Indicator: Ecological status of lakes

A graph shows the distribution of the environmental status and potential of the lakes for the years 2010 and 2015. The target for 2027 is also shown (100 percent ‘good’ or ‘very good’). In 2015, 26.4 percent showed at least a good status or good potential.Click to enlarge
Percentage of lakes in at least good status or with at least a good potential
Source: German Environment Agency / German Federal Institute of Hydrology Figure as PDF

Table of Contents

 

At a glance

  • In 2015 26 % of the lakes in Germany were in at least good ecological status or showed at least a good ecological potential.
  • The Water Framework Directive states that this figure should reach 100 % by 2015.
  • Germany is still far away achieving this target. The time up to 2027 must be used to reach these challenging objectives.
 

Environmental importance

Lakes not only provide us with recreation but also have important functions for protecting nature and the environment. For example, their shores provide habitats for a wide range of species of plants and animals. These (in places) sensitive ecosystems are threatened by nutrient inputs and, in particular, 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 only regenerate slowly, because the water in them is only exchanged very slowly. One major problem are inputs of nutrients from agriculture. If this 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 proportion of lake 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 2015 24.0 % of lakes were in a good ecological status and 2.3 % in a very good status. The fact that the values have deteriorated in comparison to 2010 is mainly due to better measurement methods. 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 this all water bodies should be in at least a good status by 2015. As this target has been missed, the two subsequent management cycles under the WFD now need 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’). To reduce this surplus the Fertiliser Ordinance was comprehensively revised and adopted in spring 2017. It is already foreseeable now that additional measures are necessary to reduce the input of nutrients into surface waters to an acceptable level.

 

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. 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 (cf. water protection policy in Germany).

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