One way of preventing flood may be by making rain! This may sound rather strange. As we know, heavy rain is the cause of floods, and in Malaysia most of the floods are caused by the annual monsoon, which brings heavy rain to the east coat. If, however, the rain could be made to fall in the China Sea, there would be no more floods since the rain clouds would not reach the east coast.
Is it possible to make clouds give up their rain? Yes, it is, and in 1973 the National Institute of Scientific and Industrial Research (NISIR) suggested that it should be tried. The Institute knew of course that it is not possible to make all clouds give up all their rain. It calculated, however, that if the Frequency of rainfall could be reduced by ten per cent, and the amount of rain that fell each time could be reduced by fifteen per cent, the total amount of flood damage would be reduced by forty to fifty per cent.
As you probably know, clouds are caused by air containing water vapor.The air rises and, since water vapor becomes water when it cols, very tiny drops of water are formed. Since these drops are very small, they float in the air and form a cloud. When the cloud rises, however, the drops become colder.
Because of this, they join together and become big drops. The big drops are no longer able to float because of their size, and they fall, As they fall they pick up more drops and become bigger. This is the cause of rain.
Rainmaking means making these bigger drops form and fall before they would normally do so. This can be done by ‘seeing’ the clouds with chemicals, like planting seeds in the ground.
Rain can be produced in this way by three chemicals:
sodium chloride (the salt we use on our food), dry ice, which is frozen carbon dioxide, and silver iodide. The seeding is done by aeroplanes which fly through the clouds.
The Institute said that sodium chloride was more effective when the clouds were warm, and silver iodide worked better when the clouds were very cold. For this reason, it was decided to use a mixture of sodium chloride and silver iodide. The experiment began in November, 1973. The Royal Malaysian Air Force supplied a Caribou transport aircraft with special equipment to carry and release the chemicals. When the monsoon clouds appeared, about forty kilometers from the coast, the Caribou took off and flew through the clouds, seeding them with the chemicals. This took place at a height of about 3,000 metres. After ten to twenty minutes, the rain began to fall.
When the experiment was over, it was estimated that six aircraft would be needed. They would have to seed the clouds from Johore to Kota Baharu for three months every year. This would cost about Rs 3,000,000 each year. This is a lot of money but it is much less than the cost of the damage caused by floods. In times of drought, moreover, the same method could be used to make rain over land.
Perhaps one day we may be to control the rainfall here in Pakistan.
By: AQSA RIAZ