Investigation of Current Status in Ba-jhang River System (The 5th River Management Office, WRA, MOEA. July, 2006)
The Fifth River Management Office of Water Resources Agency (WRA) of Ministry of Economics Affairs (MOA) held the investigation of stream status of Bajhang River as a reference to support eco-hydrological engineering planning. The duration of this project was two years long to establish required information in ecological database and webpage inquisition for further and feasible engineering management by hydro-engineers.
In the first year, it has been completed the investigation of stream status in main flow of Bajhang River as well as data collection for stream status of Pu-Tze Creek. Database format was also fulfilled. All the materials for Bajhang River have been printed out, and those of Pu-Tze Creek were assembled as another collection. In the second year, the investigation of stream status was completed for branch streams such as Touchienchi River, Chilan River, Yunshui River and Shinong River.
The investigation result in the first year includes outline of watershed, investigation of stream hydrology and hydraulics, biological investigation and ecological resource database. Establishment of inquisition system of ecological resource database includes data collection, opening of shape files, figures and image files, affiliated data, linkage of figure attribute and login system. In this project, historical research results were setup according to WRA WebGIS system format to support further data acquisition enhancement.
In order to make a proper restoration decision, a concise tool integrated spatial, chronological, physical, chemical and biological data was developed, so-called 5S model. In this study, based on the data collected in the stream status investigation, 5S (System conditions, Stream hydrology, Structures, Substances and Species) were evaluated to describe the overall river condition. Thus, the priorities of habitat restoration in Bajhang River can be established for further application in the practices of river environment management.
The Bajhang River had lengh of 80.9km, and slope of 1/42 with the drainage area of 474.7km2. TheTouchienchi River had lengh of 14.88km, and slope of 1/418 with the drainage area of 51.89km2; the Chilan River had lengh of 19.16km, and slope of 1/60 with the drainage area of 49.91km2; theYanshui River had lengh of 13.4km, and slope of 1/61 with the drainage area of 43.90km2; the Shinong River had lengh of 6.65km, and slope of 1/51with the drainage area of 17.45km2. The annual average air temperature of the basin was 23.3℃, relative humidity was 79％ and rainfall was 2337mm. The rainy season in May to October and dry season in November to April. There were 13 villages and towns within an administrative division of the Bajhang River basin covering the three counties Tainan, Chiayi, Chiaiy city. The Bajhang River of upriver was braided stream and midstream、 lower was twines. The riparian land utilization were: Many peoples walk and exercise in the Water Park under the Jun Hui bridge.
The present studies were about investigation of fish in the main stream and the branches of Bajhang River. There are 28r families 58 species fishes were found in the main stream of Bajhang River, including 22 species primary freshwater fish, 3 secondary freshwater fish and 8 diadromy or estuary fish. There were 11 families 28 species in the branch of Bajhang River, in addition of Anguilla japonica and A. marmorata , the most fish belong to freshwater fish. The abundance and diversity of fish were effect by climate, river environment and river construction.
Twenty-one crustacean and 12 mollusc species were recorded in mainstream of Bajhang River. It included 9 species of shrimps and 13 species of crabs in the sampled crustaceans. Where habitats of 19 species were estuarine and the others were freshwater species. One exotic species was found. Only 5 crustacean and 6 mollusc species were recorded in all the sampling sited of tributaries. It included 4 species of shrimps and 1 species of crab. Most abundant crustaceans and mollusks were found in the upper and down streams of the Bajhang River. It may owe water pollutions from the riparian cities in the mid stream of the Bajhang River.
The density of phytoplankton and the ratio of Cyandbacteria and Euglenoid in the middle and down-stream of Bajhang River were significantly increased indicated eutrophication problems in these region.
There are many macrophytic filamentous algae in branch streams of Bajhang River. These algae formed large mats of vegetation, free-floating（e.g., Spirogyra, Hydrodictyon）or attached（e.g., Cladophora）to substrata. They may occupy a much wider range of habitats or cover area of river, reduce flow rate and clog of river.
The total terrestrial insect specimen collected for Bajhang River were 20 orders, 151 families, and 198 species, for the aquatic insects were 9 orders, 15 families, 15 species. Touchienchi River were 16 orders, 112 families, and 204 species, for the aquatic insects were 8 orders, 19 families, 19 species. Chilan River were 18 orders, 138 families, and 230 species, for the aquatic insects were 8 orders, 32 families, 32 species. Yunshui River were 15 orders, 106 families, and 165 species, for the aquatic insects were 7 orders, 18 families, 18 species. Shinong River were 16 orders, 105 families, and 172 species, for the aquatic insects were 8 orders, 14 families, 14 species. The total terrestrial insects collected were 20 order, 206 families, 395species, 9442 individuals; for the aquatic insects were 8 order, 19families, 19species, 2991 individuals。No rare or conservation species were found during survey period.
