4.1 SOIL MOISTURE CONSERVATION AND FIELD WATER MANAGEMENT Vital to land and water productivity

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4.1 SOIL MOISTURE CONSERVATION AND FIELD WATER MANAGEMENT Vital to land and water productivity. Why is soil moisture conservation and management vital in spate irrigation?. Unpredictable floods store in the soil profile - PowerPoint PPT Presentation

Text of 4.1 SOIL MOISTURE CONSERVATION AND FIELD WATER MANAGEMENT Vital to land and water productivity

  • 4.1 SOIL MOISTURE CONSERVATION AND FIELD WATER MANAGEMENT

    Vital to land and water productivity

  • Why is soil moisture conservation and management vital in spate irrigation?Unpredictable floods store in the soil profileMajor flood season precedes crop production period pre-irrigation practice!Crops grow under extended dry spellsLarge reliance on stored soil moistureHigh evapotraspiration rate > 2000 mm, low rainfall < 400 mmLarge single irrigation gifts (200 to 1000 mm)

  • Important parametersIrrigation turns and giftsWater rights and rulesField water distribution systemsField bund height and maintenanceMaintaining or enhancing soil water holding capacity and infitration rate of the soil

  • Irrigation turns and giftsSingle gift ranges from 200 to 1000 mmTurns are unpredictable No well defined and orderly irrigation turn/scheduleIt is not totally unplanned systemRule on size of fields Rule on irrigation turns

  • Water rights and rulesMedium floods to upstream fields, moderately-large to midstream fields, large to tail-end fieldsSecond, third & fourth turn only after all fields receive one, two & three turns In a new year dry fields first

  • Irrigation turns and gifts

    Critical mass to work togetherCohesive communityStrong belief in fairnessSecuring two or more turns for optimum yield

  • Irrigation turns and giftsHighly likely scenario: two turns in July, a third in June or August; two week interval Less likely scenario: two turns in June or August, one in July, a two week intervalUnlikely, yet possible scenario: two or three turns in June or August at a weekly interval15 June to 15 August is the effective flood season July is the month when at least 50% of floods occurs; very rarely does a field get a second turn before a two week interval

  • Soil moisture storage results

  • Irrigation gift and turnsSimulated Soil Moisture Storage (SMS) for an irrigation schedule with gifts of 50 cm at 15 June, 15 July and 15 August using the Soil Water Accounting model (SWAM) and the Soil Water Atmosphere Plant model (SWAP).

  • Modification and enforcement of water rightsRule on flood sizes: Regardless of the size of the flood, if a field gets 2 turns, the subsequent floods should be supplied to downstreamSmall and medium floods are more frequent - 50% of the total number of floods that occur annuallySmall and medum floods are non-saline, while large floods were found to be moderately saline20 to 50% yield reduction in sorghum and maize production due to salinity

  • Rules on water distribution (continued)In Pakistan, it is quite common to have large areas that are only irrigated in exceptional years: this creates social tension and discourages land preparation Keep command areasmall and concentrated

  • By concentrating the command area

    Keeping the command area concentratedBy concentrating thecommand area that has reliableIrrigation and even 2-3 irrigations increases and one avoids large marginal outwash areas with very low productivityAs far as waterdistribution rulesallow

  • Additional advantages If likelihood of irrigation is high farmers will do pre-seasonal ploughing which will help the infiltration of flood waterIf the likelihood of irrigation is high there will be less conflict between haves and have-nots and cooperation among water users will be better

  • Field water distributionField-to-field water distribution system? ORIndividual controlled system?

    Chart4

    0000

    193590150

    121955100

    10154265

    8144159

    8103243

    7102538

    591832

    671420

    Small flood

    Medium flood

    Moderately-large flood

    Large flood

    Flood duration in minutes

    Flood discharge in m3s-1

    Sheet4

    Sheet1

    1.37200EC valuesDischargeEC valuesdischargeSediment conc.

