Central Pollution Control Board (CPCB) in association with the State Pollution Control Boards monitors the river water quality across the country through a network of monitoring stations under the National Water Quality Monitoring Programme. Water quality assessment for ascertaining the chemical contamination of rivers, lakes and other fresh water bodies has been carried out for 253 rivers, 133 lakes, 47 ponds and 79 tanks across the country. Chemical Oxygen Demand (COD) is a summary parameter to assess the chemical contamination of aquatic resources.