VISVESHWARAIAH TECHNOLOGICAL UNIVERSITY,BELGAUMS.D.M COLLEGE OF ENGINEERING &TECHNOLOGYDepartment of Civil EngineeringPROJECT REPORT ONSTUDY ON WATER REQUIRMENT OFCROPS FOR HUBLI AND DHARWADTALUKASUnder The Guidance OfDr A.V.SHIVAPURProf I T SHIRKOLSubmitted byAMRUT KULKARNI 2SD01CV001ANUP SHIRHATTI 2SD04CV003SHIDDAPPA PUJAR 2SD04CV016SHIVARANJAN PATIL 2SD04CV018S.D.M COLLEGE OF ENGINEERING &TECHNOLOGYDHARWAD-02Department of Civil EngineeringCERTIFICATEThis is to certify that the project report entitled Study on Water Requirement ofCrops for Hubli and Dharwad Talukas is a bonafide work carried for fulfillment forthe award of degree Bachelor Of Engineering in Civil Engineering of theVisveshwaraiah Technological University, Belgaum during the year 2007-2008.The project report has been approved as it has successfully satisfied theacademic requirements with respect to the seminar work prescribed for theBachelor of Engineering Degree.. .Project Guides: HOD Civil DeptProf. Dr A V SHIVAPUR, Dean I.S.P.D. Prof I T SHIRKOL PRINCIPALACKNOWLEDGEMENTCulmination of a PROJECTis that stage which makes the transformation a meretheoretical ideaintoavisiblereality. Our report acknowledgessomeguidance, someprovision and a lot of inspiration. It is time nowto acknowledge our obligations to allwho have extended their co-operation all along our study tenure.Wewishtoplaceonrecordour profoundprivilegeanddeepsenseof gratitudetoProfessor Dr A V SHIVAPUR and Professor I T SHIRKOL , Civil Department of theirwholehearted guidance without which this endeavor would not have been possible.Our grateful regards are also due, to Prof. V. S. HEGDE HOD, Civil Department for hiscontinuous support and inspiration to us, which contributed to our success.Wealsoextendour warmest regardstoUAS(UNIVERSITYOFAGRICULTURALSCIENCES), Dharwad and Tahashildar Office Dharwad and Hubli for continuoussupport which we will be always indebted.Lastly, with unquantifiable affection and reference we wish to express our sincerefeelingstoourparents, familymembersandfriendsintheformofwords, whicharerestrictive in expression and quantum.CHAPTERSCONTENTS PAGENO1.0 OBJECTIVES 12.0 INTRODUCTION 23.0 FACTORS AFFECTING EVAPO-TRANSPIRATION 33.1 WEATHER PARAMETERS 43.2 CROP FACTORS 43.3 WATER MANAGEMENT 43.4 CROP COEFFICIENTS 53.4.1 KC (CROP CO-EFFICIENT) 53.4.2 WATER STRESS COEFFICIENT (KS) 54.0 STUDY AREA 65.0 SOURCES OF DATA 86.0 DATA CONVERSION 107.0 METHODOLOGY 147.1 BLANEY CRIDDLE METHOD 157.2 THE STEP BY STEP COMPUTATION BY BLANEY-CRIDDLE FORMULA 167.3 PENMAN MONTIETH EQUATION 207.3 1 CALCULATION PROCEDURE 218.0 CO-EFFICIENT FOR BLANEY CRIDDLE EQUATION 369.0 CONCLUSION 3810.0 SCOPE 3911.0 BIBLIOGRAPHY 39LIST OF TABLESTABLES PARTICULARS PAGENO1.0 METEOROLOGICAL DATA 2004 102.0 METEOROLOGICAL DATA 2005 103.0 METEOROLOGICAL DATA 2006 114.0 METEOROLOGICAL DATA 2007 115.0 AGRICULTURAL WATER REQUIREMENTS 126.0 MEAN DAILY PERCENTAGE (P) OF ANNUAL DAYTIME HOURS FOR DIFFERENTLATITUDES 187.0 CALCULATION SHEET 238.0 COMPUTATION OF ATMOSPHERIC PRESSURE BASED ON ALTITUDES 289.0 COMPUTATIONS OF PSYCHOMETRIC CONSTANT 2910.0 SLOPE OF VAPOR PRESSURE CURVE () FOR DIFFERENT TEMPERATURES 3011.0 NUMBER OF THE DAY IN THE YEAR (J) 3112.0 DAILY EXTRATERRESTRIAL RADIATION 3213.0 NO OF SUNSHINE HOURS DAILY 3314.0 STEFAN-BOLTZMANN LAW AT DIFFERENT TEMPERATURES (T) 3415.0 SATURATION VAPOR PRESSURE 3516.0 WATER REQUIREMENT USING VARIOUS METHOD FOR DHARWAD 3617.0 WATER REQUIREMENT USING VARIOUS METHOD FOR HUBLI 3718.0 TOTAL WATER REQUIREMENT 38LIST OF FIGURESFIGURES PARTICULARS PAGENO1.0 EVAPOTRANSPIRATION CONCEPTS 052.0 STUDY AREA: HUBLI-DHARWAD 073.0 GIS INTERPRETATIONS 094.0 WATER REQUIREMENT FOR BLANEY-CRIDDLE 165.0 WATER REQUIREMENT FOR PENMAN EQUATION 26Civil Engineering, SDMCET DHARWAD11 OBJECTIVES- To d e t e r mi n e t h e wa t e r r e q u i r e me n t o f v a r i o u s c r o p s u s i n g mo d i f i e dp e n ma n me t h o d ( a s s u g g e s t e d b y FAO) a n d c o mp a r e t h e wa t e rr e q u i r e me n t o b t a i n e d b y Bl a n e y- Cr i d d l e me t h o d .