Journal of Environmental Protection, 2010, 1, 30-40
doi:10.4236/jep.2010.11005 Published Online March 2010 (http://www.SciRP.org/journal/jep)
Assessment of Groundwater Quality and its Suitability
for Drinking and Agricultural Uses in the Oshnavieh
Area, Northwest of Iran
Nosrat Aghazadeh1*, Asghar Asghari Mogaddam2
1Department of Geology, Urmia Azad University, Urmia, Iran; 2Department of Geology, Tabriz University, Tabriz, Iran.
Received December 8th, 2009; revised February 27th, 2010; accepted February 28th, 2010.
ABSTRACT
The Oshnavieh plain is part of the West Azarbaijan province, which is located; 100 km south of Urmia City, northwestern
of Iran, and its groundwater resources are developed for water supply and irrigation purposes. In order to evaluate the
quality of groundwater in study area, 31 groundwater samples were collected and analyzed for various parameters.
Physical and chemical parameters of groundwater such as electrical conductivity, pH, total dissolved solids, Na, K, Ca,
Mg, Cl, HCO3, CO3, SO4, NO3, NH3, PO4, Fe, F were determined. Chemical index like percentage of sodium, sodium ad-
sorption ratio, and residual sodium carbonated, permeability index (PI) and chloroalkaline indices were calculated. Based
on the analytical results, groundwater in the area is generally fresh and hard to very hard. The abundance of the major
ions is as follows: HCO3 > SO4 > Cl and Ca > Mg > Na > K. The dominant hydrochemical facieses of groundwater is
Ca-HCO3 and Ca-Mg-HCO3 type. According to Gibbs diagrams samples fall in the rock dominance field and the chemical
quality of groundwater is related to the lithology of the area. The results of calculation saturation index by computer pro-
gram PHREEQC shows that the nearly all of the water samples were saturated to undersaturated with respect to carbon-
ate minerals and undersaturated with respect to sulfate minerals. Assessment of water samples from various methods in-
dicated that groundwater in study area is chemically suitable for drinking and agricultural uses. Fluoride and nitrate are
within the permissible limits for human consumption and crops as per the international standards.
Keywords: Groundwater Quality, Hydrochemistry, Hydrogeology, Oshnavieh Plain, Water Type
1. Introduction
Understanding the aquifer hydraulic properties and
hydrochemical characteristics of water is crucial for
groundwater planning and management in the study
area. Generally, the motion of groundwater along its
flow paths below the ground surface increases the con-
centration of the chem. ical species [1–3]. Hence, the
groundwater chemistry could reveal important infor-
mation on the geological history of the aquifers and
the suitability of groundwater for domestic, industrial
and agricultural purposes. Moreover, pumping tests
with the drilling results are the most important infor-
mation available for the groundwater investigations, as
they are the only methods that provide information on
the hydraulic behavior of wells and reservoir bounda-
ries [4,5].
Hydrochemical evaluation of groundwater systems is
usually based on the availability of a large amount of
information concerning groundwater chemistry [6,7].
Quality of groundwater is equally important to its quan-
tity owing to the suitability of water for various purposes
[8,9]. Groundwater chemistry, in turn, depends on a
number of factors, such as general geology, degree of
chemical weathering of the various rock types, quality of
recharge water and inputs from sources other than water-
rock interaction. Such factors and their interactions result
in a complex groundwater quality [1,10,11]. The rapid
increase in the population of the country has led to large
scale groundwater developments in some areas. Intense
agricultural and urban development has caused a high
demand on groundwater resources in arid and semi-arid
regions of Iran while putting these resources at greater
risk to contamination [12–14]. Groundwater is an impor-
tant water resource for drinking, agriculture and indus-
trial uses in study area. In this study, physical, hydro-
geologic, and hydrochemical data from the groundwater
system will be integrated and used to determine the main
factors and mechanisms controlling the chemistry of
groundwater in the area. The relationship between
groundwater flow, hydrogeologic properties and hydro-

Assessment of Groundwater Quality and its Suitability for Drinking and Agricultural uses in the Oshnavieh Area, Northwest of Iran 31
chemistry has been studied by many researchers [2,15,
16]. The chemical quality of groundwater is related to the
lithology of the area.
