Expert casts cloud over minister's rain-making project
A senior climatologist in the committee that studied a proposal to produce artificial rain for hydropower generation has urged the Government to conduct a thorough cost- benefit analysis and environmental impact study before taking the project beyond its trial stage.
The Ceylon Electricity Board (CEB) and the Sri Lanka Air Force (SLAF) this week signed an agreement to facilitate the rainmaking initiative with technical expertise from the Thai Government. The project is expected to benefit Sri Lanka in periods of drought to avoid buying expensive power from independent power producers, Power and Energy Minister Ravi Karunanayake was quoted as saying.
But Ranjith Punyawardena, Principal Climatologist of the Department of Agriculture, expressed caution, saying the Government must not go beyond a pilot project before analysing whether the high cost initiative would have the required result of producing sufficient rainfall for hydropower generation.
Rainmaking here will involve the use of the chemicals calcium chlo- ride, calcium oxide, sodium chloride and urea. There are three steps. The first is cloud “triggering” where sodium chloride is sprayed into small clouds or cumulus. Several hours later, there is cloud “fattening” or the application of calcium chloride and calcium oxide to the clouds.
The final stage is cloud “attacking” where one aircraft sprays sodium chloride from above the cloud while the other sprays urea from the base, both at the same time. This is called a “sandwich operation” as there are two planes going through the cloud.
The exercise will be expensive for Sri Lanka. Thailand’s Royal Rainmaking Agency has 24 aircraft and hangars dedicated and especially maintained for the purpose of cloud seeding. However, Sri Lanka will use its limited SLAF planes, risking corrosion from long-term exposure to salt.
Dr Punyawardena was part of a committee that included representatives of the CEB, the SLAF, the Power and Energy Ministry, the Mahaweli Authority, the Irrigation Department, the Central Environmental Authority, the Met Department and the Department of Agriculture. With 30 years of experience in climate science, he was also doubtful that this exercise would produce the required amount of rainfall. For that reason, he insisted that it must be done as a pilot project, to be up-scaled if successful.
“Even if the trial succeeds, it must be replicated several times because atmospheric stability changes from time to time depending on the global ocean atmospheric circulation from time to time,” Dr Punyawardena said.
The initiative will be monitored by the Ministry, the CEB and the committee, said a spokesman for the utility. After some runs were conducted last year, water samples were collected from the ground and found to be affected to a “negligible level” by scientists, he said. This was still at pre-feasibility stage, he added. If implemented, formal procedures such as an Environmental Impact Assessment (EIA) may need to be conducted.
“The amount of chemicals they are going to use in this mission may be insignificant compared to the area they will spray ,” said Dr Punyawardena. “But if we are to keep on spraying regularly, there could be an accumulation of salt in the soil and water bodies. It all depends on how it is practised.”
There are concerns, too, about how effective the exercise would be in Sri Lankan conditions. Cloud seeding will be done when there is no rain. But at such times, climatologists say, the atmosphere over Sri Lanka is “highly stable” and it could be futile to apply chemicals to a stable atmosphere as it will not bring on precipitation.
Cloud seeding was done with Thai technology even in the early to mid-70s during the Sirimavo Bandaranaike government. It produced some rain, not a significant amount. What is needed, observes said, were proactive approaches--not reactive ones, such as a rainmaking through artificial means. These include conserving the Central highlands, forestation and reforestation and soil conservation.
Experts have also called for sound practices to ensure the country puts to good use the rainfall it does receive. Pakistan, with between 300400mm annual rainfall, is managing its water. However, Sri Lanka gets 800-1,500mm of rainfall per year but does not manage it well enough to maximise use.
The committee had agreed that cloud seeding will take place just before the onset of convectional rain. This means, when the land warms up, it heats the air above it, causing the air to expand and rise. As the air rises it cools and condenses. If this process continues, there will be rain.
“The sun is directly overhead Sri Lanka in March and early April and somewhere in September and October,” explained Dr Punyawardena. “This is when convectional activity is intense, just before the Yala and Maha rains. That is the time they will try this, to trigger the rainfall. I’m not sure how much it will bring down and whether there will be a gain for the amount spent on it. That has to studied.”