1. Irrigation Water Management
CNMP Core Curriculum
Section 5 — Nutrient Management

2. Core Training Curriculum
CNMP Development
Core Training Curriculum
These course materials have been developed as a cooperative effort between five land-grant universities and The Natural Resources Conservation Service.
Copyright Information
Ames, Iowa 50011, (515)
Copyright © , Iowa State University of Science and Technology. All rights reserved.

3. Objectives
The student should become familiar with the basic concepts of irrigation water management and what is required for documentation.
Speaker Notes:
Introduce the lesson objectives.
CNMP Core Curriculum

4. Required Materials
National Statement of Work for Irrigation Water Management
National Conservation Practice Standard for Irrigation Water Management
Speaker Notes:
Introduce the required course materials and how to access them.
CNMP Core Curriculum

5. Supplemental Materials
Local Irrigation District Water Management Plans and Irrigation Guides.
National Engineering Handbook, Part 652, Irrigation Guide
National Engineering Handbook, Part 623, Irrigation, Section 15, Chapters 1 through 12
Speaker Notes:
Introduce the supplemental course materials.
CNMP Core Curriculum

6. Irrigation Water Management
Speaker Qualifications:
The speaker for this topic should have at least five years of experience in the design of irrigation systems and the application of irrigation water management techniques.
Speaker Notes:
Introduce the students to the Irrigation Water Management lesson.
Required Course Materials:
United States Department of Agriculture - Natural Resources Conservation Service National Engineering Handbook, Part 652, Irrigation Guide, Chapter 9, Irrigation Water Management. Washington, D.C. Available at: Accessed 30 June 2004.
United States Department of Agriculture - Natural Resources Conservation Service National Statement of Work for Irrigation Water Management, Washington, D.C. Available at: Accessed 30 June 2004.
Supplemental Resources:
Local Irrigation District Water Management Plans and Irrigation Guides.
United States Department of Agriculture - Natural Resources Conservation Service National Engineering Handbook, Part 652, Irrigation Guide, Washington, D.C. Available at: Accessed 30 June 2004.
United States Department of Agriculture - Natural Resources Conservation Service National Engineering Handbook, Part 623, Irrigation, Section 15, Chapters 1 through 12, Washington, D.C. Available at: Accessed 30 June 2004.
Suggested Learning Exercise:
Provide the following information :
Soil name and physical soil properties table.
Crop name, effective rooting depth, managed allowed deficit, and peak irrigation water requirement.
Irrigation system efficiency and acres irrigated.
At the end of the presentation have the students calculate the total available soil water capacity, net irrigation water requirement, irrigation frequency, gross irrigation requirement and the required flowrate needed using the information provided.
CNMP Core Curriculum

7. 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.
Speaker Notes:
Present the definition of Irrigation Water Management shown on this slide to the students.
CNMP Core Curriculum

8. 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.
Speaker Notes:
Discuss why Irrigation Water Management is important when developing resource management plans.
CNMP Core Curriculum

9. Irrigation Water Management
Speaker Notes:
Present the National NRCS conservation practice standard for Irrigation Water Management shown on this slide that the students should have in their handout materials.
Explain that NRCS conservation practice standards establish the minimum level of acceptable quality of planning, designing, installing, operating and maintaining conservation practices.
Explain that each state will use the National NRCS conservation practice standard as a template to develop a standard to be used in the state. The state standard may be exactly the same as the national standard or contain additional information. It is important to obtain the current state standard to know what the minimum level of acceptable quality of planning, design, installation, operation and maintenance is needed for Irrigation Water Management.
CNMP Core Curriculum

10. Irrigation Water Management
Speaker Notes:
Present the NRCS statement of work for Irrigation Water Management shown on this slide that the students should have in their handouts.
Explain that NRCS statements of work establish the minimum deliverables for the Design, Installation, and Checkout of conservation practices. The statements of work also provide a list of references that explain NRCS policy regarding the Design, Installation, and Checkout of conservation practices.
Explain that each state will use the National NRCS statement of work as a template to develop a statement of work to be used in the state. The state version of the statement of work may be exactly the same as the national standard or contain additional information. It is important to obtain the current statement of work for the state, to know what the minimum deliverables are for the Design, Installation and Checkout of Irrigation Water Management.
Statement of Work for Irrigation Water Management
CNMP Core Curriculum

