Ecological Security Assessment Of Urban Water Environment In The Pearl River Delta

Water resource and water environment quality has become crucial problems of great concern among both scientists and politicians. In the Pearl Delta region, with rapid economic and social development in recent decades, water environment quality is getting worse and worse with increasing shortage of source water due to pollution. The situation of urban water ecosystem safety is becoming more and more serious, and thus would lead to adverse impacts on regional economy and social development. Therefore, the study on time series of urban water quality and ecosystem safety in the Pearl River Delta region would be of importance for identifying factors influencing water quality, for protecting water resources and water environment.Based on previous studies and available information and by use of statistical methods and ecological theories, the present paper carried out a case study on urban water environment security in Guangzhou, the central city in the Pearl River Delta region. The main results are listed as below:1. The temporal changes of organic pollutants in the urban water environment indicated that water quality in Guangzhou has been gradually deteriorated from 1990 to 2005; a major reason is the rapid increase of domestic sewage with the economic development and rising population density. Annual rainfall also significantly impacts the water quality.2. Grey correlation analysis on the relationship between the long-term water quality and social and economic development demonstrated that population density and the degree of urbanization were two most important factors worsening the water quality. The share of the third industry in GDP and domestic sewage discharges were also highly correlated with the water quality. The results reflect the significant influence of urbanization and population increment on water quality.3. The total value of water ecosystem services in Guangzhou was estimated to be 20.93 billion Yuan in 2005, and accounted for 4.1% of the GDP in Guangzhou. Among ecological service categories, water supply was the highest in direct services values (58%), and fishery (21%) and recreation (19%) also shared a large portion in the direct services values. Flood control and water resource storage were the most important in the indirect service values of water ecosystem (45%). 4. Main factors threatening the quality of drinking water included the unbalanced temporal and spatial distribution of water resources, lack of water utilization facilities, trans-boundary pollution, no point agricultural pollution and hydrological conditions. The annual least ecological water demand was 1.57 times of the average annual rainfall in Guangzhou, and 6.61% of the average surface runoff of Guangzhou city.5. The temporal trends of urban water ecological security in Guangzhou revealed the state index value of urban water ecological security has not evident change from 1990 to 2005. However, the response index value of urban water ecological security has been rapidly increasing because Guangzhou government increases investment of harnessing pollution and strengthens capacity for resisting ecological risk of water environment. As a result, the complex index value of urban water ecological security in Guangzhou has been gradually rising.