The Oshnavieh aquifer is part of the Gedar river
drainage basin and lies between latitudes 36°,57′ to
37°,05′ N and longitudes 45°,01′, to 45°,15′ E. Oshna-
vieh plain covers an area of 120 km2 and average ele-
vation is 1450 m a.s.l. (Figure 1). The Gedar river ba-
sin covers approximately 2010 km2 and river flow di-
rection is almost west-east with utmost discharges into
the Urmia lake. The most important drainage feature of
the study area is the Oshnavieh, Nilvan and Sheykhan
rivers. The area has a cold temperate climate and the
air temperature is highest in August (26.7℃) and low-
est in January (–1℃) with an annual average of 13.3℃.
The climate of the study area is semi-arid and it’s aver-
age annual rainfall is about 422 mm, which 70% of it
falls during the spring and winter seasons. The most
important economic activity in the area is agriculture,
with the chief crops being beet, wheat and pea.
2. Materials and Methods
Groundwater samples were collected from 31 shallow
and deep wells and springs of the area during May 2006.
The location of sampling points is shown in Figure 4.
The pH and electrical conductivity (EC) were measured
using digital conductivity meters immediately after
sampling. Water sample collected in the field were ana-
lyzed in the laboratory for the major ions (Ca, Mg, Na,
K, HCO3, CO3, SO4, Cl), nitrate, phosphate, ammonia,
iron and fluorine using the standard methods as sug-
gested by the American Public Health Association [17].
Sodium (Na) and Potassium (K) were determined by
flame photometer. Total hardness (TH) as CaCO3, Cal-
cium (Ca2+), carbonate (CO3), bicarbonate (HCO3) and
chloride (Cl) were analyzed by volumetric methods.
Magnesium (Mg) was calculated from TH and Ca con-
tents. Sulfates (SO4) were estimated using the colori-
metric technique. Nitrate (NO3), phosphate (PO4), am-
monia (NH3), iron (Fe) and fluorine (F) were determined
by spectrophotometer. The saturation indexes were de-
termined using the hydrogeochemical equilibrium model,
Phreeqc for Windows [18].
3. Results and Discussion
3.1 Geological and Hydrogeological Stting
From a geological point of view, the investigated area is
located in the Khoy-Mahabad zone of the Iran [19]. Ig-
neous, metamorphic and sedimentary rocks of different
age’s crop out in the basin and range in age from Per-
cambrian to Quaternary. Precambrian sedimentary rocks
consist of green to grey shale and siltstone. Cambrian
formations in study area chiefly comprise crystalline
limestone, siltstone, sandstone and dolomite in alterna-
tion with dark shale. The Ophiolite formation consists of
crystallized limestone and shale with serpentinized ul-
tramafic rocks, spite and some schist [20]. Igneous rocks
of late Cretaceous age outcrop in many mountain and
Turkey
Urmia
Mako
Khoy
Salmas
Oshnavieh
Chalderan
Urmia Lake
Iraq
39
38
37
45 46 47
Zolachai
Shahrchai
Aghchai
Town
Lake
River
020 Km
Sea
Caspian
Tehran
Gulf
Persian
Iran
Figure 1. Location of study area in iran

Assessment of Groundwater Quality and its Suitability for Drinking and Agricultural uses in the Oshnavieh Area, Northwest of Iran 32
including biotite granite, muscovite garnet granite, dio-
rite, monzodiorite and granodiorite. The Quaternary
sediments consist of alluvial sandy gravel, alluvial fan
consists of a clay, silt, sand, gravel and clearly sand. The
thickness of this major aquifer increases from the fan
deposits in the west towards the middle and southeast
side of plain. Figure 2 shows the distribution of the out-
cropping rock formations in the study area. The basin is
tectonically active and the most important structure that
affected the geology of the Oshnavieh basin was the
Aghbolag, Kandvola and Shivehbro fault system. The
exposed lithological units of the Oshnavieh plain range
in age from Precambrian to Quaternary and have differ-
ent hydrogeological characteristics (Figure 2). The strati-
graphic succession of study area shows in Table 1. The
units of similar hydrogeological characteristics are sum-
marized in Table 1 and qualitatively grouped as imper-
meable, semi-permeable and permeable.