11. 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
Speaker Notes:
Discuss the minimum documentation requirements for Irrigation Water Management taken from the Statement of Work-
Crops to be Grown, Cropping Sequence and Soils Information is to be obtained during the inventory process of developing the CNMP.
Volume of Water Needed per Irrigation and for the season can also be obtained during the inventory process of developing the CNMP if there is good documentation available for the design of the irrigation system.
Records Showing Date and Amount of Water Applied including the type of irrigation scheduling technique used by the irrigator. If available this information will also be obtained during the inventory process of developing the CNMP. If this information is not available, a record keeping system for irrigation scheduling will have to be developed for the landowner/operator.
Evaluation of the Irrigation System should be done during the inventory process to develop the CNMP or for the design and application of irrigation water management as a single practice.
Environmental Considerations are addressed during the inventory process for applying irrigation water management and are related to water quality, cultural resources and endangered plants and animals.
CNMP Core Curriculum

12. Irrigation Water Management
Determining Volume of Water Needed
Speaker Notes:
This slide introduces the section on how to determine the amount of water needed.
CNMP Core Curriculum

13. 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 ).
Speaker Notes:
Discuss the definition of Crop Consumptive Use (CU) as presented on this slide.
CNMP Core Curriculum

14. 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).
Speaker Notes:
Discuss the components of Net Irrigation Water Requirements as presented on this slide.
CNMP Core Curriculum

15. Irrigation Water Management
Determining Volume of Water Needed
Net Irrigation Water Requirements (Fn )
Speaker Notes:
Discuss the information needed to determine the Net Irrigation Requirements for different crops are contained in the NRCS National Engineering Handbook, Part 652, Irrigation Guide and Part 623, Chapter 2, Irrigation Water Requirements. Mention that these documents are available online at the link shown on the slide.
CNMP Core Curriculum

16. Irrigation Water Management
Determining Volume of Water Needed
Net Irrigation Water Requirements (Fn )
Speaker Notes:
Discuss that the NRCS has a computer program available at the link shown on the slide that is available for determining Irrigation Water Requirements. The program is available for downloading at the link shown on the slide.
CNMP Core Curriculum

17. Irrigation Water Management
Determining Volume of Water Needed
Net Irrigation Water Requirements (Fn )
Speaker Notes:
Discuss that local extension publications are often available that explain the irrigation water requirements for specific crops. An example of a extension publication for blueberry irrigation water requirements is shown on the slide.
CNMP Core Curriculum

18. Irrigation Water Management
Determining Volume of Water Needed
Net Irrigation Water Requirements (Fn )
Crop
Evapotranspiration in Inches
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Corn Silage
0.00
1.22
4.17
7.13
5.91
1.14
Grass Pasture
1.46
3.31
4.53
5.24
6.22
5.28
4.02
2.48
0.43
Speaker Notes:
Explain that this slide shows an example of the monthly consumptive use and net irrigation requirements for Corn Silage and Grass Pasture. Emphasize that auxiliary water needs, ground water contributions and changes in soil water content have not been considered.
Crop
Net Irrigation Water Requirements in Inches
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Corn Silage
0.00
0.47
3.62
7.13
5.83
1.06
Grass Pasture
0.08
1.57
3.15
4.57
6.22
5.12
3.46
0.87
CNMP Core Curriculum

19. 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.
Speaker Notes:
Discuss the need to increase the net irrigation requirement for leaching excess salts.
Saline Soil – This soil contains salts that provide an electrical conductivity of the soil-water extract, ECe of more than 4.0 mmho/cm, and an exchangeable sodium percentage (ESP) of less than 15. The principal anions are chloride, sulfate, small amounts of bicarbonate, and occasionally some nitrate.
Saline-Sodic Soil – This soil contains salts that provide an ECe of more than 4.0 mmhos/cm and an ESP or more than 15. It is difficult to leach because the clay colloids are dispersed.
Nonsaline-sodic Soil – This soil contains salts that provide an ECe of less than 4.0 mmho/cm and an ESP of more than 15. Soil with these characteristics are commonly referred to as “black alkali” or “slick spots”.
CNMP Core Curriculum