- To s u g ge s t a s u i t a b l e mu l t i p l yi n g c o - e f f i c i e n t f o r Bl a n e y- Cr i d d l ee q u a t i o n f o r Hu b l i a n d Dh a r wa d t a l u k a s .Civil Engineering, SDMCET DHARWAD22 INTRODUCTIONWa t e r r e q u i r e me n t i s a c o mb i n a t i o n o f t wo s e p a r a t e p r o c e s s e s s o i le v a p o r a t i o n a n d e v a p o - t r a n s p i r a t i o n . Wh e r e t h e e v a p o r a t i n g s u r f a c e i s t h es o i l s u r f a c e , t h e d e g r e e o f s h a d i n g o f t h e c r o p c a n o p y a n d t h e a mo u n t o fwa t e r a v a i l a b l e a t t h e e v a p o r a t i n g s u r f a c e a r e o t h e r f a c t o r s t h a t a f f e c t t h ee v a p o r a t i o n p r o c e s s , wh e r e t h e i n t e r v a l b e t we e n r a i n s a n d i r r i g a t i o nb e c o me s l a r ge a n d t h e wa t e r c o n t e n t i n t h e t o p s o i l d r o p s a n d t h e s o i ls u r f a c e d r i e s o u t . Un d e r t h e s e c i r c u ms t a n c e s t h e l i mi t e d a v a i l a b i l i t y o fwa t e r e x e r t s a c o n t r o l l i n g i n f l u e n c e o n s o i l e v a p o r a t i o n . I n t h e a b s e n c e o fa n y s u p p l y o f wa t e r t o t h e s o i l s u r f a c e , e v a p o r a t i o n d e c r e a s e s r a p i d l y a n dma y c e a s e a l mo s t c o mp l e t e l y wi t h i n a f e wd a ys .Ev a p o r a t i o n a n d t r a n s p i r a t i o n o c c u r s i mu l t a n e o u s l y. Ap a r t f r o mt h e wa t e ra v a i l a b i l i t y i n t h e t o p s o i l , t h e e v a p o r a t i o n f r o ma c r o p p e d s o i l i s ma i n l yd e t e r mi n e d b y t h e f r a c t i o n o f t h e s o l a r r a d i a t i o n r e a c h i n g t h e s o i ls u r f a c e . Th i s f r a c t i o n d e c r e a s e s o v e r t h e gr o wi n g p e r i o d a s t h e c r o pd e v e l o p s a n d t h e c r o p c a n o p y s h a d e s mo r e a n d mo r e o f t h e gr o u n d a r e a .Wh e n t h e c r o p i s s ma l l , wa t e r i s p r e d o mi n a t e l y l o s t b y s o i l e v a p o r a t i o n ,b u t o n c e t h e c r o p i s we l l d e v e l o p e d a n d c o mp l e t e l y c o v e r s t h e s o i l ,t r a n s p i r a t i o n b e c o me s t h e ma i n p r o c e s s .Civil Engineering, SDMCET DHARWAD33 FACTORS AFFECTING EVAPO-TRANSPIRATIONWe a t he r pa r a me t e r s , c r o p c h a r a c t e r i s t i c s , wa t e r ma na g e me nt a r ef a c t o r s a f f e c t i n g e v a p o r a t i o n a n d t r a n s p i r a t i o n .3.1 WEATHER PARAMETERSTh e p r i n c i p a l we a t h e r p a r a me t e r s a f f e c t i n g e v a p o t r a n s p i r a t i o n a r er a di a t i o n, a i r t e mpe r a t ur e , h u mi di t y a nd wi nd s pe e d . Th e e v a p o r a t i o np o we r o f t h e a t mo s p h e r e i s e x p r e s s e d b y t h e r e f e r e nc e c r o pe v a po t r a ns pi r a t i o n ( Ev a p o t r a n s p i r a t i o n ) . Th e r e f e r e n c e c r o pe v a p o t r a n s p i r a t i o n r e p r e s e n t s t h e e v a p o t r a n s p i r a t i o n f r o ma s t a nda r d i z e dv e g e t a t e d s ur f a c e .3.2 CROP FACTORSTh e c r o p t yp e , v a r i e t y a n d d e v e l o p me n t s t a ge a r e c o n s i d e r e d wh e na s s e s s i n g t h e e v a p o t r a n s p i r a t i o n f r o mc r o p s gr o wn i n l a r ge , we l l - ma n a g e df i e l d s . Di f f e r e n c e s i n r e s i s t a n c e t o t r a n s p i r a t i o n , c r o p h e i gh t , c r o pr o u gh n e s s , r e f l e c t i o n , gr o u n d c o v e r a n d c r o p r o o t i n g c h a r a c t e r i s t i c s r e s u l ti n d i f f e r e n t ET l e v e l s i n d i f f e r e n t t yp e s o f c r o p s u n d e r i d e n t i c a le n v i r o n me n t a l c o n d i t i o n s . Un d e r o p t i mu m s o i l wa t e r , e x c e l l e n tma n a g e me n t a n d e n v i r o n me n t a l c o n d i t i o n s wi l l a c h i e v e f u l l p r o d u c t i o nu n d e r t h e gi v e n c l i ma t i c c o n d i t i o n s .Civil Engineering, SDMCET DHARWAD43.3 WATER MANAGEMENTFa c t o r s t o b e c o n s i d e r e d wh e n a s s e s s i n g ET a r e g r o u n d c o v e r , p l a n td e n s i t y a n d t h e s o i l wa t e r c o n t e n t . Th e e f f e c t o f s o i l wa t e r c o n t e n t o n ETi s c o n d i t i o n e d p r i ma r i l y b y t h e ma gn i t u d e o f t h e wa t e r d e f i c i t a n d t h et yp e o f s o i l . To o mu c h wa t e r wi l l r e s u l t i n wa t e r l o g gi n g wh i c h mi gh td a ma g e t h e r o o t a n d l i mi t r o o t wa t e r u p t a k e b y i n h i b i t i n g r e s p i r a t i o n .3 . 4 CROPCOEFFI CI ENTS3 . 4 . 