In the study area, the Eocene Formations and intrusive
rocks are impermeable, and the Cambrian formations
(Zaigun, Lalum and Barut Formation) and Precambrian
Formations (Kahar Formation) are semi-permeable. The
Ruteh Formation, alluvium and old terraces are perme-
able [21].
Table 1. Stratigraphic relations of the geologic units in the
study area showing hydrogeologic properties
Hydrogeologic
properties
Lithology Unit Age
Permeable
Gravel, Sand, Clay,
Sandy clay and clearly
sand
Recent alluvium
Young alluvium
Old terraces
Cenozoic
impermeable
Limestone, Shale,
Spilite, Schist and
Serpentinite
Ophiolite Eocene
Permeable Limestone and Shale Ruteh FormationPermian
semipermeable
Siltstone, Sandstone,
Shale, Limestone and
dolomite
Zaigun, Lalum
and Barut
Formation
Cambrian
semipermeable
Schist, shale and
siltstone
Kahar Formation
Precam-
brian
impermeable
Granite, Grano diorite,
Amphibolite and diabaz
01 Km
45,1,57 45,15,28
37,5,8
36,57,50
P
I
r
Gondvola faule
Gedar River
Oshnavieh City
di
bg
II
om om om
sr
bt2
e
sh
Pe
am
Qal Nalos
Khaled abad
Kane sorkh
Paleozoic
Per.
Cambrian
(Zaigun-Lalun Fm.)
(Ruteh-Fm.)
Prec.
Sandstone
Barut Fm.
Micaceous schist
P
I
r
e
bt2
Pe
sh
Late Creta.
Biotite grani te
Diorite
Granodiorite
Marble
di
bg
mb
am Amphibolite
and schist
Cenozoic
Quaternery
Mesozoic
Late Cretaceous
Eocene
Recent alluvium
Young alluvium
Old terraces
om : Ophiolite
limestone
Serpentinite
I
sr
Qt2
Limestone
bt1
e
e2
gb
gb
ebt1
Legend
Town
Village
Anticline axis
Syncline axis
Thrust
Major faults
River
Major road
Minor road
Sea
Caspian
Tehran
Gulf
Persian
I.R. Iran
Figure 2. Location of study area showing geology and hydrogeology units

Assessment of Groundwater Quality and its Suitability for Drinking and Agricultural uses in the Oshnavieh Area, Northwest of Iran 33
Oshnavieh aquifer is occurred in Quaternary sediments,
which are distinguished by horizontal and vertical ex-
change of various lithological units. It is composed of
Pleistocene and Holocene gravel-sand sediments and
with silt-clay interbreeds. From field work and observa-
tions, groundwater occurs in the study area in two main
water-bearing layers, a lower confined aquifer and an
upper unconfined aquifer. Groundwater recharge is from
rainfall. In the study area groundwater is an important
source for domestic water supply. Groundwater and sur-
face water of Gedar rivers use for agriculture uses. Ac-
cording to Azarbaijan Regional Water Authority [22],
122 deep and 253 shallow active pumping wells operate
in the aquifer. The water abstraction from the Oshnavieh
aquifer during the 2003-2004 is about 30.738 million m3
and presented in Table 2. The hydraulic properties of
Oshnavieh aquifer was determined using pumping tests
data. The Oshnavieh aquifer is characterized by trans-
missivity that varies from 500-3000 m2/day and specific
yield of about 3 × 10-2 [22]. One of the main imperative
approaches for the identification of groundwater flow
directions is the water level contour map, which has been
used as a basis for evaluating groundwater recharge.
Hence, water heads in meters above sea level (a.s.l.) in
each piezometr were used to construct the piezometric
surface contour map using the Surfer Software. The
groundwater level contour map shown on Figure 3 sum-
marizes the distribution of piezometric head in the aqui-
fer system within the study area. The general groundwa-
ter flow direction in the aquifer is from W to E, and
depth to water table varies from 1.8 to 24.75 m below
ground level (Figure 4). Seasonal groundwater level
fluctuations indicate that the water table tends to rise
during November and April to reach peak in May and
declines from January onwards to reach minimum in
September [21].
