A Preliminary Analysis Of The Impacts Of The Cascade Hydropower Development On The Fish Biodiversity In The Upper Reach Of The Yangtze River

It is well known that the upper reach of the Yangtze River is one of the focus areas ofthe fish biodiversity conservation in the world. But the structure of the river system hasbeen significantly changed by modern human activities, especially by the cascadehydropower development, which not only changed the species composition and quantityof fish resources directly, but also led to adverse impacts on the fish genetic diversitydepending on which the fish populations survived. In recent decades, a large number ofhydropower stations were built in the main stream and tributaries along the upper reach ofthe Yangtze River basin, which constituted a large cascade reservoir group. With moreand more hydropower stations built, these adverse impacts would be worsening.The study area was the upper reach of the Yangtze River (from the Yibin section inSichuan Province to the Yichang section in Hubei Province). Based on the characteristicsof the general hydropower engineering, the impacts of the building and operation of theThree Gorges Dam, the Gezhou Dam and the cascade dams in the Jinsha River on severalimportant ecological factors of aquatic habitat were investigated. Flowingly, the biologicalcharacteristics and the fauna, resource quantity and genetic diversity of the fish wereinvestigated. Further, the response of fish to the building and operation of dams wasanalyzed.The results showed：(1) Cascade hydropower development had a significant effect on the fish habitat ofthe upper reach of the Yangtze River. Engineering construction leads to partial river bedsediment and topographic change, mass concrete, waste residue, waste water, sewage riverpollution, a lot of artificial pollution lead to aggravate the destruction of human activitiesand consumption demand. Cascade Project impoundment, section is divided into fluvialreservoir (dam)–River in the form of natural state, the river continuum damage.Reservoir waters habitat by river to lake change, dam part or most of the destruction ofNatural River. Reservoir and dam river hydrological situation will change a lot, mainlyreflected in the runoff, water level, flow velocity, water quality, sediment and temperaturechange. (2) Cascade hydropower development on the changes of fish fauna composition,resources quantity, genetic diversity, genetic differentiation and life history strategies haveimportant effects on fish; at the same time, fish response to the cascade hydropowerdevelopment.(3) Finally, based on the above results, protection and restoration measures of fish inthe upper reach of the Yangtze River are discussed.