RESULTS OF APPLICATION OF THE MODEL

When the capital investment required to develop theDrustar agricultural-industrial complex is considered, a significant part of this investment must be devoted to the development of irrigated land and the water supply facilities needed for this irrigation.

SWIM is applied to measure the benefits and water demands of various levels of irrigation development, both under normal weather conditions and under drought conditions. Two basic de- cisions are investigated:

-

How much land should be developed for irrigation?

-

How much water should be made availablefor irrigation?

The major results of these investigations are summarized in this section while the details are tabulated in Appendix 1.

3.1 Land for Irrigation

Of the 121,600 ha of arable land considered in SWIM, it is expected that between 25,000 and 40,000 hectares will be developed for irrigation by 1980, the year for which SWIM is applied. The range of development from 10,000 ha to 50,000 ha of irrigated land is investigated in 5,000 ha steps by repet- itively running SWIM on the computer, with each computer run having a different amount of irrigated land available. All

water needed is assumed to be available. Two series of computer runs were performed, one for normal weather conditions and

another for drought weather conditions. In each run, SWIM de- termines the optimal crop distribution on both irrigated and nonirrigated land to maximize production while also meeting the minimum production requirements for livestock and population.

The results for various levels of irrigated land development are shown in figures (3.1) to (3.8)

.

3.1

.I

Water Demands -

In figure (3.1), the volume of water needed, or water de- mand, for irrigation is plotted for both normal weather and drought conditions. For drought conditions, about 3900 cubic

m e t r e s p e r h e c t a r e (390 mm) a r e r e q u i r e d , which i s a n i n c r e a s e of between 25% and 55% o v e r t h e w a t e r demand i n normal w e a t h e r c o n d i t i o n s as shown i n f i g u r e ( 3 . 2 ) . I n SWIM, t h e c r o p w a t e r r e q u i r e m e n t s are i n c r e a s e d by 2 0 % f o r d r o u g h t c o n d i t i o n s and i t a p p e a r s from f i g u r e ( 3 . 2 ) t h a t f o r l a r g e a r e a s o f i r r i g a t i o n t h e w a t e r demands i n c r e a s e by a l i t t l e more t h a n 2 0 % , b e c a u s e d i f f e r e n t c r o p s a r e b e i n g i r r i g a t e d .

3.1.2 Crop D i s t r i b u t i o n

The d i s t r i b u t i o n of: c r o p s grown f o r d i f f e r e n t a r e a s o f i r r i g a t i o n u n d e r normal w e a t h e r and d r o u g h t c o n d i t i o n s a r e shown i n f i g u r e s ( 3 . 3 ) , and ( 3 . 4 ) , r e s p e c t i v e l y . I n t h e s e f i g u r e s t h e v e r t i c a l a x i s r e p r e s e n t s t h e t o t a l a r a b l e l a n d and t h e h o r i z o n t a l a x i s t h e amount of t h i s l a n d which i s i r r i g a t e d . The 45' l i n e b e g i n n i n g a t t h e o r i g i n i s t h e boundary between i r r i g a t e d and n o n i r r i g a t e d l a n d . The area o f e a c h c r o p grown f o r a g i v e n a r e a of i r r i g a t e d l a n d i s p l o t t e d c u m u l a t i v e l y i n a v e r t i c a l d i r e c t i o n , b e g i n n i n g a t t h e bottom w i t h t h e s e e d s a r e a , which i s always i r r i g a t e d , c o n t i n u i n g w i t h t h e i r r i g a t e d c r o p s , and t h e n t h e n o n i r r i g a t e d c r o p s . I n some c a s e s , one

c r o p may be grown p a r t i a l l y i r r i g a t e d and p a r t i a l l y n o n i r r i g a t e d e . g . maize s i l a g e f o r 10,000 ha i r r i g a t e d l a n d i n f i g u r e ( 3 . 3 )

.

