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

Applying Irrigation Water in Circles (vs. squares) Why it’s a little trickier? 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) Explain how area considerations affect nozzle sizing, spacing and possibly throw diameter 1 2 3 4 1 2 3 4 A1 = A2 = A3 = A4 A1 < A2 < A3 < A4

How Does this Weigh up on a Typical 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 Radius (ft.) Total Area (acres) Spoke Area (acres) Flow Required (gpm) 130 1.2 7.2 260 4.9 3.7 22.2 390 11.0 6.1 36.6 520 19.5 8.5 51.0 650 30.5 66.0 780 43.9 13.4 80.4 910 59.7 15.8 94.8 1040 78.0 18.3 109.8 1170 98.7 20.7 124.2 1300 121.8 23.1 138.6 Area calculations and how they relate to necessary flow to maintain uniform coverage

How Does this Weigh up on a Typical System? High Pressure Potential sprinkler coverage on high pressure system

How Does this Weigh up on a Typical System? Medium Pressure Potential sprinkler coverage on medium pressure system

How Does this Weigh up on a Typical System? Low Pressure Sprinkler coverage on low pressure system – indicate how this affects potential erosion

Soil / Water Intake Curves 0.2 0.3 0.4 0.5 0.1 Time (hrs) 0.0 1.0 2.0 3.0 4.0 Intake Rate (in / hr) Soil / Water Intake Curves 1.0 Family 0.5 Family 0.3 Family Example intake curves for different families

Sprinkler Pressure vs. Intake Characteristics Timed Rain Gauge Analysis Thunderstorm Intensity Illustrate how pivot moving over a point in the field applies water and what this means with respect to the soil intake characteristics of the soil

Sprinkler Pressure vs. Intake Characteristics Timed Rain Gauge Analysis Thunderstorm Intensity Low Medium High Representation of low, medium and high application pressure and where they potentially fit with respect to soil intake rates Low Medium High

CPNozzle Program Windows Version Similar Inputs Better Visualization New Version Windows Version Similar Inputs Better Visualization Residue Component Estimates Surface Storage and Runoff

CPNOZZLE Important Variables Application Rate Soil Family Field Position of Soil Family Residue Amount Slope Sprinkler Radius of Throw Hyperlink to CPNOZZLE program RUN CPNOZZLE

GIS – Toolkit Applications CPNOZZLE divides field into 10 concentric circles and indicates the potential for runoff in each one. Toolkit can be used to find the percentage of each family of soil within each circle to spatially analyze the potential affects of erosion on an entire field .

Example Composite Worksheet CPNOZZLE Example Composite Worksheet Worksheet to combine CPNOZZLE and toolkit information and summarize on for potential runoff on entire field

Irrigation System Design (Some Basic Concepts) Don’t Over - Complicate Up Here We Want To Get This FIELD WATER Begin design concept presentation

Irrigation System Design (Some Basic Concepts) Don’t Over - Complicate Up Here We Want To Get This FIELD WATER

Irrigation System Design (Some Basic Concepts) 2 Important Parameters Flow (most commonly given in gpm) Bucket–Fulls Per Unit Time Flow and pressure concepts 2)Pressure or Head (given in psi or ft. of water) Squirting Distance

FLOW DETERMINATION Crop / Soil Requirements a) effective root zone b) soil texture 2) Field Size 3) Water Source Limitations a) physical b) by permit c) other

Crop Requirements (gpm / acre) General Rule = 6 gpm / acre From NDSU: “Selecting a Sprinkler Irrigation System” ND values from North Dakota State University General Rule = 6 gpm / acre

(Crop Requirement) x (Field Size) = Flow Requirement EXAMPLE (6 gpm / acre) x (125 acres) = 750 gpm (Not Written in Stone but good guidelines to follow) May also be physical or permit demanded constraints on pumping rate which dictate

PRESSURE or HEAD 4 Main Considerations 1) To offset Elevation difference between source and delivery point 2) To compensate for Friction losses in the mainline delivery system 3) System Operational Requirements 4) Other Minor losses Pressure requirements for system operation

between water source and point of distribution Elevation Difference between water source and point of distribution Vertical distance between pumping water surface and the field delivery point (for center pivots use the highest point in the irrigated field for conservative calculations) Example 50 feet Surface Water Ground Water

Friction Losses Most friction losses in irrigation systems are developed in the system mainline (transmission pipeline) (Significant friction loss also occurs in the pivot itself but Is usually calculated and included as part of the operational pressure requirements) Transmission Pipeline Most often PVC but may also be aluminum, steel or PE

