区县尺度下的河流生态系统健康评价——以北京房山区为例

伴随郊区城市化的快速发展,高强度人工管控对河流生态系统产生持续胁迫作用,河流生态系统健康受到严重威胁甚至损害。以北京房山区河流水系为例,于2016—2017年在区域内的31处样点进行野外调查。选取河流的水环境功能、防洪效益功能、生态效益功能和支持利用功能4方面16个具体评价指标,并通过层次分析法计算权重,构建区县尺度下的河流生态系统健康评价指标体系,并进行健康状况评价。结果表明:房山区河流的防洪效益功能与生态效益功能中"健康与亚健康"状态比例分别为58.0%与41.9%,而水环境功能与和支持利用功能中"较差与差"状态比例为71.0%与41.9%;河流生态系统健康整体水平较差,勉强满足河流生态系统一般需求。同时,房山区境内的拒马河与小清河的河流生态系统健康状态远优于大石河与永定河。河流生态基流是影响河流生态系统健康的关键因素,适当释放库区截留水量与调配区外清洁水体,已成为恢复房山区河流生态系统健康的前提与基础。

Health assessment of river ecosystem at the district and county scales: A case study of Fangshan district in Beijing

With the rapid urbanization of the suburbs and the resultant persistent, high-intensity management of ecosystems by humans, the health of river ecosystems is being seriously threatened, ultimately resulting in damage. In this paper, 31 sites along regional river systems in Fangshan district, Beijing, were investigated during 2016-2017. Sixteen specific evaluation indicators were classified into four aspects of river functions, viz., water environment, flood control benefit, ecological benefit, and support and utilization. The analytic hierarchy process method was used to calculate the index weight; next, the river ecosystem health evaluation index system at the county scale was constructed for Fangshan district. The results showed that, for the streams in Fangshan district, the proportion of "health and sub-health" state was 58.0% and 41.9% in terms of the functions of flood control benefit and ecological benefit, respectively. However, the proportion of "below general" state in terms of the functions of water environment and support and utilization was 71.0% and 41.9%, respectively. Overall, the health of the river ecosystems in Fangshan district was poor and barely met the general functions of the river ecosystem. Meanwhile, comparing the health of the river ecosystems, Juma and Xiaoqing rivers were far superior to Dashi and Yongding rivers. River ecological baseflow was the key factor that affected the health of the river ecosystems. Thus, the government should divert clean water from local reservoirs and other areas to restore and improve the health of the river ecosystems in Fangshan district.