By l o o k i n g from l e f t t o r i g h t a c r o s s e a c h f i g u r e , t h e change i n t h e c r o p d i s t r i b u t i o n a s more l a n d i s i r r i g a t e d c a n be o b s e r v e d . I n normal w e a t h e r c o n d i t i o n s , soybeans i s t h e f i r s t c r o p i r r i g a t e d , f o l l o w e d by maize g r a i n once soybeans a r e c o m p l e t e l y i r r i g a t e d .

A v e r y i m p o r t a n t f e a t u r e of t h e r e s u l t s , which i s t h e sub- s t i t u t i o n o f w a t e r f o r l a n d , c a n b e o b s e r v e d by comparing t h e t o t a l a r e a s o f s o y b e a n s i n f i g u r e ( 3 . 3 ) f o r 10,000 and 15,000 h a of i r r i g a t e d l a n d . These a r e a s a r e 19925 ha and 15883 h a , re- s p e c t i v e l y . I n b o t h c a s e s t h e t o t a l p r o d u c t i o n i n t o n s o f soy- b e a n s i s t h e same b u t b e c a u s e a g r e a t e r p r o p o r t i o n o f t h e c r o p i s grown u n d e r i r r i g a t i o n i n t h e second c a s e , where it g i v e s a h i g h e r y i e l d , t h e t o t a l l a n d a r e a o c c u p i e d by s o y b e a n s d e c r e a s e s , t h u s l e a v i n g more l a n d a v a i l a b l e f o r growing o t h e r c r o p s w i t h - o u t i r r i g a t i o n . Hence w a t e r and c a p i t a l i n v e s t m e n t i n i r r i g a t i o n a r e b e i n g s u b s t i t u t e d f o r a r a b l e l a n d t o grow t h e same amount of

soybeans. T h i s i s a key f e a t u r e of t h e o p e r a t i o n of S W I M and i t u n d e r l i e s a l l t h e r e s u l t s which f o l l o w .

By comparing f i g u r e s ( 3 . 3 ) and ( 3 . 4 )

,

i t c a n be s e e n t h a t d i f f e r e n t c r o p s a r e grown under i r r i g a t i o n i n d r o u g h t c o n d i t i o n s a s compared t o normal weather c o n d i t i o n s . I n a d r o u g h t , maize s i l a g e i s i r r i g a t e d f i r s t i n s t e a d of soybeans, f o l l o w e d by maize g r a i n , and t h e n soybeans f o r l a r g e a r e a s of i r r i g a t e d l a n d .

The r e a s o n t h a t maize i s i r r i g a t e d f i r s t i s t h a t t h i s c r o p i s t h e most s e n s i t i v e t o d r o u g h t (50% l o s s i n n o n i r r i g a t e d y i e l d ) compared w i t h soybeans and s u n f l o w e r s (30% l o s s i n n o n i r r i g a t e d y e i l d ) , and l u c e r n e , wheat, and b a r l e y (15% l o s s i n n o n i r r i g a t e d y i e l d ) . The l o s s e s i n y i e l d o f n o n i r r i g a t e d s u n f l o w e r s , wheat and l u c e r n e mean t h a t l a r g e r a r e a s of t h e s e c r o p s a r e r e q u i r e d t o grow t h e p r o d u c t i o n r e q u i r e m e n t s i n d r o u g h t c o n d i t i o n s . For lower i r r i g a t e d a r e a i n d r o u g h t c o n d i t i o n s , a s m a l l a r e a of

b a r l e y i s grown a s a s u b s t i t u t e f o r maize g r a i n i n f e e d i n g l i v e - s t o c k . I n normal weather c o n d i t i o n s , t h e y i e l d of m a i z e k . g r a i n

( 4 . 7 t o n / h a ) i s much h i g h e r t h a n t h a t of b a r l e y (3.1 t o n s / h a )

,

s o t h a t i t i s more p r o d u c t i v e t o grow maize g r a i n t h a n b a r l e y , and b a r l e y d o e s n o t appear i n t h e c r o p d i s t r i b u t i o n .

