Rapid Assessment for Ponds

Rapid Assessment for Ponds – the development of the Big Pond Dip invertebrate survey method

The Big Pond Dip invertebrate survey is a simple biological quality assessment method, designed for use by the wider public, which assesses the overall ‘naturalness’ of ponds. It has been developed from the methods used for the National Pond Survey and the PSYM system (Williams et al. 1996, Williams et al. 1998, Biggs et al. 2000) which are used by professional biologists to assess pond ecological quality. Although specifically developed for garden ponds, the Big Pond Dip methods can be applied to any pond or lake up to 5 ha in area. Limited testing of the method on lakes indicates that it also reflects adequately lake invertebrate species richness on waterbodies up to about 50 ha.


A high score on the Big Pond Dip indicates that a pond supports animals typical of high quality waterbodies. Ponds with lower scores are likely to be in poorer condition, and not reaching their full potential, because of the impact of one or more stressors (e.g. water pollution, poor habitat structure, unnaturally high fish densities).

The Big Pond Dip score was first developed and used by Freshwater Habitats Trust (then Pond Conservation) in 2009. It has been applied with minor modification for the invertebrate part of the OPAL Water Survey in 2010.

This report summarises the main technical features of the Big Pond Dip and the three main stages in developing the method:

(i) selecting a potential set of easy-to-identify animals to include in the method

(ii) making a final selection of animals that was statistically related to the level of environmental stress affecting ponds.

(iii) testing the index on the National Pond Survey dataset, and on an independent garden pond dataset, to check that it reflected overall variation in pond degradation and pond quality.

For more information about the quick invertebrate survey method you can download the full technical paper here