhine watershed entailing expenses above 80 billion € during the past 30 years has had a very positive effect on Rhine water. Today, our brooks and rivers receive much less pollutants from industrial and municipal wastewater pipes. While pollutions from such point sources are mostly to be unmistakably identified at the point of input into the water body and are comparatively easy to measure, it is mostly difficult to determine substance inputs from the surface, of so called diffuse origin.
Great amounts of substances, such as nitrogen compounds, phosphorous, plant protection agents and heavy metals are discharged from surfaces into our waters. They may be airborne or washed into the waters with rainwater running off.
Nutrients such as phosphorous and above all nitrogen compounds largely of agricultural origin may lead to overfertilization (eutrophication) of water bodies and the sea. Other substances of diffuse origin, such as plant protection agents, heavy metals, organic pollutants and pharmaceuticals may be poisonous, have hormone-like or mutagenic effects. The sources of these substances are not only located in agriculture and industry. Some of them are due to uses in private households and gardening.