Research On The Aquatic Organisms And Advance Estimate Of Effects Of Hydropower Engineering In Niyang River Basin, Tibet

Niyang River Basin locates in Linzhi of southeast Tibet. It's the first level anabranch of Brahmaputra. Niyang River is not only the important habitat for the special fishes just live in Brahmaputra, but also the main water replenishment for Brahmaputra. With development of Linzhi region, hydropower is exploiting in NiYang River Basin. The hydropower is clean and reproducible, but the effect of hydropower engineering on the aquatic organisms is remarkable and unreversible. In order to deal with the relationship between hydropower exploitation and the aquatic organisms protection, it is important in that investigate the aquatic organisms in Niyang River, analyse the effects of hydropower engineering, and put forward measures to protect the special fishes.The aquatic organisms in Niyang River Basin were investigated by sampling, interview and information collection during April to June in 2007. The statuses of the aquatic organisms in Niyang River were found: There were 5 phylum 75 species (generas) of phytoplankton, and Bacillariophyta dominated the phytoplankton composition. The distributing of the phytoplankton's density and biomass was negative correlate to altitude markedly. There were 51 species (generas) of zooplankton, and Protozoa dominated the zooplankton composition. There were 9 species (generas) of zoobenthos and 2 species of aquatic macrophyte. 17 species of fish were found, included 5 alien species. The population of main fishes in Niyang River were declined. Compared with the Lilong to Paixiang reach of Brahmaputra: The aquatic organisms diversity in Niyang River was lower, the community structure was simpler and unstable; The plankton's density and biomass in Niyang River were less.Based on the investigation and the programming of cascaded hydropower exploiture in Niyang River, this paper analyzed and forecasted the effects on the aquatic organisms of the cascaded hydropower exploiture. Furthermore, the integrative estimate through Grey Relational Grade Analysis proved that the negative effects on the aquatic organisms of the cascaded hydropower exploiture were more than the positive effects. In order to protect the special fishes, some compensation and protection measures were provided in this paper.