Yang Guishan

China's lakes at present: Number, area and spatial distribution

Based on 11004 satellite images from CBERS CCD and Landsat TM/ETM, changes in the spatial characteristics of all lakes in China were determined following pre-established interpretation rules. This dataset was supported by 6843 digital raster images (1:100000 and 1:50000), a countrywide digital vector dataset (1:250000), and historical literature. Comparative data were corrected for seasonal variations using precipitation data. There are presently 2693 natural lakes in China with an area greater than 1.0 km2, excluding reservoirs. These lakes are distributed in 28 provinces, autonomous regions and municipalities and have a total area of 81414.6 km2, accounting for ∼0.9% of China’s total land area. In the past 30 years, the number of newly formed and newly discovered lakes with an area greater than 1.0 km2 is 60 and 131, respectively. Conversely, 243 lakes have disappeared in this time period.

Influence of land use/cover change on storm runoff - A case study of Xitiaoxi River Basin in upstream of Taihu lake watershed

Land use/cover change (LUCC) is one of the main boundary conditions which influence many hydrologic processes. In view of the importance of Taihu Lake Watershed in China and the urgency of discovering the impacts of LUCC on storm runoff, two flood events under five land cover scenarios in the Xitiaoxi River Basin of the upstream of Taihu Lake watershed were simulated by distributed hydrologic modeling system HEC-HMS. The influences of each land cover on storm runoff were discussed. It was concluded that under the same rainstorm the ascending order of runoff coefficient and peak flow produced by the 5 different land covers were woodland, shrub, grassland, arable land, and built-up land; the descending order of swelling time were woodland, shrub, grassland, arable land, and built-up land. Scenario of built-up land was the first to reach peak flow, then arable land, grassland, shrub, and woodland. There were close relationships between the runoff coefficients produced by the 5 different land covers. The degrees of impacts on runoff coefficient of land cover change modes were sorted by descending: woodland to built-up land, shrub to built-up land, grassland to built-up land, arable land to built-up land, woodland to arable land, shrub to arable land, arable land to grassland, shrub to grassland, grassland to arable land, and woodland to shrub. Urbanization will contribute to flood disaster, while forestation will mitigate flood disaster.

Progress of research on the relationship between the Yangtze River and its connected lakes in the middle reaches

The complicated changing water-sediment exchange relationship between the Yangtze River and its naturally connected lakes,Lake Dongting and Lake Poyang,have affected regional flood disaster control,water resources and water environmental protection and maintenance of water ecological security,which has become the core of water problems in the middle reaches of the Yangtze River.The progress of research on river-lake relationship between the Yangtze River and its connected large lakes was systematically reviewed from the point of view of the concept and connotation of river-lake interaction,the evolution process,the influencing factors and effects of changing river-lake relationship.Based on the problems in current research,the following research issues were proposed:how to define a comprehensive index for the river-lake relationship is the premise to correctly understand the relationship between rivers and lakes;how to quantify the effects of human activities and climate change contributions is the emphasis and difficulty of research on the river-lake relationship;it is a long-term task to track the impact of the Three Gorges Project on the river-lake relationship;and it is the ultimate goal to maintain healthy river-lake system pattern in the middle reaches of the Yangtze River which benefits both the Yangtze River and its connected lakes based on the optimization and controlling principles on joint operation of hydraulic engineering group for large river-lake water systems.

