Dongting Lake Area Research Articles

Mapping Paddy Rice Using a Convolutional Neural Network (CNN) with Landsat 8 Datasets in the Dongting Lake Area, China

Rice is one of the world’s major staple foods, especially in China. Highly accurate monitoring on rice-producing land is, therefore, crucial for assessing food supplies and productivity. Recently, the deep-learning convolutional neural network (CNN) has achieved considerable success in remote-sensing data analysis. A CNN-based paddy-rice mapping method using the multitemporal Landsat 8, phenology data, and land-surface temperature (LST) was developed during this study. First, the spatial–temporal adaptive reflectance fusion model (STARFM) was used to blend the moderate-resolution imaging spectroradiometer (MODIS) and Landsat data for obtaining multitemporal Landsat-like data. Subsequently, the threshold method is applied to derive the phenological variables from the Landsat-like (Normalized difference vegetation index) NDVI time series. Then, a generalized single-channel algorithm was employed to derive LST from the Landsat 8. Finally, multitemporal Landsat 8 spectral images, combined with phenology and LST data, were employed to extract paddy-rice information using a patch-based deep-learning CNN algorithm. The results show that the proposed method achieved an overall accuracy of 97.06% and a Kappa coefficient of 0.91, which are 6.43% and 0.07 higher than that of the support vector machine method, and 7.68% and 0.09 higher than that of the random forest method, respectively. Moreover, the Landsat-derived rice area is strongly correlated (R2 = 0.9945) with government statistical data, demonstrating that the proposed method has potential in large-scale paddy-rice mapping using moderate spatial resolution images.

Assessment of Heavy Metal Pollution in the Sediment of the Main Tributaries of Dongting Lake, China

Heavy metal pollution in sediment is one of the most serious problems in water bodies, including rivers, which can cause secondary pollution when environmental conditions change. In this study, surface sediment samples collected from the four main tributaries of Dongting Lake (i.e., Xiangjiang River (XR), Zishui River (ZR), Yuanjiang River (YR), and Lishui River (LR)) were analyzed for concentrations of Zn, Cr, Cu, As, Cd, and Pb. The spatial distribution, source, and potential ecological risk of these metals were determined. The results suggest a great spatial heterogeneity of heavy metals in the sediment of the studied rivers. Heavy metals had highest concentrations in the sediment of XR, especially midstream and downstream. A principal component analysis (PCA) and correlation analysis indicated that Cd and As were mainly from industrial wastewater and mineral mining, Cr came from natural process and agricultural activities, and Zn and Cu potentially from both. Pb was originated from atmospheric deposition and river inflow transportation. According to the geo-accumulation index ( I g e o ), enrichment factor (EF), and risk index (RI) assessment, heavy metals pollution was highest in the sediment of XR, and Cd was the main pollutant in the sediment of XR, presenting considerable potential ecological risk. This may contribute to heavy metal pollution in Dongting Lake. This paper provides a reference for the aquatic environmental management of heavy metals in Dongting Lake area and its tributaries.

DYNAMIC MONITORING OF LAND COVER IN DONGTING LAKE AREA BETWEEN 1995–2015 WITH LANDSAT IMAGERY

Abstract. In this paper, the Landsat imagery of 1995, 2006 and 2015 is used to monitor land cover change in Dongting Lake area. Our study mainly focuses on five types of land cover: water body, wetland, built-up area, cropland and forest. The land cover change in the Dongting Lake area is comprehensively evaluated by using land cover transfer matrix, land cover change amplitude, and landscape pattern indexes. Our study shows that: (1) the cropland area increased from 48.58 % in 1995 to 53.61 % in 2006, then decreased to 48.85 % in 2015; (2) different from the trend of cropland, the area of water body and wetland decreased in 2006; (3) the forest area steadily increased, to 2015, and there was an increase of 3.46 % during 1995–2015, due to artificial afforestation in the lake area. In terms of the landscape pattern, the landscape fragmentation decreased and the patch connectivity increased.

