[Impact on prevalence of schitosomiasis after runs of Three Gorges Reservoir Project in the section of Anhui province].
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To investigate the changes of water level and the distribution of snails in Anhui province before and after runs of the Three Gorges Reservoir Project, and to determine the relationship between the two factors and schistosomiasis transmission.The hydrologic data of Datong hydrologic station and the data of snail status and schistosomiasis morbidity in Anhui Province were collected. The data from 1991 to 2002 and 2003 to 2012 were considered as before and after the impoundment of the Three Gorges Reservoir Project. Based on the prevalence of schistosomiasis, the cases of people and cattle were speculated, and the average infection rate of people and cattle were calculated. The t-test was used to compare the difference of snail area and the density of living snails before and after the impoundment of the Three Gorges Project. The pearson method was used to analyze the relationship between water level and snail area. The spearman method was used to analyze the relationship between the water level and the distribution of snails.From 1991 to 2012, the range of the highest water level, the lowest water level, the difference between the highest and lowest water level, the mean in the abundant water seasons, the mean in the dry water seasons, and the difference between the abundant water seasons and the dry water seasons was 11.40-16.30, 3.68-5.20, 6.70-12.12, 9.92-14.40, 4.77-7.64 and 4.13-8.93 m, respectively. The snail areas was (28 613 ± 362) hm² and (29 477 ± 918) hm² (t = -3.00, P = 0.007), the density of living snails was 1.51 (1.15-2.43) and 0.43 (0.29-1.10) snails/0.11 m² (H = 4.28, P < 0.001) before and after the impoundment of the Three Gorges Project, respectively. The average infection rate of people and cattle was 1.68% (99 482/5 935 147) and 4.62% (13 923/3 011 33), and the average number of acute schistosomiasis cases was 328, before the impoundment of the Three Gorges Project; 0.60% (39 747/6 649 380), 1.65% (1 291/783 224) and 71 after the impoundment of the Three Gorges Reservoir Project, respectively. The snail areas had negative correlation with the highest water level, the difference between the highest and lowest water level, the mean in the abundant water seasons (r value was -0.514, -0.509 and -0.477; P value was 0.014, 0.015 and 0.025, respectively). The infection rate of people had positive correlation with the highest water level, the difference between the highest and lowest water level, the mean in the abundant water seasons (r value was 0.532, 0.587 and 0.446; P value was 0.011, 0.004 and 0.038, respectively). The infection rate of cattle had positive correlation with the highest water level, the difference between the highest and lowest water level (r value was 0.507 and 0.553; P value was 0.016 and 0.008, respectively). The number of acute schistosomiasis cases had positive correlation with the highest water level, the difference between the highest and lowest water level (r value was 0.481 and 0.486; P value was 0.023 and 0.022, respectively).Following the runs of the Three Gorges Reservoir Project, the change of water level in the section of Anhui Province affected the distribution of snails and the infection of people and cattle to some extent. The snail areas showed an upward trend, and the density of living snails, the infection rate of people and cattle showed a downward trend. The runs of Three Gorges Reservoir Project has certain role to reduce flood and helpful for schistosomiasis control.Keywords:
Three gorges
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To investigate the changes of water level and the distribution of snails in Anhui province before and after runs of the Three Gorges Reservoir Project, and to determine the relationship between the two factors and schistosomiasis transmission.The hydrologic data of Datong hydrologic station and the data of snail status and schistosomiasis morbidity in Anhui Province were collected. The data from 1991 to 2002 and 2003 to 2012 were considered as before and after the impoundment of the Three Gorges Reservoir Project. Based on the prevalence of schistosomiasis, the cases of people and cattle were speculated, and the average infection rate of people and cattle were calculated. The t-test was used to compare the difference of snail area and the density of living snails before and after the impoundment of the Three Gorges Project. The pearson method was used to analyze the relationship between water level and snail area. The spearman method was used to analyze the relationship between the water level and the distribution of snails.From 1991 to 2012, the range of the highest water level, the lowest water level, the difference between the highest and lowest water level, the mean in the abundant water seasons, the mean in the dry water seasons, and the difference between the abundant water seasons and the dry water seasons was 11.40-16.30, 3.68-5.20, 6.70-12.12, 9.92-14.40, 4.77-7.64 and 4.13-8.93 m, respectively. The snail areas was (28 613 ± 362) hm² and (29 477 ± 918) hm² (t = -3.00, P = 0.007), the density of living snails