River Ecology and Restoration - River Dynamics and Integrated River Management - page 701

Table 10.10 lists the species from the three sites, which shows that the river-lined riparian wetland has
much higher species richness than those from the river and isolated riparian lakes.

Table 10.10 Species richness and abundance of macro-invertebrates from river-linked riparian lake Zengjian Bay,
the main stem channel of the Zengjiang River at Zhengguo and a separated riparian lake - the Xizhijian Oxbow Lake
Zengjiang Bay

Corbiculidae C.fluminea (113); Chironomidae (four species 44); Elmidae ˈ Stenelmis (25);
Ceratopogonidae Bezzia (25); Corixidae (21); Limnodrilus(23); Semisulcospira (20);
Libellulidae (14); Ephemeridae (11); Bellamya B.Purificata (8); Macromiidae (6); Bellamya
Sp1 (5); Branchiura (4); Coenagrionidae Pseudagrion (4); Gomphidae, Trigomphus (3);
Ampullariidae (2); Psephenidae (2); Hydrophilidae Hydrobius (2); Tabanidae (2); Lepidoptera
(1); Acariformes (1); Gomphidae, Sinictinogomphus (1) ˗ Palaemonidae (1); Tricladida (1);
Baetidae (1); Heptageniidae (1); Parafossarulus (1); Elmidae, Sp1.(1)

Zhengguo 0

Xizhijiang
Oxbow Lake

Palaemonidae (13); Chironomidae (7); Hydrophilidae, Laccobius (2)

The Xizhijiang Oxbow Lake was a section of the Xizhijiang River Channel, which flows into the East
River at Huizhou, but became an oxbow lake since an artificial cutoff in the 1980s. It is separated from
the Xizhijiang River by a highway, as shown in Fig. 10.56(b). Part of the lake has been converted into a
fishpond. Because of the separation there is almost no flow velocity in the lake, while the separation also
cut off the fine sediment supply to the lake. The substrate consists mainly of sand, which has remained
unchanged for 20 years since the cut off. There is no mud layer in the lake. Analysis of samples from the
lake indicates that the species richness is only 3 and the number density is 22 ind/m 2 . The Shannon-
Weaver index and biocommunity index are H 0.89 and B 2.76, which are much lower than those for
Zengjiang Bay. To develop the oxbow lake into a good habitat for benthic invertebrates and fish, the lake
should again be connected with the river, allowing fine sediment to be carried into the lake and a mud layer
to form. The connection will also increase the flow velocity and exchange of lake water with river water.

Fig. 10.56 Location and shape of (a) Zengjiang Bay and (b) Xizhijiang Oxbow Lake

In the lower East River if riparian waters are created similar to Zengjiang Bay the ecology in the river
may be greatly improved. One example is to reconnect the Xizhijiang Oxbow Lake with the river. The
lake water may exchange with the river water and fish and invertebrates may spend a part of their life
cycle in the lake and other parts of their life cycle in the river.

10.4.5 Riparian Vegetation Restoration and Food Patches
Vegetation is a fundamental controlling factor for river eco-functions. Habitat, conduit, filter/barrier, and