In order to reveal the impact of rapid urbanization on watershed eco-environment, this paper establishes a pressure-effect-social response (PESR) model which is used to assess the regional ecological risk based on the pressure-state-response (PSR) framework model. The results show that, ERI of the watershed suffered some degree of reduction from 1993 to 2007, from level Ⅳ to level Ⅲ. PI increased continuously, and EI remained stable, while SRI decreased significantly with the strengthening of environmental protection measures. The assessment results show that despite the increasing pressure of society, the strengthening environmental protection measures could mitigate the risk dramatically.

Based on the field data in 1986?2007 in Shenzhen bay, annual changes characteristics of nitrogen and phosphate concentrations, as well as their correlations with each other are presented. Furthermore, the Nutrition Quality Index (NQI) is employed to assess the eutrophication degree of Shenzhen bay. The dissolved inorganic nitrogen(DIN) concentration shows an increasing trend, while phosphate( PO^3-₄-P) concentrations decrease gradually. Ammonia nitrogen ( NH⁺₄-N) is the primary form of inorganic nitrogen in Shenzhen bay indicating that inorganic nitrogen is in unstable thermodynamic equilibrium. The ratio of DIN/ P increased gradually before 1998, and decreased after 2002. The variation and components of nutrients could influence the community structure of phytoplankton, and the dominant red tide species have been transformed from diatom to dinoflagellate. Nutrient correlation is significant at the 0.01 level, which shows that the nutrient undergo similar biogeochemistry processes. The NQI shows that Shenzhen bay is in high eutrophic status, and it is urgent resort to effective plan for controlling water pollution in the inflow river.

Based on former research and field survey data, the discharge, loss, composition and regional features of non-point source (NPS) pollution in Shiyan City were studied with the method of pollution discharge coefficient. The results show that pollutants of total nitrogen (TN) , total phosphorus (TP) flowing into water respectively were 17900 tons and 3800 tons for various NPS in 2004. Chemical fertilizer and animal waste were the primary source of TN, respectively, accounting for 39% and 25%. The main sources of TP came from soil erosion, fertilizer pollution and aquaculture, which made up more than 60% of TP. Among the districts (counties) of Shiyan City, Danjiangkou and Yunxi had the most serious NPS pollution, while the municipal district had the smallest. Different pollution types dominated in different districts or counties. Danjiangkou was featured by aquaculture pollution type; Yunxi, the type of fertilizer pollution; Zhushan and Yunxian, the type of fertilizer-soil pollution; and municipal district, Zhuxi and Fangxian were featured by comprehensive pollution type. Those results can be referenced by local government for making scientific NPS control strategies in Danj iangkou reservoir.

As the case study of Shenzhen River, a new indicator system based on eco-environment and social economic service functions is established for river health assessment by the analysis of the relationship between river health and its functions. Combined with the calculation of index to describe the health status of each function and the analytical hierarchy process (AHP) method applied to confirm the weights at different level, a health comprehensive index (HCI) depicting the synthetic action by all the functions is defined to present river health. Results indicate that, the systems of Shenzhen River in 2006 and 1996 are destroyed in the medium degree. It is also found that ecology and self-purification functions are severely damaged. Furthermore, the health status of Shenzhen River in 2006 is worse than that in 1996. According to the analysis of water environment and social economic characteristics of Shenzhen River basin, water pollution and water shortage are the main reasons for the damage of functions. Sewage interception and water supplement will be first considered in order to improve Shenzhen River health by ecological rehabilitation in future.

Land use changes seriously in the rapid urbanization area and could impact the urban ecosystem structure and function significantly, especially changing the characteristics of Urban Ecological Water Demand(UEWD). Based on the case study of Shenzhen, this paper analyzed the changes of SI (Index of Land use Structure Subject to UEWD) and EWI (Index of Urban Ecological Water Demand) in the period from 1988 to 2006. In order to know the relationship between UEWD and land-use change under different urbanization stages, the correlations between SI and EWI of inner and outside of the Shenzhen Special Economic Zone ( SSEZ) from 1993 to 2003 were discussed respectively. The results show that 1) EWI and SI were significantly decreased with different spatial character; 2) because of the different urbanization process of inner and outside of SSEZ, the characteristics of EWI and SI changes are distinct; 3) the relationship between EWI and SI is significantly positive correlated when the regional urbanization rate is low, but the correlation no longer exist as the rate increased further.

