Environmental Engineering Reference
In-Depth Information
and the Yalutsangbu River and its tributaries. The new results from the Qinghai-Tibet Plateau agreed
with the relation obtained from the rivers shown in Fig. 11.3.
Figure 11.4 shows the relations between the taxa richness (number of species per site) and abundance
(number of individual animals per area) with the status of the fluvial process, in which “Stable” represents
stable streams, “Incised” represents incised streams, “Silting” represents streams with continuous sediment
deposition, and “Intensive ST” represents the streams with intensive bed load transportation. The biodiversity
and density are high in stable streams, lower in degraded and aggraded rivers, but the lowest in streams
with intensive sediment transportation. Compared with fluvial processes, pollution is of only any second
importance on the river ecology. Bed stability is a precondition for stream ecology and is the most
important factor for biodiversity.
Fig. 11.4
(a) Relation of species richness of macroinvertebrates and status of the fluvial process of rivers; and
(b) Relation of abundance of macroinvertebrates per area with status of the fluvial process
The stable streams provide stable and varied habitats for various species, and, therefore, support
high diversity of aquatic bio-communities. The taxa richness is represented by
Ephemeroptera
(
Baetidae,
Siphlonuridae, Ephemerellidae, Heptageniidae, Ephemeridae, Potamanthidae
and
Leptophlebiidae
)
,
Plecoptera
(
Perlidae and Nemouridae
)
, Trichoptera
(
Hydropsychidae, Brachycentridae, Leptoceridae,
Psychomyiidae, Hydroptilidae
and
Rhyacophilidae
)
, Odonata
(
Gomphidae, Coenagrionidae
and
Euphaeidae
)
; Diptera
(
Chironomidae, Tipulidae, Ceratopogonidae
and
Simuliidae
)
; Coleoptera
(
Elmidae,
Psephenidae, Hydrophilidae, Dytiscidae
and
Dryopidae
)
; Gastropoda
(
Melaniidae, Hydrobiidae,
Lymnaeidae and Planorbidae
)
, Amphipoda
(
Gammaridae
)
and
Hirudinea
. The species of the
Ephemeroptera, Plecoptera
and
Trichoptera
(EPT) imply natural conditions and very good water quality.
Therefore, the number of species and density of the EPT are used as indicators of very good ecology.
Figure 11.5 shows several representative species of
Ephemeroptera
and
Trichoptera
(Duan et al., 2010).
Incised rivers have V-shape cross sections and there is little or no floodplain. The substrate consists of
cobbles, gravel, coarse sand, and bedrock. Flow velocity is high and only species which may clasp the
bedrock or cobbles to resist the flow can live in incised streams. The taxa richness is lower than for
stable streams. Species found in incised streams include:
Ephemeroptera
(
Baetidae, Heptageniidae,
Siphlonuridae,
and
Ephemerellidae
),
Trichoptera
(
Hydropsychidae
),
Coleoptera
(
Elmidae, Haliplidae,
Chrysomelidae, Curculionidae, Hydrophilidae,
and
Lightningbugs
), and
Diptera
(
Chironomidae,
Ephydridae, Tipulidae,
and
Stratiomyiidae
). Figure 11.6 shows several representative species of
Placoptera
taken from incised rivers.
For rivers with continuous sediment deposition silt and fine sand cover the bed surface and fill in the
interstices of large solid particles. The taxa richness and abundance of macroinvertebrates are lower than
in stable and incised rivers. The biomass of invertebrates and volume of sediment deposition were
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