The Cuu An River water passing through Thanh Mien district is heavily polluted, causing mass fish deaths.

There are sections of the river where dead fish float white on the surface, emitting a very unpleasant stench. For many days now, people have not dared to use this water source for irrigation.

Doan Ket Commune has about 350 aquaculture households with an area of ​​120 hectares, of which 90 hectares use water from the Cuu An River for production. It is known that in recent years, this water source has been polluted, many aquaculture areas have been severely affected. Some households lost 2-3 tons of fish due to using water from the Cuu An River. To overcome the difficulties, currently 100% of the households in Doan Ket Aquaculture Cooperative have installed 2-4 wells to get clean water instead of using water from the Cuu An River. When pumping into the pond, people have to treat the water with lime powder and alum. This leads to increased production and farming costs, affecting the profits of households.

According to the Department of Agriculture and Rural Development of Thanh Mien district, the Cuu An river is currently providing irrigation water for about 6,000 hectares of rice and some large concentrated aquaculture areas in the district. However, every year, there will be 2-3 periods of black water in the Cuu An river appearing from upstream and then flowing to the district, causing great impacts on people's lives and production.

Previously, in September 2021, the Northern Center for Environmental Monitoring and Aquatic Diseases (Aquaculture Research Institute I) took water samples from the Cuu An River and ponds of several aquaculture households for evaluation. At the Cuu An River monitoring point, the coliform density (an assessment of water purity based on the number of bacteria present in feces) was 2.7 times higher than the allowable limit. The Center recommended that aquaculture facilities should not directly use the Cuu An River water source during the monitoring period to supply to aquaculture ponds.

To avoid damage, Thanh Mien District People's Committee requested communes, towns and related units to proactively propagate and instruct people not to use polluted river water for production and business activities; develop appropriate irrigation plans. Households using surface water for aquaculture need to proactively implement timely response measures to limit the impact of polluted water sources. The district's Irrigation Works Exploitation Enterprise monitors and supervises water sources on the river, proactively operates water replacement works to minimize pollution in the Bac Hung Hai system in the district.