Page 230 - Freshwater-Biology-and-Ecology-Handbook

CHAPTER 5 3.1.10 – 3.1.11 3.1.10 DEHLI

(Drought Effect of Habitat
Loss on Invertebrates)

DEHLI quantifies the impact of drought on in-stream
macroinvertebrate communities by assigning values to
taxa according to their likely association with key stages
of channel drying. It was devised to complement the LIFE
index, which responds to flow velocity.

DEHLI Index – Drought
Effect of Habitat Loss on
Invertebrates

DELHI identifies areas where river restoration or
revised abstraction licenses may be needed – to
increase resilience to the effect of anthropogenic
activities exacerbated by over-abstraction and
climate change.

Although DEHLI has been designed to operate at family
level, some genera need to be identified because a few
families include genera with starkly differing habitat
requirements: for example, Leptophlebiidae and
Taeniopterygidae.

Drought Intolerance Score (DIS) values between 1 and 10
are allocated to each family, based on their intolerance to
drying.

DEHLI is an average score per taxon based on DIS using
the following equation:

DEHLI = Σ DIS/n

Where n = the number of scoring
taxa in the invertebrate sample
DIS = Drought Intolerance Score

DEHLI index values of around 10 imply little or no evidence
of an ecological impact from drought. Values towards 1 imply
significant impacts associated with the advanced stages of a
drought.
Chadd et al. (2017) (92) provides a useful reference to this work.

230 | Freshwater Biology and Ecology Handbook
–