Surface water pollution in the Yangtze River Delta: Patterns and countermeasures

On the basis of field investigations, observations and experimental data combined with environmental monitoring information, the status and the spatial and temporal patterns of surface water pollution over the past ten years in the Yangtze River Delta have been assessed. The water quality of large rivers is still very good but most of the medium-sized and small rivers have been very seriously polluted. The appearance of black and odorous conditions in rivers in the urban areas has increased due to serious pollution by organic matter with consequent high oxygen demand. Annual increases in N and P concentrations in lakes have accelerated eutrophication. The water quality of rivers in small towns is rapidly deteriorating. The main sources of surface water pollution include industrial and domestic sewage, animal manures, chemical fertilizers in farmland, and polluted sediments in rivers and lakes. Countermeasures against these sources of pollution are presented. Regional laws and regulations for protection of surface waters and their enforcement are urgently required. A regional water environmental management agency should be established. The construction of sewage treatment plants of varying capacity must be accelerated to increase the proportion of sewage treated and to improve the quality of treated effluent. Animal wastes must be recycled effectively and efficiently, and the application rates of fertilizers and manures must be balanced with crop nutrient requirements to prevent diffuse pollution from agriculture. The comprehensive rehabilitation of medium-sized and small rivers should be intensified, and the delimitation and protection of the areas used as sources of drinking water should be strengthened.