SEASONALTRENDANDSPATIALPATTERNOFRAINFALLIN MYSURUDISTRICT
Dr SarithaK. AssociateProfessorofGeography,GovernmentFirstGradeCollege,K.R.Nagara,MysuruDistrict,Karnataka–571602
ABSTRACT
ThetermRainfallreferstotheamountofrainthatfallsinaplaceduringaparticularperiod.Mysurudistricthasreceivesonanaverageannualrainfallis778.4mmfrom 1990to2018.ItwasvarieswithseasonsaswellasinSpatial.ThereforethepresentpaperanalysetheSeasonalandSpatialtrendofRainfallinMysuruDistrict, forthis purpose 40 (2018) rain gauge locations Monthly rainfall data has been collected between 1990 to 2018 from District Statistical Office, Mysore. Here, Simple statistical tools like percent, average and statistical techniques like Index of concentration are used and the cartographic and Arc GIS software are used for the preparationoftrendlinesandmapsrespectively Theresultfoundthatinseasonwiseonanaverageabout47%ofannualrainfalloccursduringtheSouthwestmonsoon period,itisonlylessthan1percentinwinterorpostmonsoonseason.Thepremonsoonrainfallismoreconsistencethanthepostorwinterseasonrainfall. Inspatial level,alltalukreceivesthehighandlowrainfallinSouthwestmonsoonseasonandwinterseasonrespectively
Keywords:Rainfall,Season,Region,Indexofconcentration(IOC)
1.0:Introduction
ThetermRainfallreferstothe“amountofrainthatfallsinaplaceduringaparticularperiod”.Rainfallisanimportantelementofeconomicgrowthofanareaor region, especially in a country like India, where a large number of people are occupiedinagriculturalactivities. Inourstudyareatheamountofrainfalldoes notshowanequaldistribution,eitherinspace/region,seasonorintime. Itvaries fromheavyraintoscantyindifferentpartsofMysurudistrict.Italsohasgreatseasonalandspatialvariationsindistribution.Therefore,thestudyofrainfallspatial distributionanditsseasonalrhythmsisveryimportant,asthedistricteconomyis highlydependentonagriculture.
2.0:Studyarea: Thestudyareaextendsfrom11°44'to12°37'Northlatitudes and75°57'to77°12'Eastlongitudes. ItisboundontheNorthbyMandyaand part of Hassan districts and on the East by Chamarajanagar Kodagu forms its western boundary and the southern portion is covered by Kerala and part of Chamarajanagardistrict. ThetotalgeographicalareaofMysoredistrictis6,241 km2.Thedistrictgetsmorerainfallduringtwoseasons,namely,theSouthwest monsoonorRainyseasonduringJunetoSeptemberandNortheastorretreating monsoonseasonduringOctoberandDecember
Map:LocationmapofMysuruDistrict
3.0.Objectives:Thepresentpaperhasthefollowingobjects.
Ÿ ToanalysetheDeterminefactorsofrainfallinMysurudistrict.
Ÿ ToexaminetheSeasonaltrendandspatialpatternsofrainfallinMysuru Districtfrom1990to2018.
4.0.MethodsandMaterials: Thepresentstudyispurelybasedonthesecondary source of information. The data related to the rainfall at rain gauge station levelhavebeencollectbecausetheaverageannualorseasonalrainfallataplace doesnotgivesufficientinformationregardingitscapacitytosupportanydecision-makingprocess.Therefore,keepingthatinmind40raingaugestationsrainfalldatahasbeencollectedfrom1990to2018fromtheDistrictStatisticalOffice, Mysore.ButtheRaingaugestationsnumbersarevariesinsomeyears.Mysuru District has 49 (07) Rain gauge station in 1990, it was decreases to 48 (08) in 2010andfurtherdecreasesto41(02)in2010.
Theresearchershavebeenusingvariousstatisticalmethodsandtechniquesfor theanalysisofSeasonalandspatialtrendsofrainfallinMysurudistrict.Suchas average, Index of Concentration etc. Use the cartographic techniques andArc GISsoftwareforthepreparationofgraphsandmapsrespectively
mediumorformat)andAdapt(remix,transform,andbuilduponthematerial)undertheAttribution-NonCommercialterms.
Map.4.0:LocationofRaingaugeStationsinMysurudistrict
6.0.Discussion:
6.1:DeterminationfactorsofrainfallIMysurudistrict: Mysuru district is an admistrative district it located in the Southern part of the Karnataka state it consists of 7 taluks such as Heggada Devena .Kote, Hunsur, Krishna Raja Nagara, Mysuru, Nanjangud, Periyapatna and Tirumakudalu Narasipura. From the last 29 years Mysuru district received on an average 774.5mmrainfall,itisvariouswithinthedistrict.Thehighestandlowestaverage rainfallfoundinPeriyapattanaandNanjangudTaluksrespectively
In Mysuru district the amount of rainfall is mainly determined by the physical variablesoftheTalukslikelocation,elevation,andforestcoverareasetc...
