Transcript Document 7266203

Irrigation Water Management
An essential ingredient of
irrigation system
–design
–operation
John Busch
Irrigation Engineer
USDA-NRCS
3990 Midway Lane
Baker City, OR 97814
541-523-7121 ext 111
[email protected]
Basic IWM concepts
1. WHEN to irrigate ??
2. HOW MUCH water to apply ??
3. HOW MUCH is applied??
Irrigation Water Management
How important ???
Improper IWM can cause INUNDATION!
Irrigation Water Management
How important ???
Improper IWM can leave one HIGh & DRY!
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
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 characteristics
Coefficient 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
Precipitation
Root zone
-- Water storage

Soil-water basics
Soil
Particles
Gravitational
WaterField
Capacity
Available
Water
Unavailable
Water
Saturated
Condition
Management
Allowed Deficit
MAD
Soil Water Unavailable
To Plants
Oven Dry
Water Available
To Plants
Under Stress
Permanent Wilting Point
Soil Water Managed
by Irrigation Scheduling.
Readily
Drained Water
Field
Capacity
FC
Minimum Allowed
Field Capacity
Saturation
Soil Water Reservoir Definitions
Available
Water
Capacity
AWC
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 Information
Dispersion 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 levels
2. Know the amount of irrigation
water applied
3. Know irrigation guidelines for crops
grown
4. Track crop water use –
evapotranspiration
Measure applied water
Estimate CU
•Farm delivery
•Monthly estimate from
regional weather data
•Field application
•Daily estimate from
regional or on-site data
Soil Water
Reservoir
Measure soil water
•Field probe + feel
•Instrumentation
Three elements for IWM
ESSENTIAL
1. Estimate or measure soil moisture
2. Measure irrigation water applied
3. Estimate crop consumptive use
 Need ALL 3 items
Implementing IWM
•
Knowledge of fields, crops, irrigation
system
NO one knows the farm as well as
the manager !
•
•
Effective IWM requires judgment,
observation, and local knowledge
Use ALL available information 
proceed cautiously, test, observe
Scheduling & System Management
1. Check actual soil moisture levels
2. Know the amount of irrigation
water applied
3. Know irrigation guidelines for crops
grown
4. 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
Implementing IWM
•
Knowledge of fields, crops, irrigation
system
NO one knows the farm as well as
the manager !
•
•
Effective IWM requires judgment,
observation, and local knowledge
Use ALL available information 
proceed cautiously, test, observe
Water balance in root zone
Precipitation
Root zone
-- Water storage

Water balance in root zone
Precipitation
Root zone
-- Water storage
(Check uniformity)

System management
• Rainfall --
 measure
 measure/estimate
• Soil water --  measure/estimate
• Application --  measure/estimate
Infiltration --  measure/estimate
• Runoff --  measure/estimate
• ET --

Conclusion 

CANNOT depend on
measuring/estimating
only ONE parameter
Measure applied water
Estimate CU
•Farm delivery
•Monthly estimate from
regional weather data
•Field application
•Daily estimate from
regional or on-site data
Soil Water
Reservoir
Measure soil water
•Field probe + feel
•Instrumentation
Irrigation System
• System type
• Operating characteristics
Coefficient 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 characteristics
Coefficient 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