3.1.3 I m p o r t s and E x p o r t s

I f t h e p r o d u c t i o n from t h e complex i s n o t s u f f i c i e n t t o meet t h e l i v e s t o c k r e q u i r e m e n t s , SWIM may import maize g r a i n from o u t - s i d e t h e complex i n s u f f i c i e n t q u a n t i t i e s t o a l l o w t h e r e q u i r e m e n t s t o be m e t b u t a t a v e r y h i g h p r i c e (170 Lv/ton compared w i t h t h e normal p r i c e 113 L v / t o n ) . C o n v e r s e l y , when t h e r e i s a p r o d u c t i o n s u r p l u s , S W I M can e x p o r t maize g r a i n , wheat, b a r l e y from t h e r e g i o n .

The b a l a n c e of i m p o r t s and e x p o r t s i s g i v e n i n f i g u r e ( 3 . 5 ) , which d e m o n s t r a t e s t h a t it r e q u i r e s v e r y l i t t l e i r r i g a t i o n (6,890 h a ) f o r t h e r e g i o n t o become s e l f - s u f f i c i e n t (no i m p o r t s o r e x p o r t s ) i n normal weather c o n d i t i o n s b u t i n d r o u g h t c o n d i t i o n s a much l a r g e r a r e a of i r r i g a t e d l a n d (32,750 h a ) i s r e q u i r e d t o a c h i e v e s e l f - s u f f i c i e n c y . F i g u r e (3.6), which h a s a r a t h e r u n u s u a l s h a p e , shows t h e c o r r e s p o n d i n g t o t a l p r o d u c t i o n c o s t s , i n c l u d i n g t h e c o s t s of i m p o r t s . Under d r o u g h t c o n d i t i o n s t h e minimum t o t a l c o s t s (Lv 21.7 m i l l i o n ) a r e a t t a i n e d j u s t a t t h e p o i n t of s e l f - s u f f i c i e n c y . I f

l e s s l a n d i s i r r i g a t e d , t o t a l c o s t s r i s e b e c a u s e o f t h e c o s t of imported maize which o u t w e i g h s t h e s a v i n g s made by i r r i g a t i n g l e s s l a n d . Even i f i m p o r t e d maize were p r i c e d a t t h e e x p o r t p r i c e o f 113 Lv/ton t h e t o t a l c o s t would s t i l l r i s e s l o w l y i f l e s s l a n d i s i r r i g a t e d , assuming t h e same amounts of i m p o r t s a r e r e a u i r e d .

S i n c e i m p o r t s a r e n o t r e q u i r e d u n d e r normal w e a t h e r con- d i t i o n s , t h e t o t a l c o s t c u r v e i s c o n t i n u a l l y r i s i n g a s more l a n d i s i r r i g a t e d and t h e p r o d u c t i o n s u r p l u s i s e x p o r t e d . Another s t r i k i n g f e a t u r e o f f i g u r e ( 3 . 6 ) i s t h a t t o t a l pro- d u c t i o n c o s t s a r e v e r y s i m i l a r under b o t h w e a t h e r c o n d i t i o n s when t h e a r e a o f i r r i g a t e d l a n d i s g r e a t e r t h a n t h a t needed f o r s e l f - s u f f i c i e n c y . Of c o u r s e , t h e d i f f e r e n c e i s t h a t i n normal w e a t h e r c o n d i t i o n s , e x p o r t s a r e much l a r g e r i n t h i s r a n g e of

i r r i g a t e d l a n d development.

