Download - Irrigation Water Management
Irrigation Water Management
An essential ingredient of irrigation system –design –operation
VERY important
when applying
animal waste
John BuschIrrigation EngineerUSDA-NRCS3990 Midway LaneBaker City, OR 97814
541-523-7121 ext 111
Basic IWM concepts
1. WHEN to irrigate ??
2. HOW MUCH water to apply ??
3. HOW MUCH is applied??
Irrigation Water Management
Improper IWM can cause INUNDATION!
How important ???
Irrigation Water Management
Improper IWM can leave one HIGh & DRY!
How important ???
Important Point…..
Errors in the timing and amount of irrigation applications can be
PROBLEMATIC
Potential problems can
increase when applying animal waste through an irrigation system
NRCS IWM Job Sheet
Available on the
Oregon NRCS
Engineering Web Site
IWM Plan Specifications
An IWM Plan shall be developed to assist the irrigator or decision-maker in the proper management and application of irrigation water. Factors to be included in the IWM Plan include the following:
• Statement of objective(s) for the IWM Plan• Description of the irrigation system and its
components including water supply, water conveyance and application systems, and any water measurement devices.
• Soils information including available water capacity, depth, and limiting conditions related to irrigation water management.
• Crop information including crops grown, irrigation water requirements, and physical characteristics including rooting depth.
• Description of irrigation scheduling and system management including methods for measuring and/or estimating crop water use and soil moisture levels.
• IWM record keeping requirements of appropriate detail for the IWM objectives. The detail of IWM may be specified as Detailed or By Irrigation Cycle with the associated level of record keeping as appropriate for the level of detail.
• IWM review requirements regarding the effectiveness of the IWM Plan and its implementation.
NRCS IWM Plan Specifications
• Statement of objective(s) for the IWM Plan
• Description of the irrigation system and its components
• Soils information including available water capacity, depth, and limiting conditions
• Crop information including crops grown, irrigation water requirements, and physical characteristics
NRCS IWM Plan Specifications
• Description of irrigation scheduling and system management
• IWM record keeping requirements of appropriate detail
• IWM review
IWM Objectives
Work with cooperator to
• Identify needs• Specify objectives to meet needs
Cooperator involvement is important !
buy-in from the beginning
Irrigation System
• Irrigation system characteristics
Includes Big Guns
Irrigation System• System type
• Operating characteristicsCoefficient of Uniformity (CU) data or distribution
uniformity (DU) shall be used in selecting sprinkler spacing, nozzle size, and operating pressure
For pivots: Min CU = 85%Fixed-Solid-set, Big Gun and Periodic Move
Sprinkler: Min CU = 75 % for deep-rooted crops (4 ft +)Min CU = 85 % for shallow-rooted crops
Irrigation System• Water Source(s)• Available flow rate and total amount• Water Quality
– Salts (Sodium)– Chemicals (Boron)
Soils Information
Including• Soil characteristics• Physical data – depth, limitations,
AWC• Soil chemistry – EC, SAR
Soils Information
Water balance in root zone
ET
Applied waterPrecipitation
Runoff
Capillary rise
Deep perc (leaching)
Root zone
-- Water storage
Infiltation
Soil-water basics
Gravitational Water
Unavailable Water
Available Water
Soil Particles
Saturated Saturated ConditionCondition
Field Field CapacityCapacity
Soil W ater Reservoir DefinitionsS
atu
rati
on
Fie
ld C
apa
city
Min
imu
m A
llo
wed So
il Wat
er M
anag
edby
Irrig
atio
n Sc
hedu
ling.
Per
ma
nen
t W
iltin
g P
oin
t
Wat
er A
vaila
ble
To P
lants
Unde
r Stre
ss
Soil W
ater
Una
vaila
ble
To P
lants
Ove
n D
ryManagement Allowed Deficit
MAD
AvailableWater
CapacityAWC
FieldCapacity
FC
Flocculation is important because water moves mostly in large pores between aggregates. Also, plant roots grow mainly between aggregates.