Friction Losses Important factors in the calculation pipe friction loss are: Pipe Inside Diameter (id) Pipe Material Pipe Length Fluid Velocity or Flow Rate Friction loss is typically calculated using one of several common equations: (Hazen Williams equation or Darcy equation)

Hazen Williams Equation Friction Losses Hazen Williams Equation H = 10.44LQ1.85 C1.85d4.87 Where: H = head loss from friction (ft.) L = length of pipe (ft.) Q = flow (gpm) C = friction factor (140 – 150 for PVC pipe higher number means smoother pipe) d = inside diameter of pipe (in.) Also note Darcy equation used in CPED

Friction Losses Example 12.3 feet Hazen Williams Equation H = 10.44LQ1.85 C1.85d4.87 Example If 750 gpm is flowing through 1500 feet of new 8 inch ID PVC pipe the friction loss will be {10.44 x (1500) x (750)1.85 } / {(150)1.85 x (8)4.87} = 12.3 feet

Operational Pressure Requirements At the Center Pivot Consist of: 1) Pressure necessary to operate sprinklers and regulators satisfactorily (5 psi or greater above rated pressure of regulator) 2) Friction losses incurred in span pipe Calculation is usually combined together with sprinkler package spreadsheet Requirements are commonly given at pivot point location Elevation differences along pivot may also be included Example pivot point requirement: 45 psi @ 750 gpm

Minor Losses The majority of minor losses which will increase the overall head requirement can be caused by: 1) Small friction losses which occur due to fittings and deviations in pipeline alignment 2) Extra losses through pump and suction pipe 3) Friction loss incurred in well tubing 4) Other In large pipeline networks minor losses can be a substantial portion of the total head requirement Typically in irrigation systems minor losses are not a large part of the total head requirement – Often times it is good enough to simply add 5 to 10 feet to the final head calculation as an adjustment for any minor losses which may occur in the system

Example Pressure Totals 1) Elevation Head = 50 ft. 2) Friction losses in the mainline delivery system = 12.3 ft. 3) System Operational Requirements = 45 psi or 104 ft. (2.3 ft. of water = 1 psi) Minor losses estimate = 10 ft. Total Dynamic Head = 176 ft.

Total Dynamic Head (ft.) PUMP SELECTION 225 Full Impellor 10% Trim 85% 20% Trim 82% 30% Trim 176 Total Dynamic Head (ft.) 79% Illustrate for this example how pump would be selected. 750 1250 Flow (gpm)

Total Dynamic Head (ft.) PUMP SELECTION 225 85% 20% Trim 82% Total Dynamic Head (ft.) 79% Illustrate different operating points on pump curve. Go over how pump my operate with wear and changes in system. 1250 Flow (gpm)

PUMP STUFF 1) Pumps DO NOT make pressure (only flow) The system to which the pump is attached creates resistance to flow (pressure) 2) Pump speed is proportional to output (flow) but the head that a pump can resist is proportional to the square of speed. (which means changing speed changes pump flow reasonably but changes head characteristics a whole bunch) (pump affinity laws) 3) Typically slower running pumps are used for low head - high volume applications. 4) Common speeds for irrigation pumps: 1200 RPM (flood pumps), 1800 RPM (sprinklers with moderate head requirements), 3600 RPM (sprinklers with high head requirements).

POWER REQUIREMENTS Horsepower Required = TDH x Q 3954 x n Where n = wire to water efficiency (pump efficiency minus a little - good first guess is .75) EXAMPLE {(176 ft.) x (750 gpm)} / {3954 x .75} = 44.3 hp

CPED PROGRAM Rewritten for use by NRCS in EQIP program Evaluates sprinkler package coefficient of uniformity (must be at least 85% according to NRCS sprinkler standard) Uses pump input parameters to give an entire system evaluation Sprinkler inputs set up similar to OUTLETS program Hyperlink to CPED program RUN CPED

IRRIGATION WATER MANAGEMENT By the Checkbook Method Treats soil profile as a checkbook Water is the $ Inputs and outputs are measured or estimated and the balance is tracked throughout the growing season Can be tracked by hand, in a spreadsheet or with other software

Checkbook Account Transfers Deep Percolation (Withdrawal) Evapotranspiration (Withdrawal) Irrigation (Deposit) Rain (Deposit) Checkbook concept illustration (Account Balance) Soil Profile Deep Percolation (Withdrawal)

