From the respect of the meaning and the researching contents of land use and cover change, the methods for land use change were analyzed. Further, the methods of establishing land use dynamic change model were mainly introduced. These models include land resources quantity change model, land resources environmental quality change model, land use degree change model, land use change regional diversity model, land use spatial change model and land requirement forecasting model.

Currently, intensive land use has not only become one of the important contents of circular economy and economical society, but also is a key work in country land resource management departments. Based on the critical review on the development of international intensive land use researches, the developing trend of intensive land use has been carried out in this paper． It is found that studies on following four aspects should be strengthed. (1) On research view, the coupling relationship between the regional industry structure and land use structure should be studied further. (2) On research content, because related research is at preliminary stage, the study of standard system can not meet the demands of economical society. It is urgent to carry out the study of the investigation standard, evaluation standard and auditing standard of intensive land use. (3) At research scales, multilayer and different region intensive land use researches, including medium, small cities and agriculture, should be identified and discussed. (4) On research methodology, the application of GIS technology, systemic dynamic model and Artificial Neural Work should be developed in order to change traditional qualitative analysis and simple quantitative analysis. The results and conclusions in this paper will provide scientific basis for accelerating the study of intensive land use in China.

This paper concludes the main characteristics of international wetland science research. It shows that the wetland science has a long history, slow progress of development in the past and rapid progress in modern time. It has become a key subject and research field in the science research in the world. Its content and field of the research have been enlarged. It has been strengthened in both synthesis and split research. The uneven development of international wetland science exists in the world, and developed countries occupy advanced places in the wetland science research of the world; but the gap of research level between developed and developing countries is gradually reduced. It makes a detail introduction to the hot point, forward position field, progress, prospect and development trend of international wetland research in the 21st century. The main hot points and forward position fields of wetland research in the world are as follows; conservation and management of wetland, formation, development and succession of wetland, paleoenvironment reconstruction, ecological process and dynamics of wetland, greenhouse gases, greenhouse effect and global change, biodiversity, health and assessment of wetland and constructed wetland, restoration and reconstruction of degradation wetland, wise utilization of wetland, peatland and peat, wetland ecological engineering and application of new techniques and instrument.

The most fundamental obstacle to progress in the understanding and prediction of human impacts on environmental changes lies in the lack of a comprehensive and integrative theory of human land relationships. The recent growth of research into land use and land cover change has revealed the inadequacy of current theories. On the other hand, specific land use issues have been effectively addressed by different disciplines, such as economic geography, regional and urban economics, and law. This paper reviews the land use theories and system models that indirectly or exclusively touch the dynamics of land use in time and space. A comprehensive framework for the explanation of land use changes is proposed. The author argues that a multi disciplinary approach into land use change studies, as an alternative to a new integrative theory of human land relationships, help the establishment of a holistic understanding of the process. Analyses of land user’s economic behavior and land manager’s institutional behavior constitute the major components of the framework. Thunen and Alonso’s bid rent curve approach provides a foundation for the former analysis, while Platt’s interaction loop among land use system, environment system and institution system provides theoretical base for the latter. With the bid rent curve approach, understanding of land use change lies in an analysis of conditions for change of transference margins in the micro perspective and an analysis of conditions for change of the slope of bid rent curve in the macro perspective. All these changes will break the spatial equilibrium of land use and then constitute the driving forces of land use change. With Platt’s interaction loop approach, attention should be paid to strength of the signals from both the nature side and the society side. The author claims that changes on land use policies in China after the ’who will feed China’ debate in the mid 1990s, the large flooding on the lower reaches of the Yangtze River and the strong dust storms in North China in early 2000, reflect the impact of strong signals. The paper also discusses the intrinsic properties of land that make unique of the dynamic mechanism of land use. Of these properties, multiple suitability, constraint in area and quality, and immovability are imperative to land use changes. Trend in land use specialization and the implicative shrinking of land’s natural functions is a cue for the understanding of land use changes, and that of the overall human environment relationships as well.

