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 36,56