Remote sensing image land type data mining based on QUEST decision tree

remote sensing image land type data mining was studied based on QUEST decision tree with Dongting Lake area as the research object. First of all, the texture feature of gray level co-occurrence matrix was expounded, and the texture size was selected to construct the QUEST decision tree model; secondly, through spectrum and texture feature of remote sensing data with different resolutions and combining with other auxiliary data, Dongting land information was explored, and land type was classified. Finally, the following conclusions were reached: multi-scale texture can better describe the texture feature of land, more effectively solve with the phenomenon of “same image for different object” in the classification results, and help to improve classification accuracy of high resolution image.

Assessment and prediction of land ecological environment quality change based on remote sensing-a case study of the Dongting lake area in China

Multi-source remote sensing data is rarely used for the comprehensive assessment of land ecologic environment quality. In this study, a digital environmental model was proposed with the inversion algorithm of land and environmental factors based on the multi-source remote sensing data, and a comprehensive index (Ecoindex) was applied to reconstruct and predict the land environment quality of the Dongting Lake Area to assess the effect of human activities on the environment. The main finding was that with the decrease of Grade I and Grade II quality had a decreasing tendency in the lake area, mostly in suburbs and wetlands. Atmospheric water vapour, land use intensity, surface temperature, vegetation coverage, and soil water content were the main driving factors. The cause of degradation was the interference of multi-factor combinations, which led to positive and negative environmental agglomeration effects. Positive agglomeration, such as increased rainfall and vegetation coverage and reduced land use intensity, could increase environmental quality, while negative agglomeration resulted in the opposite. Therefore, reasonable ecological restoration measures should be beneficial to limit the negative effects and decreasing tendency, improve the land ecological environment quality and provide references for macroscopic planning by the government.

Improving the sustainability of agricultural land use: An integrated framework for the conflict between food security and environmental deterioration

In rapidly developing countries, intensive agriculture faces the conflict between food security and environmental deterioration. To improve the sustainability of agricultural land use, this paper proposes an integrated framework for risk assessment and conflict coordination to cope with these salient challenges at the administrative unit level. This framework is demonstrated using a case study conducted in the Dongting Lake area in China. Drawing upon diverse sources of statistical data concerning agricultural inputs and outputs, water resources and natural hazards as well as questionnaire surveys conducted at the household level, this paper uses the Cobb-Douglas production function and the water environmental pressure index to assess food insecurity risk and environmental risk from food production, respectively. A double matrix method is used to characterize the degree of sustainability based on the risk assessment. The results indicate that the overall food security of the region can be maintained in the negligible-risk range. However, rising agro-environmental risks from grain production in the coming years are likely to threaten the sustainability of agricultural land use in most administrative units. It is suggested that optimization of land use patterns and mitigation of natural hazards could be effective approaches to improve the sustainability of local agricultural land use.

Research on living status of Oncomelania hupensis in autumn and winter and its correlates in Eastern Dongting Lake area

To explore the dynamic changes of Oncomelania hupensis snail densities in autumn and winter and the relationship between hydrological and meteorological factors and snail growth and decline. From Octobers to Decembers of 2007 to 2014, a bottomland close to eastern Dongting Lake was selected as the study field. The snails and elevation of the points were surveyed, and the hydrological and meteorological data were collected. The snail densities and death rates of every month were calculated. The meteorological and hydrological data were described, and the relationship between the snail densities and associated factors were fitted by the multiple regression model. The snail density was highest in October 2012 (41.88 per 0.1 m2) and lowest in November 2008 (1.23 per 0.1 m2). The snail mortality was highest in November 2008 (73.72%) and lowest in October 2012 (1.09%). The multiple regression model found a linear relationship between hydrological and meteorological factors and snail densities. The correlation coefficient between the prediction of ln (snail density) and its measurements by using this model was 0.927 (P = 0.001). The average minimum temperature in January and time of starting flood have an obvious influence on the snail densities in autumn and winter.

Modelling of the estimated contributions of different sub-watersheds and sources to phosphorous export and loading from the Dongting Lake watershed, China.

