In 1985, the Transnational Centre, a social action group, took the matter of industrial effluents polluting the Tungabhadra to the Karnataka High Court. The organisation detailed the various changes that polluting effluents set in motion in a river.

The petition explains that when waste is dumped into a river, the solids sink to various levels and are attacked by either aerobes (microorganisms that require oxygen to survive) or anaerobes (microorganisms that do not require oxygen for their survival). While aerobes are found at higher levels of water, anaerobes are found at lower levels. These organisms consume the rubbish, converting the organic matter into inorganic and mineral water.

The process of conversion uses up the precious oxygen reserves of water that are deposited by algae. The algae also absorb the inorganic and mineral water produced by the aerobes. Protozoa, another kind of organisms that are usually unicellular, destroy the disease causing germs in the waste, and this, too, requires oxygen.

As the quantum of rubbish goes up, the amount of oxygen required by the aerobes and protozoa to treat the waste also goes up. If the rate or the quantity of rubbish being dumped in a river is too high, the oxygen in the water may not be enough for the aerobes and protozoa to treat the waste and these useful organisms may die out.

Besides, as the oxygen level in the upper layers of the river water falls, the anaerobes rise towards the surface and begin to attack the waste matter. The action of anaerobes produces the foul smelling hydrogen sulphide gas, which makes the water turbid. Sunlight cannot penetrate the surface. Without sunlight, the algae, which are plants, begin to die and the fish without the oxygen from the algae also die.