l8 irrigation water quality

7/28/2019 L8 Irrigation Water Quality

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Lecture 8: Irrigation Water Quality

The Islamic University of Gaza- Civil Engineering Department

Irrigation and Drainage- ECIV 5327

Prepared by

Husam Al-Najar


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Physical Parameters used in the evaluation of agricultural water quality

NTU/JTU = Nephelometric Turbidity Unit/ Jackson Turbidity Unit

Parameters Symbol Unit

Total dissolved solids

Electrical conductivity

Temperature

Color/turbidity

Hardness

sediments

TDS

EC

T

mg/l

ds/moC

NTU/JTU

mg equivalent CaCO3/l

g/l


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Chemical Parameters used in the evaluation of agricultural water quality

Parameters Symbol Unit

Acidity/basicityType and concentration of

anions and cations

Calcium

Magnesium

Sodium

Carbonate

Bicarbonate

Chloride

Sulphate

Sodium adsorption ratio

Boron

Trace metals

Heavy metals

Nitrate-nitrogen

Phosphate

Potassium

pH

Ca

Mg

Na

CO3HCO3Cl

SO4SAR

B

NO3-N

PO4-P

K

mg/l

mg/l


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All waters used for irrigation contain varying amount of salts

Salinization of soil and water is inevitable in climates where ET > precipitation

Thus, drainage, either natural or artificial is essential to manage salts

Key to sustainable irrigated agriculture in arid/semi-arid climates

Salinity

Salinity-total salt content

Electrical Conductivity (ECw)

Electrical Conductivity of saturated paste extract (ECe or sat)


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General Irrigation Water EC Classifications

Electrical conductivity (ds/m)TDS (mg/l)Class of Water

0.25< 1000Class 1, excellent0.25- 0.75Class 2, good

0.76-2.001000-2000Class 3, permissible

2.01-3.00Class 4, Doubtful

3.00 2000Class 5, Unsuitable

Permissible: leaching is needed if used

Doubtful and Unsuitable: good drainage needed and sensitive plants will have difficulty

obtaining stand.


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Plants only transpire "pure" water

Salts in irrigation water remain in soil if

not leached

Salinity Impact

Plant

Physiological drought

Increased osmotic potential of soil

Specific ion toxicity

Leaf burn

Nutrient uptake interferences


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Saline sites: salt tolerance

genotypic differences in

reaction to increasing NaCl

supply

Phaseolusbean

sugar beet

Crop Selection


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Yield vs. Evapotranspiration

Schneeklothet al, 2004


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ECe

RelativeYield(%)


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Relative Yield vs. Salinity

(Gates et al 2006)


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Salinity effects


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Crops classification according to salinity

Salinity rating group Threshold salinity

(dS/m)

Zero yield salinity

Sensitive (almond, apple,

apricot, carrot)

1.4 8.0

Moderately sensitive (corn,

grape, pepper, tomatoes)

3.0 16.0

Moderately tolerant (olive,

barley)

6.0 24.0

Tolerant (cotton, date palm) 10.0 32.0


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Sodicity (sodic) -high sodium content

SAR: sodium adsorption ratio

Where: Na, Ca, and Mg concentrations must be expressed as meq/l

2

Mg+Ca

Na=SAR

++++

+


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Generalized Classification of Salt-Affected Soils

pHSAREC (ds/m)Classification

8.5 13 4.0Saline

8.5 13 4.0Sodic

8.5 13 4.0Saline-Sodic

7.8 13 4.0High pH


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Specific Ion Concerns and Toxicities

Sodium (Na+)

Soil

sodicity

Crusting

Reduced infiltration

Lower hydraulic conductivity

Higher pH impacting nutrient uptake

Plant

Stunted plants

Toxicity and leaf burn potential


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EC and SAR

The hazard of irrigation water sodium

on soil infiltration mustbe determinedfrom the SAR/EC interaction.

As EC increases relative to SAR,

infiltration problems are reduced.

Rainfall or sprinkler irrigation withnon-saline water on soils previously

irrigated with sodic water can

increase the infiltration problem.

