Conservation Planning Existing Center Pivots

1. Conservation Planning Existing Center Pivots Runoff Assessment CPNozzle Illinois NRCS Training December 6, 2011 Springfield, Illinois

2. A Few Concepts First

3. Applying Irrigation Water in Circles (vs. squares) Why (briefly) • Economical • Low O & M • High Reliability • Central Delivery Point

4. Applying Irrigation Water in Circles (vs. squares) Why it’s a little trickier on the circle: In a circular system the area increases as the radius increases Hence, each sprinkler applies water to a differently sized Area (A) In a rectangular system each sprinkler applies water to an Identically sized Area (A) 1 2 3 4 2 3 4 1 A1 < A2 < A3 < A4 A1 = A2 = A3 = A4

5. On a Typical Pivot System? (System Capacity = 6 gpm / acre) Circle Area Computations Sprinklers are sized appropriately along length of pivot to maintain uniform applications along linear length of the center pivot machine Area = π R2

6. High Pressure Impact High Pressure

7. Medium Pressure on Drop Medium Pressure

8. Low Pressure on Drop Low Pressure

9. Soil / Water Intake Curves 4.0 3.0 1.0 Family 2.0 Intake Rate (in / hr) 0.5 Family 0.3 Family 1.0 0.0 0.0 0.1 0.2 0.4 0.3 0.5 Time (hrs)

10. Sprinkler Pressure vs. Intake Characteristics Timed Rain Gauge Analysis Thunderstorm Intensity

11. Sprinkler Pressure vs. Intake Characteristics Timed Rain Gauge Analysis Thunderstorm Intensity Low Medium High Low Medium High

12. CPNozzleProgram • Windows Version • Similar Inputs • Better Visualization • Residue Component • Estimates Surface Storage • and Runoff

13. CPNozzle Program • Green-AmptOption Should Not Be Used At This Time (12_01_11)

14. CPNOZZLE Important Input Variables • System Wetted Length (ft) • System Capacity (GPM wo-gun) • Application Depth (in) • Soil Intake Family • Slope (constant or variable) • Residue Amount (const. or variable) • Sprinkler Diameter of Throw

15. Wetted Length (ft) = length from pivot to about 75% of wetted radius of last sprinkler (exclude end gun)

16. Listing of wetted diameter ranges for typical center pivot sprinkler packages. Sprinkler Package Wetted Diameter ‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑---------------------------- High Pressure Impact (Constant Spacing) H High Pressure Impact (Variable Spacing) (80 - 110 ft) Medium Pressure Impact (70 - 90 ft) Low Pressure Impact (60 - 70 ft) Low Pressure w/Rotators (50 - 60 ft) Low Pressure Spray on Pipeline (30 - 40 ft) Low Pressure Spray on Drop Tubes (20 - 30 ft) Low Pressure Spray (180 degrees) (16 - 20 ft) Ultra Low Pressure (LEPA Spray Mode) (12 - 18 ft) Ultra Low Spray (LEPA Bubble Mode) ( 1 - 2 ft) --------------------------------------------------------------------------------------------

20. NRCS INTAKE FAMILY DESCRIPTION ----------------------------------------------------------------------------------------------------- 0.1 ‑‑‑‑‑‑‑‑ Clay, silty clay, silty clay loam ‑‑‑‑‑‑‑‑ Slowly permeable subsoils 0.3 ‑‑‑‑‑‑‑‑ Silt loam, loam, very fine sandy loam, clay loam, ‑‑‑‑‑‑‑‑ silty clay loam, sandy clay loam ‑‑‑‑‑‑‑‑ Slow to moderately slow permeable subsoils 0.5 ‑‑‑‑‑‑‑‑ Silt loam, loam, very fine sandy loam ‑‑‑‑‑‑‑‑ Moderately slow permeable subsoils 1.0 ‑‑‑‑‑‑‑‑ Fine sandy loam, loamy fine sand, silt loam, ‑‑‑‑‑‑‑‑ loam, very fine sandy loam, very fine sandy ‑‑‑‑‑‑‑‑ Moderate, moderately slow, moderately permeable, ‑‑‑‑‑‑‑‑ medium textured, moderately rapidly permeable ‑‑‑‑‑‑‑‑ subsoils underlain by bedrock or mixed sand & gravel 1.5 ‑‑‑‑‑‑‑‑ Fine sandy loam, loam, sandy loam ‑‑‑‑‑‑‑‑ Moderately rapid, rapidly, moderate subsoils underlain ‑‑‑‑‑‑‑‑ by bedrock or mixed sand & gravel 2.0 ‑‑‑‑‑‑‑‑ Loamy fine sand or loamy sand ‑‑‑‑‑‑‑‑ Moderately rapid to rapidly permeable subsoil 3.0 ‑‑‑‑‑‑‑‑ Loamy sand, loamy fine sand, fine sandy loam, fine sand ‑‑‑‑‑‑‑‑ Rapidly permeable subsoils

24. Modeling Procedure • Enter background information (Producer, Location, County, State, Designed By, Date).  • System Wetted Length (ft). – Identify, and enter the center pivot system length. • System Capacity without End Gun (gpm) – Enter the flow rate of the system with the end gun shut off, in gallons per minute. • Application Amount (in) – Enter the application amount in inches.

25. Modeling Procedure • Wetted Diameter (ft) – Enter the sprinkler/nozzle wetted diameter at the end of the pivot. • Intake Family - Enter the NRCS Intake Family of the soil type from the Soil Survey, or as found in Chapter 2 of the National Irrigation Guide, Part 652. • The program uses these values to select a soil water infiltration curve.

26. Weaselage: The field being modeled will rarely have uniform soil types and slopes, so the user must make decisions on which position in the field to evaluate the system. In some cases, the user should evaluate the system for different positions in the field, creating different input scenarios. The scenario that could potentially generate the greatest amount of runoff should be chosen.

27. Guidelines (draft 12/1/11) • Exclude separate soil type areas that are less than 10% of the total field area. • Choose a position where the system will cross the soil type with the lowest intake family value with the greatest slopes. In situations where the system would cross soil types with different intake families, model the soil with the lowest intake family value. • Use an average slope when utilizing the constant slope option.

28. Guidelines (cont) • When the steepest position in the field occurs at a higher intake family than other portions of the field, model separate scenarios (smallest intake family position, steepest slope position) and compare. • The further distance away from the center point the worst case field conditions are, the greater their impact on runoff will be. In some instances, if the worst-case field conditions are close to the center point, the remainder of the field may determine the minimum sprinkler wetted diameter.

32. RUN CPNOZZLE

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35. I can go nuts sometimes

42. CPNOZZLE Example Composite Worksheet

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