Scale-free structure of town road network in southern Jiangsu Province of China

From the viewpoint of Graph Theory this paper builds a town road network graph of regional scale, and proposes numerical vertex degree (Di), rank vertex degree (Dr) and population size vertex degree (Dp) on the base of vertex degree (D). Then the indicators of Di, Dr, Dp and mathematical statistics methods are applied to investigating scale-free structure of town road networks in the southern Jiangsu Province. The results show that the distribution of Di does not exhibit scale-free properties, but Dr and Dp do. Additionally the correlation coefficient between Dp and Di is only 0.569, but the spatial correlation between Dp and Dr is very evident on the base of correlation analysis and spatial analysis of GIS. The mutual mechanism between Dp and Dr spatially represents a “Core-Belt” model of town development of regional scale. The town development model is open and clustered, and beneficial to both economic development and ecological protection. And then we suggest that Suzhou City, Wuxi City, Changzhou City and Wujin City control towns’ high-density pattern by conducting centralization and consolidation policies, and properly controlling and planning higher rank roads; whereas Nanjing City, Zhenjiang City, Jintan City and Liyang City must strengthen the development of towns along higher rank roads.

Impacts of Non-point Source Pollution on the Water Environment of Xitiaoxi Watershed, Upper Taihu Basin

The scare of fresh water has been becoming a focus issue in the world, while water quality deterioration enhances the seriousness of the problem. To assess the water quality and its impact factors can provide basic information for water resource management. This paper verified the usefulness of water quality indices (WQI) to assess the water quality from multiple measured parameters, and to evaluate the spatial and temporal change. The WQI which takes into consideration all the measured parameters not only shows a similar trend to the results of analyzing separate parameters and the index of compositive pollution, but also display the overall water quality and can predict precisely the change trend of water quality. As a case study, we use the WQI to evaluate spatial and temporal changes in the water quality from Xitiaoxi Catchment, upper reaches of Taihu Basin, and assess the degree of factors influencing water quality. The nonpoint source pollution caused by land use produces a serious and negative effect on the water quality because only controlling and management point sources only increase 6.5% of water quality. The water quality gradually deteriorated along the river from upper reaches to lower reaches mainly due to the land use change. So, in the future, the highest priority measure to improve water quality of Xitiaoxi Catchment should be controlling non-point pollution resources.

Assessment of coastal vulnerability to environmental change in Jiangsu coastal plain

Assessment of coastal vulnerability to future environmental change has been emphasized in coastal nations or regions. The Jiangsu coastal plain, located to the north of the Yangtze River Delta in China, is most vulnerable to sea level rise and exacerbating coastal hazards. This paper develops the method of delimiting vulnerable scope and assessing coastal vulnerability through field observations and sampling and by applying remote sensing and GIS, which are suitable for great river delta and coastal plains with large area, relative complex micro-geomorphology and the protection of seawall. Applying this method, the coastal vulnerability of the Jiangsu coastal plain to relative sea level rise (approximately 50 cm up to the year 2050) and exacerbating storm surges have been assessed. The results show that, up to the year 2050, the Jiangsu coastal plain will probably lose 12.8 % of tidal flats (about 5.8x104 hm2) and 7.9 % of cultivated land (about 7.2x104 hm2). Meanwhile, 2.0 % of population, 3.8 % of original value of fixed assets, 3.2% of GDP (Gross Domestic Product), 40.3 % of salt industry and 5.8 % of aquiculture respectively will be affected due to coastal environmental change.

Impact of water level change on wetland vegetation of rivers and lakes

Water level is one of the key factors of the eco-hydrological process in wetlands. The change of water level often results in variations in wetland vegetation coverage and species composition,and leads to community succession. This article summarized the impact of water level on wetland vegetation in three different aspects: water level gradient,water level fluctuations and artificial lake / river control projects. The results showed that: 1) Wetland species exhibited grade distribution along water level gradient mainly due to their distinct responses to water level and their different competitiveness. Meanwhile,morphological plasticity influenced the distribution range of individual species; 2) The rate and duration of water level fluctuations,rather than depth,had important influence on vegetation succession; periodic water level fluctuations maintained the species diversity and ecological stability,however,a periodic water level fluctuations,mainly the flood and drought,were likely to cause vegetation succession from wetland ecosystems to terrestrial or aquatic ecosystems; 3) Artificial lake / river control projects had the same impact with water level fluctuations in theory,however,the matching mitigation strategies provide valuable references for maintaining ecological diversity and stability. The potential aspects to be attached importance in the future of the research are as follows: quantitative models based on mechanisms,differentiating impacts caused by anthropogenic and natural driving factors,simulating the water level fluctuations in laboratories and the tracking attention on the long-term impact of artificial lake / river control projects.

