Making Rain, Not War in Mumbai

Maharashtra mulls artificial rain to irrigate drought-prone areas.

Mumbai is likely to get artificial rain in two weeks. There has been below average rainfall in the city and a shortage of potable water is imminent. The state government has few options but to try artificial rain, also called weather modification, cloud-seeding or rain-making. Negotiations are on between the state government and some weather modification firms. An Israeli company with a proven track record is likely to get the contract. In the past too, such an exercise had been undertaken to irrigate the drought-prone areas of Vidharba and western Maharashtra. Officially, the state government is still deliberating on the matter. So no information was forthcoming from the Chief Minister’s Office. But Vinod Tawade, the BJP’s leader of the opposition in the Legislative Council says that the project will get a go-ahead. “It may look as if Mumbai often gets flooded. But there is a severe water shortage in the city,” Tawade says. He adds that while artificial rain may be a good way to irrigate parched land, it may not end the potable water crisis. The primary reason why people want rain is so that there is enough water to drink and for crops to grow. This season has been worryingly dry, despite predictions to the contrary by the weather bureau. And artificial rain seems to be a short-term solution. Weather modification, or cloud-seeding or rain-making, is an important component of water resource management. It is done in three stages—stimulation of clouds, a build up stage, and finally bombardment (rain). Chemicals are used to stimulate the air mass upwind of the target area, which rises and forms rain clouds. Chemicals used in the creation of artificial rain include calcium chloride, calcium carbide, calcium oxide, a compound of salt and urea or a compound of urea and ammonium nitrate. These chemicals are capable of absorbing water vapour from the air mass, thus setting off the condensation process. This is the first stage. In the second stage, silver iodide is used to ‘build up’ clouds. Though there are many methods for cloud-seeding, the most popular uses small planes to spray chemicals onto clouds. But it cannot take the place of natural rain and is seen only as a supplementary exercise.

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Haima Deshpande