1Kc( CROPCO- EFFI CI ENT) :Th e c r o p f a c t o r wh i c h i n v o l v e s Kcma i n l y d e p e n d s o n : Th e t yp e o f c r o p ,t h e gr o wt h s t a ge o f t h e c r o p a n d t h e c l i ma t e . Kc wh e n mu l t i p l i e d wi t hr e f e r e n c e e v a p o - t r a n s p i r a t i o n gi v e s wa t e r r e q u i r e me n t o f c r o p .( Fi gu r e 1 . 0 . a )3 . 4 . 2 Wa t e r s t r e s s c o e f f i c i e nt ( Ks)Th e e f f e c t s o f s o i l wa t e r s t r e s s o n c r o p ET a r e d e s c r i b e d b y r e d u c i n g t h ev a l u e f o r t h e c r o p c o e f f i c i e n t . Th i s i s o b s e r v e d i n u n i r r i ga t e d a r e a wh e r et h e wa t e r r e q u i r e me n t c a n b e a s s e s s e d b y mu l t i p l yi n g t h e c r o p c o e f f i c i e n tb y t h e wa t e r s t r e s s c o e f f i c i e n t Kswi t h c r o p f a c t o r a n d a l s o r e f e r e n c ee v a p o - t r a n s p i r a t i o n t o ge t t h e t o t a l wa t e r r e q u i r e me n t o f a r e a . ( f i gu r e 1 . 0( b ) )Civil Engineering, SDMCET DHARWAD5.(a) Irrigated cropsb) Unirrigated cropsFIG.1Evapotranspiration conceptsCivil Engineering, SDMCET DHARWAD64 STUDYAREATh e s t u d y a r e a o f Hu b l i a n d Dh a r wa d t a l u k a s ( FI GURE2 . 0 ) wa s j u d i c i o u s l yc h o s e n o n t h e c r i t e r i a o f a v a i l a b i l i t y o f c r o p a r e a i n f o r ma t i o n , a n d a l s oHu b l i a n d Dh a r wa d f a l l i n z o n e 8 o f e v a p o t r a n s p i r a t i o n h e n c e t h ec a l c u l a t i o n d o n e f o r e v a p o t r a n s p i r a t i o n i s a p p l i c a b l e t h r o u gh o u t wh i c hc o me s i n t h e n o r t h e r n p a r t o f Ka r n a t a k a . Ar e a o f i r r i g a t e d a n d u n -i r r i ga t e d a gr i c u l t u r a l l a n d i n wh i c h Ra b i a n d k h a r i f , a n d p l a n t a t i o n s a r e ao f c r o p s gr o wn i n t h e s e v i l l a g e s a r e 5 5 2 . 7 3 , 3 6 5 . 0 5 a n d 1 3 . 6 2 k m2r e s p e c t i v e l y. Th e r e gi o n i s h a v i n g a n e l e v a t i o n r a n gi n g f r o m 6 2 0 ms l t o7 3 1 . 5 ms l . Th e l o n gi t u d e a n d l a t i t u d e a r e t a k e n i n t o a c c o u n t a n d l i e sb e t we e n 7 404 0 3 1 , 1 504 0 1 0 An d . 7 505 3 1 , 1 505 2 2 . Cr o p s g r o wn i nd i f f e r e n t v i l l a ge s i s t a k e n f r o m t h e Ta h a s h i l d a r o f f i c e a n d i s d i g i t i z e di n t o e x c e l s s h e e t s . Th e s e a r e a s a r e i n h e c t a r e s a n d a r e c o n v e r t e d t o m2a n d t h e n t h e s e a r e mu l t i p l i e d wi t h c o r r e s p o n d i n g wa t e r r e q u i r e me n t s o fd i f f e r e n t me t h o d s t o ge t t h e t o t a l wa t e r r e q u i r e me n t o f HUBLI a n dDHARWADt a l u k a s .Civil Engineering, SDMCET DHARWAD7(a) (b)FI G. 2STUDYAREA: HUBLI DHARWAD( a ) Study talukas( b ) Lo c a t i o n o f s t u d y t a l u k a sDHARWADHUBLICivil Engineering, SDMCET DHARWAD85 SOURCES OF DATACr o p a r e a o b t a i n e d f r o mt a h a s h i l d a r o f f i c e Hu b l i a n d Dh a r wa dRa i n f a l l d a t a , h u mi d i t y, t e mp e r a t u r e , wa t e r r e q u i r e me n t s , o b t a i n e df r o ma g r i c u l t u r a l u n i v e r s i t y, Dh a r wa d .To p o s h e e t s o b t a i n e d f r o m s u r v e y o f I n d i aCa d a s t r a l ma p s o f a l l v i l l a ge s o f Hu b l i a n d Dh a r wa d Ta l u k a so b t a i n e d Fr o mDe p a r t me n t o f l a n d r e c o r d sCivil Engineering, SDMCET DHARWAD96 Data ConversionTh e t e mp e r a t u r e d a t a wa s d a i l y d a t a wa s c o n v e r t e d t o mo n t h l y a n du s e f o r b o t h b l a n e y c r i d d l e me t h o d a n d p e n ma n e q u a t i o n ( t a b l e 1 - 4 ) . Th er e l a t i v e h u mi d i t y d a t a wa s a l s o c o mp u t e d f o r mo n t h l y d a t a . Al s o t h ea g r i c u l t u r a l wa t e r r e q u i r e me n t wa s g o t f r o mb o o k a d h i k a i l u v a r i k i ge g a g es u d h a r i t a b e s a ya k r a ma g a l u - Un i v e r s i t y o f a g r i c u l t u r a l s c i e n c e s ,Dh a r wa d . ( t a b l e 5 )Al l t h e d i g i t i z e d d a t a i s f e d i n t o a Ge o g r a p h i c a l I n f o r ma t i o n S ys t e ms o f t wa r e ( GEOMEDI A) a n d i n t e r p r e t a t i o n s c a n b e ma d e u s i n g t h e d a t a s ot h a t i t c a n b e u t i l i z e d b y d e c i s i o n ma k e r s t o s u i t t h e r e n e e d s . Fo r e . g. weh a v e u s e d a l l t h e wa t e r r e q u i r e me n t s a n d a r e a e x t e n t i n d i f f e r e n t v i l l a g e sa n d c a n b e s h o wn b y u s i n g a s p e c i a l QUERY t o o l i n s o f t wa r e c a l l e ds p e c i a l i n t e r s e c t i o n . ( Fi g 3 )Civil Engineering, SDMCET DHARWAD10(a)(b)F i g 3 . 