The Iranian government has made great efforts to reduce the consequences of drought by introducing novel irrigation methods, optimizing water consumption in urban and industrial sectors, and promoting dam construction, Tehran-based English newspaper, Iran Daily wrote.
Cloud seeding is another method used to increase precipitation and solve the drought problems.
Although the issue of cloud seeding was first proposed in 1967, it became operational in 1997.
To get familiar with the process, advantages and disadvantages of cloud seeding, Iran Daily conducted an exclusive interview with Mohammad Mehdi Javadian-Zadeh, the head of the National Cloud-Seeding Research Center.
The full text of the interview follows:
IRAN DAILY: According to experts, in the last few years, rainfall has declined in dry areas and increased in areas with high rainfalls. Is this true? Why has the government decided to use cloud seeding to solve drought-related problems?
Javadian-Zadeh: This hypothesis is absolutely true. Climate change takes place in the long run and is accompanied by temperature declining in cold areas and rising in warm areas. Consequently, rainfall increases in areas with high rainfall and decreases in areas with low rainfall.
Because of climate change, rainfall will differ in different regions.
Surprisingly, the problem in Iran is not the change of rainfall volume, but the change from snowfall to rainfall.
Unlike rain, which turns into surface runoffs and has low capacity for storage, snow will melt throughout the year and is more useful for supplying water.
The runoff ratio has declined sharply due to the declining levels in water reservoirs or excessive use of underground water resources.
Assessments indicate average rainfall in Iran’s provinces is fairly adequate, but the problem lies in the form of precipitation, which was mentioned earlier.
Cloud seeding has a long history in Iran. Its executive plan was first proposed in Iran in 1967. In 1968, the plan was ratified as Iran Waters Law, which was not implemented until 1974 due to a number of reasons.
In 1974, Iran signed a contract with a Canadian company and in 1979 cloud-seeding operations were carried out in the plains of Tehran for the first time. However, when the Pahlavi regime was overthrown, the Canadian company left Iran.
In 1997, the National Cloud Seeding Research Center was launched in Iran.
In the previous water year (mid-September, 2014-May 21, 2015), cloud-seeding operations covered almost 11 provinces, which was unprecedented.
Q: What’s the criteria for selecting provinces for cloud seeding?
A: Since meteorology and weather systems are necessary for cloud seeding, only provinces equipped with weather radars can undertake the operations.
At present, three weather radars belonging to Energy Ministry in the Central Iranian Plateau cover parts of Kerman, Yazd, Isfahan and Fars provinces.
Seven other radars belonging to Iran Meteorological Organization are located in Tehran and western and northern provinces.
After the meteorological requirement is fulfilled, water companies announce the need for such operations to the governorate.
Ultimately, cloud-seeding operations will be launched after feasibility studies are completed.
Q: How many sorties were conducted for cloud seeding last year?
A: A total of 70 sorties were conducted in the year ending March 20. Cloud seeding is annually executed in Iran from mid-September till mid-May.
During this period, more cold clouds with seeding capacity are formed.
Q: What parameters are considered for selecting the clouds?
A: Clouds with sufficient moisture are appropriate for seeding. The height of cloud is also of significance. In addition, the thickness of clouds must be at least one kilometer.
Q: Under what circumstances, cloud seeding is aborted?
A: In addition to the criteria for selecting the clouds, we also have measures to stop the operations. In many cases, the conditions for cloud seeding were appropriate, but Iran Meteorological Organization stopped the operations. Because it was possible that cloud seeding would threaten the area with flood and hailstone.
Q: When were cloud-seeding operations last carried out? How many operations were allocated for Tehran?
A: Usually, operations begin from mid-October, but this year they were launched on January 5 and ended on May 10.
Flight permission must be issued by Iran Civil Aviation Organization (ICAO). Two AN−26 aircraft are considered for cloud seeding. They must be checked before getting the permission to fly.
This year, because the process of controlling the aircraft became longer, ICAO issued the permission after a two-month delay.