was 1.51 (1.15-2.43) and 0.43 (0.29-1.10) snails/0.11 m² (H = 4.28, P < 0.001) before and after the impoundment of the Three Gorges Project, respectively. The average infection rate of people and cattle was 1.68% (99 482/5 935 147) and 4.62% (13 923/3 011 33), and the average number of acute schistosomiasis cases was 328, before the impoundment of the Three Gorges Project; 0.60% (39 747/6 649 380), 1.65% (1 291/783 224) and 71 after the impoundment of the Three Gorges Reservoir Project, respectively. The snail areas had negative correlation with the highest water level, the difference between the highest and lowest water level, the mean in the abundant water seasons (r value was -0.514, -0.509 and -0.477; P value was 0.014, 0.015 and 0.025, respectively). The infection rate of people had positive correlation with the highest water level, the difference between the highest and lowest water level, the mean in the abundant water seasons (r value was 0.532, 0.587 and 0.446; P value was 0.011, 0.004 and 0.038, respectively). The infection rate of cattle had positive correlation with the highest water level, the difference between the highest and lowest water level (r value was 0.507 and 0.553; P value was 0.016 and 0.008, respectively). The number of acute schistosomiasis cases had positive correlation with the highest water level, the difference between the highest and lowest water level (r value was 0.481 and 0.486; P value was 0.023 and 0.022, respectively).Following the runs of the Three Gorges Reservoir Project, the change of water level in the section of Anhui Province affected the distribution of snails and the infection of people and cattle to some extent. The snail areas showed an upward trend, and the density of living snails, the infection rate of people and cattle showed a downward trend. The runs of Three Gorges Reservoir Project has certain role to reduce flood and helpful for schistosomiasis control.
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To understand the changes of hydrological regime in the Yangtze River and schistosomiasis endemic situation in Nanjing City after the implementation of Three Gorges Project.The data of hydrological regime of the Yangtze River, schistosomiasis epidemic situation, and Oncomelania hupensis snail status were collected and analyzed in Nanjing City from 2002 to 2012.After the implementation of the Three Gorges Project in 2003, the water level of the Yangtze River slightly rose from January to April, the average water levels in May and August both reduced compared with those in 2002, and the time of water withdrawal was moved up. The water level of the Yangtze River slightly reduced from November to December. The endemic situation of schistosomiasis showed a decline tendency in the areas along the Yangtze River in Nanjing City. In 2012, the rates of human and bovine infected with Schistosoma japonicum both reduced by 100% as compared with those in 2002, and the snail area, infected snail area and snail density were reduced by 48.45%, 100% and 95.76% respectively as compared with those in 2002.After the implementation of the Three Gorges Project, the schistosomiasis endemic situation shows a decline tendency in the areas along the Yangtze River in Nanjing City, but the long-term monitoring still need to be carried out.
Oncomelania hupensis
Three gorges
Yangtze river
Oncomelania
Schistosoma
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The Three Gorges Dam (TGD) is a remarkable, far-reaching project in China. This study was conducted to assess the impact of TGD on changes in the ecological environment, snail distribution and schistosomiasis transmission in Dongting Lake area.Hydrological data were collected from 12 monitoring sites in Hunan section of Yangtze River before and after TGD was established. Data on snail distribution and human schistosomiasis infection were also collected. Correlation analyses were performed to detect the significance of snail distribution to changes in ecological environmental factors and human schistosomiasis infection.A series of ecological environmental factors have changed in Dongting Lake area following the operation of TGD. Volume of annual runoff discharged into Dongting Lake declined by 20.85%. Annual sediment volume discharged into the lake and the mean lake sedimentation rate decreased by 73.9% and 32.2%, respectively. From 2003 to 2015, occurrence rate of frames with living snails and mean density of living snails decreased overall by 82.43% and 94.35%, respectively, with annual decrements being 13.49% and 21.29%. Moreover, human infection rate of schistosomiasis had decreased from 3.38% in 2003 to 0.44% in 2015, with a reduction of 86.98%. Correlation analyses showed that mean density of living snails was significantly associated with water level (r = 0.588, p<0.001), as well as the mean elevation range of the bottomland (r = 0.374, p = 0.025) and infection rate of schistosomiasis (r = 0.865, p<0.001).Ecological environmental changes caused by the TGD were associated with distribution of snails, and might further affect the transmission and prevalence of schistosomiasis. Risk of schistosomiasis transmission still exists in Dongting Lake area and long-term monitoring is required.
