The water pollution in river is measured by the dissolved amount of

1. The question asks how water pollution in a river is measured. 2. Water pollution, especially by organic waste, leads to depletion of dissolved oxygen in the water as microorganisms consume oxygen while decomposing the waste. 3. The amount of dissolved oxygen (DO) is a key indicator of water quality and the health of an aquatic ecosystem. Low DO levels indicate pollution. 4. Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) are measures of how much oxygen would be consumed by pollutants, but the direct measure of the river's state related to this pollution is the actual dissolved amount of oxygen. 5. While Chlorine might be present as a disinfectant or pollutant, Ozone is used in water treatment but not typically measured in rivers as a pollution indicator, and Nitrogen compounds are pollutants, the overall health indicator related to organic pollution is dissolved oxygen. 6. Therefore, water pollution (specifically organic pollution) in a river is often measured by the dissolved amount of Oxygen.