Taking Shenzhen City as a case study, Equal Standard Pollution Load Index and Equal Standard Pollution Load per Product were used to analyze the characteristics of heavy metals discharge from industrial pollution sources, including pollutant species, temporal-spatial distribution, and industrial contribution. The comparison analysis between 1996 and 2007 was made to examine the characteristics of heavy metals discharged in the recent ten years. The results exhibit as follows: 1) The ranking of average heavy-metal equal standard pollution load was given in the order from large to small as Cr( Ⅵ) , Cd, Pb, Hg and As over the last decade. 2) The amount of heavy-metal discharge increased whereas the amount of heavy metals per product decreased from 1986 to 2007. 3) Compared with other administrative districts and river basins, Longgang District and Pingshan River Basin occupied the highest proportions of pollution load and pollution load per product in 1996, whereas Futian District and Shenzhen River Basin were the highest in 2007. 4) Electronic & Communicating Equipment Manufacturing( ECEM) Industry and Metal Product Manufacturing (MPM) Industry were the top two industries with the maximum pollution load and pollution load per product in 1996 and 2007. The results indicate that Cr( Ⅵ) is the priority pollutants and efforts should be fixed on the ECEM and MPM industry.

The interruption of human with the urban ecosystems will change the land use structure dramatically and result in deterioration of environmental quality as well as the remarkable change of ecological water requirements. Based on the case study of Bao’an, Shenzhen, this paper presents the quantitative relationship between urban ecological water requirements (UEWR) and the characteristic index for land use structure (SI). The driving mechanism of human activitiesto the land use change and UEWR is studied by Partial Least Squares Regression model. The estimation results indicate the significant negative correlation between UEWR and SI. The human driving forces can explain 50 % ～90 % of the deviation of the land use, especially more than 90 % of the urban construction area and SI. The explanation ability of the same driving forces to the ecological water requirements are 60 % ～80 %. The coefficients of the regression model represent the weight of the driving forces, among which the population is of the most important contribution. Through the same human driving mechanism, the UEWR can be explained and predicted by the simple index of SI.

A newindex of long-termflood impact on sustainability (LFIS) was proposed, considering the multiple impact of flood on the complex social-economic-environmental system. This index extended the current economic loss basedflood risk analysis into a more comprehensive perspective. Rapid assessment approach was applied for the evaluation and ranking of LFIS using 2359 counties/cities of mainland China as mapping units. The mainland China was zonedinto five kinds of regions, classified in terms of different grades of LFIS, i.e. very high, high, medium, low and very low. The spatial characteristics of LFIS were discussed for regional, provincial and urban levels. The results are helpful for the decision-making of integrated sustainable flood prevention, mitigation and recovery.

Based on the case study of Bao’an, Shenzhen, this paper analyzes the characteristics of Urban Ecological Water Requirements( UEWR) during 1988-2004. The relationships among UEWR, water resources and land use are studied. The results are summarized as below: the amount of UEWR of Bao’an decreased remarkably from 2.12×10⁸m³ in 1988 to 1.60×10⁸m³ in 2004. The components of UEWR including forest, grassland and water ecosystems show the different trends. The significant positive correlation between UEWR and land use is found in this study. The ratio of UEWR in water resources structure is about 24%-33%. Water resources allocated to human society should be limited by 60%-70% in order to maintain the healthy ecosystemand urban sustainable development.

The interruption of human with the urban ecosystems will change the land use structure dramatically and result in deterioration of environmental quality as well as the remarkable change of ecological water requirements. Based on the case study of Bao’an, Shenzhen, this paper presents the quantitative relationship between urban ecological water requirements (UEWR) and the characteristic index for land use structure (SI). The driving mechanism of human activitiesto the land use change and UEWR is studied by Partial Least Squares Regression model. The estimation results indicate the significant negative correlation between UEWR and SI. The human driving forces can explain 50 % ～90 % of the deviation of the land use, especially more than 90 % of the urban construction area and SI. The explanation ability of the same driving forces to the ecological water requirements are 60 % ～80 %. The coefficients of the regression model represent the weight of the driving forces, among which the population is of the most important contribution. Through the same human driving mechanism, the UEWR can be explained and predicted by the simple index of SI.

As one of the major parts of environmental risk assessment, the ecological risk assessment provides tools or frameworks for ecological analysis and thus serves environmental risk management and decision-making. An overview is particularly made on basic concepts and primary methods for ecological risk assessment and management. Existing problems are discussed for current ecological risk assessment and practices, and perspectives are given in the paper.