Assessment of irrigation water quality - CIHEAMom.ciheam.org/om/pdf/a31/CI971550.pdf · Assessment...

Assessment of irrigation water quality

Kirda C.

in

Dupuy B. (ed.). Aspects économiques de la gestion de l'eau dans le bassin méditerranéen

Bari : CIHEAMOptions Méditerranéennes : Série A. Séminaires Méditerranéens; n. 31

1997pages 367-377

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Kirda C. Assessment of irrigation water quality. In : Dupuy B. (ed.). Aspects économiques de la

gestion de l'eau dans le bassin méditerranéen . Bari : CIHEAM, 1997. p. 367-377 (Options

Méditerranéennes : Série A. Séminaires Méditerranéens; n. 31)

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http://om.ciheam.org/article.php?IDPDF=CI971550

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http://om.ciheam.org/

C.

Çukurova University

Faculty Agriculture

Adana, Turkey

SUMMARY - World wide extent of saline of water resources is briefly discussed. Sampling techniques and methods of analysis of water samples with reference to irrigation quality assessment are briefly reviewed. A chronological review of irrigation-water quality criteria is presented and its limitations are discussed. It is shown that water quality alone would not suffice to evaluate potential salinity hazard of irrigation water unless consideration is given to crop, soil, climate and existing agronomic and irrigation management practices. Importance of drainage, land preparation crop rotation, specific irrigation methods and management are discussed as regard their influence on salt balance in the plant root zone.

Key words: Irrigation water quality, irrigation, salinity, salt leaching.

RESUME - La vaste étendue des ressources en eau salée dans le monde est brièvement discutée. Les techniques d'échantillonnage et les méthodes d'analyse des échantillons d'eau avec référence aux normes de qualité pour l'irrigation sont examinées. Une revue chronologique des critères de qualité de l'eau d'irrigation est présentée et leurs limites sont discutées. II est montré que la qualité de l'eau seule n'est pas sufisante pour évaluer les risques de salinité potentielle de l'eau d'irrigation, moins de prendre aussi en considération les plantes, le sol, le climat, les pratiques agronomiques et la conduite de l'irrigation existantes. L'imporfance du drainage, la préparation du sol, la rotation des cultures, les méthodes d'irrigation spécifiques sont discutées du point de vue de leur influence sur I'équilibre en sel dans la zone racinaire de la plante.

Mots-clés: Qualité de l'eau d'irrigation, irrigation, salinité, lessivement.

is the input plant in Bulk weight of all

living consists of 80 to 90 % plant is met with

in plant conditions, is with is essential in to maintain soil

at an optimum level to

ment of in plant than All

in dissolved salts face of

only with to its

ity

Options Méditerranéennes, Sér. A /n031, 1997 Séminaires Méditerranéens

CIHEAM - Options Mediterraneennes

Serie A: Seminaires mediterraneens

368 C.

to its effects on soils, to com- pensate linked to

to note that not all soil deg- like salinity, soil toxicity etc.

can be to

Total salt of not be used as a single to its use in

Even with high salt can still be used without

soil management could take into account all

affecting point is how to maintain existing salt balance in plant zone. Total salt of field sails is

than salt tion than what is

actually needed, table to and salt becomes 40-50 times of that This condition can be

with such cases, the

issue to deal with is the 1 gives of

in selected to one

uses (1954) alone, 67 and 40% of the should not have been used and

of such a high salt content still being used in these and no

effect has been management implemented in these it must salt accumulation. quality is not the only to assess suitability of

Table l - conductivity of irrigation water sources in selected countries (Amon, 1972)

ECx 106 USA INDIA 25 "C

1018 79 576 1507 250- 750 53 5 13 36 750 - 2250 37 28 35 60

2250 - 4000 - 28 22 3 2250 - 5000 10 - r - 4000 - 6000 18 18 1 5000 - 20000 21 -

Sampling

One needs 2 its analysis in is that

the sample must special to that. of sampling depending on such

must be mid-way

along the width of the

should come the and the deepest of the lake. is best if fi-om dams comes ftom the the leaves the take

the mounts the lakes. Samples deep wells must be taken 15 to 20 min-

utes schemes taken

to that no mixing takes place with tail Som the fields. Samples

in 1 to 2 glasses to the should be ana-

lyzed without delay to biological mation.



Assessment of irrigation water quality 369

of analysis

of

to

g.m-3, me.lt-' and the like.