A STUDY ON EQUILIBRIUM COASTAL PROFILES OF THE CLOSE TIDAL FLAT -A Case Study of Fengxian Tidal Flat

The article analyses the temporal-spatial changes of profiles by EOF (Empirical Orthogonal Function) analysis and DTM analysis of GIS. These profiles, which are not affected by engineering, are chosen from the coast with successive field monitoring data from 1990 to 1999. Temporal and spatial EOF indicates the obvious stability of coast profile parameters in Fengxian tidal flat. In spatial scale, high tidal flats and deep-water terraces are in a balance state while upper clino with steep slopes are sensitive and the stability is easy to be destroyed. In temporal scale, the erosion and deposition in this area are kept in balance in a whole. There are almost no change below −8 – −9.5m. At the same time, it is the lower limit of tidal affection and the erosion and deposition process from it to high tidal flat keep in balance for many years. So the closure depth is appointed to from −8m to −9.5 m (Wusong datum mark).

MAJOR PROBLEMS OF SUSTAINABLE DEVELOPMENT ALONG THE BANK AREA OF THE CHANGJIANG RIVER

Developing the Changjiang (Yangtze) River and building a developed economic zone along the bank area of the Changjiang River is a great strategic decision of the national macroeconomic development distribution. This decision has both given an impetus to fast development of the regional economy and exacerbated the contradiction among economy and resources and environment. In this paper, some major problems existing in economic sustainable development, such as scattered industrial structure, duplicated construction of the great projects, enlarging the development gap of the regional economy and deteriorated environment etc., have been studied. The results show that scattered structure and duplicated distribution of some key industries and projects, especially automobile, electronics and petrochemical industry and communication, power installations, is one of the reasons for low industrial economic benefit; the great development gap among upper, middle and lower reaches areas are enlarging since the 1990’s; soil erosion, flood disaster and environmental pollution are still exacerbating due to unreasonable over-development. Based on the above analysis, this paper brings out some countermeasures and proposals for increasing the ability of regional sustainable development, including transregional reorganization of industrial structure linking by assets and speeding the process of regional economy integration; gradually controlling and reducing the development gap among upper, middle and lower reaches areas through regional cooperation on a mutually beneficial basis; as well as strengthening ecological construction and environmental protection and increasing environmental bearing capacity etc.

Impacts of future sea level rise on salt water intrusion in the Changjiang River Estuary

Sea level rise could increase the salinity of an estuary by altering the balance between fresh water and salt water. The implications of sea level rise for increasing salinity have been examined in the Changjiang (Yangtze) River estuary. By correlative analysis of chlorinity, discharge and tidal level and calculation of two-dimensional chlorinity, distribution of the Changjiang River estuary, the changes of the intensity and lasting hours of salt water intrusion at Wusong Station and the changes of chlorinity distribution in the South Branch of the Changjiang River estuary have been estimated when future sea level rises 50–100 cm. The intensity of salt water intrusion in the future will be far more serious than current trend.Sea level rise could increase the salinity of an estuary by altering the balance between fresh water and salt water. The implications of sea level rise for increasing salinity have been examined in the Changjiang (Yangtze) River estuary. By correlative analysis of chlorinity, discharge and tidal level and calculation of two-dimensional chlorinity, distribution of the Changjiang River estuary, the changes of the intensity and lasting hours of salt water intrusion at Wusong Station and the changes of chlorinity distribution in the South Branch of the Changjiang River estuary have been estimated when future sea level rises 50–100 cm. The intensity of salt water intrusion in the future will be far more serious than current trend.