Through carrying out a systematical review on the research progress of various Western academic schools on spatial patterns and dynamic mechanisms of urban land use growth, this paper highlights that its focus has shifted from summarizing spatial evolutionary models to exploring dynamic mechanisms during the decision making process of land development, from free land market to smart growth management. Historical experiences at home and aboard demonstrate that, while the monopoly administrative allocation system would force urban land use development to become an affiliated part of administrative powers and result in inefficiency and inequality, the free market mechanism would probably push urban land development to become an growth machine solely controlled by the motivation of profit making and deliberately destroy un renewable resources and amenable ecological environment. Therefore, in order to realize sustainable urban development and coordinate the conflicts among urban development, conservation of cultivated land, and construction of ecological environment, China should, on one side, continue to accelerate its reform on urban land use system to significantly increase the importance of the market mechanism on urban land development, and establish an equal and efficient supervising mechanism on the operation of urban land market, on the other side, strengthen the macro management function of the Governmental agencies and rationally control urban land use growth motivated by the market mechanism through various growth management policies.

Due to recent housing reforms in China, individual consume of urban population has become the principal part of the real estate market, and residents now can select their own home rather than have a home assigned to them by the government. This paper focuses on the main factors that influence the residents who live in cities and towns to select a residential location under the new housing system. The author thinks that the price of the house is the objective condition which affects the urban population to choose their residential location. Once they determine the money that they want to pay for the house, the residential location space is roughly decided. In addition, the traffic convenience and the environment of the residential location are the important objective factors that affect the resident to make decisions. The social, economic and cultural characteristics of the residents themselves and different favoritism they showed for the residential location and environment influence the process and result of the residential location selection as well. Divided social stratum due to different income also affects the division and isolation of the residential space. Overall, since many factors influence the residential location selection in various ways, real estate developers should fully consider the general requirement and consume behavior of residents purchasing houses. Only in this way can developers make the housing development match with the demand of the residents.

This article reviews the theories and progress of farmer land utility and protection, and analyzes the scientific basis and developing process of farmer land protection. This article pointed out that land productivity study is the scientific basis to ascertain the amount of the protected farmer land, that land evaluation and assessment is the basis of farmer land protection planning, and that the land plan and regulations is the shield of practice of farmer land protection. At the same time, this article further analyzes several theoretical and practical problems with farmer land use and protection in China, and some suggestions are given based on the practices of farmer land protection in foreign countries.

Land use and land cover change (LUCC) is one of the important focuses in the area of global change research because it is not only the significant component but also the major reason of global change. Some results of LUCC research, such as causes, driving forces, LUCC modeling and effects on environment, have been reported in China, but many aspects need to be further studied, compared with international research on it. Based on reviewing them, this paper presents that the following contents should be emphasized and put priority in LUCC study in the coming period of time. (1) The united theory system of LUCC research. (2) More advanced and dynamic LUCC models of various scale of spatiality which should include data processing and better understanding the interaction of LUCC and driving forces. (3) Relations between LUCC and global change or sustainable development, especially to pay more attention to local and regional effects on environment.

Rural tourism is such a new industry which combines primary industry with tertiary industry. Rural tourism is based on agriculture, aiming at developing tourism in rural area and serving the urban residents by providing various services. Rural tourism can develop landscape resources in rurban fringe to promote eco-tourism and to realize the coordinated development of the cities and countryside. In China, rural tourism successively experiences three stages, eg. early rising stage, initial development stage and later normative operating stage. This paper, based on the background and the concept of rural tourism, comprehensively discusses the development of rural tourism in China, analyzes the current situations and the main patterns of rural tourism, and puts forward some relevant countermeasures for the current problems. Finally, the paper discusses the prospect of the future sustainable development of rural tourism in China.