InMysurudistricttheamountofrainfallgraduallydecreasesfromWesttoEast directionthereforethewestdirectiontaluksofthedistrictlikeH.D.Kote,Hunsur, Periyapatna received above district average rainfall with 852.7, 830.7 and 856mmrespectivelyandtherestofthetalukslikeK.R.Nagara,NanjanguandT NarasipuraarelocatedintheNorthandEastdirectionthereforetheyarereceived belowdistrictaveragerainfallwith747.9683.6and721.1mmrespectively(see location Map). The taluk like Mysuru located in the centre of the district as a resultitsaveragerainfall(774.7mm)isequaltothedistrictaverage.
The amount of the rainfall is also influenced by the elevation of theTaluks. In Mysurudistrictthemealsealevelofthelandisgraduallydeceasesfromwestto east direction. The taluks like Periyapatna, Hunsur H.D.Kote and K.R.Nagara arelocatedat849,792,694and788meterabovetheMeanSealevelrespectively and the east direction taluks like Mysuru, T.Narasipura and Nanjangude are locatedat770,638and657meterabovethemeansealevel.Therefore,theelevated taluks received the above district average rainfall remaining taluks receivedthebellowdistrictaveragerainfall.
Anotheronemostimportantvariabletodeterminetheamountoftherainfallin Mysurudistrictisforestorvegetationcoveredarea.Thepercentofforestareato thetotalGeographicalareaisalsodecreasedfromwesttoeastdirectionofthedistrict. The forest area of district comes under the Mysuru circle. Mysuru circle comprisesthreeterritorialdivisions,namely,Mysuru,MandyaandHunsurforestdivisions. AmongtheseterritorialMysuruandHunsurforestdivisionscomes undertheMysurudistrict.
MysuruforestdivisionissituatedinthesouthernpartofKarnatakastate,andit consists of taluks like Mysuru, T Narasipura, Nanjangud and H.D. Kote. The totalextentofforestareaofthedivisionis16,037hectareswhichconstituteonly about3.73oftheGeographicalareaofthedivision(4,300Km²).Therestofthe talukslikeperiyapattna,HunsurandK.R.Nagaracomesunderthehunsurforest divisions.TheextentofnotifiedforestsofHunsurdivisionis13,636.95hectares which constitute about 5.6 of the Geographical area of the division (2,432.91 Km²). It indicates the western taluks have nearly one to double forest area compere with eastern taluks of the Mysuru district. Therefore, western taluks receivedabovethedistrictaverageandeasterntaluksreceivedthebelowthedistrictaveragerainfall.
Source: Compiled by the author
Overall,inMysuredistricttherhythmsofrainfallaredeterminedbythelocation, elevationandforestcoverareaofthetaluks.AllthesevariablesaremorefavourableinwesterntalkuslikePeriyapattna,HunsurandK.R.NagaraandunfavourableineasterntalukslikeT.Narasipura,NanjangudandH.D.Kote.Therefore, thetalukesPeriyapattna,HunsurandK.R.Nagarareceivedtheabovedistrictaveragerainfallfromthelast29yearsandtherestofthetaluksreceivedthebelowthe districtaveragerainfall.Abovethetable6.0andMap6.0shownthattheconcentrationofrainfallfromthelast29years.Accordingtothesetableandmapabove thedistrictaverage,belowthedistrictaverageandnormalrainfallconcentrated inthewesterntaluks,easterntaluks,andcentretalukofthedistrictrespectively
6.2:TheSeasonaltrendandspatialpatternsofrainfallinMysuruDistrict from1990to2018.
TheMetrologicaldepartmentofOldMysorestateandtheMetrologicalcentreof Bengaluruhavedividedtheyearintofourseasons.Theyare:
1. WinterorColdweatherorPostMonsoonSeason:JanuarytoFebruary
2. SummerorHotweatherorPre-MonsoonSeason:MarchtoMay
3. SouthwestMonsoonSeason:JunetoSeptember
4. RetreatingorNortheastMonsoonSeason:OctobertoDecember
Source:Compiledbytheauthor
Table 6.1: Seasonal and Spatial trend of Rainfall (in MM)in Mysuru District between1990and 2018
In season wise on an average about 47% of annual rainfall occurs during the Southwestmonsoonperioditisonlylessthan1percentinwinterorPostMonsoonseason.ThePre-Monsoon/Summerseasonrainfallismoreconsistencethan thepostorwinterseasonrainfallinthedistrictandalltaluks.
6.2.1:TalukwiserainfalldistributioninwinterorcoldweatherorpostMonsoon season
In winter season,Taluks like H.D.Kote, Hunsur and Mysuru received the high rainfallwiththevalueofabove1.0ofIndexofconcentration.Remainingtaluks receivedthelowrainfallwithlessthan1.0ValueofIOC.
compiledbytheauthor
Table6.2:Taluk wiseDistributionofRainfallbetween1990to2018
InregionallevelalltalukreceivesthehighrainfallinSouthwestmonsoonperiod andlowestrainfallinwinterseason. Rainfallsgenerallydecreasefromwestto east therefore taluks like Periyapatna, H.D.Kote and Hunsur receives the high rainfall.MysuruandK.R.Nagarareceivestheaverageandremaningtalukslike T.NarasipuraandNanjangudreceiveslowrainfall.