3.2 Groundwater Chemistry
The chemical composition of groundwater results from
the geochemical processes occurring as water reacts with
the geologic materials which it flows [23]. The water
quality analyses included all major anions, cations, ni-
trate, phosphate, ammonia, iron and fluorine. The allover
groundwater pH and electrical conductivity (EC) values
of the study area are ranging from 7.1 to 8.4 and 290 to
990 μS cm-1, respectively. Total dissolved solids (TDS)
in the study area vary between 182 to 582 mg/l. The
groundwater in the study area falls under fresh (TDS < 1,
000 mg/l) types of water [2]. The total hardness (as
CaCO3) ranges from 125 to 448 mg/l.
Table 2. Total Abstraction from Groundwater and springs
during 2004
Water
Re-
source
Num. Min.Dis-
charge(lit/s)
Max.Dis-
charge(lit/s)
Annual Dis-
charge(MCM)
Agri-
cultural
uses
(MCM)
Drinking
uses
(MCM)
Springs231.5 35 6.927 6.3410.585
Wells3752.4 44 23.811 19.264.55
Total893- - 30.738 25.6015.135
Town
Oshnavieh
01 Km
1400 Iso-Water Table Max.
Flow Line
(m)
37,05,08
36,57,50
45,01,57 45,15,28
Figure 3. Groundwater level contour map of the aquifer system in the Oshnavieh plain (in meters above mean sea level)

Assessment of Groundwater Quality and its Suitability for Drinking and Agricultural uses in the Oshnavieh Area, Northwest of Iran 34
Town
Oshnavieh
01 Km
Water Sample
P1
P2
P3 P4
P5
P6
P7
P8
P9
P10
P11
P12
P13
P14
P15
P16
P17
P18 P19
P20
45,01,57 45,15,28
36,57,50 37,05,08
Piezometer
Iso- Dept. Max.(m)
10
Figure 4. Depth groundwater contour map of the aquifer system in the Oshnavieh plain (in meters below ground level) and
location of groundwater samples
In the study area, the Na and K concentrations in
groundwater range from 2 to 52 and 0 to 11.7 mg/l,
respectively. The concentrations of calcium range from
20 to 142 mg/l, which is derived from calcium rich
minerals like feldspars, pyroxenes and amphiboles. The
major source of magnesium (Mg) in the groundwater is
due to ion exchange of minerals in rocks and soils by
water. The concentrations of Mg and HCO3 ions found
in the groundwater samples of study area are ranged
from 12–51 and 140 to 506 mg/l respectively. The con-
centration of chloride ranges from 3.5 to 43 mg/l and
increases from the recharge to discharge area. Sulfate
varies from 8 to 48 mg/l. The nitrate concentration in
May 2006 groundwater samples range from 8 mg/l to
62 mg/l with an average value of 16.6 mg/l. The source
of nitrate in area is N fertilizers (commonly urea, ni-
trate or ammonium compounds) that are used for agri-
cultural practices. Fluoride is one of main trace ele-
ments in groundwater, which generally occurs as a
natural constituent. Bedrock containing fluoride min-
erals is generally responsible for high concentration of
this ion in groundwater [24,25]. The concentration of
fluoride in groundwater of the study area varies be-
tween 0.11-0.42 mg/l during May 2006 with an average
value of 0.22 mg/l and all samples groundwater in
study area are suitability for drinking. Figure 5 shows
that Ca, Mg and HCO3 are dominant cations and anion,
respectively. A further illustration of this is shown in
Figure 5 where the median values of HCO3 exceeded
50% of total anions in milli-equivalent unit. The abun-
dance of the major ions in groundwater is in following
order: Ca > Mg > Na > K and HCO3 > SO4 > Cl > NO3 > CO3.
Minimum, maximum and average values of physical
and chemical parameters of groundwater samples are
presented in Table 3. The concentration of dissolved
ions in groundwater samples are generally governed by
lithology, nature of geochemical reactions and solubil-
ity of interaction rocks. The functional sources of dis-
solved ions can be broadly assessed by plotting the
samples, according to the variation in the ratio of
Na/(Na+Ca) and Cl/(Cl+HCO3) as a function of TDS
[26]. The Gibbs plot of data from study area (Figure 6)
indicates that rock is the dominant processes control-
ling the major ion composition of groundwater.