Forest is the first major form of terrestrial ecosystem and plays an important dominant role in global carbon cycle. In this study, we developed an age - based volume - to - biomass method to estimate the carbon storage of Chinese forests between 1973 and 2003 by using inventory data of six periods and forest biomass data obtained from direct field measurements. The results show that the total vegetation carbon storage of Chinese forests in the six periods (1973～ 1976, 1977～1981, 1984～1988, 1989～1993, 1994～1998 and 1999～2003) is 3.8488 PgC, 3.6960 PgC, 3.759 PgC, 4.1138 PgC, 4.6563 PgC and 5.5064 PgC, respectively. Although the results of different periods is fluctuates their trends are an increase with the time. Especially, since 1980s the total vegetation carbon storage of Chinese forests has increased 1.8104PgC and accumulated about 0.0823PgC per year. It means that Chinese forests play a role as a significant sink of atmospheric carbon dioxide in that period. On the other hand, the mean carbon density of Chinese forests has increased 3.001Mgha^{- 1} since 1970s, and that of young and middle- aged forests has increased 5.2871 and 0.6022Mgha ^{- 1}, respectively, but that of mature forests has decreased by 0.7581Mgha^{- 1}. This phenomenon suggests that the carbon fixation ability of Chinese forests primarily derives from forest plantation and it would be enhanced with carbon storage and carbon density increasing of young and middle- aged forests. The carbon stocks and densities of Chinese forests vary greatly in space. The larger carbon storage is primarily found in north eastern and south western regions, and higher C density mostly occurs in north eastern, south western and north western regions. These spatial distribution characteristics of carbon storage and mean C density in Chinese forests are prominently determined by human activities.

Land use and land cover change is one of the most important components and major causes to global environmental changes, and study on it has been the frontier all the while after entering the new millenniumThe paper reviewed firstly the major relevant research results of "Regional Geographical Conference of 2002"held by International Geographical Union(IGU)in Durban, South Africa in August this yearThen the authors put forward that the study on LUCC has made the most recent progresses in such five aspects: LUCC’s inspecting, assessing and mapping by means of using RS and GIS; analysing on countryside and agricultural land use/cover change;analysing on urban land use/cover change;the dynamics of land use/cover change and land use/cover change and eco environment. These aspects reflect that LUCC’s research scope is now extending and it’s research content deepening.

On the basis of introduction of the concept of urban internal spatial structure, the authors divide the process of research on urban internal spatial structure in China into three phases, including the introducing phase (from the early 1980s to the late 1980s), the developmental phase (from the early 1980s to 1995), and the accelerating phase (from 1996 to the present) Then the authors review the new progress of research on urban internal spatial s tructure from four aspects as follows: first, the research on population and urb an internal spatial structure; second, research on the internal spatial structur e of urban economy; third, research on the internal spatial structure of urban s ociety; and fourth, research on China’s suburbanization At last, the authors analyze the gap of research on urban internal spatial struc ture between China and the west countries From the theoretical system, to the content and method of research on urban internal spatial structure, China lags m uch behind the west world The authors point out that the fifth census and the publication of its data provides us a good opportunity in studying urban interna l spatial structure With the success of China’s economic transition, the empha sis of research on urban internal spatial structure is changing In the future, scholars should lay much more emphasis on the process, characteristics and mech anisms of the restructuring of urban internal space in the transition period or in the process of suburbanization It is an urgent task to develop the theories of China’s suburbanizaiton and models of urban internal spatial structure On the basis of the above mentioned.

As a principle index to measure water resources security, water resources carrying capacity relates with the problem of water resources security closely and becomes an emphases of water resources study which has important effection on the recognization and construction of water resources security system. Based on the definition of water resources carring capacity, this paper brings forward the theories about the study of water resources carrying capacity, concerning with the sustainable development, water resources-socialeconomy-environment coupling system and water cycle in duality mode. After a overall review of the contents and evaluation index system, the paper summarizes the evalauation methods of water resources carrying capacity study, including the imitate model with system dynamics theory, the decision model of multiple-purpose planning etc.. Finally, the paper points out that the further study of water resources carrying capacity should strengthen integration study of different subject, apply the new technology of GIS and RS actively and pay more attention to the study of region diversity.