Considerable growth in the economy and population of the Dongting Lake watershed in Southern China has increased phosphorus loading to the lake and resulted in a growing risk of lake eutrophication. This study aimed to reveal the spatial pattern and sources of phosphorus export and loading from the watershed. We applied an export coefficient model and the Dillon-Rigler model to quantify contributions of different sub-watersheds and sources to the total phosphorus (TP) export and loading in 2010. Together, the upper and lower reaches of the Xiang River watershed and the Dongting Lake Area contributed 60.9% of the TP exported from the entire watershed. Livestock husbandry appeared to be the largest anthropogenic source of TP, contributing more than 50% of the TP exported from each secondary sub-watersheds. The actual TP loading to the lake in 2010 was 62.9% more than the permissible annual TP loading for compliance with the Class III water quality standard for lakes. Three primary sub-watersheds-the Dongting Lake Area, the Xiang River, and the Yuan River watersheds-contributed 91.2% of the total TP loading. As the largest contributor among all sources, livestock husbandry contributed nearly 50% of the TP loading from the Dongting Lake Area and more than 60% from each of the other primary sub-watersheds. This study provides a methodology to identify the key sources and locations of TP export and loading in large lake watersheds. The study can provide a reference for the decision-making for controlling P pollution in the Dongting Lake watershed.

Scenario analysis of the impacts of socioeconomic development on phosphorous export and loading from the Dongting Lake watershed, China.

Socioeconomic development in lake watersheds is closely related with lake nutrient pollution. As the second largest freshwater lake in China, the Dongting Lake has been experiencing an increase in nutrient loading and a growing risk of eutrophication. This study aimed to reveal the likely impacts of the socioeconomic development of the Dongting Lake watershed on the phosphorous pollution in the lake. We estimated the contributions from different sources and sub-watersheds to the total phosphorous (TP) export and loading from the Dongting Lake watershed under two most likely socioeconomic development scenarios. Moreover, we predicted the likely permissible and actual TP loadings to the Dongting Lake. Under both two scenarios, three secondary sub-watersheds-the upper and lower reaches of the Xiang River watershed and the Dongting Lake Area-are expected to dominate the contribution to the TP export from the Dongting Lake watershed in 2020. Three primary sub-watersheds-the Dongting Lake Area, the Xiang River, and the Yuan River watersheds-are predicted to be the major contributors to the TP loading from the entire watershed. The two scenarios are expected to have a slight difference in TP export and lake TP loading. Livestock husbandry is expected to be the predominant anthropogenic TP source in each of the sub-watersheds under both scenarios. Compared to 2010, permissible TP loading is not expected to increase but actual TP loading is predicted to grow significantly in 2020. Our study provides methodologies to identify the key sources and regions of lake nutrient loading from watersheds with complex socioeconomic context, and to reveal the potential influences of socioeconomic development on nutrient pollution in lake watersheds.

Impact of the Three Gorges project on ecological environment changes and snail distribution in Dongting Lake area.

BackgroundThe 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.MethodsHydrological 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.FindingsA 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).ConclusionEcological 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.

Rodents, goats and dogs - their potential roles in the transmission of schistosomiasis in China.

Schistosomiasis in China has been substantially reduced due to an effective control programme employing various measures including bovine and human chemotherapy, and the removal of bovines from endemic areas. To fulfil elimination targets, it will be necessary to identify other possible reservoir hosts for Schistosoma japonicum and include them in future control efforts. This study determined the infection prevalence of S. japonicum in rodents (0-9·21%), dogs (0-18·37%) and goats (6·9-46·4%) from the Dongting Lake area of Hunan province, using a combination of traditional coproparasitological techniques (miracidial hatching technique and Kato-Katz thick smear technique) and molecular methods [quantitative real-time PCR (qPCR) and droplet digital PCR (ddPCR)]. We found a much higher prevalence in goats than previously recorded in this setting. Cattle and water buffalo were also examined using the same procedures and all were found to be infected, emphasising the occurrence of active transmission. qPCR and ddPCR were much more sensitive than the coproparasitological procedures with both KK and MHT considerably underestimating the true prevalence in all animals surveyed. The high level of S. japonicum prevalence in goats indicates that they are likely important reservoirs in schistosomiasis transmission, necessitating their inclusion as targets of control, if the goal of elimination is to be achieved in China.

