连日来，暴雨持续袭扰长沙，城区低洼路段、区域积水猛涨，影响出行。漫天大雨中，长沙火车站短短两小时排走3.2万m³积水——相当于15个国家专业游泳池水量，上演防汛“长沙速度”，引发网络热议。

暴雨积水为什么这么快能排走?排走的积水都流向了哪里?这背后，是一条长沙版的红旗渠。

长沙红旗渠并非传统意义上的水渠，而是城区地下四通八达的雨污排水管网系统。该系统始建于上世纪七十年代，能实现雨水排入江河、污水进入污水处理厂净化后排放的双重功能。由于部分水渠腐蚀严重，长沙正进行红旗渠水系排水改造，预计2025年8月完工。

红旗渠水系排水改造工程完工后，将承担雨水管网功能，新建截污干管将承担污水管网功能，实现长沙老城区雨污分流。届时，不仅将有效防止污水流入河流，保护浏阳河水环境，还将发挥地下管网排水调蓄功能，助力城区防灾度汛。（来源：华声在线记者：张梅、贺思帜通讯员：彭程浩）

Over the past few days, torrential rains continue to hit Changsha, low-lying sections of urban areas, areas of water surging, affecting travel. Changsha Railway Station drained 32,000 m³of water in just two hours amidst heavy rains，which was the equivalent of 15 national professional swimming pools. This staged flood control "Changsha speed", triggered the network hot discussion.

How did the storm water drain away so quickly? Where did the drained water go? Behind this is a Changsha version of the Red Flag Canal.

Changsha Red Flag Canal is not an aqueduct in the traditional sense, but a well-connected system of rainwater and sewage drainage pipes under the city. The system was built in the 1970s and can fulfill the dual function of discharging rainwater into rivers and sewage into sewage treatment plants for purification and discharge. Changsha is undergoing a drainage renovation of the Red Flag Canal system, which is expected to be completed in August 2025, due to severe corrosion of some of the canals.

Upon completion of the Red Flag Drainage Improvement Project, it will assume the function of a stormwater network. The new intercepting trunk sewers will assume the function of sewage network and realize the rainwater and sewage diversion in Changsha. Not only will effectively prevent sewage into the river, protect the Liuyang River water environment, but also will play the underground pipe network drainage storage function, help urban disaster prevention and flood control.（翻译：万姗姗 视频：实习生 王泽宇）