Environmental Engineering Reference
In-Depth Information
(continued)
Parameter
Units
Degree of restriction on use
None
Slight to
moderate
Severe
SAR
b
0-3
meq/l
>0.7
EC
w
0.7-0.2 EC
w
<0.2
EC
w
SAR
3-6
meq/l
>1.2
EC
w
1.2-0.3 EC
w
<0.3
EC
w
SAR
6-12
meq/l
>1.9
EC
w
1.9-0.5 EC
w
<0.5
EC
w
SAR
12-20
meq/l
>2.9
EC
w
2.9-1.3 EC
w
<1.3
EC
w
SAR
20-40
meq/l
>5.0
EC
w
5.0-2.9 EC
W
<2.9
EC
w
Sodium (Na
+
)
Sprinkler
irrigation
meq/l
<3
>3
Sodium (Na
+
)
Surface irrigation
meq/l
<3
3-9
>9
Chloride (Cl
−
)
Sprinkler
irrigation
meq/l
<3
>3
Chloride (Cl
−
)
Surface irrigation
meq/l
<4
4-10
>10
Chlorine (Cl
2
)
Total residual
mg/l
<1
1-5
>5
Bicarbonate (HCO
3
-)
mg/l
<90
90-500
>500
Boron (B)
mg/l
<0.7
0.7-3.0
>3.0
Hydrogen sulphide (H
2
S)
mg/l
<0.5
0.5-2.0
>2.0
Iron (Fe)
Drip irrigation
mg/l
<0.1
0.1-1.5
>1.5
Manganese
(Mn)
Drip irrigation
mg/l
<0.1
0.1-1.5
>1.5
Total nitrogen (TN)
mg/l
<5
5-30
>30
pH
Normal range 6.5-8
Trace elements (see Table A1.2)
TDS, total dissolved solids; TSS, total suspended solids
Sources: Ayers & Westcot (
1985
); Pescod (
1992
); Asano and Levine (
1998
)
a
EC
w
means electrical conductivity in deciSiemens per metre at 25°C
b
SAR means sodium adsorption ratio ([meq/l]
1/2
); see section A1.5
Source: WHO (
2006b
: 178)
USEPA guidelines for the interpretation of water quality for irrigation
1
Degree of Restriction on Irrigation
Potential Irrigation Problem
Units
None
Slight to Moderate
Severe
Salinity
(affects crop water availability)
2
EC
w
dS/m
<0.7
0.7-3.0
>3.0
TDS
mg/L
<450
450-2,000
>2,000
(continued)
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