In recent times, Hanoi has implemented many synchronous solutions with the goal of getting the To Lich River out of the vicious cycle of pollution.
In mid-August 2025, the city completed the collection of all 245 wastewater discharge gates on the To Lich River, ending the situation of wastewater discharged directly into the river.
From September 9, water from West Lake was officially replenished for the To Lich River. On September 20, Yen Xa Factory continued to replenish wastewater after treatment into To Lich River to "revive" this river.
Since the water was brought in, To Lich River has had a clear change: the water is less black, the odor is reduced, the landscape is brighter.
However, according to people's reflection in recent days, some river water areas have changed from deep blue to black. The phenomenon of dead fish also appeared on this river.
Informing about this, a representative of the Hanoi Technical and Agricultural Infrastructure Construction Investment Project Management Board (Hanoi Agricultural Board) said that in recent days, rivers and lakes (including To Lich River) have been lowering water levels to prevent storms. In addition to ensuring landscape, To Lich River also has the function of draining water and preventing flooding.
To prevent the storm, rivers and lakes in the city must lower the water level, causing water discharged from the lakes via pipes flowing into the To Lich River, causing waste in the pipes to cross the overflow threshold into the river.
In addition, the process of lowering the water level on the To Lich River combined with operating the bottom discharge at the dam also caused some areas to turn black. The reason is that although the city has dredged up sediment and silt, there are still many, many of which are still silted up to 80cm in some locations.
The representative of the Agricultural Committee explained that when the water level is lowered, it can lead to many locations where this sediment can be directly seen, combined with conditions such as heavy rain, and species existing in the river, causing the mud layer to stir up, causing the water to turn black.
In fact, people throwing a lot of garbage into sewers and rivers such as old clothes, blankets, foam boxes, raincoats, etc. also greatly affects the river environment and directly causes traffic jams in wastewater collection pipes along the To Lich River. This causes difficulties in the operation of the pipeline.