Constructed wetland is an integrated ecosystem ，it has particular mechanism and function on treatment of wastewater. Many countries are paying more attention to it increasingly. Based on the research of all the world , this paper concisely introduces the mechanism and classification of treatment technology of wastewater and analyzes its advantages and deficiencies by the numbers. The advantages of constructed wetland are correspondingly low investment,variety and pertinence of treatment systems , efficient purification capability and especial virescence benefit. The deficiencies are mainly the large-scale land requirement ，more saturation phenomena and limitation with climate than traditional wastewater treatment plants ，but these deficiencies can be hurdled through continuous research. After expatiating the present status of research and application , the paper points out the widely applied prospects of treatment technology of wastewater using constructed wetland in China ，especially in the rural areas and small cities. At last , the author brings forward strategical viewpoint on how to develop it at present. It includes enhancing perception extent ，developing scientific research with focal points and taking ripe technology as chief choice with enough argumentation.

The role of terrestrial ecosystems on global carbon cycle dynamics is more and more noticed. At present, the rate of forest cover in China is 13 92% and it will be 15% at the end of twentieth century. This is more contribued to the balance of global carbon. However, carbon fluxes of terrestrial ecosystems are not accurately defined in China, and people do not recognize enough its importance to global climate change. Not defining accurately the carbon storage of Chinese vegetation and NPP has caused a large difference in carbon flux of terrestrial ecosystems in China. This paper adopts measured data in site and appliys technique of GIS, to acquire cover data of natural vegetation in China, and to calculate carbon and carbon density of every type of natural vegetation. The study establishs a database of terrestrial natural vegetation biomass in China. Meanwhile, we have researched simply the spatial distribution of terrestrial natural vegetation carbon storage in China Then, forest is the main body of natural vegetation in carbon cycle. This paper can provide basic data and analysis methods for global change research and scientific support for policy determination of CO 2 emission in China.

In this paper, a set of index and method on assessment of fragile environment is separately established. This is a systematic, complete, objective and flexible method of assessment of Fragile Environment. And it can be easily used in practice. At last, its practicality and accuracy are tested by using it to assess fragile degrees of environment within 26 provinces of China.

Land consolidation plays an important role in rational re arrangement of land resources, increasing profit of land and keeping dynamic balance of amount of cultivated land. Therefore, it has become the focus of society attention. The denotation of land consolidation is discussed in this paper. According to the differences between eastern, middle and western regions of China, the suggestions of land consolidation are put forward combined with national target. (1)In eastern region with high economic level, high land use ratio, and serious human land contradiction, more attention should be paid to agricultural land consolidation, aiming at improvement of land quality, management and benefit associated with the adjustment of agricultural structure. At the same time, non agricultural land consolidation can be gradually performed in order to mitigate pressure of construction land against cultivate land.(2)In middle region with medium economic level and land use ratio, it is necessary to convert the objectives of land consolidation concentration from increasing quantity of cultivated land to promoting its quality, based on keeping dynamic balance of cultivated land amount.(3)For western region associated with low land use ratio and low economic level, land consolidation should not only combine with return of cultivate land to woodland and grassland as well as control of water and desert to improve environments, but promote scientific and technological input to existing cultivated land to increase its output ratio. In addition, it is urgent to constitute, revise and improve laws and regulations related to land consolidation. In order to achieve multiple collective methods of land consolidation funds, it is helpful to explore establishment of land bank and corporations’ participation in land consolidation process.

