Xu Youpeng

Impacts of urbanization on hydrology in the Yangtze River Delta, China

The Yangtze River Delta is one of the most developed regions in China and the rapid development of urbanization have greatly influenced regional hydrology and water resources. Taking several typical urbanizing areas in the Yangtze River Delta as examples, this paper probes into the impacts of urbanization on hydrologic cycle and hydrological process with the support of RS, GIS and hydrological model. The research centers on the impacts of urbanization on precipitation, hydrological process, river networks, and water environment in some typical cities. The results show that: (1) Urban rain island effect is not evident when the process of urbanization is slow, while the differences of annual precipitation and flood season precipitation between urban and suburban areas increased to a certain extent in the booming stage of urbanization. (2) The annual runoff depth and the runoff coefficient increased with the development of urbanization, and the effect will be more notable when the urban areas expand to a certain size; (3) River network systems, especially low-grade rivers have been greatly destroyed in the process of urbanization, which increases the risk of flood and water degradation, so it is very important to protect natural river systems. Based on the results, some proposals of sustainable utilization and protection of water resources is also addressed.

The environment evolution of Wuliangsuhai wetland

The environment evolution of Wuliangsuhai wetland since 1986 is analyzed based on the remote sensing principle. The total water area of Wuliangsuhai lake has been increased during the past 17 years. The open water area had an increasing trend before 1987, and the trend was decreasing up to 1996, then the trend has increased again since 2000; the variation of the water area with dense aquatic weed is basically contradictory to the variation of open water area. The natural reed area had been decreased before 1987, and then it has been increased. The areas of shallow water and swamp have been slightly increased, in fact, the variations are quite steady. The artificial reed area has been increased since the reed plantation was started in 1988. The relationships of the water environment, the climate, hydrology and different types of areas are discussed, and then the technological measures for sustainable development and utilization of Wuliangsuhai lake water environment are proposed.

The impacts of human activities on the Wuliangsuhai wetland environment

Wuliangsuhai is the large-scaled multi-function lake-wetland with high ecological and social value in the semi-desert area of China,the biggest freshwater lake in the Yellow River basin,and also the unique carrying and drainage way to the Hetao irrigation area.The major recharge sources of Wuliangsuhai wetland are irrigation re- turn with high-density nitrogen and phosphorus,industrial wastewater and sewage.On the basis of Landsat TM or ETM data of 19 years from 1986 to 2004,integrating with historical materials,the impacts of human activities on the wetland water environment were analyzed.These impacts mainly include the increase of artificial reeds area and dense water weed area,the deterioration of water environment,the rising of lake eutrophication,and the reduction of aquatic resources.Though the applications of the project diverting water from Yellow River to Wuliangsuhai wet- land slow down the process of the deterioration of the wetland environment,the Wuliangsuhai wetland still confronts with serious threat.

Change of Flood Patterns in China under the Influences of Climate Change and Human Activities

Abstract Based on the flood affected area (FA) data of the provinces in China from 1950 to 2005, the article discusses the change of the flood patterns in China, and investigates its relationship with climate change and human activities. The flood center shifted from North China and the Yangtze–Huaihe basin in the 1950s towards the south, north and west of China, and located in the south of the Yangtze River and South China after the 1990s. The FA in the western provinces was continuously on the rise since the 1950s. There are two characteristics for the future flood pattern in China. The pattern of “flood in the south and drought in the north” depends on the north–south shift of the maximum rainfall region in eastern China. The flood intensification to the west of Hu Huanyong’s line mainly results from the increase of rainfall, extreme precipitation and the melting of glaciers under the background of human activity magnification.

RESEARCH ON SYSTEM OF FLOOD DISASTER CONTROL AND REDUCTION SUPPORTED BY GIS IN MEDIUM AND SMALL BASINS

Southeast China coastal areas belong to subtropical monsoon climatic zone, thus easily affected by floods resulted from typhoons and rainstorms. Since the areas of river basins are small, rivers flood regulation capacities are low, and therefore flood hazard is grave. In this paper, taking the Yongjiang basin in southeast China as an example, the approaches and methods of geographic information system (GIS) applied to flood disaster control and reduction research on small basin are explored. On GIS help the rainfall-runoff calculation model and the river channel flood routing model are developed. And the evaluating flood submerged area and the damage assessment models are built supported by digit elevation models. Lastly the decision support system on GIS supported for flood control in research basin has been set up. This greatly improves flood-proofing decision-making capacities in river basin, and provides valuable information and a mode for flood prevention and reduction in the medium and small basin. Meanwhile, the research indicates that technologies of GIS provide a powerful tool for flood disaster control.