Temporal and spatial distribution of Schistosoma infection of population and its risk factors in Eastern Dongting Lake area in 2012 and 2014

To investigate the temporal and spatial distribution of Schistosoma infection of population and its risk factors in Eastern Dongting Lake area in 2012 and 2014, so as to provide the reference for formulating effective intervention measures. Junshan District was selected as a study field in Eastern Dongting Lake area. The method of spatial autocorrelation analysis was applied to analyze the change of spatial distribution of Schistosoma infection in Junshan District in 2012 and 2014. The spatial regression model was fitted to detect the risk factors for human infection. The livestock infection rate in 2013 was lower than that in 2011. The average infection rate of schistosome was reduced to 0.55% in 2014. The spatial autocorrelation existed on the distribution of schistosomiasis in Junshan District in both 2012 and 2014 and 4 high incidence villages were identified. The results of the spatial error model showed that the prevalence of human infection was positively correlated with the infection rate of the livestock and the area of the susceptible environment in 2012. The spatial lag model showed that the prevalence of human schistosomiasis was positively correlated with the area of the susceptible environment, but not with the infection rate of livestock. The measures involving grazing prohibition and phasing out cattle and sheep are remarkably effective and should continue on the basis of the current spatial distribution of schistosomiasis in this area.

Impact of the Three Gorges Project operation on the water exchange between Dongting Lake and the Yangtze River

The Three Gorges Project (TGP) is a world known project to utilize and manage the water resources of the Yangtze River. The reservoir stores water at the end of the flood season, and replenishes downstream reaches with water in dry seasons. In addition to such benefits, the TGP has irreversibly changed the hydrological process and the river-lake relation of the middle and lower reaches. In this paper, a hydrodynamic model was established to quantify the impact of the TGP׳s operation on the water exchange between Dongting Lake and the Yangtze River during 2009–2013. The results indicated that: the operation of the TGP has considerably reduced the peak discharge and the flood volume of the main stream and the Dongting Lake area. The inflow volume from the Yangtze River to Dongting Lake via three outlets decreased by 1.9–3.5 billion m3/yr, while the outflow volume from Dongting Lake to the Yangtze River at Chenglingji increased by 0.3–1.6 billion m3 in September and 0.4–0.6 billion m3 in October, respectively. This research provides valuable information for flood control, irrigation, and water allocation in the middle and lower reaches of the Yangtze River, and serves as a typical case for investigating the impact of other hydropower projects around the world.

Spatial-temporal evolvement of ecosystem service value of Dongting Lake area influenced by changes of land use

With the technology of geographic information system (GIS), the ecosystem service va-lue (ESV) coefficient of different types of land use in Dongting Lake area was estimated in this paper by interpreting the remote-sensing image for years and combining its economic development statistics. Meanwhile, the temporal-spatial evolvement characteristics of the ESV were investigated by employing the methods of spatial statistics analysis such as spatial autocorrelation, highland clustering analysis and hotspot analysis. The results showed that the ESV of Dongting Lake area increased slightly during 2000-2013, from 3868.39 billion yuan to 3886.62 billion yuan due to the increase of wetland in the area. The areas with high ESV and low ESV were infiltrated into each other, while the areas with second high ESV embraced those areas with high and low ESV. The characteristics of ESV and its dynamic evolvement in Dongting Lake area were obviously of spatial autocorrelation and high and low value clustering, but the trend was weakened. The focus of ESV hotspot of Dongting Lake area moved to northwest slightly with a "S" track in a obviously phased manner of "quick-slow-quick".

