Abstract:The South-to-North Water Diversion Project (SNWDP) is the key national water conservation project in China to improve water resources and relieve water shortage in the northern part of China. The water intake of the Eastern Route Project (ERP) of SNWDP is located in Jiangdu County, Jiangsu Province, which is a breeding site of Oncomelania hupensis, the intermediate host of Schistosoma japonicum. The water diversion route of ERP will cross Baoying County (33°15′ N latitude), the northern limit of the current distribution of the snails in China and then pass through regions where the snails do not currently exist. In order to investigate the possibility of survival and reproduction of snails in their new habitats, two areas along the diversion route of the ERP, namely Jining City of Shandong Province (35°23′ N latitude) and Xuzhou City of Jiangsu Province (34°21′ N latitude) were selected as field study sites. A longitudinal study on the survival and reproduction of the snails in the north was made using the quantitative techniques over a period of 8 years. Changes of the gonads of the snails moved north were measured using a range of histological, histochemical, enzyme-histochemical and electron microscopic techniques. The results showed that, the survival time of the transferred snails and their offspring in Xuzhou was limited to a period of 8 years, comparing with survival time of 1.5 years for snails moved to Jining. The gonads of the male and female snails were atrophied after being moved north for 3-6 months, while abnormal changes in the histochemistry and metabolic enzymes occurred. It is indicated that if the snails moved to the areas between 33°15′ and 34°21′ N latitude, though the snails were able to survive in Xuzhou for a limited period, the snail populations decreased gradually due to the decline in the rate of reproduction. If the snails moved to the northern part of 35°23′ N latitude, they can hardly survive. It is concluded that if the snails moved to north of 33°15′ N latitude, it is difficult to survive and reproduce, and further create new snail habitats for Oncomelania hupensis snails.