20. Irrigation Water Management
Determining Volume of Water Needed
Net Irrigation Water Requirements (Fn ), Auxiliary Water Needs for Salinity Management
Speaker Notes:
Explain that the figures 11-5, 6, and 7 of the Agricultural Waste Management Field Handbook provide a way to determine the amount of water to add for the dilution of waste water to prevent saline or sodic problems in soils. Figure 11-8 in the handbook can be used to determine the maximum amount of non diluted waste water that can be applied to soils without causing saline or sodic problems.
CNMP Core Curriculum

21. Irrigation Water Management
Determining Volume of Water Needed
Net Irrigation Water Requirements (Fn ), Auxiliary Water Needs for Salinity Management
Speaker Notes:
Discuss how to determine the amount of irrigation water to be applied for leaching salts. Explain that figure 2-33 shown on the slide can be used to calculate the leaching requirement to prevent saline and/or sodic problems from occurring in the soil profile.
ECt is the salt tolerance of the crop that can be determined from table 2-34.
ECaw is the electrical conductivity of the applied water used for leaching.
Lr is the leaching requirement.
CNMP Core Curriculum

22. Irrigation Water Management
Determining Volume of Water Needed
Net Irrigation Water Requirements (Fn ), Auxiliary Water Needs for Salinity Management
Aw =
ETc
(1/Lr – 1)
where:
Aw = Auxiliary Water Needs for Salinity Management in inches.
ETc = Seasonal Crop Evapotranspiration in inches.
Lr = Leaching Requirement from Figure 2-33 of the NRCS National Engineering Handbook, Part 623, Chapter 2 - Irrigation Water Requirements.
Speaker Notes:
The formula for determining the amount of auxiliary water required salinity management is shown on this slide.
If the seasonal crop evapotranspiration is 25 inches and the leaching requirement is 0.2 the auxiliary water requirements would be 6.25 inches.
Ask the students when the auxiliary water requirement for salinity management should be applied?
Per irrigation
At the beginning of the irrigation season
At the end of the irrigation season
After crop harvest
Explain that applications of water for leaching salts should be applied after crop harvest to prevent leaching of other possible contaminants such as nitrates and other agrichemicals to ground water sources.
CNMP Core Curriculum

23. Irrigation Water Management
Determining Volume of Water Needed
Net Irrigation Water Requirements (Fn ), Contribution of Ground Water (GW)
Speaker Notes:
Discuss the need to consider the contribution of ground water when determining the net irrigation requirements. Guidance on determining the contribution from groundwater can be found in the NRCS National Engineering Handbook, Part 623, Chapter 2 – Irrigation Water Requirements.
CNMP Core Curriculum

24. Irrigation Water Management
Determining Volume of Water Needed
Net Irrigation Water Requirements (Fn )
Fn = ETc + Aw – Pe – GW - ΔSW
where:
ETc = Crop evapotranspiration in inches
Aw = Auxiliary water needs for leaching, temperature modification, crop quality in inches.
Pe = Effective precipitation in inches
GW = Estimated contribution from ground water in inches.
ΔSW = Change in soil water content for the period considered.
Speaker Notes:
Remind the students that the Net Irrigation Requirement computation can be based on annual, monthly, or daily time periods and that published values usually do not include auxiliary water needs, contributions from ground water or changes in soil water content.
CNMP Core Curriculum

25. Irrigation Water Management
Determining Volume of Water Needed
Available Water Capacity of Soils (AWC)
Speaker Notes:
Explain that the soil profile is the reservoir from which plants get water from so the available water capacity (AWC) of the soil must be determined. The available water capacity (AWC) is the amount of water that a soil can store after all of the gravitational water has drained off and is usually expressed in inches per inch or inches per foot of soil depth.
Explain that the AWC for a soil can be estimated using texture of the soil and Table 2-1 in the NRCS Irrigation Guide.
CNMP Core Curriculum

