Indicator: River eutrophication by phosphorus

A graph shows the distribution of total phosphorous quality classes (QC) II-III and below for 1982 to 2016. The proportion of higher exceedance (QC IV) has dropped markedly, that of lower exceedance (II-III) has risen sharply.Click to enlarge
Sampling sites which exceed the requirement for good status for total phosphorus
Source: German Environment Agency from data provided by the German Working Group on water issues of the Federal States and the Federal Government Figure as PDF

Table of Contents

 

At a glance

  • Elevated phosphorus concentrations are recorded at almost two thirds of all river measurement stations.
  • This proportion has declined by around one-fifth since the beginning of the 1980s. Very high levels of pollution are very rare nowadays.
  • The Federal Government's aim is to meet the requirements for good status for phosphorous in all water bodies by 2030 at the latest.
  • This primarily requires a change in fertiliser practices in agriculture. Small sewage treatment plants also need to remove phosphorus in accordance with current technology.
 

Environmental importance

The term ‘eutrophic’ comes from Greek (eu trophos) and means ‘well fed’. Eutrophication is caused by human activities which lead to an accumulation of nutrients in previously nutrient-poor water bodies. Algae and water plants can then become overabundant and deprive other species of plants, many microorganisms and animals of essential resources.

Germany's water bodies are not in a good status. One of the biggest problems is the eutrophication of water bodies (cf. indicators of the ecological status of rivers, lakes and seas). The key factor when determining the degree of eutrophication is pollution by phosphorus. According to the ‘law of the minimum’, the growth of organisms is restricted primarily by the resource in shortest supply. In the case of algae and water plants, in most water bodies this is phosphorous.

 

Assessing the development

At the beginning of the 1980s excessive phosphorus concentrations were measured at over 80 % of sampling sites. In 2016 this proportion was still almost two thirds. However, if the poorer quality classes are considered, then a noticeable improvement can be seen. The proportion of sampling sites where the requirement for phosphorus was exceeded by a maximum of twice the value (quality class II-III) rose from 12 % to almost 57 % between 1982 and 2016. The worse classes declined accordingly. This improvement is mainly the result of introducing phosphate-free washing powders and phosphate precipitation in the larger sewage treatment plants.

According to the European Water Framework Directive (EU Directive 2000/60/EC), all water bodies must achieve a good ecological status by 2027. In Germany almost two thirds of water bodies have concentrations of phosphorus which are too high to meet this requirement. In order to remedy this, fertilising practices in agriculture need to change. Small sewage treatment plants also need to remove phosphorus using state-of-the-art technology. This is already happening in the bigger plants. According to the German Sustainable Development Strategy, the requirements for good status for phosphorus need to be met by 2030 at the latest (Federal Government 2016).

 

Methodology

The Federal States send measurements to the German Environment Agency from approximately 250 representative sampling sites. The 3-year mean phosphorous concentration is calculated for each sampling site for classification into a water quality class. This value is compared with the concentration which should not be exceeded for good ecological status in each of the types of water body. Details are regulated in the Surface Waters Ordinance (cf. water protection policy in Germany). The indicator gives the proportion of sampling sites which have a water quality less than ’good’ (Class II) in terms of total phosphorus.