0 : GI S I N T E RP RE T A T I O NS( a ) T o t a l i r r i g a t e d a n d u n i r r i g a t e d a r e a w i t h a r e a o f e x t e n t g r e a t e r t h a n 9 0h e c t a r e s o f a p a r t i c u l a r v i l l a g e( a ) T o t a l a r e a o f e x t e n t s wi t h wa t e r r e q u i r e m e n t g r e a t e r t h a n 5 l a k h c u m e cCivil Engineering, SDMCET DHARWAD11TABLE1 : METEOROLOGICAL DATA 2004*TABLE2 : METEOROLOGICAL DATA 2005*** University of agricultural science, DharwadCivil Engineering, SDMCET DHARWAD12TABLE3 : METEOROLOGICAL DATA 2006,TABLE4 : METEOROLOGICAL DATA 2007* University of agricultural science, DharwadCivil Engineering, SDMCET DHARWAD13Table 5: AGRICULTURAL WATER REQUIREMENTS*a d h i k a i l u v a r i k i g e g a g e s u d h a r i t a b e s a y a k r a ma g a l u - sourcea p u b l i c a t i o n o f UA SD h a r wa dSLNO CROPWATER DEMANDPER HECTARE(LOCAL)WATERDEMANDPERHECTARE(HYV) BASE PERIODCm (CM) DAYS1 JOWAR 45 60 1002 MAIZE 50 65 1103 HYBRID COTTON 80 90 1804 GROUNDNUT 40 50 905 SOYABEAN 40 50 906 WHEAT 45 55 1007 SAFFLOWER 40 55 908 BENGAL GRAM 30 35 909 SUNFLOWER 40 50 9011 REDGRAM 50 60 9012 COWPEA 40 45 9013 GREENGRAM 35 40 9014 SUNFLOWER 45 5 9015 Sugarcane 100 110 30016 SAVI 40 45 10017 RAGI 40 45 10018 NIGER 40 45 7019 CHILLI 40 45 7020 VEGETABLES 40 45 7021FRUIT ANDPLANTATION 40 50 7022 CASTOR 80 90 11023 CORIANDER SEEDS 40 45 7024 FRENCH BEANS 40 45 7025 POTATO 40 45 7026 BRINJAL 40 45 7028 CHILLI 40 45 70Civil Engineering, SDMCET DHARWAD147 METHODOLOGYHe r e we h a v e c o n s i d e r e d t wo me t h o d s f o r c o mp u t i n g e v a p o t r a n s p i r a t i o n .1 . Bl a n e y c r i d d l e e q u a t i o n2 . Pe n ma n e q u a t i o nBl a n e y c r i d d l e e q u a t i o n i s a go o d e q u a t i o n wh i c h i s u s e d i n e s t i ma t i n ge v a p o - t r a n s p i r a t i o n b u t t h e o n l y d r a w b a c k i s i t d o e s n o t c o n s i d e r t h ee f f e c t o f wi n d o n e v a p o t r a n s p i r a t i o n . PENMAN S e q u a t i o n i s o n e o f t h emo s t a c c u r a t e me t h o d s i n d e t e r mi n i n g t h e e v a p o t r a n s p i r a t i o n a n d wi d e l ya c c e p t e d .Civil Engineering, SDMCET DHARWAD157. 1 BLANEYCRI DDLEMETHODBl a n e y Cr i d d l e me t h o d c a n b e u s e d t o c a l c u l a t e Ev a p o t r a n s p i r a t i o n . Th i sme t h o d i s s t r a i gh t f o r wa r d a n d r e q u i r e s o n l y d a t a o n me a n d a i l ytemperatures(table1-4). The Blaney-Criddle formula is:( ) 8 46 . 00+ =meanT p ETwh e r e :1 . Ev a p o t r a n s p i r a t i o n = r e f e r e n c e c r o p e v a p o t r a n s p i r a t i o n ( mm/ d a y)2 . Tm e a n= me a n d a i l y t e mp e r a t u r e ( C)3 . p = me a n d a i l y p e r c e n t a ge o f a n n u a l d a yt i me h o u r s .Civil Engineering, SDMCET DHARWAD16FI G. 4 . 0 : WATERREQUI REMENTFORBLANEY- CRI DDLECivil Engineering, SDMCET DHARWAD177.2 The step by step computation by Blaney-Criddle formulaSt ep 1: Det er mi nat i on of t he mean dai l y t empe r at ur e: TmeanThe Bl ane y - Cr i ddl e met hod al ways r ef er s t o mean mont hl y v al ues ,bot h f or t he t emper at ur e and t h e Ev ap ot r ans p i r at i on . I f i n a l oc almet eor ol ogi c al s t at i on t he dai l y mi ni mumand max i mumt emper at ur esar e meas ur ed, t he mean dai l y t emper at ur e i sCal c ul at ed as f ol l ows :Tm a x= s u mo f a l l Tm a xv a l u e s d u r i n g t h e mo n t hNu mb e r o f d a ys o f t h e mo n t hTm i n= s u mo f a l l Tm i nv a l u e s d u r i n g t h e mo n t hNu mb e r o f d a ys o f t h e mo n t hTm e a n= Tma x+Tmi n2Civil Engineering, SDMCET DHARWAD18St e p2 : De t e r mi n a t i o no f t he me a nda i l y pe r c e nt a g e o f a nnua l da y - t i meho ur s : p Su p p o s e t h e p v a l u e f o r t h e mo n t h Ma r c h h a s t o b e d e t e r mi n e d f o r a na r e a wi t h l a t i t u d e o f 1 5 NORTH. Fr o mTa b l e 6 i t c a n b e s e e n t h a t t h eAVERAGE p v a l u e = 0 . 