3.3 Saturation Index
Saturation indexes are used to evaluate the degree of
equilibrium between water and minerals. Changes in
saturation state are useful to distinguish different stages
of hydrochemical evolution and help identify which geo-
chemical reactions are important in controlling water
chemistry [27–29]. The saturation index of a mineral is
obtained from Equation (1) [30].

Assessment of Groundwater Quality and its Suitability for Drinking and Agricultural uses in the Oshnavieh Area, Northwest of Iran 35
Table 3. Minimum, maximum and average values of physical and chemical par a me ter s of groundwater samples
Average Maximum Minimum Units Parameters
7.52
592
374
7.14
1.91
45.16
25.9
17.97
297.6
2.1
23.75
294
1.25
7.14
–1.01
42.9
–0.33
–0.18
–0.24
–0.62
–2.26
8.4
910
582
34.78
11.7
142
51
43
506
60
48
448
1.8
34.78
2.3
66
0.64
0.37
0.12
–0.12
–1.77
7.1
290
182
2.63
0
20
12
3.5
140
0
8
125
0.074
2.63
–2.93
30
–0.7
–0.44
–0.82
–1.84.
–2.82
-
S/cmμ
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
-
%
meq/l
%
meq/l
meq/l
-
-
-
-
pH
EC
TDS
Na
K
Ca
Mg
Cl
HCO3
CO3
SO4
TH
SAR
%Na
RSC
PI
CAI,1
CAI,2
SI calcite
SI dolomite
SI gypsum
SI anhydrate
RSC: Residual sodium carbonate
PI: Permeability index
CAI: Chloro alkaline index
SI: Saturation index
EC: Electrical conductivity
TDS: Total dissolved solids
TH: Total hardness
SAR: Sodium adsorption ratio
Figure 5. Pie diagram of median values of major ions
SI = log (IAP/Kt) (1)
where IAP is the ion activity product of the dissociated
chemical species in solution, Kt is the equilibrium solu-
bility product for the chemical involved at the sample
temperature. An index (SI), less than zero, indicate that
the groundwater is undersaturated with respect to that
particular mineral. Such a value could reflect the charac-
ter of water from a formation with insufficient amount of
the mineral for solution or short residence time. An index
(SI), greater than zero, specifies that the groundwater
being supersaturated with respect to the particular min-
eral phase and therefore incapable of dissolving more of
the mineral. Such an index value reflects groundwater
discharging from an aquifer containing ample amount of
the mineral with sufficient resident time to reach equilib-
rium. Nonetheless, super saturation can also be produced
by other factors that include incongruent dissolution,
common ion effect, and evaporation, rapid increase in
temperature and CO2 exsolution [23,29]. In Table 2 the
SI for calcite, dolomite, anhydrate and gypsum are
shown. Figure 7 shows the plots of SI against TDS for
all the investigated water. Nearly all water samples were
saturated to undersaturate with respect to calcite, dolomite
and aragonite and all samples undersaturated with respect
to gypsum and anhydrite, suggesting that these carbonate
mineral phases may have influenced the chemical com-
position of the study area. In Ca-HCO3 water type the
Ca
Na K
Mg
SO4
Cl
HCO3

Assessment of Groundwater Quality and its Suitability for Drinking and Agricultural uses in the Oshnavieh Area, Northwest of Iran 36
Cl/(Cl+HCO3)
TDS(mg/l)
00.2 0.4 0.60.8 1.0
10
100
1000
10000
EVAPORATION
CRYSTALIZATION
DOMINANCE
ROCK
DOMINANCE
PRECIPITATION
DOMINANCE
Na / (Na+Ca)
TDS (mg/l)
00.2 0.4 0.60.8 1.0
10
100
1000
10000
EVAPORATION
CRYSTALIZATION
DOMINANCE
ROCK
DOMINANCE
PRECIPITATION
DOMINANCE
Figure 6. Mechanisms governing groundwater chemistry (after gibbs, 1970)
A nhydrate
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0100 200 300400 500 600 700
TDS (mg/l)
Saturation Index
Gups um
-3
-2.5
-2
-1.5
-1
-0.5
0
0100 200 300400 500 600 700
TDS (mg/ l )
Saturation Index
Calcite
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0200 400600 800
TDS (mg/l)
Saturation Index
Dol o mit
-2
-1.8
-1.6
-1.4
-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0100 200 300 400 500 600 700
TDS (mg/l )
Saturation Index
Figure 7. Plots of saturation indexes with respect to some carbonate minerals against total dissolved solids (TDS)
mean values of SIcal , SIdol , SIgyp, SI anhy are –0.24, –0.617,
–2.26 and –2.49, respectively.