Comparison of land-use structure fractal dimension based on vector and raster data:A case study of Suzhou City

Land use system is the product of natural and human activities,and typically as a complex nonlinear dynamical system,its structure is irregular,unstable,complex and non-linear.Fractal theory,as a new technique,has been proved to be practical for analyzing irregular and nonlinear objects.The fractal dimension,one of the most important indices in fractal theory,is often calculated from raster data,but most land-use data are stored as vector data.Conversion of vector data to grid images to calculate fractal dimension may result in inaccurate values.Accuracy of the calculation on raster data is closely related to the grain size of the grid images.Taking a case study of the 1:100000 land use data of Suzhou City in 2008,this paper first analyzed the fractal characteristics of the study area by calculating the fractal dimension,investigated the scale effects of land use fractal dimension by changing the grain size of raster data,and then established a quantitative relationship between fractal dimension and the grain size,and lastly used the math model to calculate fractal dimensions from vector data based on the raster data.The results showed that land use structure of Suzhou City followed the general rules of fractal theory,which proved that this method was suitable for the analysis of the characteristics of land use system in such a rapidly urbanizing area.Furthermore,the overall land use degree of Suzhou City was high;human activities have different effects on the different land types.For example,under the influence of human activities the structures of arable land and construction land were relatively simple,but unused land and forest-grassland are quite complex.The morphology of water was less complex than other land use types,indicating that water was more affected by human activities such as water conservation facilities and irrigation ditches.The effect of the grain size on the fractal dimension in this area showed that the fractal dimension increased with expanding grain size,and the result of statistical analysis suggested that the relationship between fractal dimension and the grain size fit with the quadratic-polynomial-model which provided a bridge between the vector data and raster date for the calculation of the fractal dimension.If the vector data were viewed as raster data of 0 m grain size,vector fractal dimension can be calculated from raster data according to the quadratic-polynomial-model.The difference between the calculated results and the fractal dimension values directly using the vector data was minimal.Thus,fractal dimension of vector land use data(the grain size is 0 m×0 m) could be deduced by this relationship within the margin of error.

Hydrologic series characteristics analysis of the major rivers around the Taklimakan Desert

This paper firstly analyses the hydrologic characteristics of the major rivers around the Taklimakan Desert with the method of mathematical statistics. Secondly, structure features of annual runoff series of these rivers are discussed both in time domain and in frequency domain with the method of time series analysis. From the analysis, it can be learnt that the nature quantity of water in the rivers in this area is generally steady and the annual runoff series of rivers is mostly independent stationary random sequence. Therefore, this paper can provide scientific basis for runoff variation law research and reasonal exploitation and utilization of water resource in this area.

An analysis of water resource characteristics of the rivers in the northern slope of the Kunlun Mountains

There are 43 rivers of varying sizes in the northern slope of the Kunlun Mountains, all of which originate from the Kunlun Mountains. Supplied by precipitation and melting water of glacier, the total runoff amounts to 87 × 108m3. The analysis shows that water quantity distribution of the rivers in the area is more in the west, and less in the east. While in the west, the water quantity of the Hotan River amounts to more than half of the total, in th eeast, most rivers are seasonal rivers except the Keriya River and the Qarqan River, which have relatively large amount of waters. From the analysis of inner structures of the runoff series of the major rivers, we can see that the annual runoff series of all rivers are mainly stable independent random series. Such characteristics of the time series are determined by the supply characteristics of the rivers. Some measures of rationally using water resources are proposed finally.There are 43 rivers of varying sizes in the northern slope of the Kunlun Mountains, all of which originate from the Kunlun Mountains. Supplied by precipitation and melting water of glacier, the total runoff amounts to 87 × 108m3. The analysis shows that water quantity distribution of the rivers in the area is more in the west, and less in the east. While in the west, the water quantity of the Hotan River amounts to more than half of the total, in th eeast, most rivers are seasonal rivers except the Keriya River and the Qarqan River, which have relatively large amount of waters. From the analysis of inner structures of the runoff series of the major rivers, we can see that the annual runoff series of all rivers are mainly stable independent random series. Such characteristics of the time series are determined by the supply characteristics of the rivers. Some measures of rationally using water resources are proposed finally.