Cloud Seeding Experiments in Andhra Pradesh

 

Dr. J. V. M Naidu,

Director, Cyclone Warning Centre, Visakhapatnam

E-mail: [email protected]

and

 Prof. T. Shivaji Rao,

Director, Centre for Environmental Studies,

GITAM Engineering College,Visakhapatnam-45

E-mail: [email protected]

 

 

The South West Monsoon rains of the year 1987 failed in India creating one of the worst drought years of the century. The All India rainfall during June to September in this year  was of 81% of the normal. During this period Andhra Pradesh also experienced drought conditions in coastal districts with a rainfall of 68%  of the normal while Rayalaseema and Telangana had a normal rainfall for the season. However, then the State Government took a decision to experiment on augmentation of water resources so as to face any future threat to the water resources. Fortunately the 3 cyclonic storms that crossed coastal Andhra Pradesh in October and November 1987 gave copious rainfall abating the drought conditions.  

 

The Forest Department of Government of Andhra Pradesh conducted a seminar in March 1988 on Artificial Rains and Aerial Seeding to update the knowledge on Artificial rain making with a committee headed by Hon’ble Minister for Forests, Government of Andhra Pradesh as the Chairman. This committee  included experts like Prof. P. Koteswaram, former Director General of Meteorology, Prof. T. Shivaji Rao, Prof. of Environmental Engineering, Andhra University, and Sri. J. Raja Rao, former Secretary to Irrigation as members. To implement the resolutions  of the report on artificial rain a Government order was issued through G.O.Ms.No.178,dt.9-6-1988 ENERGY,FOREST, ENVIRONEMNT, SCIENCE & TECHNOLOGY DEPARTMENT, Government of Andhra Pradesh http://www.geocities.com/jvmnaidu/actionplan.html. The report presents some  results on cloud seeding experiments carried out by Dr. A. S. R. Murthy and his team during 1979 to 1986  at Indian Institute of Tropical Meteorology, Pune.

 

Subsequently under the supervision of Dr. P. Sanakara Rao, Hon’ble Minister of Irrigation, Government of Andhra Pradesh some trial experiments were conducted  on cloud seeding using silver iodide (AgI) . In the ground  based generators the coke was burnt to reach a temperature about 1200^oC where the silver iodide is burnt in small quantities 5 –10 gm  so that it becomes  vapour and gets into the developing cumulus cloud. Prof. T. Shivaji Rao was closely associated with the experiment while the necessary meteorological information was supplied by Meteorological Centre, Hyderabad.

 

The experiments were conducted at twin lakes of Hyderabad.  The results showed an increase of 2ft water level in Osmansagar where the ground generators were located on the southwest/western side of the catchment area.  Silver was detected in traces in the samples of rainwater collected in the catchment area.  Conspicuously the Himayat sagar lake which is part of the twin lakes located on the other side of the ridge line did not report any increase in the water levels.  They indicated the first success of the experiment conducted in July 1993. 

 

The second experiment was conducted in Anantapur, the drought prone district of Andhra Pradesh under the supervision of – Hon’ble Minister Paritala Ravi , Minister for Labour,  under the instructions of the  then Chief Minister Sri. N. T. Rama Rao. The experiments were same as ground based generators of burning AgI, as carried out at twin lakes of Hyderabad.   The experiment conducted in July 1995 for 16 days, yielded some interesting results with a record rainfalls of 95mm  reported at 0830 hrs IST of the next day of seeding at Anantapur on 27^th July 1995 shown in Table-1A. The increase in monthly rainfall in July and August to a tune of more than 100% of the normal indicate that the rainfall has substantially increased due to cold cloud seeding from the ground based generators. The meteorological information was provided from Meteorological office, Bangalore.

 

 

Table-1A  DETAILS OF EXPERIMENTS CONDUCTED FOR ARTIFICIAL RIANS IN ANANTAPUR  IN 1995

 

 

Table 1B. RAINFALL INCREASE IN SEEDED MONTHS OF JULY AND AUGUST 1995

 

For all the above experiments the following criteria was adopted as thresholds viz., 1.The relative humidity at ground level to be >  75%,  2) the base of the cloud shall be within 1 to 1.5 km from the ground,  3) the height of the cloud was more than 5 km. 4) the surface wind speed less than 15 kmph. The generators were located at the distance 15 to 20 km apart in the West or Southwest sectors of the targeted area.

 

Although success was seen, the experiments were not continued as the South West Monsoon was normal for subsequent years since 1988 . Obviously this weakened the project of cloud seeding as most of the reservoirs continued to maintain some good levels. 

