Contamination of water of these rivers started taking a serious turn with the onset of the lean period as siltation in their sources in the upstream disrupted their normal flow. Thousands of cubic metres of lethal industrial wastes are dumped every day in the almost stagnant waters of the rivers.

The Buriganga, Turag and Balu rivers stop receiving water from their sources when canals and rivers from the Jamuna in the upstream dry up at their mouths. Movement of water in these rivers during the lean period is caused only by high and low tides from the downstream.

Dead fishes were seen floating in the Buriganga near Basila yesterday, where 22,000 cubic metres of tannery wastes are dumped directly into the river every day. Moreover, thousands of cubic metres of other industrial wastes are also dumped into the river through 22 large outlets along the rivers.

Dispersion of these wastes stopped due to lack of water flow from the upstream. As a result, the rivers virtually turn into septic reservoirs killing all aquatic life. Thousands of dead fish fries, particularly prawns, were seen along the shore in Waaspur area.

Several dead cubs of Gangetic dolphins floated near Jhaochar last week. Many people including children were seen catching small fish with their bare hands yesterday. The water looked black and smelt foul.

Locals at Shoulmachi on the bank of the Turag said the river water would remain highly contaminated until fresh water starts coming in the rainy season.

" Tannery wastes have taken away our livelihood. We can supply the city market with enough fish every day if the river water is pollution-free," said one local, Abu Musa.