基于不同保护目标的河道内生态需水量分析——以琉璃河湿地为例

为探索不同阶段保护目标下的河道内生态需水量,以北京市房山区琉璃河为研究区域,基于琉璃河湿地工程的特殊性,在同一工程项目中不同阶段创新应用环境需水量和生态需水量两种方法,分别计算在截污工程完成前满足水质要求的河道内环境需水量和截污工程完成后满足以生态修复及维系为目标的河道内生态需水量。结果表明:(1)在考虑景观娱乐水量的情况下,二者一次生态需水量均为196.78万m~3;(2)以消纳污水为目标的河道内,在考虑河道稀释及自净能力的情况下,利用水环境容量法计算净化需水量为30.39万m~3/d,景观娱乐需水量为180.43万m~3,河道内的土壤储水量为16.136万m~3,水体年蒸发量为78.03万m~3,日均0.21万m~3,水体渗透量21.69万m~3,日均渗漏量0.03万m~3;(3)以生态修复及维系为目标的河道中,河道内的水生生物栖息地需水量为71.73万m~3。(4)在截污工作未完成之前,琉璃河内需每日注入30.39万m~3/d的湿地出水以保持水质。在不同保护目标下,如何依据河流实际情况,满足不同的需求,完善生态需水的计算方法,维持生态系统的稳定健康,将是未来关注的重点。

Analysis of ecological water requirement of rivers for different purposes: the case of Liuli River

In order to explore the ecological water requirement of rivers for different purposes, the case of Liuli River in Beijing Fangshan district was studied. The meaning and methods of calculation of environmental water requirement and ecological water requirement were defined. In this paper, environmental water requirement and ecological water requirement were calculated in the same project for the first time. Because the sewage treatment plant will be operated in 2021, sewage will continue to be discharged into Liuli River in 2019 and 2020. Before the operation of sewage treatment plant, the function of environmental water requirement is to eliminate sewage. However, after operation, the function of ecological water requirement would beto maintain the ecological balance. Both types of water requirement were calculated in this paper. The results indicated that both of the ecological and environmental water requirements were 1967800 m³. For eliminating sewage, the amount of purified water requirement was 303900 m³ considering water dilution and self-purification. The amount of landscape water demand was 1804300 m³. The amount of soil water storage was 161360 m³. The amount of annual evaporation from the river was 780300 m³. The amount of annual infiltration of the river was 216900 m³. For maintaining ecological balance, the water requirement for the habitat of aquatic organisms was 717300 m³. Future studies should be focused on the methods of coordinating the needs of different targets, refining the calculation methods of ecological water requirement, and maintaining a stable and healthy ecosystem under different situations.