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According to the analysis of typical hydrological years,the impact of Three Gorges reservoir on Poyang Lake has been briefly estimated in this paper. The change of water level in the exit and inside of lake by the operation of Three Gorges reservoir was calculated. It is found that due to the water storing of Three Gorges reservoir after floodsing season,the water level of Hukou hydrological gauge would fall 0.4～1.6m. Correspondingly, the water level inside Poyang Lake would fall 0.3～1.2m. The low water period would come earlier,and it would not only reduce the ability of anti-drought,but also change the wetland eco-environment of the lake. Finally,optimizing the water storing schedule of Three Gorges reservoir and cooperation with the reservoirs located in five tributaries of Poyang Lake have been proposed for mitigating the impacts.
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Water storage
Seiche
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Objective:To investigate the influence of the variation of Changjiang water level in Anhui province after the building of the Three Gorges dam on the snail distribution and epidemic of schistosomiasis.Methods:Calculating the variation of water level at Tiemao islet of Tongling county according to the data of water level presented by the Changjiang committee of water conservancy,and investigating the snail distribution and human activities in different altitude beaches.Results:After the building of three gorges' dam,the water level will rise between Jan.and Apr,change hardly between May and Sept,and descend between Oct.and Dec;the time of water retreating in fall will be earlier.The snails are distributed on the beach of all altitude,and people's activities are mainly on the lower and upper altitude parts of the beach. Conclusion:The variation of water level due to the building of the Three Gorges dam will lead to transmission of snails in the lower altitude beach,and increase people's chance and time of water contact.
Three gorges
Low altitude
Water body
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Abstract As the largest hydropower project in the world, the Three Gorges Dam (TGD) has drawn extensive concern in terms of its impact on downstream areas. In this study, an improved time delay estimation and wavelet analysis were used to investigate the influence of the TGD on the streamflow and sediment in the middle and lower Yangtze River, using time series of the daily discharge and sediment concentration data from three hydrological stations downstream of the dam. The results indicated that all of the time series at the three stations have prominent annual cycles, but the cycle of daily mean sediment concentration was nearly nonexistent after the impoundment of the TGD. Changes in discharge and sediment between the Yichang and the Hankou stations are larger than those between the Hankou and the Datong stations, which is mainly attributed to the streamflows of tributaries and Dongting Lake and the flood diversion area of Jingjiang. The transmission time of discharge for the whole Yichang–Datong river section is approximately 6 days. In addition, the attenuation of discharge from the Yichang station to the Datong station is 20%–30%. In contrast, the transmission of suspended sediment is slower than that of discharge, which takes 7–7.5 days to move from the Yichang station to the Datong station. The attenuation of sediment is approximately 30% in the Yichang–Datong river section and shows a clear increasing trend after 2006, mainly because a large amount of sediment was trapped by the TGD, and the dynamic balance of sediment was disturbed.