Eight sorties have been conducted for cloud seeding in Tehran since January 5.
Q: Do cloud-seeding operations create environmental problems?
A: Actually, cloud-seeding operations have a 60-year history in the world. During this period, a number of shortcomings were addressed. Experts argue that cloud-seeding operations have two negative impacts and proposed two questions:
The first question is whether cloud seeding in high-pressure areas lowers rainfall in low-pressure areas?
The second question is whether the materials used in cloud seeding have any adverse environmental impacts?
World Meteorological Organization, with over 180 member-states and territories, issues a statement on cloud seeding every four years. In the last statement released in 2007, it said, “cloud-seeding project has been examined and it showed that it causes no adverse impact. However, this does not mean countries must not study its impacts in future”.
Q: What was the scientific justification for rejecting the impacts?
A: Experts maintain that rainy clouds have the capacity of causing 10 percent rain. Based on the method used by us, this capacity will increase to 11-11.5 percent.
Thus, practically there will be no harm to the raining capacity of the clouds. In other words, it can’t be said that cloud seeding in high-pressure areas will decrease rainfall in low-pressure areas.
With respect to the second shortcoming, I'd say that the major material used in cloud seeding is silver iodide. The US, for instance, implements cloud seeding in all its states.
Weather Modification Association (WMA) conducted an extensive research on any destructive environmental impacts of silver iodide. After conducting numerous studies on regions where cloud seeding was used for 40 consecutive years, WMA announced that the said material has no destructive impact on soil, water, animals and humans, and thus it is not harmful to the environment.
Q: Which countries import the raw materials for silver iodide and what is the annual cost of cloud seeding in Iran?
A: Annually, $2.6 million to $3.3 million are spent on preparation, renting aircraft, purchasing the raw materials and upgrading the equipment.
At present, silver iodide is supplied by Russia, but recently, contracts have been planned with other silver iodide producers in India and China.
However, the current administration intends to manufacture the raw material for cloud seeding domestically.
Q: Which countries are using cloud seeding?
A: Although the US has the longest history in using cloud seeding, China and India also apply the method extensively.
Other countries, namely South Korea, Japan, Thailand and Syria, also use the method sporadically.
Q: To what extent cloud seeding has increased the water level of dams?
A: Once cloud seeding operations are completed, assessment is carried out, which lasts for six months.
Assessments have shown that in the last 10 years, the method caused a 15-percent increase in rainfall in target regions.
The rise in rainfall does not mean a rise in runoffs. An amount of rainwater will penetrate into the ground or evaporate. The volume saved in dams is then measured.
This measurable water is called 'recoverable water', which costs almost $0.006 per cubic meter.
Generally, the final cost of supplying water through cloud seeding is meager, compared to other methods, such as artificial feeding, dam construction, wastewater treatment and seawater desalination.
Q: Do these sorties pose any risk to the flight team?
A: Cloud-seeding sorties are very dangerous, because the team flies in dangerous weather conditions.
Cold clouds chosen for seeding are like an iceberg; in case they hit the aircraft, it will be completely destroyed.
It happened several times that despite weather forecast, we were surrounded by clouds, but fortunately we passed through them because of the pilot's skill.
Q: What are the future plans of Energy Ministry for cloud seeding?
A: Following the Energy Ministry’s directives, two five-year plans have been considered for expanding the cloud-seeding plan.
First, all regions viable for cloud seeding must be recognized and the aviation equipment must be upgraded.
Increasing the number of weather radars and using other cloud-seeding methods, such as those involving ground-based generators, is also on the agenda.
Q: How does the ground-based generator work?
A: These generators are installed in mountains. Once seeded clouds pass over them, these generators, fed with silver iodide, can create smoke by remote control, which will hit the clouds and trigger rainfall.
9060**1771
Tehran, May 11, IRNA - Since Iran is located in a low-rainfall region, the scourge of drought invariably strikes some parts of the country. This has created several social and economic problems in recent years.
