关键词: 城区河道, 水环境综合整治, 指标体系, 评价方法

Abstract: Urban rivers are hybrid ecosystems and exert different key ecological and societal roles within urban ecological systems. With the acceleration of urbanization and rapid development of social economy, the urban river pollution is becoming more problematic for many cites in China, as well as in Ningbo, a city located in the middle of the coastal line of the Chinese Mainland. To recover river social functions, restore ecosystem services and improve the environmental quality of urban human settlements, many integrated control measures were employed in urban river comprehensive restoration, which involved a lot of investment and efforts. To reduce the cost of control measures, an evaluation framework was needed to assess the efficiency and guide the practical work of urban river comprehensive restoration; it was also an important tool to support the work of managers of urban river environments. The purpose of this paper was to propose an evaluation methodology to meet the need of urban rive management. An evaluation index system and corresponding evaluation method were established by using expert investigation and systematical analysis, in which, the evaluation index system comprised four layers and the individual evaluation indexes reflecting various requirements of the question. Then, the proposed evaluation method was applied in Ningbo urban river management. In the case study, the water quality monitoring and public surveys were conducted before and after the river comprehensive treatments of 11 urban rivers in Ningbo in March and October in 2012. The monitoring water indices included transparency, water temperature, total phosphorus(TP), total nitrogen(TN), ammonia nitrogen(NH₃-N), dissolved oxygen (DO), permanganate index(COD_Mn), chlorophyll a (chla). The comparison of monitoring results showed that before urban river interventions, the average concentrations of TP, TN, NH₃-N, COD_Mn and DO were 1.05, 13.64, 9.51, 10.96 and 7.4 mg/L, respectively, and chlorophyll a was 58.2 mg/m³; after urban river interventions, the average concentrations became to be 0.61, 10.8, 7.95, 9.02, 4.8 mg/L and 41.5 mg/m³, respectively, and the tropic level index, water quality index and the black and stink index in most of the 11 rivers get lower than before. Moreover, many integrated control measures, including sewage interception, sediment dredging, phytoremediation, landscape construction and ecological embankment were employed in urban river comprehensive restorations, which tended to focus on societal and ecological benefits rather than water quality improvements, so instead of using the traditional water quality evaluation method, the proposed method was applied to evaluate the effects of the integrated control measures used in Ningbo urban river. The average evaluation of urban river comprehensive restorations in Ningbo scored from 48.4 to 91.4, and the urban river comprehensive restorations got some good effect. Because of the sewage influents from riparian to some rivers after intervention, for example, the Nanbei River, Zuguanshan River, and Zhujia River, the efficiencies of urban river comprehensive restorations were not always conspicuous, and the Zhiluo River had no effect. The case study shows that the index system and evaluation method are scientific, reasonable, and easy to put into practice for relevant personnel and branches. It needs to be stated that the evaluation indexes is not perfect enough, and water ecological index should be appended according to the characteristic of urban river and the needs of management.

Key words: urban river, river comprehensive treatments, evaluation index system, evaluation method