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Yangtze river
Discharge
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The Three Gorges dam, under construction on the Yangtze River in China, might affect the transmission of Schistosoma japonicum on the Jiang Han plain, which is downstream of the dam. To study this possibility, the prevalence of schistosomiasis was investigated in relation to a range of malacological, hydrological and meteorological factors. The general water level in the Yangzte over a year had a marked effect on the distribution of the intermediate host (Oncomelania hupensis) and the prevalence of human schistosomiasis in that year. Disease prevalence showed significant correlations with the density of the snail hosts, the level of the water table, annual rainfall, yearly evaporation, and altitude. Once the dam is complete, the flow of water downstream will probably be maintained at a level between those currently occurring in flood and dry weather, and this may have implications for schistosome transmission. Systematic monitoring is necessary to investigate the impact of the environmental changes brought about by the dam on transmission.
Oncomelania hupensis
Three gorges
Schistosoma
Oncomelania
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The operation of the Three Gorges Project( TGP) modified water sand regime in the middle and lower reaches of Yangtze River,affected on water level in Lake Poyang and correspondingly brought series new problems on water resources utilization,water quality,wetland and ecology. Analysis of daily water level turn out: yearly variation of water level in the lake includes four stages—low level stage,level rising stage,backwater stage,and recession stage; water level in lake is determined by Yangtze discharge in backwater stage,and is affected by both Yangtze discharge and discharge at Hukou station in the other three stages. The operation of TGP does not change the basic feature of Lake Poyang—lake-like with high water level and river-like with low water level,but actually changes values of water level. Physical model experiments have been carried out to study the effect of TGP on water level in Lake Poyang,and the results indicate: TGP impoundment caused decline in water level,the average( maximal) value of decline at Duchang station is 0. 94 m( 2. 58 m),and corresponding decline ratio of water-surface area of Lake Poyang is68%; TGP pre-discharge caused increase in water level,the maximal value at Duchang station is about 1 m,corresponding increase ratio of water-surface area is 32%; the operation of TGP in dry season affects little on water level in Lake Poyang.
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Yangtze river
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To investigate the effect of environmental change in marshland after the implementation of the Three Gorges Reservoir Project on schistosomiasis in Jiangsu Province.The hydrologic data of Nanjing City in Jiangsu section of the Yangtze River, and the data regarding the marshlands, the snail status and schistosomiasis morbidity in areas adjacent to the Yangtze River in Jiangsu Province were collected, and field snail surveys were performed in typical marshlands.Following the implementation of the Three Gorges Reservoir Project, the water level in Nanjing section of the Yangtze River appeared a year-dependent gradual decline tendency. The mean peak water level on January to March, 2012 (spring) increased by 0.41 m as compared to that before the construction of the project in 2002, while the peak water level on April to December, 2012 decreased by 0.32 m as compared to that before the construction of the project in 2002. The endemic situation of schistosomiasis showed a decline tendency in areas adjacent to the Yangtze River in Jiangsu Province. The area with infected snails along the Yangtze River was 0, the positive rates of serological tests and parasitological tests of the population were 0.73% and 0.004%, respectively in 2012.Both the schistosomiasis morbidity and snail status appear a decline tendency in areas adjacent to the Yangtze River along the lower reaches of the Yangtze River, Jiangsu Province after the implementation of the Three Gorges Reservoir Project.
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Yangtze river
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Exceptional low flow happened over the Yangtze River in 2006 and had some significant influences on water usage and environment.By using the runoff data of main hydrological station and weather data,as well as taking the influence of TGP water storage into account,the runoff characteristics and its cause were studied.It is found that the decrease in discharge this year is mainly due to the significant loss of water in flood season and the discharge is characterized by exceptional low during that time.The maximum reduction of runoff and water level of hydrological stations occur during August and September.Maximum runoff reduction is all beyond 50% and the water level has significant drop at the same time.Compared with that in the same time of history,the water-income from Dongting Lake and Hanjiang River is significantly less while the water from Poyang Lake is plentiful which to some extent lightens the severe low discharge in the main stream.The extreme low precipitation and high temperature over upper reaches(especially the area between Pingshan and Yichang) is the main cause of the exceptional low discharge.There is a good relationship between variation of weather and runoff.Water storage of Three Gorges Project decreases the October discharge of Yichang hydrological station by 50% and the influential index to the discharge decrease of Datong hydrological station from October to November is 18.7%.
Three gorges
Yangtze river
Water year
Discharge
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