2 8Table 6 MEAN DAILY PERCENTAGE (p) OF ANNUAL DAYTIME HOURS FORDIFFERENT LATITUDESLatitudeNorthJanFebMar AprMay June July Aug Sept Oct Nov Dec AVGSouth July Aug Sept Oct Nov Dec JanFebMar AprMay June p60 0.15 0.200.260.32 0.380.410.40 0.340.280.22 0.170.1355 0.17 0.210.260.32 0.360.390.38 0.330.280.23 0.180.1650 0.19 0.230.270.31 0.340.360.35 0.320.280.24 0.200.1845 0.20 0.230.270.30 0.340.350.34 0.320.280.24 0.210.2040 0.22 0.240.270.30 0.320.340.33 0.310.280.25 0.220.2135 0.23 0.250.270.29 0.310.320.32 0.300.280.25 0.230.2230 0.24 0.250.270.29 0.310.320.31 0.300.280.26 0.240.2325 0.24 0.260.270.29 0.300.310.31 0.290.280.26 0.250.2420 0.25 0.260.270.28 0.290.300.30 0.290.280.26 0.250.2515 0.26 0.260.270.28 0.290.290.29 0.280.280.27 0.260.25 0.2810 0.26 0.270.27 0. 80.280.290.29 0.280.280.27 0.260.265 0.27 0.270.270.28 0.280.280.28 0.280.280.27 0.270.270 0.27 0.270.270.27 0.270.270.27 0.270.270.27 0.270.27Civil Engineering, SDMCET DHARWAD19STEP 3: CALCULATE EVAPOTRANSPIRATION:Us i n g t h e f o r mu l a :Ev a p o t r a n s p i r a t i o n = 8) + Tmean (0.46 p = ET0 Th e r e l a t i o n s h i p b e t we e n t h e r e f e r e n c e gr a s s c r o p a n d t h e c r o pa c t u a l l y gr o wn i s gi v e n b y t h e c r o pf a c t o r , Kc , a s s h o wn i n t h e f o l l o wi n gf o r mu l a : Ev a p o t r a n s p i r a t i o n Kc = ETc r o pWi t hETc r o p = c r o p e v a p o t r a n s p i r a t i o nKc = c r o p f a c t o rEv a p o t r a n s p i r a t i o n =r e f e r e n c e e v a p o t r a n s p i r a t i o n ( mm/ d a y )CALCULATION:Tmean = (31.075+18.45+28.491+18.64+30.86+18.17+30.59+18.65)/8=24.36Evapotranspiration = p (0.46 T mean + 8)=.28*(.46*24.36+8)=5.25mm/day (obtained from FIG 3.0)Civil Engineering, SDMCET DHARWAD207.3 PENMAN MONTIETH EQUATIONAc o n s u l t a t i o n o f e x p e r t s a n d r e s e a r c h e r s wa s o r ga n i z e d b y FAOi n Ma y1 9 9 0 , i n c o l l a b o r a t i o n wi t h t h e I n t e r n a t i o n a l Co mmi s s i o n f o r I r r i ga t i o na n d Dr a i n a ge a n d wi t h t h e Wo r l d Me t e o r o l o g i c a l Or g a n i z a t i o n , t o r e v i e wt h e FAOme t h o d o l o gi e s o n c r o p wa t e r r e q u i r e me n t s a n d t o a d v i c e o n t h er e v i s i o n a n d u p d a t e o f p r o c e d u r e s .THE PENMAN- MONTI ETH EQUATI ON AS SUGGESTED BY FAO0.34u2) + (1 +ea) - (es u2 273)) + (900/(T G) - (Rn 0.408= ET0A AWhe r eE va pot r a ns pi r a t i on r ef er enc e ev a pot r a ns pi r a t i on [ mm da y- 1] ,Rn= net r a di a t i on a t t he c r op s ur f a c e [ MJ m- 2da y- 1] ,G =s oi l hea t f l ux dens i t y [ MJ m- 2da y- 1] ,T =mea n da i l y a i r t emper a t ur e a t 2 m hei g ht [ C] ,u2 =wi nd s peed a t 2 m hei ght [ m s- 1] ,Civil Engineering, SDMCET DHARWAD21es =s a t ur a t i on v a por pr es s ur e [ k Pa ] ,ea =a c t ua l va por pr es s ur e [ kPa ] ,( es - ea) =s a t ur a t i on va por pr es s ur e def i c i t [ k Pa ] ,= s l ope va por pr es s ur e c ur ve [ kPa C- 1] ,= ps y c home t r i c c ons t a nt [ kPa C- 1] .7. 31 CALCULATI ONPROCEDUREEv a p o t r a n s p i r a t i o n c a n b e e s t i ma t e d b y me a n s o f t h e c a l c u l a t i o n s h e e tp r e s e n t e d i n c a l c u l a t i o n s h e e t . Th e c a l c u l a t i o n s h e e t r e f e r s t o t a b l e s i nTABLES 7 - 1 5 f o r t h e d e t e r mi n a t i o n o f s o me o f t h e c l i ma t i c p a r a me t e r s .Th e c a l c u l a t i o n p r o c e d u r e c o n s i s t s o f t h e f o l l o wi n g s t e p s :1 . De r i v a t i o n o f s o me c l i ma t i c p a r a me t e r s f r o mt h e d a i l y ma x i mu m( Tm a x)a n d mi n i mu m( Tm i n) a i r t e mp e r a t u r e ( TABLE- 1 - 4 ) , a l t i t u d e ( z ) =6 8 0 me t r e sa b o v e me a n s e a l e v e l a n d me a n wi n d s p e e d ( u2) =2 m/ s ( As s u me d ) .2 . Ca l c u l a t i o n o f t h e v a p o u r p r e s s u r e d e f i c i t ( es- ea) . Th e s a t u r a t i o nv a p o r p r e s s u r e ( es) i s d e r i v e d f r o mTm a xa n d Tm i n, wh i l e t h e a c t u a l v a p o rp r e s s u r e f r o mma x i mu m( RHm a x) a n d mi n i mu m( RHm i n) r e l a t i v e h u mi d i t y,f r o m t h e ma x i mu m ( RHm a x) ( t a b l e n o 1 - 4 ) , o r f r o mme a n r e l a t i v e h u mi d i t y( RHm e a n) .Civil Engineering, SDMCET DHARWAD223 . De t e r mi n a t i o n o f t h e n e t r a d i a t i o n ( Rn) a s t h e d i f f e r e n c e b e t we e n t h en e t s h o r t wa v e r a d i a t i o n ( Rn s) a n d t h e n e t l o n g wa v e r a d i a t i o n ( Rn l) . I n t h ec a l c u l a t i o n s h e e t , t h e e f f e c t o f s o i l h e a t f l u x ( G) i s i gn o r e d f o r d a i l yc a l c u l a t i o n s a s t h e ma gn i t u d e o f t h e f l u x i n t h i s c a s e i s r e l a t i v e l y s ma l l .Th e n e t r a d i a t i o n , e x p r e s s e d i n MJ m- 2d a y- 1, i s c o n v e r t e d t o mm/ d a y( e q u i v a l e n t e v a p o r a t i o n ) i n t h e FAO Pe n ma n - Mo n t e i t h e q u a t i o n b y u s i n g0 . 