Ballari: When the usually pristine and sparkling waters in the massive Tungabhadra reservoir, which acts as the lifeline for several parched districts in north Karnataka and neighbouring Andhra Pradesh, turns an ugly green, it is bound to send shivers down the spine of millions of farmers and villagers who can't imagine surviving without the water.
The water has turned dark green in the last few days with experts attributing it to algae blooms - a rapidly growing algae or cyanobacteria which creates coloured scum that collects on the water surface.
Samad Kottur, naturalist and researcher, says this has happened due to pollution of the river. Farmers upstream use chemical fertilisers extensively which get washed into the river during the rains. In addition, industries release effluents that are not treated which results in eutrophication (excess nutrients) and algal blooms.
The algal blooms usually multiply after cloudy weather, followed by sunshine. Though they are short-lived, they absorb all the dissolved oxygen in the water and make use of nutrients to grow rapidly. Experts say the long-term consumption of such water could lead to liver disease and if people swim in the water, they are likely to develop skin rashes. It is advisable to avoid drinking this water for the next 10-15 days, and cattle too should be kept away, they warn.
“We have been observing this phenomenon for long, but in the last four-five years it has been happening too often" said Kanimappa, a farmer in Gunda village.
However, senior officers of the Tungabhadra Board claimed that the green coloured water is not harmful. According to them, this is happening because of the heavy rains and a lot of fertiliser getting washed off from the fields into the reservoir. But the algae form only in the top water layer which is warm, they contend. For instance, on Thursday, the water level was at an approximate 80 feet, and the greenish colour was observed in the top one-and -a-half feet of water.
“We examined the water long back, it will continue to remain green for a maximum of one month. It will in no way affect drinking water quality as drinking water outlets are situated way below and not on the surface of the reservoir,” the officers asserted.