    0.55600.318251.3720041

    0.484450.371310.556027

    0.484400.379280.4844121

    0.56580.4360.4844519

    0.4370.411350.565822

    0..371310.429380.43615

    0.471410.471400.3713114

    0..379350.484410.4714017

    0..578650.484450.3792811

    0.951800.513560.5786526

    0.586670.535580.9515038

    0.429380.55600.5867027

    0.603660.56580.4293816

    0.513560.578650.6036725

    0.535610.586700.5135621

    0.318250.603670.5355820

    0.411360.951800.31825101.3741

    1.372000.41135150.5527

    0.48421

    0.48419

    Flood 1top samplebottom sample0.5622minm3

    TwtWt sediment% sedimentTwtWt sediment% sediment0.415000

    546.983.615576.189.15150.37114143020

    550801557886150.47117136012

    549761457583140.379111012010

    546551057660100.5782681808

    54650957862110.953882406

    54749957666110.5862773606

    54644857572130.4291654805

    54541.5857678140.6032566005

    0.51321

    Flood 2top samplebottom sample0.53520

    TwtWt sediment% sedimentTwtWt sediment% sediment0.31810minm3%

    616.586.714616.380.6130.41115000

    615.386.814615.38414303519

    607.388.11560591.615601915

    59480.514578.586151201513

    60577.913605.281.5131801413

    593.859.610563.962.61112401011

    538.143.3853953.8103601010

    480910

    Flood 1top samplebottom sample60079

    TwtWt sediment% sedimentTwtWt sediment% sediment

    65920832643.4175.627

    613.8110.2118613.3114.11900

    604.885.414602.885.5143090720

    581.4555.710572.360.6116055

    607.683.314605.182.31412042

    606.577.113609.575.81218041

    579.656.910577.5631124032

    575.651.4956747.8836025

    48018

    60014

    Flood 1top samplebottom samplemim3/s

    TwtWt sediment% sedimentTwtWt sediment% sediment00

    1108.4487441564.14582930150

    1675.4502.35301483.63242260100

    659.6178276041682812065

    15212781815183152118059

    15563252115163212124043

    548.381.5115520.990.251736038

    544.86412516.268.21348032

    5877513566.473.91360020

    m3%

    0

    14

    13

    Calibration Line of Sodium (water samples 1 to 18)1000000

    mg/labsorbtion(flame emission photometry)830193590150

    0.010.48860121955100

    0.020.663712010154265

    0.030.79351808144159

    0.050.98962408103243

    0.081.1993607102538

    480591832

    600671420

    NaCaMg

    sampleNa (mg/Lme/L(mg/L)me/L(mg/L)me/LSAR (me/L)

    1167.27.2748824.422018.331.5727

    244.781.9529.51.4751008.330.8792

    30.340.01884.4504.170.0071

    425.381.1032.31.615272.250.7938

    50.340.011447.2504.170.0062

    626.421.1527.21.361008.330.5218

    729.571.2913.70.685806.670.6706

    817.20.75271.35403.330.4887

    913.820.601226.11008.330.2237

    1026.771.1644.22.21191.580.8451

    11153.456.6722611.360050.001.2051

    1210.450.452201115012.500.1325

    133.710.1621210.6403.330.0611

    1458.862.56432.15383.171.5696

    1537.611.6438.31.91560.501.4881

    1639.791.7341.32.065907.500.7911

    1718.10.7980.410.081.6008

    1825.381.1027.81.3940.331.1888

    19

    20

    The equivalent weight of an element or radical is equal to its atomic weight or formula weight divided by the valence it assumes in compounds.

    Flood 1top samplebottom sample

    TwtWt sediment% sedimentTwtWt sediment% sedimentm3top(%)

    546.983.615576.189.151500

    550801557886152014

    54976145758314129

    546551057660101010

    546509578621185

    547499576661166

    546448575721364

    54541.58576781452

    53

    Flood 2top samplebottom sample

    TwtWt sediment% sedimentTwtWt sediment% sediment

    616.586.714616.380.613

    615.386.814615.38414

    607.388.11560591.615

    59480.514578.58615m3%

    60577.913605.281.51300

    593.859.610563.962.61113520

    538.143.3853953.8101918

    1513

    Flood 1top samplebottom sample1415

    TwtWt sediment% sedimentTwtWt sediment% sediment107

    65920832643.4175.627109

    613.8110.2118613.3114.11998

    604.885.414602.885.51475

    581.4555.710572.360.611

    607.683.314605.182.314

    606.577.113609.575.812

    579.656.910577.56311

    575.651.4956747.88

    m3%

    00

    Flood 1top samplebottom sample9036

    TwtWt sediment% sedimentTwtWt sediment% sediment5526

    1108.4487441564.1458294227

    1675.4502.35301483.6324224123

    659.617827604168283224

    1521278181518315212521

    1556325211516321211817

    548.381.5115520.990.25171413

    544.86412516.268.213

    5877513566.473.913

    m3/s%

    00

    15046

    10039

    6532

    5933

    4327

    3828

    3222

    2017

    NaCaMgSARClSO4HCO3

    mg/Lme/Lmg/Lme/Lmg/Lme/Lme/L)me/Lme/L

    167.27.2748824.422018.331.57275.20.0444.7642

    44.781.9529.51.4751008.330.87921.60.1110.0459.5

    0.340.01884.4504.170.00711.40.117.076.8

    25.381.132.31.615272.250.79381.60.123.2453.5

    0.340.011447.2504.170.00621.40.139.859.5

    26.421.1527.21.361008.330.52182.20.28.448

    29.571.2913.70.685806.670.670630.165.4855.3

    17.20.75271.35403.330.48871.60.193.643.55

    13.820.61226.11008.330.22371.20.0913.7413.5

    26.771.1644.22.21191.580.84510.80.114.043.98

    153.456.6722611.3600501.205150.0562.9258

    10.450.452201115012.50.13252.20.1121.6420

    3.710.1621210.6403.330.06111.20.1212.7712.5

    58.862.56432.15383.171.56960.60.077.217

    37.611.6438.31.91560.51.48812.40.21.4551.4

    39.791.7341.32.065907.50.79111.20.129.9759.8

    18.10.7980.410.081.600820.80.470.5

    25.381.127.81.3940.331.18881.40.111.311.29

    HCO3 (me/L)Ca (me/L)HCO3/CaEcw (ds/m)Cax (me/L)Mg (me/L)Na (me/L)SAR (me/L)Rna (me/L)Rna:SAR n %

    4224.41.721.41.4918.337.271.57282.3094

    9.51.4756.440.60.538.331.950.88070.9265

    6.84.41.550.51.494.170.010.00480.0059

    3.51.6152.170.51.142.251.10.79130.8449

    9.57.21.320.61.714.170.010.00420.0058

    81.365.880.40.598.331.