Ngoc Khanh Lake, one of large lakes in Hanoi center, was upgraded in June 2015 but after the renovation project finished in February 2016, the lake has given out a smell. Local people are suffering from the stench.

Explaining the phenomenon, Nguyen Manh Hung, Deputy Director of the Management Board of Hanoi Drainage Projects, said after being renovated, green algae usually appears in lakes. 

After days of growth, algae will die and rise to the water surface, decompose and causeodor. This process lasts about 1 to 1.5 months. The authorities are handling the phenomenon. By May 6, pollution decreased by about 70%.

The West Lake, the section along Thanh Nien - Nguyen Dinh Thi road full of waste, discharged by boat restaurants and bars.

Dead fish and green water in Den Lu Lake in Hoang Mai District.

Floating fish, snails in Van Quan Lake in Ha Dong District.

Hao Nam Lake was narrowed to serve the elevated rail project. The remaining area of the lake is full of scum and garbage.

According to the latest report of the Center for Environmental and Community Research (CECR), in 2010 Hanoi had 122 lakes, with 86 of them having embankments. Among the lakes with embankment, many lakeshores are used by locals to sell food.

Van Chuong Lake of 13,000 m2 large is one of the most polluted lakes in Hanoi because of untreated wastewater discharged from households and restaurants.

Kim Lien Lake of 3,000 m2 covered with weeds and water-ferns.