In all but the sandiest soils, dispersed clays plug soil pores and impede water infiltration and soil drainage.
Soils InformationDispersion and surface sealing from
sodium
Dispersion and surface sealing
Crop Information
• Crops grown• Irrigation water requirements• Rooting depth• Other physical characteristics
Scheduling & System Management
1. Check actual soil moisture levels2. Know the amount of irrigation
water applied3. Know irrigation guidelines for
crops grown4. Track crop water use –
evapotranspiration
Soil Water Reservoir
Measure applied water•Farm delivery
•Field application
Estimate CU•Monthly estimate from regional weather data
•Daily estimate from regional or on-site data
Measure soil water•Field probe + feel
•Instrumentation
Three elements for IWM
1.Estimate or measure soil moisture
2.Measure irrigation water applied
3.Estimate crop consumptive use
Need ALL 3 items
ESSENTIAL
• Knowledge of fields, crops, irrigation system
• Effective IWM requires judgment, observation, and local knowledge
• Use ALL available information proceed cautiously, test,
observe
Implementing IWM
NO one knows the farm as well as the manager !
Scheduling & System Management
1. Check actual soil moisture levels2. Know the amount of irrigation
water applied3. Know irrigation guidelines for
crops grown4. Track crop water use –
evapotranspiration
IWM Records
• Date and duration of each irrigation• Water applied in each irrigation• Dates and amounts of effective rainfall• Crop water use
– Daily evapotranspiration– Water use estimate between
irrigations• Soil moisture status
IWM Review
• Notes on how well IWM goals were met
• Description of crop response to IWM Plan
• Observations of soil erosion, etc.
• Notes on water/environmental quality issues (Relate to CNMP)
• Notes on irrigation system operations and maintenance
Thoughts,
Questions,
Comments??
NRCS IWM Plan Specifications
• Description of irrigation scheduling and system management
• IWM record keeping requirements of appropriate detail
• IWM review
• Knowledge of fields, crops, irrigation system
• Effective IWM requires judgment, observation, and local knowledge
• Use ALL available information proceed cautiously, test,
observe
Implementing IWM
NO one knows the farm as well as the manager !
Water balance in root zone
ET
Applied waterPrecipitation
Runoff
Capillary rise
Deep perc (leaching)
Root zone
-- Water storage
Infiltation
Water balance in root zone
ETApplied
water
Precipitation
Runoff
(erosion)
Capillary rise
Deep perc (leaching)
Root zone
-- Water storage
(Check uniformity)
Infiltation
System management
• Rainfall -- measure
• ET -- measure/estimate
• Soil water -- measure/estimate
• Application -- measure/estimate Infiltration -- measure/estimate
• Runoff -- measure/estimate
Conclusion
CANNOT depend onmeasuring/estimating
only ONE parameter
Soil Water Reservoir
Measure applied water•Farm delivery
•Field application
Estimate CU•Monthly estimate from regional weather data
•Daily estimate from regional or on-site data
Measure soil water•Field probe + feel
•Instrumentation
Irrigation System• System type
• Operating characteristicsCoefficient of Uniformity (CU) data or distribution
uniformity (DU) shall be used in selecting sprinkler spacing, nozzle size, and operating pressure
For pivots: Min CU = 85%Fixed-Solid-set, Big Gun and Periodic Move
Sprinkler: Min CU = 75 % for deep-rooted crops (4 ft +)Min CU = 85 % for shallow-rooted crops
Irrigation System• System type
• Operating characteristicsCoefficient of Uniformity (CU) data or distribution
uniformity (DU) shall be used in selecting sprinkler spacing, nozzle size, and operating pressure
For pivots: Min CU = 85%Fixed-Solid-set, Big Gun and Periodic Move
Sprinkler: Min CU = 75 % for deep-rooted crops (4 ft +)Min CU = 85 % for shallow-rooted crops