Early Holocene groundwater table fluctuations in relation to rice domestication in the middle Yangtze River basin, China

Abstract The early Holocene environmental amelioration stimulated the trajectory of Neolithic farming cultures and specific geographic settings played a role in determining the nature of these cultures. Using microfossil evidence, the present study reveals that the fluctuations of the groundwater table substantially influenced rice domestication in the Dongting Lake area of the middle Yangtze River basin in the early Holocene. Our 14 C-dated sediment core taken from the Bashidang (BSD) Neolithic site contains evidence that the site was a floodplain prior to human occupation ca . 8600 years ago. Poaceae, which contained wild rice ( Oryza sp.) as indicated by combined pollen and phytolith evidence, and low counts of freshwater algae indicated a moist site condition. The area then gradually evolved into wetlands as the water table rose, in response to the increasing monsoon precipitation during the early Holocene. This favored rice domestication, assisted by firing and clearing, that continued to flourish for several hundred years. Finally, rice domestication declined during the late stage of the Pengtoushan culture, accompanied by evidence of the expansion of wetlands reflecting the effects of a rising groundwater table that had caused the cessation of rice farming at the Bashidang site after ca. 8000-7900 cal yr BP. This study shows that there are local effects at particular sites that may differ from the trend at the regional scale, necessitating a careful interpretation of the available evidence.

Spatiotemporal distribution and historical evolution of polders in the Dongting Lake area, China

Dongting Lake is the largest lake in the middle reaches of the Yangtze River in China. For centuries, people inhabiting the Dongting Lake area have been reclaiming land and constructing dams for flood resistance, agricultural production, and rural settlement, forming geographical entities known as polders. In this study, the regional spatial distributions of polders in the Dongting Lake area in 1949, 1998, and 2013 were obtained using historical maps and modern remotely sensed data, revealing changes since the establishment of the People’s Republic of China. Nanxian County was then selected to demonstrate polder changes at the county level, because it has undergone the most dramatic changes in the area. Different polder change models for the Datonghu, Yule, and Renhe polders were analyzed for eight periods: 1644 (the early Qing Dynasty), 1911 (the late Qing Dynasty), 1930 (the Republic of China), 1949 (the People’s Republic of China), 1963, 1970, 1998, and 2013. Three resulting polder evolution models are: 1) reclaiming polders from lakes, 2) integrating polders by stream merging, and 3) abandoning polders for flood release. The polder evolution models demonstrate the wisdom of local people in using land resources according to the specific regional conditions. Throughout their long-term historical evolution, the spatial distribution of polders in the Dongting Lake area tended to be homogeneous, and the degree of human disturbance tended to be stable. However, a shift occurred, from pure polder area growth or removal to more comprehensive management and protection of the regional environment.

Malachite green and chloramphenicol in aquatic products from regions around Dongting Lake in Hunan, China

ABSTRACTAquatic products are important sources of animal proteins in human diet, especially in developing countries. As such, the safety of aquatic products is of primary concern. In this study, a standard method is used to detect malachite green (MG) and chloramphenicol (CAP) and to analyse the contents of these banned chemicals in turtle, mandarin fish and grass carp sampled from the region surrounding Dongting Lake area in Hunan, China. Results showed that 10.6% of the samples were MG-positive, most of them turtles. CAP was found in 8.3% of the samples, mostly in mandarin fish. These data indicated that these banned substances are still used in the surveyed area. Hence, adequate strategies must be implemented by the local government to control these banned substances.

Abstract Book

Major control efforts over many decades have resulted in a substantial reduction in the prevalence of schistosomiasis japonica in the People’s Republic of China, although pockets of new infection continue to arise, particularly in the mountainous areas of the south. As well, the completion of the Three Gorges Dam, which crosses the Yangtze River and other large irrigation projects underway, may have significant environmental and ecological impacts likely resulting in expansion of the habitats for the intermediate snail host Oncomelania hupensis in some areas, thereby increasing the risk of human and bovine infection, and resulting in potentially new challenging consequences for control. The epidemiological picture for China will be briefly summarised and the current effective control strategies highlighted. The situation in the Philippines will also be briefly outlined but the picture is far less encouraging as there is limited national funding for schistosomiasis control; since the termination of the World Bank Loan program for schistosomiasis control in the late 1990’s, both schistosome prevalence and the associated morbidity have rebounded to former levels. Some results of recent surveillance studies we have undertaken in the Philippines will be described which indicate that schistosomiasis japonica is now far more prevalent, both in humans and bovines, than has been appreciated. Results of a large intervention trial we have completed in China - in the highly endemic Dongting Lake area downstream of the Three Gorges Dam, aimed at field-testing integrated strategies, including the use of a bovine transmission blocking vaccine, for schistosomiasis control, will be presented. The results of the trial in China will provide parameters for mathematical modelling of future control methods so as to define the long-term impact and cost-effectiveness of integrated control measures for both China and the Philippines. We believe that such an integrated approach, incorporating bovine vaccination, can lead to the future elimination of schistosomiasis from China.

