stagnant

(of water or air) not moving and therefore often smelling unpleasant นิ่ง, น้ำทรง

Residents demanded in Tuesday's rally that all sluice gates on Khlong Maha Sawat be opened wider so the stagnant floodwater in their communities would be drained through Bangkok.

Simply mix a tablespoon of the powder with 20 litres of water, leave for 30 minutes to two hours, then pour into the stagnant water, and the smell will gradually disappear and the water will become clearer in about 1-4 weeks.

Stagnant floodwaters bring out insects such as scorpions and centipedes, poisonous snakes and reptiles.