海绵城市建设下的生态效应分析——以常德市穿紫河流域为例

Evaluation on ecological effects under the sponge city construction at the Chuanzi River catchment in the Changde city, China

海绵城市建设被认为是解决城市内涝、水污染和水资源短缺、热岛效应等问题的有效途径之一。中国自2015年起共确立30个海绵城市建设试点城区,为今后海绵城市建设在全国范围的推广提供示范。基于实地调研、查阅资料并对比分析穿紫河流域海绵城市建设前后的水文、植被和气候等自然要素变化。结果表明:常德市城市内涝有效缓解,但在暴雨发生时局部仍出现积水和内涝现象;穿紫河水质总体上由劣Ⅴ类转变为Ⅲ类,但在冬季周期性恶化及污染物富集;穿紫河流域生物多样性显著增加,同时也表现出植物种类单一、具有环境净化功能的植物种类较少、生态系统不完整和管理不善等问题;常德市夏季的热岛效应有一定程度缓解。常德市2004-2019年的海绵城市建设显著提升了穿紫河流域的生态效应,为该地区的社会经济发展和人居环境改善提供了重要的生态基础,也为合理评价其他试点城区海绵城市建设效果提供借鉴。

Sponge city construction (SCC) is regarded as one of the effective ways to solve the urbanization problems in China, such as waterlogging, water pollution, water shortage and heat island. Since 2015, a total of 30 pilot cities had been set up as sponge cities for providing the models of a nationwide SCC in the future. Nevertheless, the studies about the SCC mainly concentrated on its concept, planning and goal in some pilot cities, few are known about the changes of the ecological effects under the SCC. As the first city in China to accept the sponge city concept and put it into practice, the Changde city, Hunan province, with the Chuanzi River catchment as the study area, provides the ideal area to evaluate the ecological effects under the SCC in China due to a longer SCC history over the period of 2004-2019. In this study, the ecological effects under the SCC in this catchment were analyzed based on field investigation and the comparsion of the measured data of hydrology, vegetation, and temperature before and after the SCC. The results showed that the SCC effectively alleviated the waterlogging in the Changde city, but some waterlogging sites still presented at the different areas in the catchment under the rainstorm. Meanwhile, the water quality in the Chuanzi River had been generally improved from bad Ⅴ to Ⅲ grade, but there was periodically deterioration due to the pollutants enrichment in the water during the winter seasons, which were the results from both closed water system and low temperature environment. In addition, the biodiversity in the catchment had significantly increased, but it also showed some existing problems at the same time including single plant species, few plants with environmental purification functions, incomplete ecosystem and poor management. Besides, the SCC had alleviated the heat islands in summer in the Changde city to some extents. As a result, the SCC over the period of 2004-2019 in the Changde city has significantly improved the ecological effects at the Chuanzi River catchment, which provides an important ecological basis for the socio-economic development and the improvement of the living environment in this area, and provides the reference for the reasonable evaluation on the SCC effects in other pilot cities in China.