26. Irrigation Water Management
Determining Volume of Water Needed
Available Water Capacity of Soils (AWC)
Speaker Notes:
Explain that a better estimation of available soil water (AWC) can be obtained from NRCS soil survey data. The physical soil properties table published in soil surveys contains information on AWC. Most soil survey manuscripts are available on the website shown on this slide.
CNMP Core Curriculum

27. Irrigation Water Management
Determining Volume of Water Needed
Available Water Capacity of Soils (AWC)
Speaker Notes:
The most up-to-date soils information is available from the Soil Data Mart on the internet. The address for the Soil Data Mart website is shown on this slide. The reports generated on the Soil Data Mart website can be produced for just the soils the user is interested in. This slide shows a report for the soil physical properties table which includes AWC.
Explain that if a CNMP is being developed the user is going to need the soil erosion factors on the table shown on this slide to address water and wind soil erosion issues.
CNMP Core Curriculum

28. Irrigation Water Management
Determining Volume of Water Needed
Available Water Capacity of Soils (AWC)
What depth to use in computing AWC?
Speaker Notes:
This slide shows crop root depths for several crops. Keep in mind that these root depths are not the typical managed root zone for irrigation purposes and would not occur if soil depth were limited or soil moisture was inadequate for full root development.
Discuss the need to consider the depth of soil vs. the managed root depth of the crop being grown when determining the available water capacity to the crop. Plants growing in a fairly uniform soil will extract 40% of their moisture needs from the top ¼ of their root zone.
If the soil depth is less than the managed crop root depth, then use the soil depth to determine the available water capacity of the soil. If the soil depth is greater than the managed crop root depth, the use the managed crop root depth to determine the available water capacity of the soil.
CNMP Core Curriculum

29. Irrigation Water Management
Determining Volume of Water Needed
Available Water Capacity of Soils (AWC)
Speaker Notes:
Explain that guidance on what the managed root zone is for different crops can be found in table 3-2 in the NRCS National Irrigation Guide.
CNMP Core Curriculum

30. Irrigation Water Management
Determining Volume of Water Needed
Available Water Capacity of Soils (AWC)
Given:
Silty Clay Loam Soil
Soil Depth = 3 feet
AWC = 0.20 in/in from 0 to 24 inches of soil depth
0.10 in/in from 24 to 36 inches of soil depth
Managed Crop Rooting Depth = 4 feet
What is the total plant available soil water capacity for the crop being grown?
Speaker Notes:
This slide presents the soils and crop data needed to compute the total plant available soil water content for the crop being grown.
Suggested Learning Exercise:
Have the class compute the total available soil water content from the information given on this slide.
CNMP Core Curriculum

31. Irrigation Water Management
Determining Volume of Water Needed
Available Water Capacity of Soils (AWC)
Determine total plant available soil water capacity:
Use 3 feet to determine total plant AWC since the soil depth is less than the managed crop rooting depth.
AWC = 0.20 in/in x 24 inches = 4.8 inches
0.10 in/in x 12 inches = 1.2 inches
Total Plant AWC = inches
Speaker Notes:
This slide presents the total plant available soil water content for example presented on the previous slide.
CNMP Core Curriculum

32. Irrigation Water Management
Determining Volume of Water Needed
Management Allowed Depletion (MAD)
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.
Speaker Notes:
Discuss the definition of the Management Allowed Depletion (MAD) presented on this slide. Mention that clay soils will store more water that sandy soils but do not release soil water as easily as sandy soils so the plant has to work harder to get water from clay soils. The objective is to allow the plant to extract water from the soil without causing it to work so hard to do so it does not produce the intended growth response.
CNMP Core Curriculum

33. Irrigation Water Management
Determining Volume of Water Needed
Management Allowed Depletion (MAD)
Speaker Notes:
The recommended Management Allowed Depletion (MAD) of soil water for different crops can be found on table 3-3 in the NRCS National Irrigation Guide. Note that local irrigation guides may have better information to use for MAD so it is always a good idea to check to see what information is available locally.
CNMP Core Curriculum

