© Hugh Venables (CC BY-SA 2.0 DEED). Photo of Breckland mere

The following is a short summary of the habitat type and how to create/enhance it to a "good" condition. For an informed position, please refer to official up-to-date UKHAB documentation or the UK Government's Condition Assessment Sheet.

Aquifer-fed naturally fluctuating water bodies are natural water bodies that exhibit extreme fluctuations in water levels as part of their natural cycle.

These fluctuations include periods where the water body may be completely or almost completely dry. These water bodies do not have consistent inflow or outflow streams visible at the surface, except at times of very high water level, when temporary out-flows may develop. Instead, they are directly connected to the underlying groundwater system, and periodically empty and are recharged via swallow holes or smaller openings in their beds. In the UK, two known variants of this habitat are:

- Turloughs: These are typically found over Carboniferous limestone in Northern Ireland and Wales.

- Fluctuating Meres: These occur over chalk in the Norfolk Breckland.

How to Create / Enhance to a "Good" condition

There are a set of criteria that are used to judge the condition of this habitat. These are listed below.

Condition Assessment Criteria

The Freshwater Biological Association ‘Habitat Naturalness Assessment’ is used to assess the condition of lakes. Scores for four attributes (physical, hydrological, chemical, and biological naturalness) are averaged to generate an overall 'habitat naturalness assessment score' which can then be translated into a condition score for use in the metric (see below).

There are other elements considered in the lake naturalness assessment, but these are not included when calculating the condition assessment score.

Details of the methodology for assessing naturalness of lakes are available at: Contribute naturalness data – Discovering Priority Habitats in England

The key documents are:

Lake naturalness assessment – guidance document (PDF)

Annex I – Printable lake naturalness survey form to use in field (PDF)

Annex II – Physical naturalness photographs (PDF)

Annex-III - Hydrological naturalness photographs (PDF)

Annex IV – Chemical naturalness photographs (PDF)

Annex V – Plant functional group photographs (PDF)

Annex VI – Further species recording (PDF)

We encourage recording of data on lakes on the Freshwater Biological Association ‘Habitat Naturalness Assessment’ website portal: Contribute data – Discovering Priority Habitats in England (wpengine.com)

Average 'Habitat Naturalness Assessment' Class	Condition Assessment Score
1 Natural	Good (3)
2	Fairly good (2.5)
3	Moderate (2)
4	Fairly poor (1.5)
5 Least natural	Poor (1)