Environmental Engineering Reference
In-Depth Information
Fig. 11.5
Representative species of
Ephemeroptera
and
Trichoptera
taken from stable streams (See color figure at
the end of this topic)
Fig. 11.6
Representative species of
Placoptera
taken from incised rivers (See color figure at the end of this topic)
measured in a 100 m long section of the Diaoga River and the results are shown in Fig. 11.7 (Yu, 2008).
The abundance of benthic macroinvertebrates (abundance) decreases with increasing sedimentation
volume and increases again as the sedimentation volume reduces. Species found in the silting streams
include:
Diptera
(
Chironomidae, Tipulidae,
and
Ceratopogonidae
),
Coleoptera
(
Dytiscidae, Hydrophilidae,
and
Elmidae
),
Ephemeroptera
(
Ephemeridae, Caenidae,
and
Ephemerellidae
),
Odonata
(
Gomphidae,
Cordulegastridae,
and
Coenagrionidae
),
Oligocheata
(
Tubificidae
), and
Amphipoda.
In the rivers with intensive bed load transportation there is no stable habitat for benthic animals. The
taxa richness and abundance of macroinvertebrates are extremely low. For instance, in the Jiangjia Ravine
the bed material is composed mainly of gravel but the bed load transport is intensive. Only three species
were found in the samples from the Jiangjia Ravine and the abundance was extremely low (only 1
ind./m
2
). In the Xiaobaini and Dabaini ravines and the lower Yellow River, the bed material consists
mainly of coarse and fine sand and the rate of bed load transportation is high. Only one species was
found from the samples and the abundance was nearly zero.
Stable streams provide stable habitats for diverse bio-communities. If the boundary of a stream remains
stable even during extreme flood events the stream is in a state of
super-equilibrium
. The beautiful
Search WWH ::
Custom Search