To d e t e r m i n e w h e t h e r i t i s economic t o d e v e l o p more i r r i - g a t e d l a n d t h a n t h a t n e e d e d t o a c h i e v e s e l f - s u f f i c i e n c y , t h e v a l u e of t h e s u r p l u s p r o d u c t i o n which c a n be e x p o r t e d s h o u l d be com- p a r e d t o t h e e x t r a c o s t s n e c e s s a r y t o produce t h i s s u r p l u s . These e x t r a p r o d u c t i o n c o s t s c a n be found by s u b t r a c t i n g t h e t o t a l p r o d u c t i o n c o s t t o a c h i e v e s e l f - s u f f i c i e n c y from t h e t o t a l p r o d u c t i o n c o s t s when more l a n d i s i r r i g a t e d t o produce e x p o r t s . The n e t v a l u e , o r n e t b e n e f i t , of e x p o r t s i s t h e n found by sub- t r a c t i n g t h e s e e x t r a p r o d u c t i o n c o s t s from t h e v a l u e ~ f t h e ex- p o r t s , and i s p l o t t e d i n f i g u r e ( 3 . 7 ) , which shows t h a t t h e n e t v a l u e o f e x p o r t s c o n t i n u a l l y i n c r e a s e s , i n a l i n e a r f a s h i o n , a s more l a n d i s i r r i g a t e d . The b e n e f i t - c o s t r a t i o , which i s t h e v a l u e o f e x p o r t s d i v i d e d by t h e e x t r a p r o d u c t i o n c o s t s , i s f a i r l y c o n s t a n t a t 2.0 f o r normal w e a t h e r c o n d i t i o n s and 2.4 i n d r o u g h t c o n d i t i o n s .

3.1.4 Value of I r r i u a t e d Land

While it m i g h t b e e x p e c t e d t h a t t h e c o s t of d e v e l o p i n g e a c h new u n i t ( h e c t a r e ) o f l a n d f o r i r r i g a t i o n would n o t change g r e a t l y w i t h t h e scale of development, the v a l u e o f e a c h new u n i t o f i r r i g a t e d l a n d m i g h t change q u i t e c o n s i d e r a b l y w i t h t h e s c a l e of development. I n t u i t i v e l y , it seems c l e a r t h a t t h e f i r s t

u n i t s of i r r i g a t e d l a n d w i l l have t h e g r e a t e s t v a l u e , a s

measured by e x t r a p r o d u c t i o n , b e c a u s e t h e c r o p s g i v i n g t h e b e s t r e s p o n s e t o w a t e r c a n b e i r r i g a t e d . A s more l a n d i s i r r i g a t e d , l e s s r e s p o n s i v e c r o p s a r e i n c l u d e d s o t h a t v a l u e of e a c h new u n i t , o r m a r g i n a l v a l u e , of i r r i g a t e d l a n d d e c r e a s e s w i t h t h e

s c a l e of i r r i g a t i o n development. . ( T h i s m a r g i n a l v a l u e i s t h e shadow p r i c e of t h e c o n s t r a i n t on i r r i g a t e d l a n d i n SWIM.) I n t h e economics of s u p p l y and demand, t h e o p t i m a l s c a l e of i r r i g a t e d l a n d development o c c u r s when t h e c o s t of d e v e l o p i n g e a c h new u n i t of i r r i g a t e d l a n d i s e q u a l t o t h a t u n i t ' s m a r g i n a l v a l u e .

F i g u r e ( 3 . 8 ) s h o w s t h e demand c u r v e f o r i r r i g a t e d l a n d which i s t h e change i n t h e m a r g i n s 1 v a l u e o f i r r i g a t e d l a n d w i t h t h e scale of i r r i g a t e d l a n d development, f o r normal w e a t h e r and

d r o u g h t c o n d i t i o n s . A s e x p e c t e d , t h e m a r g i n a l v a l u e of i r r i g a t e d l a n d i n d r o u g h t c o n d i t i o n s i s much h i g h e r t h a n i n normal w e a t h e r c o n d i t i o n s . I n f i g u r e ( 3 . 8 ) e a c h demand c u r v e i s composed of h o r i z o n t a l s e g m e n t s , where t h e m a r g i n a l v a l u e d o e s n o t c h a n g e w i t h t h e a r e a of i r r i g a t e d l a n d , and i n c l i n e d se9ments ( d a s h e d ) i n which t h e r e a r e c o n s i d e r a b l e d i f f e r e n c e s i n m a r g i n a l v a l u e . I n t h e s o l u t i o n s of SWIM, t h e h o r i z o n t a l segments o c c u r when e a c h new h e c t a r e of l a n d i s b e i n g u s e d t o i r r i g a t e t h e same c r o p as t h e p r e v i o u s h e c t a r e , w h i l e t h e i n c l i n e d segments o c c u r when a new c r o p b e g i n s t o b e i r r i g a t e d , o r when s e l f - s u f f i c i e n c y i s a t t a i n e d . A c t u a l l y , i f a l l p o s s i b l e a r e a s of i r r i g a t e d l a n d had been e v a l u a t e d , t h e d a s h e d segments would b e v e r t i c a l , a n d