(Coi'), and in

with anion (SOL') is usually analyzed with method. Sulfate is out with addition solution to the

with is in the sample. Calcium

and magnesium of the in

and the simplest method of

potassium is to some using tion if available.

classìflcatìons

Scofield (1935) is among the putting to assess had

toxic effects of Cl-' and Soi2 in tion 2).

classification and ne- glected potential toxicity (Table tion suggested by Wilcox and to

called "effective salinity" (ES) to solubility of dif-

salts likely to in can simply be calculated by tions of Ca and fkom the total salt

it is that they can out in soil a new

he also gave con- to soil 5).

Table 2 - Concentration limits for irrigation water quality (ScoJield, 1935).

Class ECxl Total salt Na ratio cl-l

(PPW % s04m2

25" C (mel) (me/l) 1. Very good c250 c1 75 c4 c4 2. Good 250- 750 175- 525 20- 40 4- 7 4- 7 3. Can be used 750- 2000 525- 1400 40- 60 12 7- 12

Use with caution 2000- 1400- 2100 80 12- 20 12- 20 5. Harmful 21 8 0 ~ 20C 20c

Table 3 - water

Class 1 25" C

Total salt Na ratio Boron (PPW % (PPm)

1. c1 c700 c60 ~ 0 . 5 2. 1000- 3000 700- 2000 60- 75 0.5- . 2.0 3. 2000c 75< 2.0c



3 70 C.

Table 4 - water classes. (Doneen, 1954)

Class Class Class

good hazardous very hazardous Criteria Very good - Good - Hazardous -

E C x l C O00 1000- Boron, ppm

o< ~~

Table 5 - Classijìcation of irrigation water based on (Doneen, 1958)

Soil characteristics ES Class Class Class

Little or no leaching me/l . 3 - (Clay soils) PPm c1 165 - Low leaching, drainage is me/l - 10 o< restricted (Silty soils) PPm - Good drainage (Sandy me/l - soils) PPm -

Long-time effects of physical of soil depend mainly on total salt, tion of initial soil ties of soil itself. a concept called to assess

influence on physical of soils. The can be calculated using

gation the two constituents of the classes of saliity

to assess Salinity is based on conductivity

A concept called sodium ad-

value is calculated using

= + JHCOL' ) l Cations [l 1

ion given in me.1-l. 1 can be used to assess the long-time influence of soil

soil soil as well

developed by US Saliity (1954) has wide acceptance in many Total salt con-

of the

given in me/l. 2 can be used to classes in which a given can be placed using EC and values.

et al. (1977) have to use a to assess

quality. They defined 6 classes of tion total salt sodium value, sodium effective salinity and of the



Assessment irrigation water quality 371

TOTAL SALTS, L-'

O

O

O

O

O

O

O



3 72

C2-S4

G2-S

c2-S2

\

d c3-S

n

c4-s3

2 - Diagram for irrigation water quality classification (ìX'SL, 1954).

Table 6 - Limit values to assess irrigation water quality

Quality ~ ~ ~ 1 0 3 Na Na2C03 ES Boron

% (meIl> (me/l) (meIl> (PW) 3 3

1 .o 10

4 3.0 3.0 3.0 90 20 32

*

* Values are higher than those of quality




OF

including fiom

that it was not possible, to define

of main emphasis of was on ionic com- position of the they did not con-

salt of plant species,

in a given A class of in a given may well be

quality in a to use

only as a and to plant, soil and climatic conditions in the final evaluation of the

Guidelines for irrigation water quality

Committee of Con- "guidelines", which evolved fiom

long of finding of US Salinity (Table 7) tackle mainly ability, toxicity and miscellaneous. The guidelines

flexible and should be modified in with special

climate, method of in the

Table 7 - Guidelines for irrigation water quality (Ayers, 1977)

Problems and Water quality guidelines

related constituent No problem Increased prob. Severe prob.

Salinity ECw

Permeability ECw ~ 0 . 5 adj .SAR ~ 6 . 0

Specific ion toxicity 1 .Root adsorption Na(adj.SAR) Chloride

me.]-" 0.0 >l o PPm <l

Boron, ppm ~ 0 . 5 2.0-1 0.0

Na 2. Foliar application

me.]-' -- PPm <l --

3. Micelleneous NH4-N, NO3-N for sensitive crops

HC03 with overhead sprinkler PPm

me.¡-" <l .5 l PPm

PH normal range



3 74

Soil conditions

Salt accumulation is closely to soil ability. Salinization of soils with heavy clay

is than that of light sandy soils. Use of high Na

(i.e., > 10) in soil of low meability may cause in the ability. Thus, the salinkation

of high salt long of time with no indication of salinization, in

in no salinization is possibly

due to light soil Additionally, specific used in such

highly salt some cases,

blocks, is to

high 2300 used, but only in sandy soils with systems. some of example the

has an unusual1 high salt 8000 to 10000 mg.1- .