34. Irrigation Water Management
Determining Volume of Water Needed
Net Irrigation Application (Fa ) based on Plant AWC:
Fa =
MAD * Plant AWC
100%
Speaker Notes:
This slide presents how to compute the net irrigation application based on the available water capacity of the soil.
where:
Fa = Net Irrigation Application in inches
MAD = Moisture Allowed Depletion in percent(50% for Corn Silage)
Plant AWC = Plant Available Water Capacity of soils (6 inches)
CNMP Core Curriculum

35. Irrigation Water Management
Determining Volume of Water Needed
Net Irrigation Application (Fa ) based on Plant AWC for Corn Silage:
Fa =
50% * 6 inches
100%
Use this value
Speaker Notes:
This slide shows the results of the computation for the net irrigation application based on the available water capacity of the soil (AWC) and what the net irrigation requirement is for corn silage.
Ask the class to determine what value should be used to determine the Irrigation Water Management parameters. Explain to the class that the net irrigation application should be based on the available soil water capacity since it is less than the net irrigation requirement which is based on the peak monthly irrigation requirement for corn silage. Also explain that because the net irrigation requirement is greater than the available soil water capacity, it will take approximately 2.5 irrigations to supply the net irrigation requirements of 7.13 inches shown on the slide.
Fa = 3 inches
Net Irrigation Application (Fa ) based on Net Irrigation Requirement (Fn ):
Fa = inches for Corn Silage
Fa = inches for Pasture
CNMP Core Curriculum

36. Irrigation Water Management
Determining Volume of Water Needed
Gross Irrigation Application Requirements
d = Fa Ea
where:
d = Gross application, inches
Fa = Net application, inches
Ea = Application efficiency of
the irrigation system
Speaker Notes:
This slide shows the formula for determining the gross application needed for the irrigation system. Explain that if the application efficiency of the irrigation system is known then the gross application can be determined.
CNMP Core Curriculum

37. Irrigation Water Management
Determining Volume of Water Needed
Gross Irrigation Application Requirements
Speaker Notes:
This slide shows the range of application efficiencies for several different irrigation systems. These ranges of application efficiencies can be found in the design sections for different irrigation systems in the NRCS National Irrigation Guide.
CNMP Core Curriculum

38. Irrigation Water Management
Determining Volume of Water Needed
Gross Irrigation Application Requirements
Use a net irrigation application (Fa ) of 3.00 inches. A traveling big gun irrigator with an application efficiency of 60% will be used to irrigate Corn Silage and Pasture.
Speaker Notes:
This slide shows the results of the computation for the gross irrigation application based on the net irrigation application determined on a previous slide.
Discuss with the class if the same gross application can be used for both the corn silage and pasture. Since the net irrigation application was based on available soil water capacity, which was less that the net irrigation requirement for both the corn silage and pasture, it can be used for both crops if they are grown on the same soils.
d =
3.0 inches x 100%
60%
d = 5 inches
CNMP Core Curriculum

39. Irrigation Water Management
Determining Volume of Water Needed
Irrigation Frequency (f):
MAD x Plant AWC
Daily ETc
f =
where:
MAD = Management Allowed Depletion (%).
Plant AWC = Plant Available Water Capacity (inches).
Daily ETc = Daily Evapotranspiration or Consumptive Use for the crop being grown (inches/day).
Speaker Notes:
This slide shows the formula for determining the irrigation frequency (f). Explain to the class that the MAD x AWC has already been determined on a previous slide so the only unknown for the equation is the Daily Evapotranspiration (Etc).
CNMP Core Curriculum

40. Irrigation Water Management
Determining Volume of Water Needed
Irrigation Frequency (f):
where:
MAD = 50% for Corn Silage
Plant AWC = 6.0 inches
Daily ETc = Daily Evapotranspiration or Consumptive
Use for Corn Silage in inches
Speaker Notes:
This slide shows the computation for the irrigation frequency needed to meet the peak daily consumptive use for Corn Silage.
Daily ETc =
7.13 inches for July
31 days
Daily ETc = 0.23 in/day
50% x 6.0 inches
100% x 0.23 in/day
f =
f = 13 Days
CNMP Core Curriculum

