The preventive measures are:
i) Use of herbicides, insecticides, fungicides and pesticides should be limited.
ii) Proper drainage for industrial for industrial, human and other waste should be provided. Domestic waste water and various industrial effluents should be treated suitably before releasing them into the water bodies. Effluents from industries should not be allowed to flow into agricultural fields.
iii) Excessive chemicals should not be used for water purification. Large scale water purification methods should be adopted.
Some measures undertaken by Government are:
Save Ganga Plan
Removal of industries near to water bodies,
Filtration of wastes expelled into the water bodies,