, specific to to maintain

existing soil is only allowed once in two Only deep soils (2 - 3m) of light Salts accumulated the season can easily

,ing 400-600 mm a n n d y . Additional limitation is that such as maize and tomato can be grown successfully, in these

Y

Crop salt tolerance

in light of salt a given quality of gation significant yield

effect may be ob- special-

ists, f m should salt as in

evaluation of 1977).

is than in climates.

calls up high amount of application, which in turn, salt in

annual is quality may not be of con-

if land Annual tion amounting 400-500 mm may be quite adequate to salt accumulation

Seasonal changes of water quality

Quality of is not seasons. Salt of lakes and man made the end of

change of the de- of the

the salt change is only 10-20 % in bodies of it may be as high as 100 % in

small ponds, lakes and Nile, example, has the least salt floods; salt is ing the show the least fluctuations in salt shallow wells may show changes.

of sessed its seasonal fluctuations in salt

TO

Salt balance in plant zone depends on tion scheduling and on soil and climatic conditions. Guidelines discussed below may help to

salinity.

is the gated systems complemen- tary is not adequate. is essential that an

open system must be implemented in the age, continuity of existing soil will al-

Climate

Annual in a given influences signifi- cantly salt balance in plant zone. and is




irri- soil Occasional deep ploughmg in soils

methods being used. Land levelling

may a completely soil in

such that it should in- to salinity (Fig. 3).

3 - of seed bed and soil salinity in&rrow irrigation (Bernstein et al., 1955).

Crop rotation

When it is high salt should also be included in the

salt balance in plant it

application which leaches excess salts left in a good field

cultivation is essential.

methods and management

basin to to minimize salinization

when good quality of is not in

leaching of excess soil salts, is not used.

of but applied

soil allowed to fluctuate within a

to field capacity. such cases,

has been shown that is effective in leaching of saline soils et al., 1972; et al., 1974) than meth-

in amount of in tems than systems, some salt accumulation may be evident



376 C.

within the soil at the end of each season. annual is not enough to leach accumulated salts, to maintain the salt balance. low tion systems, like meth-

is applied in small quantities, on daily basis. soil is kept high in such soil content cause low osmotic potential (i.e., low salt salt contents of 2000 to 3000 can be safely used without any significant

some salt accumulation is unavoidable at the end of the season. annual is not enough to leach the accumulated salts, the leaching

requirement

quality of is such that it may cause soil salinity,

to accumulation of salts in plant zone. Seasonal changes of salt

tion in plant zone is it should not be of soil salinity to show an the

in a the existing management system needs to be examined.

Each application salts to plant zone. Although accumulation of salts can be

season, soil salinity must not be allowed on an-

nual basis fiom to that

to maintain salt balance within the soil salinity balance in

is as as balance within plant zone (i.e., soil

as

c31

is G capil- fiom ET

and one can salt balance equation as

[41

C is of

nents shown with indexes. the balance equation, salt and salt ET and assumed to Us- ing equations [3] and [4] and assuming that

is no seepage hom high lands the following 1973)

Ctk -

-

Ctk - Ci

[51

soil defined as Ctk is soil salt concen- at field capacity with additional equalities

of The equations [5] and [6] can also be in conductivity units:

-

-

~ 7 1

ECe and in (dS.m-') of soil satu-

of tively. EC of

EC of with the equation both coefficient

out flow) and estimated using the equations

[7] and [8], salt accumulation is essentially nil. methods

is applied may cause salt accumulation the annual

is not sufficient to leach out the accumulated salts such systems, then salt leaching is essential off-season should be commented that less amount of salts is new methods of

such as the like, as to meth-

leaching of annually accumulated salts should not be of a annual may be sufficient the leaching. the



Assessment irrigation water quality 377

is sustain soil

is not enough to

is not possible to classifl of

well as existing and in a given in the final

specialists

to potential salinity if the quality of

guideline to tices in to maintain existing soil with the benefits of high

Amon, J. in and London.

Ayers, (1977). Quality ASCE, 103:135-154.

Bernstein, in Valley, 4. pp16..

Christiausen, J.E., Olsen, E.C., Willardson, (1977). quality. J. ASCE 103: 155-169.

(1954). Salinization of soils by salt in

(1958). Quality of on Quality of (ed) No. 14., pp 208.

Sym. Ann. 213-218.

Biggar, J.W. on leaching. Soil Sci. 117: 323-330.

salt - Cument assessment. J. and ASCE 103: 115-134.

G.J. (1972). and ponding techniques saline 11 15-1 117.

Scofield, C.S. (1935). Salinity of Annual 275-287.

Alkali Soils. 60,

(1973) Salt balance and and Aplications

Wilcox, (1943). of and Salt of U.S. of



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