Options Méditerranéennes : Série A. Séminaires Méditerranéens; n. 31 1997
pages 367-377
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--- Kirda C. Assessmen t of irrigation water qu ality. In : D upuy 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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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 sontdiscutées 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 condi-
tions, 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
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 con- tent still being used in these and no
effect has been man-
agement 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 32250 - 5000 10
-
r-
4000
-
6000 18 18 15000 - 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
intion 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
E C x l 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
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
-
10o<
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 con-
cept 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 [l1
ion given in me.1-l.
1 can be used to assess the long-time in-
fluence 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 so-
dium value, sodium
effective salinity and of the
Assessment irrigation water quality 371
TOTAL SALTS, L-'
O
O
O
O
O
O
O
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
Assessment of irrigation water quality 373
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 guidelinesrelated 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
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 condi- tions. 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
Assessment of irrigation water quality 375
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 al-
lowed 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
within the soil at the end of each
season. annual is not enough to leach ac- cumulated 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 sa- linity,
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 bein conductivity units:
-
-
~ 7 1
ECe and in
(dS.m-') of soil satu- of
tively. EC of
EC of with the equa-
tion 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 accu- mulated 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
