Further study on possibility of diffusion of Oncomelania hupensis with water in river channels of the east route of South-to-North Water Diversion Project / 中国血吸虫病防治杂志

ABSTRACT

Objective To study the drifting law of floats and potential risks of Oncomelania hupensis diffusion in the water diversion rivers of the east route of South?to?North Water Diversion Project. Methods The O. hupensis snails in the river chan?nels were monitored by the salvage method and snail luring method with rice straw curtains,and the diffusion possibility of snails along with water was assessed through the drift test of floats with GPS. Results In the flood seasons from 2006 to 2013, totally 8 338.0 kg of floats were salvaged,and 2 100 rice straw curtains were put into water in the Li Canal and Jinbao shipping channel,but no Oncomelania snails were found. The drift test of floats with GPS before water diversion showed that the flow ve?locity on water surface(northbound)was 0.45 m/s,the average drift velocity of the floats was 0.56-0.60 m/s,and the average drift distances each time were 999.70- 1 995.50 m in the Gaoshui River section,while there were no obvious drift in Jinbao shipping channel section. During the water diversion period,the flow velocity on water surface(northbound)was 0.45 m/s,the average drift velocity of the floats was 0.35-0.41m/s,and the average drift distances each time were 1 248.06-1 289.44 m in the Gaoshui River,while in Jinbao shipping channel section,the flow velocity on water surface was 0.28 m/s,the average drift velocity of the floats was 0.25- 0.27 m/s,and the average drift distances each time were 477.76- 496.38 m. The drift test showed that the floats gradually closed to the river bank as affected by water flow,wind direction and ship waves,when blocked by the reeds,water plants or other obstacles,and they would stopped and could not continue to drift without outside help. Con?clusions There are no Oncomelania snails found in the river channels of the east route of South?to?North Water Diversion Proj?ect. The drifting distance of the floating debris along with the water is restricted by the flow rate and shore environment.