Ayers and Westcott, 1985


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Chloride (Cl-)

Contributes to EC

Essential in low amounts

Sensitive crops affected at high concentration

Leaf burn potential under sprinkler

Burn higher with daytime irrigation


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Chloride tolerance criteria

Effect on cropChloride (mg/l)

Generally safe for all plants< 70

Sensitive plants show injury70-140

Moderately tolerant plants show injury141-350

Can cause sever problems> 350


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Boron (B)

Essential in low amounts (alfalfa)

Toxic to sensitive crops (>1.0 to 2.0 ppm)

Fertility Sufficient in low concentrations


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Degree of restrictionPotential irrigation problem unit

None Slight tomoderate

Sever

SalinityECTDS

ds/mmg/l

< 0.7< 450

0.7-3450-2000

> 3.0> 2000

Permeability

SAR= 0-3 and EC =3-66-1212-2020-40

ds/m > 0.7> 1.2> 1.9> 2.9> 5.0

0.7-0.21.2-0.31.9-0.52.9-1.35.0-2.9

< 0.2< 0.3< 0.5< 1.3< 2.9

Specific Ion toxicity

SodiumSurface irrigationSprinkler irrigation

ChlorideSurface irrigationSprinkler irrigation

SARmg/l

mg/lmg/l

< 3< 70

< 140< 100

3-9> 70

140-350> 100

> 9

> 350

Miscellaneous effects

pHResidual chlorine (overheadsprinkler only)

mg/lNormal range 6.5-8.4

< 1.0 1-5 > 5.0

The Guidelines for the use of effluent waste water quality in irrigation (Takashi,

1990)


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Saline sites: management

(Jordan valley)

Management Options


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Saline sites: plant adaptations- screening for salt tolerance of avocado


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Field Diagnosis


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N deficiency symptoms: corn


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Nitrogen cycle

leaching

biological N2

fixation(N2R-NH2)

Soil

nitrification

(NH4+NO3

-

)

uptake

mineralization(R-NH2NH4+)

N2O, NOx,

N2

Atmosphere

denitrification(NO3

-N2O, NOx, N2)

organicmatter

N2

NO3-

NH4+

NO3- fertilizers

NH4+ fertilizers,

urea

organic

fertilizers

(manure...)

legumes


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P deficiency sypmtoms


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K deficiency symptoms


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Calcareous sites: B toxicity -soybean


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Saline sites: salttolerance genotypic

differences in reaction to

increasing NaCl supply

Phaseolusbean

sugar beet


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Catego

ry

Reuse condition Exposed group Intestinal

nematodes(arithemetic

mean no. of eggs

per litre)

Fecal coliform(geometric mean no.

per 100 ml)

A Irrigation of crops likely to be

eaten uncooked, sports fields,

public parks

Workers,

consumers public

< 1 < 1000

B Irrigation of cereal crops,

industrial crops, fodder crops,

pasture and tries

Workers < 1 No standard

recommended

C Localize irrigation of crops incategory B if exposure of

workers and the public does not

occur

None Not applicable Not applicable

Recommended microbiological quality guidelines for wastewater use in

agriculture


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Crop Type North Gaza Middle Khanyuns Rafah Total

Citrus 2,200 5,812 3,522 173 893 12,600

Olives 145 6,200 5,552 8,000 3,000 22,897

Date Palm Only small area remaining

Almonds 2 0 511 900 1,750 3,163

Fruits 301 2,992 2,552 3,831 657 10,333

Vegetables

(protected)

4,754 286 2,347 6,470 7,525 21,382

Vegetables 6,756 3,532 5,860 17,376 13,520 47,044

Field crops 2,494 3,423 5,135 21,680 3,830 36,562

Flowers 13 0 10 10 481 514

ornamentals 12 0 0 120 0 132

Total 16677 22245 25489 58560 31656 154,627

Crop type and areas in the Gaza Strip (dunum) Source: Ministry of agriculture, 2004


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Parameter Palestinian Standards

Irrigation Recharge

BOD (mg/l) 20-60 20

TSS (mg/l) 30-90 30

TDS (mg/l) 1500 1500

EC (ms/cm) - -

T-N (mg/l) 45 100

Na (mg/l) 200 230

Cl (mg/l) 500 600

SAR 9 -

B (mg/l) 0.7 1

F. Coliform (MPN/100ml) 200-1000 200-1000

Nematodes (ovum/l)

l8 irrigation water quality

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