Annals of Arid Zonp.-23(4), 327-334,1984

Incidence of droughts and its impact on food productionin Rajasthan

G. G. S. N. RAo, Y. S. RAMA KRISHNA, B. V. RAMANARAO AND R. S. PUROHITCentral Arid Zone Research Institute, JOdhpur-342 003

ABSTRACT

Incidence and spread of drought over Rajasthan during the years 1972,1974 and 1979, were analysed on the basis of departures from the normal aridityindex during different months of the southwest monsoon season. Productivity ofpearlmillet and pulses was considerably affected by drought conditions. Theimpact of drought on fall in productivity of these crops is more pronounced inwestern Rajasthan than in easlern Rajaslhan. The study brought out that thevariations in the productivity of the rainfed crops can he explained satisfactorilyby the pattern of incidence and the spread of droughts.

INTRODUCTION

Failure of the monsoon rains leadingto drought conditions is more commonin the Rajasthan State. Work on the in-cidence and the spread of drought in thewestern Rajasthan by Rama Krishna andSastry (1980), Sastry and Rama Krishna(1982) and Sastry and Malakar (1982)indicated a pattern associated with theincidence and the spread of droughts.However, the above studies did not re-late the impact of droughts of differentintcnsities on the food pi oduction.

Th~ present paper reports the studyon the influence of incidence and thespread of drought in Rajasthan, on cropproduction during the years 1972, 1974

and 1979 when moderate to severedrought conditions prevailed.

MATERIAL AND METHODS

District averages of monthly rainfaIlfor all the 26 districts in the RajasthanState for the years 1972, 1974 and 1979were obtained from the daily rainfallrecords of the Rajasthan State: Monthlywater balance computation were done byusing the book keeping procedure ofThornthwaite and Mather (1955) to esti-mate actual evapotranspiration (AE),water deficit (WO) and water surplus(WS) during each month. The potentialevapotranspiration (PE) values estimatedby Rao et al. (1971) for different stations

328 : G. G. S. N. RAO et al.

in the Rajasthan State were used in waterbalance computations.

The incidence and the spread ofdrought from June to September duringthe drought years under study were ana-lysed after Rama Krishna and Sastry(1980). This technique is based on thedepartures of monthly aridity index (la)values from its normal value expressedin tenths of unit. The departure valuesfor each district from June to Septemberwere calculated and plotted on the mapto find out the incidence and the spreadof droughts. Agricultural crop produc-tion in the State during the drought yearsand the highest productions were notedfrom the'StatisticalAbstracts ofRlljasthan'and the' Agricultural Situation in India'.

RESULTS AND DISCUSSION

Incidence and spread of drought

The average rain fall in the State de-creased by 32, 18 and 7% dUJing thedrought years 1972, 1974 and 1979. res-pectively. Consequently 84, 68 and 86%of the total area was affected by droughtin the respective years in the State. Forthe entire country, 42 and 47% of thetotal area was affected by droughts in1972 and 1979 (Appa Rao et al., 1983).Departures of monthly Ia values expressedin tenths of units for the months June toSeptember for the year 1972. 1974 and1979 are presented in Figs. 1, 2 and 3,respectively. It is observed that highestvalues of the departures are first ob-served either in the eastern parts or inthe southern parts situated in the high

rainfall zones of the State. This is inagreement with the earlier findings (RamaKrisbna and Sastry, ) 9~O; Sastry andMalakar, 1981 and Rama Krishna et al.,1984) on the origi 11 and the spread ofdrought.

In 1972, departures of la greater than100 units were seen during June (Fig. 1)

in the eastern parts of the State compris-ing Alwar, Bharatpur, Sawai Madhopur,Kota and Jhalawar districts. During July,approximately 75% of the total area ofthe State was under the influence ofsevere drought which coincided with theactive growth period of tbe pearl milletand short duration pulse crops. Thp,production decreased by 44 to 88% and80 to 96% in case of the pearlmillet andshort duration pulses, respectively in thedrought core districts of the State viz.,Ajmer, Nagaur, Pali, Sikar and Jhunjhunu.Even though drought free conditionsexisted during August in most of thesedistricts with the drought core lying intbe extreme western districts of the State,it could not help in revIving the growthof the already drought affected crops. Inmany places, resowing was taken upduring August. The core, however, movedeastwards during S::ptember occupyingthe south-eastern parts of the State. Lateresowings during August and stressconditions during September contributedfor lower yields of the crops in 1972.

In 1974, departures of la valuesgreater than 200 units were observed inthe southern parts of the State duringJune (Fig. 2). By July entire arid regionwas under the influence of drought with

DROUGHT IMPACT ON FOOD PRODUCTION 329

the core lying over Ja lore district. Thecore remained in the same part of theState with an expansion into the adjoin-ing districts and a second core was ob-served in the north-eastern districts duringA ugust. Severe drought conditions inthe entire arid region during July andAugust have adversely affected the cropat the seedling and the vegetative stagesresulting in 67 to 100% and 76 to 100%fall in production of the pearlmillet andshort duration pulses. Fall in production

(55 to 78% in the pearlmillet and 47 to97% in pulses) was observed in the east-ern Rajasthan also as most of the areaexperienced drought free conditions onlyduring July and, to some extent, duringAugust and by September the whole Statewas under the influence of drought withthe core, which was in the south-westerndistricts earlier, moving eastwards intoUdaipur and Pali districts and the se-cond drought core in the north-easternparts getting further intensified. Thus,

330 : {J, G. S. N. RAO £'1 al.

the drought during the year ]974 wasprevalent mostly in the western parts ofthe Rajasthan State.

