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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.



• 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.


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


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 ).



– 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).



– 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.



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)


Irrigation Water Management• Irrigation Scheduling


Irrigation Water Management• Irrigation SchedulingImportant 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.


Irrigation Water Management• Irrigation System Evaluation


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


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.


Irrigation Water Management• Learning Exercise

Refer to the packet of materials in your course notebook for the learning exercise.


Thank You!

Download - Irrigation water management 111012011501

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