Resent advances in remote sensing, geographic information systems, and computer technology make the use of distributed hydrological model, based on digital elevation model (DEM), an attractive approach or tool to studying hydrological processes and evolution laws of water resources under changing environment. But distributed hydrological model is not perfect compared with lumped hydrological model. In order to promote its development, based on DEM, this paper discusses and sums up the characteristics of distributed hydrological model, then probes into two main ways and means of constructing distributed hydrological model. One way is like SHE model, another is like SWAT model. Although distributed hydrological models can be made in different ways, the primary structure of the model is quite similar. A typical structure of DEM based distributed hydrological model is provided in this paper. To better study the impact of the changing environment on hydrological processes, a watershed must be divided into subunits. This paper expressly discusses the three most common techniques used to discretize a watershed, which are respectively grid cell discretization, representative hillslope discretization and subwatershed discretization. In the final, as to the problem of constructing model, the methods of building the components of the distributed hydrological model is set forth from three aspects: input module, unit hydrology model and river routing model. A brief comment on the current distributed hydrological model research and some advice are given in the conclusion. All these will provide a guidance for making distributed hydrological model based on DEM.

Ecological footprint theory and its application achievements in global and regional sustainable development system are studied,finding that the application of ecological footprint theory to regional sustainability evaluation leads to a perplexity that the indicated result is inconsistent with the philosophy of sustainable development theory.It is thought that the reason of the perplexity is that the ecological footprint theory based on global ecosystem is improperly adopted in regional sustainable development system, and the essential one is the faulty of the ecological footprint theory.A modification on this theory is made by introducing consumptive ecological footprint and productive ecological footprint, in which the latter is taken as the indicator of regional sustainability.The development impartiality can be demonstrated by comparison between the globe ecological deficit per capita and regional consumptive ecological deficit per capita.

Although the research of Land Use/Cover Change (LUCC) involves many scientific issues, there exist some inherent relations. Based on the analysis to the fundamental goal of the LUCC Plan, the author points out that the essential relationship among those issues is causality. According to this relation, the research on LUCC can be simply divided into three components: reasons of LUCC, states of LUCC and results of LUCC, and four research aspects: drivers and mechanisms of LUCC, states of LUCC, effects and processes of LUCC and models and simulations of LUCC. After reviewing the current research situation of LUCC, this paper also puts forth several prospects on its future development: the whole trend will be synthesis, the environmental effect and the micro mechanism of LUCC are still the research hotspots, and the synthesis of scales and the establish of models will be the research difficulties.

Accessibility denotes the ease with which activities may be reached from a given location using a particular transportation system. Accessibility reflects the opportunities and potentialities of a particular region to exchange with other regions. There is a number of accessibility measures, some accessibility indicators are generalized and compared in this paper: time of access to city centre, mean travel costs, opportunity accessibility, economic or population potential. Also, the progress of accessibility measures is reviewed. Accessibility indicators is applied both on regional and metropolitan dimension, such as the regional development, the impact of new infrastructure, the urban land use, the providing of social facilities, the urban social problems, and so on. Relative to the overseas there is rarely research on accessibility in our country. Therefore, some problems are put up in the end and accessibility research needs to be improved.

Spatial data sharing is necessary for socialized Geographical Information Systems. It requires integrating spatial data in different formats. Data exchange through interchange file formats is a popular way to share data between different GIS or cartography software. Data exchange is a time and labor concerning way. We have to run one software package to export data to a specified interchange file, such as DXF, then, run another software tool to import it. The process is too complicated, and it will take us a lot of time when we need to frequently exchange mass data. Spatial Data Interoperation is an ideal way provided by Open GIS Consortium (OGC) to share spatial data among software packages. In this way, GIS software data accessing interfaces should comply with the standards formulated by OGC. We can then share spatial data among different software without exporting or importing. It requires each software package has OGC’s standard data accessing interfaces. Now, this is still not a practical way for spatial data sharing. The Seamless Integration of Multi source Spatial data (SIMS) technology is a spatial data accessing architecture. SIMS consists of three tiers, including data providers, data agent and data consumers. In this model, data consumers, such as analysis components, access data through data agent instead of directly accessing data providers. It has one data agent but can have more than one data provider. Each data provider is implemented for a specified software file format. SIMS not only provide capabilities to access (read and write) spatial data in different formats, but also gives user abilities to perform analyses among several kinds of spatial data formats. In this paper, the authors describe the SIMS technologic architecture, and discuss its development and application.