 

The 2002 southwest monsoon had been below normal leaving vast areas of Andhra Pradesh under deficit rainfall category.  Most of the reservoirs under river Krishna in Andhra Pradesh were nearly at the dead storage levels by September 2002.  The Cuddapah district recorded the lowest of 53% while Anantapur and East & West Godavari districts of coastal Andhra Pradesh recorded 57% of the rainfall for the monsoon season. As the rainfalls in Krishna river catchment were also around 70% , the water was  not released to Andhra  Pradesh from Karnataka. This created  wide spread  wilting of  already transplanted  paddy in many of the fields.

 

At the middle of October 2002 the water availability  for the city of Visakhapatnam at the reservoirs was for 100 days while the requirement was for 260 days till next Monsoon.  Consequently under the direction of Prof. T. Shivaji Rao, Visakhapatnam Municipal Corporation conducted both warm and cold cloud seeding in the catchment areas of the reservoirs on a trial basis on 12, 13 and 14^th October 2002.   The ground generators were used, burning silver iodide of about 500 grams on Simhachalam hills at a height of 500 meters above the ground level on 12^th ,13^th  and 14^th during the afternoon hours from 3 to 5  p.m. On 14^th at 08.30 hrs observation of Visakhapatnam air port recorded a  rainfall of 37 mm and at Waltair it was 30.6 mm. The rainfalls on 13^th and 15^th were of  a few millimeters in the city.

 

The rainfall collected from Mandal Headquarters in the district showed good rainfalls ranging up to 133 mm with in about  40  km from the seeded area where sodium chloride of 200 kg was sprinkled at 2 to 3 km height using helicopters. The aerial spraying was done  up  to 40 km distance from Visakhapatnam   in the west and southwest sectors.  The rain falls in  several   places ranged from a few mm to 133 mm. At Nathavaram, located at about 80 km southwest from Visakhapatnam and 40 km from warm cloud seeded area the highest rainfall of 133 mm was recorded on 14^th.  This is also the highest Rainfall recorded in the district during  the month.   The rainwater samples collected at various sites in the seeded areas showed silver up to 10 micrograms/liter, which is well below the safe limit of 50 micrograms/liter as prescribed in USA. 

 

The weather conditions prevailed on this day were a trough of low  pressure area over Bay of Bengal off coastal Andhra Pradesh. The Precipitable water content on these days ranged from 4 to  6 cm in unit area. The conditions were favourable with good  updraft and with overcast skies. The surface winds were also less than 20 kmph during most of the times at Visakhapatnam. 

 

All these trial experiments indicate an augmentation in the rainfall due to cloud seeding which need to be exploited.  The experiments conducted by IITM, near Pune showed an increase of rainfall of 24% in the semi arid areas near western ghats.  Such experiments in the coastal areas may yield better rainfalls in view of high moisture content and frequent conditions of updraft associated with low pressures/depressions.  Although the number of days, that are  favorable for cloud seeding in a drought year are low one has to explore this possibility of augmenting the  rainfall so as to protect the wilting crops and to  increase water resources. At present the Krishna and Cauvery delta for the Kharif crop has already suffered severe crisis which may likely to continue even for Rabi.  The hydro electric power production has become negligible which would be continuing  till July 2002 , when there are substantial  inflows from  catchment areas of  the reservoirs.

 

 In the years to come with the increase of population there may be a severe stress on the water resources as envisaged by Prof. Shivaji Rao. Vide    http://www.bbc.co.uk/dna/360/A787656, http://www.bbc.co.uk/dna/360/A788628   given  in tables 2 and 3. 

 

Table – 2 FOOD-SHORTAGE FORECAST IN INDIA FOR “2025 to 2050 A.D”.

 

 

 

The present storage capacity of reservoirs in the country  is about 200 billion cubic meters. 

 Assuming the utilisation to be one and half times of the storage the  reservoirs

the short fall at present is about 30% of the demand   for irrigated crops in the country which will increase  in the years to come.

 

 

Table-3 FOOD SHORTAGE IN SOUTH INDIAN STATES (1991-2050) Population, Rice Demand, Production and Deficit

 

 

     

 

 

NOTE: Population  (in Millions);  Rice production, Demand and shortages (in Million tons);

Pop(Population), dem(Demand), Prod(Production), def(Deficit)

 

So obviously there is an urgent need to look into management and augmentation for water resources so as to have a sustained growth and better disaster preparedness.  Scientists and Engineers should give more thinking on this lines.

 

Some useful Reference sites on cloud seeding:

http://www.nawcinc.com/wmfaq.html

http://www.xmission.com/~nawc/wm.html

http://www.dar.csiro.au/publications/cloud.htm

http://cloudseeding.dri.edu/Program/Synopsis.html

http://www.swc.state.nd.us/arb/graphics/QandA.pdf

http://dir.yahoo.com/Science/Earth_Sciences/Meteorology/Weather_Modification/

http://www.license.state.tx.us/weather/summary.htm

http://www.wmo.ch/web/arep/guidelines_wm.html

http://www.rap.ucar.edu/staff/vidal/seeding/