4 0 8 a s t h e c o n v e r s i o n f a c t o r wi t h i n t h e e q u a t i o n .4 . Ev a p o t r a n s p i r a t i o n i s o b t a i n e d b y c o mb i n i n g t h e r e s u l t s o f t h e p r e v i o u ss t e p s .Civil Engineering, SDMCET DHARWAD23TABLE 7 : CALCULATION SHEETGiven the monthly average climatic data of of study are located at15N and at an elevation of 2 m:Parameters values units remarksMonthly average daily maximumtemperature (Tmax) =31.08 C Values of temperature Obtainedfrom table 1-4Monthly average daily minimumtemperature (Tmin) =18.45 CMonthly average daily vapour pressure(ea) =3.08 -Monthly average daily wind speed (u2) = 2.00 m/s WIND SPEED Measured at 2 m(assumed)Monthly average sunshine duration (n) = 8.50 - -Mean monthly average temperature(Tmonth, i) =28.60 TEMPERATURE for AprilMean monthly average temperature(Tmonth, i-1) =28.05 TEMPERATURE For MarchTmean = [(Tmax = 34.8) + (Tmin = 25.6)]/2=24.75 C = 0.18 kPa/C VAPOUR PRESSUREOBTAINED FROM TABLE 10Altitude = 2.00 m ATMOSPHERIC PRESSUREAND PSYCHOMETRICCONSTANTS8 AND 9P(atmospheric constant)= 93.30 kPa (psychometric constant)= 0.06 kPa/C(1 + 0.34 u2) = 1.68 /[+ g (1 + 0.34u2)] = 0.246/[(0.246 +0.0674 (1.68)] =0.64 CALCULATION (1)g /[D + g (1 + 0.34u2)] = 0.0667/[0.246 +0.0674 (1.68)] =0.19900/(Tmean + 273) u2 = 6.05Civil Engineering, SDMCET DHARWAD24Vapour pressure deficite(Tmax) = 4.62 kPa VAPOUR PRESSUREOBTAINED FROMTable15Tmin = 18.45 Ce(Tmin) = 2.13 kPaes = (5.56 + 3.28)/2 = 3.375 kPaea = 3.075 kPaVapour pressure deficit (es - ea) = (4.42 -2.85) =0.3 kPaRadiation (for month = April)J = (for 15 April) 365 - RADIATION ANDDAYLENGTHOBTAINED From Table11 AND 12Latitude = 1344'N = (13 + 44/60) = 15.25 NRa = 38.06 MJ m-2day-1Day length N = 12.51 hoursn/N = (8.5/12.31) = 0.68 -Rs = [0.25 + 0.50 (0.69)] 38.06 = 22.45 MJ m-2day-1Rso = (0.75 + 2 (2)/100000) 38.06 = 28.55 MJ m-2day-1-Rs/Rso = (22.65/28.54) = 0.79 - -Rns = 0.77 (22.65) = 17.65 MJ m-2day-1-Tmax = 30.75 C Stefan-BoltzmannvaluesFrom Table 14Tmax K440.75 MJ m-2day-1Tmin = 18.50 C From Table1535.48 MJ m-2day-1Civil Engineering, SDMCET DHARWAD25(Tmax K4+Tmin K4)/2 38.12 MJ m-2day-1ea = 2.85 kPa Table 150.10 -Rs/Rso = 0.79 -(1.35 Rs/Rso-0.35) = 0.72 -Rnl = 41.58 (0.10)0.72 = 2.84 MJ m-2day-1-Rn = (17.44-2.84) = 14.80 MJ m-2day-1-G =0.14 (30.2-29.2) = 0.08 MJ m-2day-1-(Rn - G) = (14.33-0.14) = 14.73 MJ m-2day-1-0.408 (Rn - G) = 6.01 mm/day -calculation 2Grass reference evapotranspiration0.408 (Rn - G) /[ + g (1+0.34 u2)] =(5.79) 0.685 = 3.82 mm/day (1)900 u2/(T + 273) (es - ea) g /[D + g (1+0.34u2)] = 5.94(1.57)0.188 =0.30 mm/day(2)ETo = (3.97+1.75) = 4.12 mm/day (1)+(2)The grass reference evapotranspiration is 4.12 mm/day.Civil Engineering, SDMCET DHARWAD26FIG 5.0: water requirement of crop by penmanCivil Engineering, SDMCET DHARWAD27CALCULATION DATATABLE8-COMPUTATION OFATMOSPHERIC PRESSUREBASED ONALTITUDESz(m)P(kPa)z(m)P(kPa)z(m)P(kPa)z(m)P(kPa)0 101.3 1000 90.0 2000 79.8 3000 70.550 100.7 1050 89.5 2050 79.3 3050 70.1100 100.1 1100 89.0 2100 78.8 3100 69.6150 99.5 1150 88.4 2150 78.3 3150 69.2200 99.0 1200 87.9 2200 77.9 3200 68.8250 98.4 1250 87.4 2250 77.4 3250 68.3300 97.8 1300 86.8 2300 76.9 3300 67.9350 97.2 1350 86.3 2350 76.4 3350 67.5400 96.7 1400 85.8 2400 76.0 3400 67.1450 96.1 1450 85.3. 2450 75.5 3450 66.6500 95.5 1500 84.8 2500 75.0 3500 66.2550 95.0 1550 84.3 2550 74.6 3550 65.8600 94.4 1600 83.8 2600 74.1 3600 65.4650 93.8 1650 83.3 2650 73.7 3650 65.0700 93.3 1700 82.8 2700 73.2 3700 64.6750 92.7 1750 82.3 2750 72.7 3750 64.1800 92.2 1800 81.8 2800 72.3 3800 63.7850 91.6 1850 81.3 2850 71.8 3850 63.3900 91.1 1900 80.8 2900 71.4 3900 62.9950 90.6 1950 80.3 2950 71.0 3950 62.51000 90.0 2000 79.8 3000 70.5 4000 62.1Civil Engineering, SDMCET DHARWAD28TABLE 9-COMPUTATION OF PSYCHOMETRIC CONSTANT BASED ONALTITUDESz(m)kPa/Cz(m)kPa/Cz(m)kPa/Cz(m)kPa/C0 0.067 1000 0.060 2000 0.053 3000 0.047100 0.067 1100 0.059 2100 0.052 3100 0.046200 0.066 1200 0.058 2200 0.052 3200 0.046300 0.065 1300 0.058 2300 0.051 3300 0.045400 