3.4 Hydrochemical Facies
The values obtained from the groundwater samples ana-
lyzing, and their plot on the Piper's diagrams [31] reveal
that the dominant cation is Ca and the anion is HCO3. In
the study area, the major groundwater type is Ca-HCO3
and Ca-Mg-HCO3 (Figure 8). Chadha [32] has proposed
new diagram for geochemical data presentations. The
proposed diagram is a modification of Piper diagram
with a view to extend its applicability in representing
water analysis in the possible simplest way. Results of
analyses were plotted on the proposed diagram to test its
applicability for geochemical classification of ground-
water and to study hydrochemical processes (Figure 9).
The plot shows that all of the groundwater samples fall
under the subdivision of alkaline earths exceeds alkali
metals and weak acidic anions exceed strong acidic ani-
ons (Ca-Mg-HCO3water type).

Assessment of Groundwater Quality and its Suitability for Drinking and Agricultural uses in the Oshnavieh Area, Northwest of Iran 37
2
4
7
9
8
56
3
1
3
5
9
2
4
7
9
4
6
1
100
100
100
100
0
0
0
50
50
50
50
SO4+Cl
Na+K
HCO3+CO3
Ca+Mg
Figure 8. Chemical facies of groundwate r in pipe r diagr am
20
40
60
80
-20
-40 -60 -80 20 40 60 80
-20
-40
-60
-80
1
5 3
4
7
2
8
6
Y
X
(Ca+Mg)-(Na+K)
Millieqivalent percentage
(CO3+HC O3)-(C l+SO 4)
Millieqiva le nt percenta ge
Ca-Mg-HCO3 Water Type
Na-HCO3 Water Type
Na-Cl Water TypeCa-Mg-Cl Water Type
Figure 9. Diagram showing geochemical classification and
hydrochemical parameters of groundwater (after chadha,
1999)
3.5 Drinking and Irrigation Water Quality
The analytical results have been evaluated to ascertain
the suitability of groundwater of the study area for
drinking and agricultural uses. The drinking water
quality is evaluated by comparing with the specifica-
tions of TH and TDS set by the World Health Or-
ganization [33,34]. According to WHO specification
TDS up to 500 mg/l is the highest desirable and up to
1500 mg/l is maximum permissible (Table 4). Based
on this classification, 87% of samples are belonging
to highest desirable category and remaining samples
are belonging to maximum permissible category. The
hardness values range from 125 to 448 mg/l during
May 2006. The classification of groundwater based on
total hardness [35] (Table 5) shows that 59% of the
groundwater samples fall in the very hard water cate-
gory, 35% hard category and remaining samples fall
in moderately hard category(Table 5). Maximum al-
lowable limit of TH for drinking is 500 mg/l and the
most desirable limit is 100 mg/l as per the WHO in-
ternational standard. Based on this classification it in
Table 4. Groundwater samples of the study area exceeding the
permissible limits p rescribed b y WHO for drinking purposes
WHO international standard (1971, 1983)
Amount in
Groundwater
samples
Maximum
Allowable
limits
Most
desirable
limits
Parameters
7.1–8.4 9.2 7–8.5 PH
182–582 1500 500 TDS(mg/l)
125–448 500 100 TH(mg/l)
2–52 200 - Na(mg/l)
20–142 200 75 Ca(mg/l)
12–51 150 50 Mg(mg/l)
3.5–43 600 200 Cl(mg/l)
8–48 400 200 SO4(mg/l)
8–62 - 45 NO3(mg/l)
0–0.05 0.5 0.05 NH3(mg/l)
0.115–0.425 1.5 - F(mg/l)
0–0.141 1 0.1 Fe(mg/l)
Table 5. Suitability of groundwater based on hardness
Total hardness
as CaCO3(mg/l) Water class
<75
75–150
150–300
>300
Soft
Moderately hard
Hard
Very hard
dicates that all of the groundwater samples are not ex-
ceed the maximum allowable limits.