In this paper, the definition of urban wetlands was given based on analyses of the existence and connotation of urban wetlands. Urban wetlands are defined as those kinds of natural and artificial wetlands that distribute in urban areas and compose the ecoenvironmental foundation of cities. Chief directions and advances of urban wetlands studies at home and abroad were summarized, the differences of urban wetlands studies between China and other countries were analyzed, the main domains and existing problems of urban wetlands studies were pointed out, and the subject frame of urban wetlands science was constructed primarily. A basic definition of urban wetlands science was proposed in this paper as the science which studies the distribution, type, function, evoluation and management of urban wetlands. The studies would have positive significance to the development of wetland science.

With the development of computer technology and intercross subjects, the methods of hydrology simulation have great advances. The remarkable trends of watershed hydrological models are the research of physically distributed based models and the use of Geography Information System (GIS) and Remote Sensing (RS) technology. The hydrological model integrated with GIS has many advantages, but it does not mean that the model itself is with high quality. The data arrived from RS is difficult to use in hydrological model directly. Study on mechanism of runoff and streamflow has great foreground to build hydrological model coupled with GIS and RS, and hydrological scale problems should always be paid attention to.

The importance of culture upon the land has long been a leading theme in cultural geography, and cultural landscape has exercised strong attractions on geographers, particularly those of Berkeley School. The author believes that cultural landscape can be defined as landscape created intentionally by man to satisfy some of his needs, taking use of materials in the environment. In the following parts of the paper, the author gives us a thorough discussion of the inventory and progress of cultural landscape research from six aspects: 1) evolution; 2) perception and interpretation; 3) constitution; 4) classification; 5) ecology and 6) conservation and planning.

“Vulnerability”is a new research frontier in the domain of sustainability science and global environment change, and the term is now a central concept in a variety of research contexts such as natural hazards, climate change, land use change, and sustainable development; meanwhile, vulnerability research is perceived by many researchers as a new science which deals with the mechanism, the process of interactions between human and environment, and the regional sustainable development. Finding a generally applicable conceptual framework and robust assessment methods of vulnerability which are key factors to determine the development of vulnerability science, is a challenge facing vulnerability science. Recent years, researchers from different disciplines draw growing attention to the concept and assessment methods of vulnerability, leading to a rapid progress on the concept and assessment methods of vulnerability. The paper analyzed the different definitions of vulnerability from literatures both abroad and domestic, and illustrated the convergences and divergences among these definitions; based on this, we discussed the exact meaning of the term, maintaining that the sensitivity and coping capacity of system to perturbations impinging on it are the main characteristics of vulnerability of system. In addition, we reviewed the methods used in vulnerability assessment, and classified these methods into five categories according to their assessing process. we evaluated the weaknesses and strengths of each method respectively, then put forward some principles that should be followed in the process of vulnerability assessment, such as choosing simple assessment methods at first and then, with complicated ones later, paying attention to the trade- off between data transformation and results interpretation, focusing on key processes of the generation of vulnerability and making use of multiple methods in a complementary manner. Finally, according to the new trends in vulnerability research, the paper brought forward some issues which should receive more attention in the vulnerability assessment research, such as the vulnerability to multiple perturbations, the vulnerability of coupled systems, the uncertainties of complex system, and the scale issue in vulnerability assessment.