IRRIGATION SCHEDULING by the CHECKBOOK METHOD NDSU software Baled Lotus spreadsheet which tracks soil depletion throughout growing season Estimates crop water use based on daily high temperature input and days past emergence of particular crop Soil available water inputs are entered at setup Contains historical weather record for several sites in ND and MN. Actual soil water measurements can be entered to keep record closer to actual Run NDSU checkbook program RUN IRRIGATION

Irrigation Water Management Plan EQIP Irrigation Water Management Plan Worksheet Example

1) Plan Purpose / General Details General statements outlining where the producer is currently at and how he plans to improve his water management through the use of an irrigation scheduling and or crop water monitoring plan. Open with regards to the producers beginning and ending points. Producer must implement the use of checkbook type irrigation scheduling by the end of the three year contract as a minimum.

Daily Application Rates at ____ efficiency 2) System Capacity / Field Information Flow(gpm) 750 Total Area(acres) 132 System Efficiency(%) 75 Daily Application Rates at ____ efficiency Daily application rate at 100% efficiency (in / day) = (0.053) x Flow(gpm) / Area(acres) 100% 0.30 90% 0.27 80% 0.24 70% 0.21

Cumulative Available Water to depth (in.) 3) Soils Information Soil Name Farland Grail Stady Bryant Field Acreage 46 44 38 2 Field Percentage 35.4 33.9 29.2 1.5 Irrigation Group 8c 10c 6i Cumulative Available Water to depth (in.) Top 1 foot 2.5 Top 2 feet 4.5 Top 3 feet 6.5 5.5 Top 4 feet 8.5 6.0 Top 5 feet 10 10.5 10.0

4) Crop Data 2006 2007 2008 Corn Potato Wheat 4.0 2.0 3.5 50 40 25.9 Year 2006 2007 2008 Crop Corn Potato Wheat Full Rooting Depth (ft.) 4.0 2.0 3.5 Suggested MAD (%)* 50 40 Avg. Annual Water Use 25.9 23.2 18.8 Est. annual no. days crop water use exceeds system capacity 25 23 18

Data taken from North Dakota Ag. Weather Network Data taken from North Dakota Ag. Weather Network. 5 year averages illustrate on average how much producer will need to rely on soil water storage or natural rainfall to meet water requirements of crop

5) Water Management Plan Year 2006 2007 2008 Crop Corn Potato Wheat Managed Soil Farland Stady Managed Crop Rooting Depth (ft.) 4.0 2.0 3.0 Managed Available Water Total (in.) 8.5 4.5 6.5 MAD (in.) 4.25 1.8 3.25 Deficit for Rainfall (in.) 0.50 0.1 Managed Soil Water (in.) 3.75 1.7 2.75 Minimum Soil Available Water (in., %) 4.25,50 2.70,60 3.25,50 Producer needs to analyze field soil percentages and select which one to use for the water management of each crop or divide management spatially dependant upon soil location in field

CSP Irrigation Water Management Evaluation Sheet Evaluates an irrigation system and management scheme for placement/eligibility in the CSP program RUN CSP program CSP worksheet hyperlink

Irrigation Handbook Modifications Located in Section II of EFOTG Chapter 1: Definitions of useful terminiology Chapter 2: Irrigation group classification designations and descriptions (These have changed with this version of the guide) Individual County Soils Classification (in soils section) ND EFOTG information

Cnty Soils Link

CH 1 link CH 2 link

Electrical Center Pivot Operation 3 Phase Electric Power so that motors can be easily reversed and consequently the machine will reverse directions Motor power is 480 V 3Ph, Control power is 120 V 1Ph Main power supply is delivered to main control panel at pivot point. Control and motor power is delivered to each tower via a 10 or 11 conductor cable mounted on top of span Timer circuit controls last tower, it runs when timer is activated. The rest of the towers play catch up through the use of micro-switches General pivot operation info

Electrical Center Pivot Operation Tower map

Electrical Center Pivot Operation Last Tower Controlled By Percent Timer Percent timer controls how often last tower moves - allows application rate (in. / acre) to be varied.

Electrical Center Pivot Operation Next Tower Follows When Micro-switch Triggers Micro switch keys following towers to “catch up” with last tower

Electrical Center Pivot Operation All Other Towers Follow Similarly

Center Pivot 10 Conductor Span Cable Timer Forward End Gun Reverse Safety Neutral Ground Discuss basics on how each circuit works. How they can potentially be modified if necessary. Power Power Power

THE END