Salinity and indices such as, sodium absorption ratio
(SAR), sodium percentage (Na %), residual sodium car-
bonate (RSC), and permeability index (PI) are important
parameters for determining the suitability of groundwater
for agricultural uses [36,37]. Electrical conductivity is a
good measure of salinity hazard to crops as it reflects the
TDS in groundwater. The US Salinity Laboratory [38]
classified ground waters on the basis of electrical con-
ductivity (Table 6). Based on this classification, 16% of
samples are belonging to the doubtful category and 84%
to good category. Sodium adsorption ratio (SAR) is an
important parameter for determining the suitability of
groundwater for irrigation because it is a measure of al-
kali/sodium hazard to crops [9]. SAR is defined by
Table 6. Classification of groundwater for irrigation based
on EC, SAR
Quality of
water
Electrical conductivity
(S/cm)
Sodium adsorption
ratio(SAR)
Excellent
Good
Doubtful
Unsuitable
<250
250–750
750–2250
>2250
<10
10–18
18–26
>26

Assessment of Groundwater Quality and its Suitability for Drinking and Agricultural uses in the Oshnavieh Area, Northwest of Iran 38
Karanth [39] as Equation (2).
SAR=Na/[(Ca+Mg)/2]1/2 (2)
where all ionic concentrations are expressed in meq/l.
The SAR values range from 0.074 to 1.84 and according
to the Richards [40] classification based on SAR values
(Table 6), all of samples are belong to the excellent cate-
gory. SAR can indicate the degree to which irrigation
water tends to enter into cation-exchange reactions in
soil. Sodium replacing adsorbed calcium and magnesium
is a hazard as it causes damage to the soil structure and
becomes compact and impervious [37]. The analytical
data plotted on the US salinity diagram [40] illustrates
that 77% of the groundwater samples fall in the field of
C2S1, indicating medium salinity and low sodium water,
which can be used for irrigation on all types of soil with-
out danger of exchangeable sodium (Figure 10). The
sodium percent (%Na) is obtained by the Equation (3).
%Na=[Nark]×100/[Ca+Mg+Na+K] (3)
where all ionic concentrations are expressed in meq/l.
The Wilcox [41] diagram relating sodium percentage
and total concentration shows that %26 of the groundwa-
ter samples fall in the field of good to permissible and
74% of the groundwater samples fall in the field of ex-
cellent to good for irrigation (Figure 11).
Residual sodium carbonate (RSC) has been calculated
to determine the hazardous effect of carbonate and bicar-
bonate on the quality of water for agricultural purpose
and has been determined by the Equation (4).
RSC=(CO3 +HCO3)-(Ca+ Mg) (4)
where all ionic concentrations are expressed in meq/l
[42]. The classification of irrigation water according to
the RSC values is waters containing more than 2.5 meq/l
Figure 10. Rating of groundwater samples in relation to
salinity and sodium hazard
0500 750 1000 1500 2000 2500 3000 3500
10
20
30
40
50
60
70
80
90
100
Percent Sodium
Electrical Conductivity (micromhos/cm) at 25 C
Unsuitable
Doubtful
to
Good
Permissible
Excellent
to
to
to
Good
Permissible
Doubtful
Unsuitable
Figure 11. Rating of groundwater samples on the basis of
electrical conductivity and percent sodium (after wilcox,
1955)
of RSC are not suitable for irrigation, while those having
–2.93 to 2.3meq/l are doubtful and those with less than
1.25 meq/l are good for irrigation. Based on this classifi-
cation, all of groundwater samples belong to the good
category except one sample. The permeability index (PI)
values also indicate that the groundwater is suitable for
irrigation. It is defined as follows (Equation (5))
PI=100×[([Na]+[HCO3]1/2)/[Na]+[Ca]+[Mg] (5)
where all the ions are expressed in meq/l [44]. WHO [45]
uses a criterion for assessing the suitability of water for
irrigation based on permeability index. The PI range
from 30% to 66% and the average value is about 43%
during May 2006. According to PI values, the groundwa-
ter of in the study area can be designated as class II (25–
75%) that shows the groundwater in study area is suitable
for irrigation purposes.