Table.6.4:SpatialdistributionofRainfallinSummerSeason
Table.6.3:SpatialdistributionofrainfallinWinterseason
6.2.2: Taluk wise distribution of rainfall in summer or hot weather or PreMonsoonseason
Duringthesummerseason,H.D.KoteandMysurutaluksreceivedthehighrainfall with above 1.0 Value of Index of concentration. Hunsur and Periyapatna talukreceivednormalrainfallwith1.0IOCvalue.K.R.Nagara,Nanjangudand T NarasipuraTaluksreceivedthelowrainfallwithlessthan1.0IOCvalue.
6.2.3:TalukwisedistributionofrainfallinSouthwestMonsoonSeason
MysurudistrictreceivedthehighrainfallduringtheSouthwestMonsoonseason andtheamountofrainfallisgraduallydecreasedfromsouthwesttonortheast direction of the district. The taluks are located in SW direction have hills and goodforestresourcessuchasNagaraholle,Bandipura, Thereforethetaluklike Periyapatna,H.D.KoteandHunsurreceivehighrainfallwithabove1.0valueof IOC, Mysuru receive average with 0 92 And remaining taluk such as K.R.Nagara, Nanjangud,and T.Narasipurareceiveslowrainfallwithbelow1.0 valueofIOC duetotheirlocation.
unscientific practises ofAgriculture methods, lack of propare management of rainfall.Therfeore,Governmentandotherspanningauthoritiesgivemoreattentiontotheseareasandtrytocontrolthedeforestionandpramotetheaforestion otherwiseshortlyourstatekarnatakaconvertedintodesertland.
REFERENCES
1. B.Mahalingamet.al(2014):“Rainfallvariabilityinspaceandtime,AcaseofMysore district, Karnataka, India”. Current Trends in Technology and Science ISSN: 22790535.Volume:3,Issue:3(Apr-May 2014).
2. Dr.Ranganath(2022):“GeographyofKarnataka”,Mysurubookhouse,pp30-45.
3. Dr.Saritha.K: “Regional Rhythms of Rainfall in Mysuru District, Karnataka. India”, UGCcarelistJournal,science,TechnologyandDevelopment.ISSN:0950-0707,VolumeXIssueVIJune2021.
4. Jayawardene,Sonnadara,Jayewardene(2005):“TrendsofRainfallinSriLankaover theLastCentury”,SriLankanJournalofPhysics,Vol.6,pp:7-17
5. Karnatakastategezetteer,part-I(1982):GovernmentofKarnataka.pp66-75.
6. Khan,Asim (2000):ASpatio – TemporalAnalysisof rainfall in the canal command areasoftheIndusplains,InternationalWatermanagementInstitute,ReportNo:R-104 pp:1-35.
Table.6.6:SpatialdistributionofrainfallinNorthwest Monsoonseason
6.2.4:TalukwisedistributionofrainfallinRetreatingorNortheastMonsoonseason
In Retreating or Northeast Monsoon season Hunsur, K.R.Nagara, Mysuru and T.NarasipuraTaluksreceivethehighrainfallwithabove1 valueof IOC value. H.D.Kote,PeriyapatnaandNanjangudtaluksreceiveslowrainfallwithlessthan 1valueofIOC.
OveralltheseasonalandspatialrythamsofrainfallinMysurudistcirtfromthe last29years.ThetalukslikePeriyapatna,H.D.Kote,HunsurAndMysurutaluks receivesonanaverageabovethedistrcitaverageofveryhigh,highandnormal rainfall. The rest of taluks like K.R.Nagra, T.Narasipura and Nanjangud receivedthebelowonanaveageofhighandaboveonanaverageoflowandvery lowrainfallofthedistrictduetotheirlocation.
7.0:Findings
Ÿ Inourstudyarea,thelocation,elevationandforestcoveredareaditermine theamountoftherainfall.Theforethehighaltitudeandhugh forestarea coveredtalukreceivedthehighandtherestofthetaluksreceivedthenormalormrginalnormalrainfall.
Ÿ Mysurudistrictreceivesanaverageannualrainfallis778.4mmfrom1990 to2018.Itisvariouswithseasonsaswellasinregion.
Ÿ Inseasonwiseonanaverageabout47%ofannualrainfalloccursduring theSouthWestmonsoonperioditisonlylessthan1percentinWinteror PostMonsoonseason.
Ÿ InregionlevelalltalukreceivesthehighrainfallinSouthWestmonsoon periodandlowestrainfallinWinterseason.
Ÿ The rainfall generally decreases from West to East as a result taluk like Periyapatna,H.D.KoteandHunsurreceivesthehighrainfallandremainingtaluksreceivesthelowrainfall.
8.0: Conclusion: In our study area the amount of the rainfall is mainly determinedbytheLocation,altitude,forestareaandurbanizationprocessect.. andit variousfromoneseasontoseasonandregiontoregion.Karnatakaisthesecond high drought prone area after the Rajashan in India due to the deforestation,