Xu Jiangang

Large and episodic decrease of water discharge from the Yangtze River to the sea during the dry season

Abstract A diagnostic study on the large and episodic decrease of discharge from the Yangtze River to the sea is presented. No trend has been detected so far in the time series of river flow recorded at Datong, but a large and short-term drop is evident through analysing the yearly minimum discharges. Water abstractions in the middle reach are evidently responsible for the large and episodic drop recorded at Datong. Downstream of Datong the discharge further decreases due to water abstraction by sluices and pumping stations, with a capacity comparable to the average discharge from Datong in dry months. Such large-scale water diversions may greatly reduce the water discharge into the sea during droughts, if countermeasures are not prepared. An increasing seasonal variability will exacerbate the existing water and environmental problems in the Yangtze Delta and estuary. An integrated management system is necessary for sustaining sufficient freshwater discharge into the sea.

Urban Spatial Restructuring in Transitional Economy —Changing Land Use Pattern in Shanghai

For almost three decades, China has been undergoing significant transition from a planned economy to a market economy. Fast-paced economic growth and urbanization, interacting with market-oriented reforms in land resources allocation, have caused profound spatial restructuring of Chinese cities. This paper examines urban expansion and land use reconfiguration in Shanghai’s central city from 1979 to 2002, with a special focus on the effect of the adoption of the land-leasing system in 1988. The empirical research, which employs GIS-based spatial analysis techniques to explore land use data for multiple years, indicates fundamental changes in the spatial characteristics of urban development in Shanghai after this important land policy reform.

Research and Practice on the Third Generation Urban Planning E-government Platform - Taking Nanjing as an Example

This paper takes the third generation urban planning e-government platform of Nanjing as an example, introduces its background and working target, describes its main characteristics and general system framework, discusses the key technologies of platform construction. Simultaneously, the authors illuminate exploration and practice of platform on aspects such as system integration, resources integration, government affairs transparency, then lastly prospects its recent development.

A Study on Topographic Map Revision and Virtual Scene Creation by Integrating Photograph, Video and High Resolution Remote Sensing Imagery with Virtual Reality Technology

Topographic maps are basic information needed for spatial analyses of planning and designing. In our study area, Jinling Prison of Nanjing, China, complex topography with significant changes and lack of basic topographic maps with good currency makes it difficult to do any analysis without a revised terrain model. Our study focuses on the process of topographic map revision and virtual scene creation by integrating scanned maps, photos, video clips and high-resolution image data from different sources. The process is done in GIS and VR environment interactively. The resulted revised terrain data can meet the demands of spatial analysis in planning and 3D virtual scene creation. The built VR scene greatly helps decision-making in urban planning and designing processes. The practical approach given in this paper is applicable in similar situations which may exist in many developing countries.

A Practice of Cumulative CA Model for Urban Spatial Development Simulations Using Vector Datasets

Cellular automata (CA) has been proven to be an effective method in simulating urban spatial development. The paper describes the concept model of a cumulative CA model. By putting the model into practice using ArcGIS as basic spatial data processing platform, a prototype system is built. The system is designed to process vector datasets as its data sources. Several cumulative values are calculated from these vector source datasets for each cell to represent the cells certain properties. And cumulative affection values used to determine the transition of states between stages are calculated for each cell in every stage of computing. By applying the system into practice, different parameters which represent different approaches of urban planning can be put into simulations. The simulated urban development processes and final scenarios can help people to understand the specific urban area better, as well as help decision makers make and establish urban development policies more effectively.