Indicator: Ecological status of lakes | Umweltbundesamt

At a glance

• In 2021 24.7 % of the lakes in Germany were in at least good ecological status or showed at least a good ecological potential.
• According to the Water Framework Directive the target was 100 % by 2015. Now there is a deadline extension until 2027.
• Germany is still far from achieving this target. The timeframe until 2027 must be used to achieve these ambitious goals.

Environmental importance

Lakes not only provide us with recreational value but also have important functions for protecting nature and environment. Their shores, for example, provide habitats for a wide range of species of plants and animals. These (in part) sensitive ecosystems are threatened by nutrient inputs and especially by increasing use.

There are numerous reasons why many lakes do not reach an optimal ecological status. Biological, chemical, physicochemical and structural (hydromorphological) aspects all contribute. Lakes regenerate slowly because their water is exchanged very slowly. A major problem are inputs of nutrients from agriculture. If these inputs are reduced, a restoration effect can only be achieved with a delay. It usually takes many years until a lake recovers from excessive nutrient inputs.

Assessing the development

The share of water bodies in a good or very good ecological status is considerably higher in the case of lakes than in other types of water bodies. In 2021 22.7 % of lakes were in a good ecological status and 2.0 % in a very good status. The fact that the values have slightly deteriorated in comparison to 2015 is mainly due to an extension of the monitoring. The real status of the lakes has remained roughly constant overall.

Germany is still far away from achieving the targets laid down in the European Water Framework Directive (WFD, EU Directive 2000/60/EC). According to it all water bodies should be in at least a good status by 2015. As this target has been missed, the next management cycle under the WFD now needs to be used to reach the ambitious targets by 2027 at the latest. The Federal States drew up management plans defining measures for improving water quality.

A major problem for the status of many lakes is the use of too large amounts of agricultural fertilisers (cf. ‘Agricultural nitrogen surplus’).

Methodology

Determining the ‘ecological status’ of a lake relies mainly on a comparison of the presence of a range of species with what would naturally be present in that type of water body. Here, phytoplankton is one of the most important indicators.  Five status classes are defined from ‘very good’ to ‘poor‘, depending on the degree of divergence and other assessment factors. An ecological potential is assessed for artificial and significantly modified water bodies. The highest potential is present when all measures to improve the ecological quality have been taken. However, these must not have a significant negative impact on use. The classification is laid down in the Surface Waters Ordinance.

More detailed information: 'Zustand der Seen' (in German only).