41. Irrigation Water Management
Determining Volume of Water Needed
Irrigation System Capacity Requirements
Q =
453 * A * d
f * H
where:
Q = flow rate (gpm)
A = area to be irrigated is 40 acres
d = gross application depth is 5.0 inches
f = irrigation frequency is 13 days
H = 16 hours of operation per day is desired by the client.
Speaker Notes:
This slide shows that all of the parameters are known for computing the irrigation system capacity requirements base on calculations for gross application and irrigation frequency from previous slides. The area to be irrigated comes from inventory plan map. The hours of operation per day are based on the landowner/operators preference.
CNMP Core Curriculum

42. Irrigation Water Management
Determining Volume of Water Needed
Irrigation System Capacity Requirements
Q =
453 * 40 acres * 5.0 inches
13 days * 16 hours/day
Q = 436 gpm or 0.97 cfs
Speaker Notes:
This slide shows the results of the computation for the irrigation system capacity requirements which is one of the deliverable items needed for irrigation water management.
Note:
The existing or planned irrigation system must be able to supply 436 gpm and irrigate the 40 acres of Corn Silage every 13 days to meet the crop evapotranspiration needs during the peak water use period in July.
CNMP Core Curriculum

43. Irrigation Water Management
Determining Volume of Water Needed
Irrigation System Application Rate
Assume a traveling “Big Gun” will be used to irrigate with. Select the system flowrate and wetted diameter from Table 6-6:
Speaker Notes:
The application rate (I) must be computed base on the type of irrigations system existing or planned to ensure enough water can be applied at a safe rate. Explain that for each type of irrigation system there is a unique way to calculate the application rate. Explain that since we are dealing with a dairy for this example, a traveling “Big Gun” sprinkler system common as it can be used to make applications of irrigation water as well as wastewater.
Discuss the selection of the flowrate and wetted diameter for a traveling “Big Gun” irrigation system. Note that if a flowrate is selected that meets the irrigation flow requirement, the economics of pumping that amount is probably not favorable and the application rate will probably be excessive. Explain that if the sprinkler flowrate is less than the irrigation flow requirement then more than one system will be needed to meet the demand or the crop will be stressed due to a lack of adequate soil moisture to provide evapotranspiration needs.
CNMP Core Curriculum

44. Irrigation Water Management
Determining Volume of Water Needed
Irrigation System Capacity Requirements
The application rate for a traveling “Big Gun” is computed using the following formula:
It =
C * Q
R2 * Deg
Speaker Notes:
Discuss the equation shown for calculating the application rate for traveling “Big Gun” sprinkler systems.
where:
It = average application rate in inches/hour
C = unit conversion constant, 13,624
Q = Gun discharge in gallons per minute
R = wetted radius in feet
Deg = portion of circle receiving water in degrees, usually does not exceed 270o.
CNMP Core Curriculum

45. Irrigation Water Management
Determining Volume of Water Needed
Irrigation System Capacity Requirements
The application rate for a traveling “Big Gun” is computed using the following formula:
It =
13,624 * 225
1632 * 270
Speaker Notes:
Discuss the results for calculating the application rate for traveling “Big Gun” sprinkler systems.
It = 0.43 in/hr
CNMP Core Curriculum

46. Irrigation Water Management
Determining Volume of Water Needed
Irrigation System Capacity Requirements
Speaker Notes:
This slide shows the estimated ranges of soil intake rates in inches per hour based on soil texture. Be sure to note that these values should only be used if intake rates for soils are not available in local publications.
Discuss the need for the application rate of the irrigation system should be less than the intake rate for the soil being irrigated. Mention that if the average application rate of the irrigation system is slightly greater than average intake rate of the soil, there probably will not be a problem. The main things to keep in mind when addressing irrigation system application rates and soil intake rates are the slope of the land, surface storage available, and type of crop being grown.
< I = 0.43 in/hr
CNMP Core Curriculum

47. Irrigation Water Management
Irrigation Scheduling
Speaker Notes:
This slide presents the introduction to irrigation scheduling. Explain that irrigation scheduling involves monitoring soil-water content and/or crop water use.
CNMP Core Curriculum