0.064 1400 0.057 2400 0.051 3400 0.045500 0.064 1500 0.056 2500 0.050 3500 0.044600 0.063 1600 0.056 2600 0.049 3600 0.043700 0.062 1700 0.055 2700 0.049 3700 0.043800 0.061 1800 0.054 2800 0.048 3800 0.042900 0.061 1900 0.054 2900 0.047 3900 0.0421000 0.060 2000 0.053 3000 0.047 4000 0.041Based on = 2.45 MJ kg-1at 20C.Civil Engineering, SDMCET DHARWAD29TABLE 10 - Slope of vapor pressure curve () for different temperatures (T)TCAkPa/CTCAkPa/CTCAkPa/CTCAkPa/C1.0 0.047 13.0 0.098 25.0 0.189 37.0 0.3421.5 0.049 13.5 0.101 25.5 0.194 37.5 0.3502.0 0.050 14.0 0.104 26.0 0.199 38.0 0.3582.5 0.052 14.5 0.107 26.5 0.204 38.5 0.3673.0 0.054 15.0 0.110 27.0 0.209 39.0 0.3753.5 0.055 15.5 0.113 27.5 0.215 39.5 0.3844.0 0.057 16.0 0.116 28.0 0.220 40.0 0.3934.5 0.059 16.5 0.119 28.5 0.226 40.5 0.4025.0 0.061 17.0 0.123 29.0 0.231 41.0 0.4125.5 0.063 17.5 0.126 29.5 0.237 41.5 0.4216.0 0.065 18.0 0.130 30.0 0.243 42.0 0.4316.5 0.067 18.5 0.133 30.5 0.249 42.5 0.4417.0 0.069 19.0 0.137 31.0 0.256 43.0 0.4517.5 0.071 19.5 0.141 31.5 0.262 43.5 0.4618.0 0.073 20.0 0.145 32.0 0.269 44.0 0.4718.5 0.075 20.5 0.149 32.5 0.275 44.5 0.4829.0 0.078 21.0 0.153 33.0 0.282 45.0 0.4939.5 0.080 21.5 0.157 33.5 0.289 45.5 0.50410.0 0.082 22.0 0.161 34.0 0.296 46.0 0.51510.5 0.085 22.5 0.165 34.5 0.303 46.5 0.52611.0 0.087 23.0 0.170 35.0 0.311 47.0 0.53811.5 0.090 23.5 0.174 35.5 0.318 47.5 0.55012.0 0.092 24.0 0.179 36.0 0.326 48.0 0.56212.5 0.095 24.5 0.184 36.5 0.334 48.5 0.574Civil Engineering, SDMCET DHARWAD30TABLE11- Number of the day in the year (J)DayJanuaryFebruaryMarch*April*May*June*July*August*September*October*November*December*1 1 32 60 91 121 152 182 213 244 274 305 3352 2 33 61 92 122 153 183 214 245 275 306 3363 3 34 62 93 123 154 184 215 246 276 307 3374 4 35 63 94 124 155 185 216 247 277 308 3385 5 36 64 95 125 156 186 217 248 278 309 3396 6 37 65 96 126 157 187 218 249 279 310 3407 7 38 66 97 127 158 188 219 250 280 311 3418 8 39 67 98 128 159 189 220 251 281 312 3429 9 40 68 99 129 160 190 221 252 282 313 34310 10 41 69 100 130 161 191 222 253 283 314 34411 11 42 70 101 131 162 192 223 254 284 315 34512 12 43 71 102 132 163 193 224 255 285 316 34613 13 44 72 103 133 164 194 225 256 286 317 34714 14 45 73 104 134 165 195 226 257 287 318 34815 15 46 74 105 135 166 196 227 258 288 319 34916 16 47 75 106 136 167 197 228 259 289 320 35017 17 48 76 107 137 168 198 229 260 290 321 35118 18 49 77 108 138 169 199 230 261 291 322 35219 19 50 78 109 139 170 200 231 262 292 323 35320 20 51 79 110 140 171 201 232 263 293 324 35421 21 52 80 111 141 172 202 233 264 294 325 35522 22 53 81 112 142 173 203 234 265 295 326 35623 23 54 82 113 143 174 204 235 266 296 327 35724 24 55 83 114 144 175 205 236 267 297 328 35825 25 56 84 115 145 176 206 237 268 298 329 35926 26 57 85 116 146 177, 207 238 269 299 330 36027 27 58 86 117 147 178 208 239 270 300 331 36128 28 59 87 118 148 179 209 240 271 301 332 36229 29 (60) 88 119 149 180 210 241 272 302 333 36330 30 - 89 120 150 181 211 242 273 303 334 36431 31 - 90 - 151 - 212 243 - 304 - 365Civil Engineering, SDMCET DHARWAD31TABLE 12 Daily extraterrestrial radiation (Ra) for different latitudes for the 15thday of the monthCivil Engineering, SDMCET DHARWAD32TABLE 13: No of sunshine hours dailyCivil Engineering, SDMCET DHARWAD33TABLE-14Stefan-Boltzmann law at different temperatures (T)With = 4.903 10-9MJ K-4m-2day-1and TK = T[C] + 273.16T(C)(MJ m-2d-1)T(C)(MJ m-2d-1)T(C)(MJ m-2d-1)1.0 27.70 17.0 34.75 33.0 43.081.5 27.90 17.5 34.99 33.5 43.362.0 28.11 18.0 35.24 34.0 43.642.5 28.31 18.5 35.48 34.5 43.933.0 28.52 19.0 35.72 35.0 44.213.5 28.72 19.5 35.97 35.5 44.504.0 28.93 20.0 36.21 36.0 44.794.5 29.14 20.5 36.46 36.5 45.085.0 29.35 21.0 36.71 37.0 45.375.5 29.56 21.5 36.96 37.5 45.676.0 29.78 22.0 37.21 38.0 45.966.5 29.99 22.5 37.47 38.5 46.267.0 30.21 23.0 37.72 39.0 46.567.5 30.42 23.5 37.98 39.5 46.858.0 30.64 24.0 38.23 40.0 47.158.5 30.86 24.5 38.49 40.5 47.469.0 31.08 25.0 38.75 41.0 47.769.5 31.30 25.5 39.01 41.5 48.0610.0 31.52 26.0 39.27 42.0 48.3710.5 31.74 26.5 39.53 42.5 48.6811.0 31.97 27.0 39.80 43.0 48.9911.5 32.19 27.5 40.06 43.5 49.3012.0 32.42 28.0 40.33 44.0 49.6112.5 32.65 28.5 40.60 44.5 49.9213.0 32.88 29.0 40.87 45.0 50.2413.5 33.11 29.5 41.14 45.5 50.5614.0 33.34 30.0 41.41 46.0 50.8714.5 33.57 30.5 41.69 46.5 51.1915.0 33.81 31.0 41.96 47.0 51.5115.5 34.04 31.5 42.24 47.5 51.8416.0 34.28 32.0 