3.6 Chloroalkaline Indices (CAI)
It is essential to know the changes in chemical composi-
tion of groundwater during its travel in the sub-surface
[45]. The Chloro-alkaline indices CAI 1, 2 are suggested
by Schoeller [46], which indicate the ion exchange be-
tween the groundwater and its host environment. The

Assessment of Groundwater Quality and its Suitability for Drinking and Agricultural uses in the Oshnavieh Area, Northwest of Iran 39
Chloro-alkaline indices used in the evaluation of Base
Exchange are calculated using the Equations (6,7).
1) Chloro Alkaline Indices
1 = [Cl–(Na+K)] / Cl (6)
2) Chloro Alkaline Indices
2 = [Cl–(Na+K)]/(SO4+HCO3+CO3+NO3) (7)
If there is ion exchange of Na and K from water with
magnesium and calcium in the rock, the exchange is
known as direct when the indices are positive. If the ex-
change is reverse then the exchange is indirect and the
indices are found to be negative. The CAI 1, 2 are calcu-
lated for the waters of the study area as given in Table 2.
Chloro Alkaline Indices 1, 2 calculations shows that 26%
of the groundwater sample is negative and 74% positive
ratios.
4. Conclusions
Interpretation of hydrochemical analysis reveals that the
groundwater in study area is fresh, hard to very hard. The
sequence of the abundance of the major ions is in the
following order: Ca > Mg > Na > K and HCO3 > SO4 >
Cl. Alkali earths slightly exceed alkalis and weak acids
exceed strong acids. Falling of water samples in the rock
dominance area in Gibbs plot indicates the interaction
between rock chemistry and the chemistry of the perco-
lating precipitation waters in the sub-surface. The results
of calculation saturation index show that the nearly all of
the water samples were saturated to undersaturated with
respect to carbonate minerals (calcite, dolomite and ara-
gonite) and undersaturated with respect to sulfate miner-
als (gypsum and anhydrite). In the study area, the domi-
nant hydrochemical facieses of groundwater is Ca- HCO3
and Ca-Mg-HCO3. Distribution of the groundwater sam-
ples in rectangular diagram reveals that all of the ground-
water samples fall under the calcium-magnesium-bicar-
bonate category. According to classification of water
based on TDS, 87% of samples are belonging to highest
desirable category and remaining samples are belonging
to maximum permissible category. Irrigation waters clas-
sified based on SAR has indicated that 83% of samples
belong to the excellent, 11% samples good and remain-
ing samples belong to doubtful category. The Wilcox
diagram relating sodium percentage and total concentra-
tion shows that 26% of the groundwater samples fall in
the field of good to permissible and 74% of the ground-
water samples fall in the field of excellent to good for
irrigation. The analytical data plotted on the US salinity
diagram illustrates that 77% of the groundwater samples
fall in the field of C2S1, indicating medium salinity and
low sodium water. Base on the classification of irrigation
water according to the RSC values, all of groundwater
samples belongs to the good category. According to PI
values, the groundwater of in the study area can be des-
ignated as class II (25–75%) that shows the groundwa-
ter in study area is suitable for irrigation purposes. As-
sessment of water samples from various methods indi-
cated that groundwater in study area is chemically suit-
able for drinking and agricultural uses. Chloroalkaline
Indices 1, 2 calculations shows that 26% of the ground-
water sample is negative and 74% positive ratios. The
positive values indicate absence of base-exchange reac-
tion.
5. Acknowledgements
This study was supported by the Islamic Azad University
of Urmia. The authors gratefully acknowledge the Azar-
baijan Regional Water Authority for supplying the exist-
ing relevant data and also wish to thank Ms. Hajilar for
the water chemistry analysis. We would like to thank Mr.
E. Eliassi for their kindly help during the field visits and
the collection of data.
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