In the year ]979, excepting fOf nodrought conditions over a small patch inthe south-eastern parts of the RajasthanState, the rest of the State expel'iencedmild drought conditions with two cores- one situated in the north-western andthe other in the south-western sectors ofthe State. During Ju]y, the drought corein the north-eastern parts of the State

further intensified and moved slightlywestwards. The intensity of drought corelying in the south-eastern sector decreaseddue to good rainfall conditions. Majorityof the districts in the central and thesouth-eastern parts had drought freeconditions due to heavy rains (receivedduring the second fortnight of July)which caused flash floods in the Luniriver catchment area. During Augustthree distinct drought cores with varyingintensities in the north-eastern, easternand the south-eastern parts of the State

DROUf,IIT IMPACT ON FOOD PRODUCTION 331

covered more than 60% of the total areaof the State. Low intensity of droughtduring August in Harmer, Jodhpur,Jaipur, PaJi and Alwar districts resultedin slightly higher production compared tothe drought affected districts in otherparts of the State. The decrease in pro-duction of pearmiJIet and pulses in thedrought affected districts was 68 to 98%and 73 to 96%, respectively. In additionto droughts, the damage caused by floodsand delayed sowing might have also con-tributed significantly to the Jaw produc-tion of agricultural crops during 1979.

Impact On food production

Although the average rainfaJl of t~~State was only 7% less than its normalvalue during 1979 it appears to be severecompared to tbat during 1972 and 1974.The overaJl fall in production of thepearl millet was 86% and in pulse crops89% (Table 1). Compared to the pro-duction during 1970, the Jowar andmaize production was lower by 69 and37%, respectively in the eastern Rajas-than. This is due to the fact that 86%of the total area of the State was affectedby drought and also by floods, in certain

332 (,, cr. S. N. RAn et al'.

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DROTIGHT IMPACT ON FOOD PRODTtCTlON : 333

districts. During the drought year, fallin production of both pearl millet andpulse crops was very high in the westernRajasthan which contributes significantlyto the total crop production of the State.Fall in production amounted to about1.5 to I.R million tonnes/year in pearlmillet and 0 35 to 0.39 million tonnes/year in pulses in the western Rajasthanand 0 25 to 051 million and 34 to 96thousand tonnes/year in pulses in theeastern Rajasthan (Table 1).

The yields of the pearl millet and thepulses in the eastern Raj'lsthan Wen~threeto five times higher compared to theyields in the western Rajasthan. The de-crease of yields in the State during threedrought years varied from 61 to 92% inthe pearlmiIJet and 71 to 86% in pulsecrop. Decrease of 16 to 69% and 29 to45% in Jowar and Maize were recordedduring drought years in the easternRajasthan.

The study clearly confirms the earlierfindings on the origin and spread ofdrought in the Rajasthan State and canbe used, by further studying its probabili-ties, for forecasting the spread of droughtin different regions. In the absence ofweekly meteorological data, the departureof monthly la from its normal values canbe utilised for assessing the impact ofdrought on regional crop production.The fall in production, to thetune of 1.5 to I 8 million tonnes inthe pearlmillet and 0.35 to 0.39 miliiontonnes in the pulse crop in the westernRajasthan during drought years show that

the impact of drought On food productionin the western Rajasthan is mor.e pro-nounced as compared to the easternRajast han,

REFERENCES

Appa Rao, G .• Abhyankar, V. P. andMahajan, A. V. 1981. Analysis of1979 kharif agricultural droughtsover India. India MeteorologicalDepartment Scientific Report No.81/2.

Rao, K. N., George, C. J. and Rama-sastry, K. S. 1971. Potential evapo-transpiration over India. India Me-teorological Department ScientificReport No. 136.

Rama Krishna, Y. S. and Sastry,A. S. R. A. S. 1980. Studies on in-cidence of droughts over westernRajasthan. National GeographicalJournal of India. 26 (I & 2) : 44-49.

Rama Krishna, Y. S., Sastry, A.S.R.A.S.,Rao, G. G. S. N. and Ramana Rao,B.V. 1984. On prediction of droughtin Indian arid region. Mausam35 (3) : 353-358.

Sastry, A. S. R. A. S. and Malakar, A. R.1981. Climatological analysis ofdrought over northwest India duringthe year 1979. Mausam 32 (3) :259-262.

Sastry, A. S. R. A. S. and Rama Krishna,Y. S. 1982. Drought during 1979over western Rajasthan - a climaticperspective. Ann. Arid Zone. 21U): 41-47.

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Subrahmanyam, V. P. 1967. The prob-lem of illcidence and spread ofcontinental drought. Technical Notew. M. 0., I. M. D.-II, Geneva.

Subrahmanyam, V. P. and Sastry, C. V. S.1971. New techniques in drought

analysis. Ann. Arid Zone. 10: 120--155.

Thornthwaite, C. W. and Mather, J. R1955. The water balance. DrexelInstitute of Technology, Report8 (1), 104 p.