l o c a t e d a t t h e e x a c t p o i n t where a new c r o p b e g i n s t o b e i r r i g a t e d . The c o s t o f i r r i g a t e d l a n d development of 1 0 3 . 2 5 Lv/ha,

which i s assumed i n SWIM i s a l s o p l o t t e d i n F i g u r e ( 3 . 8 ) . S i n c e t h i s c o s t l i n e a l w a y s l i e s below t h e demand c u r v e s , it may b e c o n c l u d e d t h a t t h e m a r g i n a l v a l u e of i r r i g a t e d l a n d i s a l w a y s g r e a t e r t h a n t h e u n i t c o s t o f d e v e l o p i n g it w i t h i n t h e r a n g e o f a r e a c o n s i d e r e d and t h e a c c u r a c y o f SWIM.

3.2 Water For I r r i q a t i o n

shown i n f i g u r e (3.1 3 )

,

t h e m a r g i n a l v a l u e of w a t e r i s h i g h e r i n d r o u g h t c o n d i t i o n s t h a n i n normal w e a t h e r c o n d i t i o n s , and f o r b o t h w e a t h e r c o n d i t i o n s t h e demand c u r v e s l i e above t h e u n i t c o s t of pumping w a t e r (0.022 Lv/m 3 ) s o t h a t it i s always o p t i m a l t o s u p p l y a l l t h e w a t e r demand.

3 . 3 I n p u t Resources

B e s i d e s l a n d and w a t e r , SWIM a l s o d e t e r m i n e s t h e r e q u i r e d amounts of t h e o t h e r i n p u t r e s o u r c e s : s e e d s , f e r t i l i z e r s , f u e l , l a b o r , and machinery. A s c a n be s e e n from t h e t a b u l a t e d r e s u l t s i n Appendix 1 , t h e s e amounts do n o t v a r y a g r e a t d e a l i n t h e v a r i o u s s o l u t i o n s of SWIM, s o o n l y a v e r a g e d a t a a r e g i v e n i n t h i s s e c t i o n .

The d i s t r i b u t i o n o f w a t e r r e q u i r e d o v e r t h e i r r i g a t i o n s e a s o n from A p r i l t o August i s a p p r o x i m a t e l y a s f o l l o w s : A p r i l , 2 % ; May, 8 % ; J u n e , 20%; J u l y , 30% and August 40%.

The r e q u i r e d i n p u t r e s o u r c e s when 40,000 ha o f l a n d a r e i r r i g a t e d c o n s i s t o f :

-

2870 ha o f l a n d f o r s e e d p r o d u c t i o n ;

-

24,000 t o n s of ammonium s u l p h a t e ; 30,000 t o n s o f s u p e r p h o s p h a t e ; 7,500 t o n s o f p o t a s s i u m s u l p h a t e ;

-

7 m i l l i o n l i t r e s of f u e l ;

-

240,000 h o u r s o f l a b o r f o r o p e r a t i n g m a c h i n e s ;

-

120 t r a c t o r s ;

-

75 combine h a r v e s t e r s - ;

-

35 s i l a g e c h o p p e r s ;

-

710 c e n t r e - p i v o t s p r i n k l e r s .

Area of Irrigated Land (Ha)

Figure 3.1 Water Demand vs. Area of

irrigated

Land 200

Water Demand

150 (millions

of cubic metres)

100

50

0

- -

- -

' A

I I I I 1

10000 20000 30000 40000 50000

Area nf Irrigated Land (Ha) 80

% increase 60 in water

demands due to 40 drought

20

Figure 3.2 Increase in Water Demands due to Drought us.. Area of Irrigated Land

- I 1 I I I

'

-

-

I I I I I

-

120.). SF-- SF---3F-SF-- S F - S F - SF--- SF - S F

1 1 1

S u n f l o w e r s ( 1 0 , 5 0 0 h a )

t

I

L u c e r n e (19,517 h a )

