This document outlines topics to be covered in a three-day course on irrigation water management for CNMP development. The course will cover determining the volume of water needed for crops including consumptive use, net irrigation requirements, and management allowed depletion. It will also discuss irrigation scheduling and the importance of considering crop, soil, climate and irrigation system factors. Finally, the document outlines three levels of conducting irrigation system evaluations for clients.

1. CNMP Development Course November 16-18, 2004
Irrigation Water Management

2. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Irrigation Water Management is the
process of determining and
controlling the volume, frequency,
and application rate of irrigation water
in a planned, efficient manner.

3. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Why is Irrigation Water Management
Important?
– Manage soil moisture to promote desired crop
response.
– Optimize the use of available water supplies.
– Minimize irrigation induced erosion.
– Decrease non-point source pollution of surface
and groundwater resources.
– Manage salts in the crop root zone.
– Manage air, soil or plant micro-climate.

4. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Minimum Documentation:
– Crops to be Grown, Cropping Sequence and
Soils Information.
– Volume of Water Needed per Irrigation and for
the season.
– Application rate of irrigation water.
– Records Showing Date and Amount of Water
Applied.
• Include type of irrigation scheduling technique used
by the client.
– Evaluation of the Irrigation System
– Environmental Considerations

5. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Determining Volume of Water Needed

6. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Determining Volume of Water Needed
– Crop Consumptive Use (CU)
The amount of water used by the crop
in transpiration and building of plant
tissue, and that evaporated from
adjacent soil or intercepted by plant
foliage. It is expressed as depth in
inches or as volume in acre inches per
acre. It can represent the daily, design,
monthly, or seasonal quantity of water
needed for plant growth. Often referred
to as Crop Evapotranspiration (ETc ).

7. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Determining Volume of Water Needed
– Net Irrigation Water Requirements (Fn )
• Crop Evapotranspiration (ETc ).
• Auxiliary water needs such as leaching,
temperature modification and crop
quality (Aw ).
• Effective precipitation (Pe ).
• Groundwater contribution (GW).
• Change in soil water content for the
period of consideration (ΔSW).

8. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Determining Volume of Water Needed
– Net Irrigation Water Requirements (Fn ),
Auxiliary Water Needs for Salinity
Management
• Soils in arid areas have the potential to become
saline or sodic.
• Saline or sodic soils will cause poor seed
germination and reduced yields.
• Additional water must be added to soils with a
potential to have saline or sodic problems to
leach excess salts.
• Where the soluble salt content of wastewater is
high enough to cause problems, the wastewater
must be diluted with good quality water or
applications must be limited.

9. CNMP Development Course November 16-18, 2004
Irrigation Water Management
MAD is defined as the percentage of the
available soil water that can be depleted
between irrigations without serious plant
moisture stress. MAD is expressed as:
– a percentage of the total Plant Available
Water Capacity (AWC),
– a soil-water deficit (SWD) in inches, or
– an allowable soil-water tension level.
• Determining Volume of Water Needed
– Management Allowed Depletion (MAD)

10. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Irrigation Scheduling

11. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Irrigation Scheduling
Important factors to keep in mind when developing a
irrigation scheduling tool for a client:
• The scheduling tool must consider information
about the crop, soil, climate, irrigation system,
water deliveries and management objectives.
• An irrigation scheduling tool needs only be
accurate enough to determine how much water
to apply and when.
• A good rule of thumb to follow when developing
an irrigation scheduling tool is to keep it simple
and easy for the client to understand.

12. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Irrigation System Evaluation

13. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Irrigation System Evaluation
Irrigation system evaluation is the analysis of any
irrigation system and management based on
measurements taken in the field under normal
conditions and management.
There are three levels of irrigation system
evaluations that can be performed:
Simplified
Abbreviated
Detailed

14. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Irrigation System Evaluation
There are 3 levels of Irrigation System Evaluations:
Simplified – This type of evaluation provides enough
information to the landowner/operator to make
management and operation decisions. This
evaluation usually takes a few hours to complete.
Abbreviated – This type of evaluation provides enough information
for the landowner/operator to make management
and operation decisions plus identify any problems
with the system. This evaluation takes a half to full
day to complete.
Detailed – This type of evaluation provides the landowner/
operator with a report and a comprehensive
irrigation system operation and maintenance plan.
This evaluation can take up to one to five days to
complete.

15. CNMP Development Course November 16-18, 2004
Irrigation Water Management
• Learning Exercise
Refer to the packet of materials in your
course notebook for the learning exercise.

16. CNMP Development Course November 16-18, 2004
Thank You!