Irrigation Water Management

1. Irrigation Water Management

2. 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. 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. Irrigation Water Management

5. Irrigation Water Management

6. 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

7. Irrigation Water Management • Determining Volume of Water Needed

8. 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 ).

9. 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).

10. Irrigation Water Management • Determining Volume of Water Needed • Net Irrigation Water Requirements (Fn ) http://www.info.usda.gov/CED/

11. Irrigation Water Management • Determining Volume of Water Needed • Net Irrigation Water Requirements (Fn ) http://www.wcc.nrcs.usda.gov/nrcsirrig/irrig-mgt-models.html

12. Irrigation Water Management • Determining Volume of Water Needed • Net Irrigation Water Requirements (Fn )

13. Irrigation Water Management • Determining Volume of Water Needed • Net Irrigation Water Requirements (Fn )

14. 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.

15. Irrigation Water Management • Determining Volume of Water Needed • Net Irrigation Water Requirements (Fn ), Auxiliary Water Needs for Salinity Management

16. Irrigation Water Management • Determining Volume of Water Needed • Net Irrigation Water Requirements (Fn ), Auxiliary Water Needs for Salinity Management

17. Irrigation Water Management ETc (1/Lr – 1) Aw = • Determining Volume of Water Needed • Net Irrigation Water Requirements (Fn ), Auxiliary Water Needs for Salinity Management • 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.

18. Irrigation Water Management • Determining Volume of Water Needed • Net Irrigation Water Requirements (Fn ), Contribution of Ground Water (GW)

19. 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.

20. Irrigation Water Management • Determining Volume of Water Needed • Available Water Capacity of Soils (AWC)

21. Irrigation Water Management • Determining Volume of Water Needed • Available Water Capacity of Soils (AWC) http://soils.usda.gov/

22. Irrigation Water Management • Determining Volume of Water Needed • Available Water Capacity of Soils (AWC) http://soildatamart.nrcs.usda.gov/

23. Irrigation Water Management • Determining Volume of Water Needed • Available Water Capacity of Soils (AWC) What depth to use in computing AWC?

24. Irrigation Water Management • Determining Volume of Water Needed • Available Water Capacity of Soils (AWC)

25. 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?

26. 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 = 6.0 inches

27. 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.

28. Irrigation Water Management • Determining Volume of Water Needed • Management Allowed Depletion (MAD)

29. Irrigation Water Management MAD * Plant AWC 100% Fa = • Determining Volume of Water Needed • Net Irrigation Application (Fa ) based on Plant AWC: • where: • Fa = Net Irrigation Application in inches • MAD = Moisture Allowed Depletion in percent(50% for Corn Silage) • Plant AWC = PlantAvailable Water Capacity of soils (6 inches)

30. Irrigation Water Management 50% * 6 inches 100% Fa = Use this value • Determining Volume of Water Needed • Net Irrigation Application (Fa ) based on Plant AWC for Corn Silage: Fa = 3 inches • Net Irrigation Application (Fa ) based on Net Irrigation Requirement (Fn ): Fa = 7.13 inches for Corn Silage Fa = 6.22 inches for Pasture

31. Irrigation Water Management 453 * A * d f * H Q = • Determining Volume of Water Needed • Irrigation System Capacity Requirements where: Q = flow rate (gpm) A = area (acres) d = gross application depth (in) f = irrigation frequency (days) H = hours of operation per day

32. Irrigation Water Management Fa Ea d = • Determining Volume of Water Needed • Gross Irrigation Application Requirements where: d = Gross application, inches Fa = Net application, inches Ea = Application efficiency of the irrigation system

33. Irrigation Water Management • Determining Volume of Water Needed • Gross Irrigation Application Requirements

34. Irrigation Water Management 3.0 inches x 100% 60% d = • 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 the Corn Silage and Pasture. d = 5 inches

35. Irrigation Water Management 453 * A * d f * H Q = • Determining Volume of Water Needed • Irrigation System Capacity Requirements where: Q = flow rate (gpm) A = area to be irrigated is 40 acres d = gross application depth is 5 inches f = irrigation frequency (days) H = hours of operation per day

36. 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).

37. Irrigation Water Management 50% x 6.0 inches 100% x 0.23 in/day f = 7.13 inches for July 31 days Daily ETc = • 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 Daily ETc = 0.23 in/day f = 13 Days

38. Irrigation Water Management 453 * A * d f * H Q = • Determining Volume of Water Needed • Irrigation System Capacity Requirements • 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.

39. Irrigation Water Management 453 * 40 acres * 5.0 inches 13 days * 16 hours/day Q = • Determining Volume of Water Needed • Irrigation System Capacity Requirements Q = 436 gpm or 0.97 cfs 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.

40. Irrigation Water Management < I = 0.43 in/hr • Determining Volume of Water Needed • Irrigation System Capacity Requirements

41. Irrigation Water Management • Irrigation Scheduling

42. 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.

43. Irrigation Water Management • Irrigation Scheduling

44. Irrigation Water Management • Irrigation System Evaluation

45. 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

46. 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.

47. Irrigation Water Management • Irrigation System Evaluation

48. Irrigation Water Management • Irrigation Water Management Jobsheet

49. Irrigation Water Management • Irrigation Water Management Jobsheet

50. Irrigation Water Management • Irrigation Water Management Jobsheet