I

I I

B R $ Wheat (17 4 3 5 h a )

1

I

1

Maize S i l a g e (1 1 ,6 7 9 h a )

I r r i g a t e d Area ( t h o u s a n d s of h a )

F i g . 3 . 3 Crop D i s t r i b u t i o n v s . Area o f . 1 r r i g a t e d Land (Normal w e a t h e r ) ( s h a d e d p o r t i o n i s a r e a i r r i g a t e d )

l ? U + SF-. S r --.SF - - F F

-

- 5 ^{3 1} -SF --.- ^{S f - SF --. SF}

+

s u n f l o w e r s ' ( 1 5 , 0 0 0 h a )

L u c e r n e ( 2 2 , 9 1 6 h a )

I .

Rl? [!s - -RR- OR ,g@ 5 0 ---- s ^[) $u---Sr!

4

^{.J rt 1. .'}

B a r l e y / I S B

1

^!5tI//

S B /

I r r i g a t e d A r e a ( t h o u s a n d s o f h a )

F i g . 3 . 4 C r o p D i s t r i b u t i o n v s . A r e a o f I r r i g a t e d Land ( D r o u g h t ) ( s h a a e d p o r t i o n i s a r e a i r r i g a t e d )

2 0 ^I I 1 I I

15

_

Exports Normal Weather

10

-

5 , ( m i l l i o n s

(6,890 ha) (32,750 ha)

5

- -

Imports

10 ,

-

15

- ^-

-

2 5 ^I I I I I

10000 20000 30000 40000 50000

Area of I r r i g a t e d Land (Ha)

Figure 3.5 Value of Imports and Exports v s . Area of ~ r r i g a t e d Land

Total 25 Cost

(millions 20 of Leva)

Drought ~onditions

= Lv 21,700,000

Normal weather conditions Cost of self-sufficiency

= Lv 15,490,000

Net Value

of

Exports 5 . (millions

of Leva)

Area of Irrigated Land (Ha)

Figure 3.6 Total Costs vs. Area of Irrigated Land

10000 20000 30000 40000 50000 Area of Irrigated Laild (Ha). ^{. . . .}

Figure 3.7 Net Value of Exports vs. Area of Irrigated Land

Marginal Value

0 f I r r i g a t e d

Land (Lv/Ha)

C o n d i t i o n s \

Normal \

C o n d i t i o n s

b

^D5

\

^{n .#}

- 0 1

D e p r e c i a t e d c o s t of i r r i g a t e d l a n d developmen

- - - - --- \ -- 4

Area of I r r i g a t e d Land (Ha)

F i g u r e 3.8

em and'

c u r v e s f o r I r r i g a t e d Land E x p l a n a t i o n of Regions of Demand Curves:

D l - Maize g r a i n b e g i n s t o be i r r i g a t e d , b a r l e y a r e a d e c r e a s i n g D2- More i r r i g a t e d maize g r a i n grown, b a r l e y a r e a d e c r e a s i n g D3- Barley n o t grown, soybeans b e g i n t o be i r r i g a t e d

D4- Region becomes s e l f s u f f i c i e n t , maize g r a i n b e g i n s t o be e x p o r t e d D5- ^' I n c r e a s i n g i r r i g a t i o n of soybeans and maize g r a i n

N1- More soybeans i r r i g a t e d , n o n i r r i g a t e d maize g r a i n grown N2- A l l soybeans i r r i g a t e d , maize g r a i n b e g i n s t o be i r r i g a t e d N3- More maize g r a i n i r r i g a t e d

I I 1 I I I I

- - -

- -

Normal Weather Conditions

-

-

Drought Conditions

-

I I I I I 1 I

-

20 4 0 6 0 80 100 120 140 160

Available Water (millions of cubic metres) Figure 3.9 Area of Irrigated Land vs. Available Water

b a t

Fig 3.10 Crop Distribution vs. Available Water (Normal Weather) (shaded portion is irrigated area)

C: ? P 4 0 b 0 R n 1 M C ~

Available Water

(millions of cubic metres)