The terrestrial insects collected were Collembola, Odonata, Plecoptera, Orthoptera, Blattaria, Mantodea, Dermaptera, Psoptera, Thysanoptera, Hemiptera, Homoptera, Megaloptera, Trichoptera, Neuroptera, Lepidoptera, Coleoptera, Diptera, Hymenoptera and Arachnida. Among them, the dominant order Collembola, Homoptera, Diptera, Hymenoptera and Arachnida. No significant difference was shown among the sampling sites. The vegetation will affect the diversity and abundance of terrestrial insect and the data were responded to the data of vegetation survey. The aquatic insects collected were Odonata, Ephemeroptera, Plecoptera, Hemiptera, Megaloptera, Trichoptera, Neuroptera, Lepidoptera, Coleoptera and Diptera, and Hymenoptera. Rainfall, dry season and raining season had played an important role on the diversity and abundance of aquatic insects as the third season data has shown in the first year survey. The degree of water pollution will influence the presence of the species diversity. For example, the Ephemeroptera, Plecoptera are preferred unpolluted habitat. However, Odonata, Trichoptera, Megaloptera, and Coleoptera are able to stay at slightly polluted habitat.
During the survey of Bajhang River, Typhoon Mindulle has occurred which had made the landslide, the flood and the sand have buried the vegetation. Therefore, the diversity and species richness of both the terrestrial and aquatic insects had declined dramatically. Fortunately, the insects come bask slowly on the next sampling date. Estuary of Bajhang River had full of mud and organic matter which has brought midges as a dominant familiy.
An inventory of bird resources were proceed in the watershed of Bajhang River with 24 sampling sites from 2004 to 2006. The species of birds were collected and their relative abundance was estimated. The results of the survey indicated that there were 127 species of birds in 15 orders and 44 families with 5 endemic species, 33 endemic subspecies, and 23 protected species. Separately, we found 109 species of birds in Bajhang River, 70 species of birds in Touchienchi River, 69 species of birds in Chilan River, 64 species of birds in Yunshui River, and 63 species of birds in Shinong River. Accordingly, the watershed of Bajhang River had rich avies resources. By the way, there was a strong relationship between the species composition and the geographic location of sampling sites, possibly due to agriculture, vegetation, and human disturbance.
In the terrestrial ecosystem, there were 17 species of mammals. In general, most of the species were typical animals that represented the ecological status in the region.
In the two years investigation, the bionomic surveys have recorded 15 species from 5 families, 1 order of amphibians and 21 species from 8 families, 2 order of reptiles at the main and branch stream of Bajhang River, with a total abundance of 2803 and 407 individuals respectively. Total amphibians and reptiles have recorded 36 species, 13 families of 3 orders, of which 3 species amphibians and 3 species reptiles were endemic species. And of which 5 species amphbians and 8 species reptiles were listed as protected species. The most species are the 35 species recorded at the main stream of Bajhang River and the least species are the 25 species recorded at the Shinong River. The species have been affected mostly by the development extent and different kinds of plants of sample area among investigation stations, which results in the difference in the composition of species. In addition, the river- land- engineering buildings have caused habitat separateness and fall off the variety of environment habitats. And this also affects the species distribution of amphbian and reptlies.
Paper Mul-berry and White Popinac (Bajhang River), Indian Sesbania, Paper Mul-berry and Elephant's Ear (Touchienchi River), India-charcoal Trema and Paper Mul-berry (Chilan River), Betel Palm, Paper Mul-berry and Elephant's Ear (Yunshui River), India-charcoal Trema, Paper Mul-berry and Elephant's Ear (Shinong River) above woody plants are the dominant plants. Wild Sugarcane, Para Grass and Flute-reed (Bajhang River), Para Grass, Flute-reed and Japanese Silver-grass (Touchienchi River), Wild Sugarcane, Napier Grass and Para Grass (Chilan River), Big Bidens, Acalypha indica and Wild Sugarcane (Yunshui River), Wild Sugarcane, Para Grass and Big Bidens (Shinong River) above riparian vegetations are the dominant plants. Lumnitzera, Milky Mangrove, Black Mangrove and Merremia Hederace are rare plnats, and Ludwigia × taiwanensis, Taiwan Golden-rain Tree, Taiwan Cotton Rose, Long-shoot Bamboo and Taiwan Hairy Passiflorain are endemic plants in the Bajhang River. Taiwan Cotton Rose, Long-shoot Bamboo, Incense Machilus, Litsea hypophaea and Pingtung Litsea that are endemic plants have been found in the branch of Bajhang River. The nature degree of Bajhang River is diversity and the branches of Bajhang River are level 2 mainly.