Assessing environmental risks for high intensity agriculture using the material flow analysis method--a case study of the Dongting Lake basin in South Central China.

This study primarily examined the assessment of environmental risk in high intensity agricultural areas. Dongting Lake basin was taken as a case study, which is one of the major grain producing areas in China. Using data obtained from 1989 to 2012, we applied Material Flow Analysis (MFA) to show the material consumption, pollutant output and production storage in the agricultural-environmental system and assessed the environmental risk index on the basis of the MFA results. The results predicted that the status of the environmental quality of the Dongting Lake area is unsatisfactory for the foreseeable future. The direct material input (DMI) declined by 13.9%, the domestic processed output (DPO) increased by 28.21%, the intensity of material consumption (IMC) decreased by 36.7%, the intensity of material discharge (IMD) increased by 10%, the material productivity (MP) increased by 27 times, the environmental efficiency (EE) increased by 15.31 times, and the material storage (PAS) increased by 0.23%. The DMI and DPO was higher at rural places on the edge of cities, whereas the risk of urban agriculture has arisen due to the higher increasing rate of DMI and DPO in cities compared with the counties. The composite environmental risk index increased from 0.33 to 0.96, indicating that the total environmental risk changed gradually but seriously during the 24 years assessed. The driving factors that affect environmental risk in high intensity agriculture can be divided into five classes: social, economic, human, natural and disruptive incidents. This study discussed a number of effective measures for protecting the environment while ensuring food production yields. Additional research in other areas and certain improvements of this method in future studies may be necessary to develop a more effective method of managing and controlling agricultural-environmental interactions.

Three Gorges Dam: Impact of Water Level Changes on the Density of Schistosome-Transmitting Snail Oncomelania hupensis in Dongting Lake Area, China.

BackgroundSchistosomiasis remains an important public health issue in China and worldwide. Oncomelania hupensis is the unique intermediate host of schistosoma japonicum, and its change influences the distribution of S. japonica. The Three Gorges Dam (TGD) has substantially changed the ecology and environment in the Dongting Lake region. This study investigated the impact of water level and elevation on the survival and habitat of the snails.MethodsData were collected for 16 bottomlands around 4 hydrological stations, which included water, density of living snails (form the Anxiang Station for Schistosomiasis Control) and elevation (from Google Earth). Based on the elevation, sixteen bottomlands were divided into 3 groups. ARIMA models were built to predict the density of living snails in different elevation areas.ResultsBefore closure of TGD, 7 out of 9 years had a water level beyond the warning level at least once at Anxiang hydrological station, compared with only 3 out of 10 years after closure of TGD. There were two severe droughts that happened in 2006 and 2011, with much fewer number of flooding per year compared with other study years. Overall, there was a correlation between water level changing and density of living snails variation in all the elevations areas. The density of living snails in all elevations areas was decreasing after the TGD was built. The relationship between number of flooding per year and the density of living snails was more pronounced in the medium and high elevation areas; the density of living snails kept decreasing from 2003 to 2014. In low elevation area however, the density of living snails decreased after 2003 first and turned to increase after 2011. Our ARIMA prediction models indicated that the snails would not disappear in the Dongting Lake region in the next 7 years. In the low elevation area, the density of living snails would increase slightly, and then stabilize after the year 2017. In the medium elevation region, the change of the density of living snails would be more obvious and would increase till the year 2020. In the high elevation area, the density of living snails would remain stable after the year 2015.ConclusionThe TGD influenced water levels and reduced the risk of flooding and the density of living snails in the study region. Based on our prediction models, the density of living snails in all elevations tends to be stabilized. Control of S. japonica would continue to be an important task in the study area in the coming decade.