The heart of sustainability study is measurement, and the ecological footprint (EF) model gradually becomes an important way to measure sustainability. Since it adopts a common standard, the study results of EF model could be comparable and easily understood. The EF analysis is designed to calculate the demand of a given population on nature by a common unit, namely bio-productive area, and its goal is to estimate the sustainable state by studying whether the demand exceeds the available supply. The purpose of this paper is to review the history of its application in China and abroad systematically. EF model has now been applied to measure the sustainability of many nations, cities and regions as well as for globe itself. And its applied field has been extended to land demand forecast, tourism sustainability measurement, environment impact assessment and so on. With the development of application, the EF method has been gradually modified and upgraded. To get integrated trade information, some studies took input and output calculation instead of original calculation method. The system of local productivity parameter is applied to show the regional characteristic. The bio-productive area types have been reclassified to consider greenhouse gases other than CO₂ and emission sources other than energy use. The goal of long time-series research is to overcome static weakness. With other sustainable development indices, it could be easily to make available policies. At last, the paper gives a prospect on the development of EF models’ application. The index system should be modified to present the characteristic of study object. We must enhance the EF’s forecast ability and boost up the development of application in environmental, social and economic fields in China.

Since the 1970s,the eutrophicated problem of the Lake Dianchi,Yunnan province has been more and more serious, which becomes an important factor limiting sustainable development of the Lake Dianchi Basin. Applying nutrient indexes-chlorophyll-a(Chla), total phosphorustal(TP), total nitrogen(TN), chemical oxygen demand(CODMn) and transparency(SD) as evaluating factors, this paper synthentically evaluated and analyzed the characters and causes of eutrophicated phenomenon in the Lake Dianchi. Based on above study, forepassed control meatures were summarized in detail. And some main problems were specially put forward, which were particularly bias stress on external sources, incomplete defending tree fence and immoderate bed silt cleanup measures. On further thoughts, new control strategies were emphasized on resolving the eutrophicated problem of the Lake Dianchi. They could be concluded as follows: to restore Dianchi ecosytem, to control the pollutants from internal and external sources and to strengthen environmental management in the Lake Dianchi Basin.

Accessibility is a research topic in the field of geography, civil engineering and transportation economics. Currently, a range of accessibility measurement approaches have been widely used in transportation network and urban development planning, transportation infrastructure effects evaluation on regional economy, location- allocation researches, landscape planning, social culture researches, to name a few. With rapid increasing of application demands and unceasing development of technology researches, accessibility measurement approaches also develop swiftly and the methodology is being formed. Based on a comprehensive exposition of accessibility concept, this paper systematically discusses the state - of- arts of accessibility measurement approaches, carries out a classification of these approaches from the perspective of network characteristics, and comparably elaborates and evaluates these approaches according to their influencing factors. Then application of various approaches are discoursed and analyzed in detail, consistent with different application areas. Finally the research priorities of accessibility research are thoroughly discussed.

SWAT (Soil and Water Assessment Tool) model is a river basin, or watershed, scale model developed to predict the impact of land management practices on water, sediment, and agricultural chemical yields in large, complex watersheds with varying soils, land use, and management conditions over long periods of timeThe model is physically based and enables users to study long term impacts This paper mainly introduces and discusses the issues of the hydrological theory, the structure and functions of SWAT modelSWAT separates the hydrology of a watershed into two major divisionsThe first division is the land phase of the hydrologic cycle which controls the loadings to the main channel in each subbasinThe second division is the water or routing phase of the hydrologic cycle which can be defined as the movement of water, sediments, etcthrough the channel network of the watershed to the outletSWAT uses a command structure for routing runoff and chemicals through a watershedUsing a routing command language, the model can simulate a basin subdivided into grid cells or subbasin In case study, SWAT model was used to simulate the hydrology of Heihe (Yingluo Valley) Basin in the cold Northwest ChinaFirst, Based on DEM, Heihe (Yingluo Valley) Basin was subdivided into four subbasinsBy building user soil type database and modifying land use coding, the model made a good runoff simulation result on a daily time step,and the model NSE (Nash Sutcliffe error judge standard) is up to 083So.