48. 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.
Speaker Notes:
This slide presents important factors to keep in mind when developing an irrigation scheduling tool.
CNMP Core Curriculum

49. Irrigation Water Management
Irrigation Scheduling
Speaker Notes:
This slide presents a water balance irrigation scheduling worksheet that is available in chapter 9 of the NRCS National Irrigation Guide. Mention that there may be worksheets developed locally by extension, irrigation districts or NRCS for irrigation scheduling.
CNMP Core Curriculum

50. Irrigation Water Management
Irrigation System Evaluation
Speaker Notes:
This slide presents the introduction to Irrigation System Evaluations.
CNMP Core Curriculum

51. 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
Speaker Notes:
This slide presents the basic definition of a irrigation system evaluation. Also presented are the three levels of irrigation system evaluations that can be performed. The simplified evaluation is the minimum requirement for designing the irrigation water management practice.
CNMP Core Curriculum

52. 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 one to five days to complete.
Speaker Notes:
This slide presents the definition of the three levels of irrigation evaluations that can be performed and the estimated time required for each level of evaluation.
CNMP Core Curriculum

53. Irrigation Water Management
Irrigation System Evaluation
Speaker Notes:
Guidance is provided in chapter 9 of the NRCS National Irrigation guide on how to perform simplified, abbreviated and detailed Irrigation System Evaluations. Shown is page 1 of 5 of a worksheet used to document a detailed evaluation of a continuous move, large gun type, sprinkler irrigation system.
CNMP Core Curriculum

54. Irrigation Water Management
Irrigation Water Management Jobsheet
Speaker Notes:
This slide presents the introduction to the example NRCS Irrigation Water Management Jobsheet and shows the first 2 pages of the jobsheet. Be sure to emphasize that this is just an example jobsheet and that the class should contact the local NRCS office to see what worksheets are used locally for implementing Irrigation Water Management.
The first page of the jobsheet gives some general information about the Irrigation Water Management conservation practice that includes the definition, purpose, where it is used. The first page also provides some information on conservation management systems and irrigation water management planning.
The second page of the jobsheet describes what permits are required, gives guidance on operation and maintenance aspects of the practice and describes what is in the specifications part of the jobsheet. The second page of the jobsheet also provides information on how to determine water flowrates an gives some unit conversion factors.
CNMP Core Curriculum

55. Irrigation Water Management
Irrigation Water Management Jobsheet
Speaker Notes:
This slide presents the 3rd and 4th page of the jobsheet.
Explain that the 3rd page of the jobsheet asks for some basic information about the Client, Job Approval Requirements, Client Acknowledgement Statement and Checkout Certification Statement. Explain that the section on client information, job approval and client acknowledgement statement would be completed before the practice is implemented. The Checkout section is completed once the practice is implemented and documentation is provided by the client that shows the minimum requirements have be met.
Explain that the 4th page shown on this slide is a worksheet for performing a simplified irrigation evaluation which meets the minimum documentation requirements. This page would be completed and attached to page 3 when the practice has been implemented.
CNMP Core Curriculum

56. Irrigation Water Management
Irrigation Water Management Jobsheet
Speaker Notes:
This slide presents the 5th and 6th page of the jobsheet.
Explain that the 5th page of the jobsheet shown on this slide provides a worksheet to determine the volume of water required.
Explain that the 6th page shown on this slide is a worksheet for the landowner to record irrigation applications.
CNMP Core Curriculum

57. Irrigation Water Management
Irrigation Water Management Jobsheet
Speaker Notes:
This slide presents the 7th and 8th page of the jobsheet.
Explain that the 7th page of the jobsheet shown on this slide provides a worksheet for the client to use to schedule irrigations based on the water balance method.
Explain that the 8th page shown on this slide is a worksheet for the landowner to use to schedule irrigations based on installing tensiometers and monitoring soil moisture.
CNMP Core Curriculum

58. Irrigation Water Management
Questions?
Speaker Notes:
Click on “Class Exercise” to present the class exercise problem statement. Indicate to the class that resource information for this exercise are located at the back of this presentation in the course notebook.
Class Exercise
CNMP Core Curriculum