Figure 3.12 Production Costs vs. Available Water

Available Water (millions of cubic metres)

D5- No more barley grown, export of maize begins, exports of wheat decrease D6- Exports of wheat cease

N1- Irrigated maize grain begins to be grown N2- Irrigated area becomes limiting, factor

4. CONCLUSIONS ^{' -}

The development of land and water for irrigation in the Drustar agricultural-industrial complex in 1980 is investigated for both normal weather and drought conditions. The major re- sults are:

a) 33,000 ha of irrigated land and 135 million cubic metres per year of water are needed for the complex to be self-

sufficient in drought conditions. At this level of development, 100,000 tons of maize grain could be exported from the complex under normal weather conditions.

b) The total costs of crop production are minimized at the point when the complex is just self-sufficient.

c) The marginal values of land and water developed for irrigation are always greater than their unit costs of supply in the range of development considered.

d) The optimal distribution of crops to be grown on both irrigated and nonirrigated land is determined for all cases in- vestigated.

These results are preliminary and should only be inter- preted as being indicative of the kind of questions the model can answer. However, we consider that the data and structure of the model could be improved and extended through further

discussion with Bulgarian experts to make the model sufficiently reliable for actual decision-making. Improvements in the data could include:

-

Crop yields without irrigation for various weather conditions.

-

The relation between crop yields and water applied by irrigation.

-

Costs and technology of crop production, especially for irrigation.

Extensions to the structure of the model could involve:

-

Breaking down t h e c m p h x on the basis of soil type into sub-regions which have different crop yields and water requirements.

-

Introducing the livestock of the complex into the model and considering different diets for them.

-

~ a k i n g account of other crops which could be grown in the ~ o m p l e x .

-

Adding the dynamics of change from year to year, such as crop rotations and grain storage.

-

Incorporating the facilities needed for water supply, such as dams, pumps, and channels.

REFERENCES

Carter, H., C. Csaki, A. Propoi,.PZann.ing Long Range Agricultural Investment Projects:

A

Dynamic Linzar

Programming Approach, IIASA RM-77 -3 8, June 1 97 7.

Donev, K., Razvitie na~~ioitelnite Sistemi i Povishavane na efectivnostta im (Development of Irrigation

Systems and Increasing their Efficiency), published by Zemizdat, Sofia, 1972.

Ministry of Information and Communications, Statisticheski godishnik (Statistical Yearbook)

for Peoples Republic of Bulgaria, Sofia 1975.

Propoi, A.

,

Dynamic Linear Programming Models for Live- stock Fams, IIASA RM-77-29, June 1977.

Appendix 1

TABLES OF COMPUTATIONAL RESULTS

The f o l l o w i n g f o u r t a b l e s g i v e t h e d e t a i l e d d a t a produced by,SWIM computer p r i n t o u t s f o r e a c h of t h e s e r i e s of computer r u n s c a r r i e d o u t : v a r y i n g t h e amount of i r r i g a t e d l a n d , and t h e amount of w a t e r , b o t h under normal w e a t h e r c o n d i t i o n s and d r o u g h t c o n d i t i o n s . A g l o s s a r y of t h e terms used i n t h e p r i n t - o u t s i s i n c l u d e d t o a i d i n t h e i n t e r p r e t a t i o n of t h e r e s u l t s .

A L U I

U N I T

* - Y O

9 0 m = b l l *

a o - e n w n e e _{- . r e}

..-

-

^m

O Q O I P . -YILIfA - L O G

-0..

a a a m O I L ₀

-

w

:=: ^:

h

r a w 'II . . . Y 0 0 -

--

It:

m i - _{0 0 -}

... _--

₌

2

0 - &

L Q 6 e a c

- . .

8 4 _yl

-

9 0 r

--el

L U *

m m a

....

_{O O *}

C O B

ae4- - - m

-

⁰

m . r Q e O C * - C C I n o r

~ C Co n - O C + m * e -41 (s 4

.)

Im Dokument Agricultural Water Demands: Preliminary Results of Silistra Case Study (Seite 27-99)