42.52 48.0 52.16Civil Engineering, SDMCET DHARWAD34.Table 15: Saturation vapor pressure (e(T)) for different temperatures (T)TCeskPaTCe(T)kPaTCe(T)kPaTCeskPa1.0 0.657 13.0 1.498 25.0 3.168 37.0 6.2751.5 0.681 13.5 1.547 25.5 3.263 37.5 6.4482.0 0.706 14.0 1.599 26.0 3.361 38.0 6.6252.5 0.731 14.5 1.651 26.5 3.462 38.5 6.8063.0 0.758 15.0 1.705 27.0 3.565 39.0 6.9913.5 0.785 15.5 1.761 27.5 3.671 39.5 7.1814.0 0.813 16.0 1.818 28.0 3.780 40.0 7.3764.5 0.842 16.5 1.877 28.5 3.891 40.5 7.5745.0 0.872 17.0 1.938 29.0 4.006 41.0 7.7785.5 0.903 17.5 2.000 29.5 4.123 41.5 7.9866.0 0.935 18.0 2.064 30.0 4.243 42.0 8.1996.5 0.968 18.5 2.130 30.5 4.366 42.5 8.4177.0 1.002 19.0 2.197 31.0 4.493 43.0 8.6407.5 1.037 19.5 2.267 31.5 4.622 43.5 8.8678.0 1.073 20.0 2.338 32.0 4.755 44.0 9.1018.5 1.110 20.5 2.412 32.5 4.891 44.5 9.3399.0 1.148 21.0 2.487 33.0 5.030 45.0 9.5829.5 1.187 21.5 2.564 33.5 5.173 45.5 9.83210.0 1.228 22.0 2.644 34.0 5.319 46.0 10.08610.5 1.270 22.5 2.726 34.5 5.469 46.5 10.34711.0 1.313 23.0 2.809 35.0 5.623 47.0 10.61311.5 1.357 23.5 2.896 35.5 5.780 47.5 10.88512.0 1.403 24.0 2.984 36.0 5.941 48.0 11.16312.5 1.449 24.5 3.075 36.5 6.106 48.5 11.447Civil Engineering, SDMCET DHARWAD35Table16: WATER REQUIRMENT OF CROP: DHARWADCivil Engineering, SDMCET DHARWAD36Table17: WATER REQUIRMENT OF CROPS: HUBLICivil Engineering, SDMCET DHARWAD378 CO-EFFICIENT FOR BLANEY CRIDDLE EQUATIONWe k n o w t h a t b l a n e y c r a d l e e q u a t i o n d o e s n o t c o n s i d e r wi n d a s af a c t o r u t a s we c a n s e e t h a t i f we g i v e a s u i t a b l e r e c t i f i c a t i o n f o r b l a n e yc r i d d l e e q u a t i o n we c a n a p p l y i t f o r t h i s r e g i o n .As we c a n s e e i n b o t h t a b l e s 1 5 a n d 1 6 t h e s t a n d a r d d e v i a t i o n i s a l mo s tt h e s a me a s p e r o u r c a l c u l a t i o n we a r e s u g ge s t i n g MULTI P LYI NGFACTOR o f 0 . 3 5 TABLE f o r b l a n e y c r i d d l e e q u a t i o n f o r DHARWADAND. 2 9 f o r Hu b l i r e gi o n . Bu t f o r i n d i v i d u a l c r o p s we c a n u s e i n d i v i d u a lc r o p c o e f f i c i e n t s i n t a b l e 1 5 a n d 1 6 . f r o mt h e b e l o wt a b l e we o b s e r v e t h a tp e n ma n gi v e s t h e l e a s t a mo u n t o f wa t e r r e q u i r e me n t .Ta bl e 18: TOTAL WATER REQUI REMENTEstimation method Hubli (cum) Dharwad ( cum)Total(cum)Agriculture 1,427,834,197 3,081,152,0004508986197Penman 335,775,822.9 861,316,096.61197091919.5Blaney-CRIDDLE 1,177,136,453 2,586,364,4353763500888Civil Engineering, SDMCET DHARWAD389 CONCLUSIONWa t e r r e q u i r e me n t o f v a r i o u s c r o p s f o r b o t h u n - i r r i ga t e d a n d i r r i ga t e du n d e r d i f f e r e n t v i l l a ge s o f Hu b l i a n d Dh a r wa d t a l u k i s e s t i ma t e d b y b o t hPe n me n a n d Bl a n e y - c r i d d l e e q u a t i o n a n d t h e d a t a a r e f e d i n t o GI S mo d e .Us i n g a GI S t o o l wa t e r r e q u i r e me n t f o r a n y v i l l a ge u n d e r s t u d y c a n b eo b t a i n e d . Th e wa t e r r e q u i r e me n t o f c r o p i s d e t e r mi n e d u s i n g Mo d i f i e dPe n ma n Eq u a t i o n s u g g e s t e d b y FAOSt a n d a r d s . Mo d i f i e d p e n ma n mo n t i e t hTh e v a l u e s o b t a i n e d a r e c o mp a r e d wi t h v a l u e s o b t a i n e d b y Bl a n e y - c r i d d l eme t h o d a l s o . An d a s u i t a b l e mu l t i p l yi n g f a c t o r f o r Bl a n e y c r i d d l ee q u a t i o n a p p l i c a b l e f o r Dh a r wa d a n d Hu b l i r e g i o nCivil Engineering, SDMCET DHARWAD3910 SCOPE- I d e n t i f i c a t i o n o f wa t e r s o u r c e s , l o c a t i o n s b o t h s u r f a c e a n dg r o u n d wa t e r t o c a l i b r a t e t h e n e e d o f l o c a l d e ma n d .- Re f i n e me n t a n d c a l c u l a t i o n u s i n g t h e r a i n f a l l d a t a .- Su g ge s t i o n f o r a l t e r n a t e c r o p s o r s wi t c h i n g t o c o mme r c i a l c r o p sb a s e d o n s u i t a b i l i t y a n d l a n d a v a i l a b i l i t y, wa t e r - r e s o u r c e s a n dc l i ma t e .- Es t i ma t i o n o f s o i l e r o s i o n .11 BIBLIOGRAPHY1 . 0 Garg, S .K, I r r i g a t i o n En gi n e e r i n g , Khanna Publishers, fourth edition, 1996.2 . 0 Michael I r r i g a t i o n t h e o r y a n d p r a c t i c e , New Delhi, EDITION: 19833 . 0 www.fao.org/docrep/X0490E/x0490e00.htm