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Applying Irrigation Water in Circles (vs. squares). Why (briefly ). Economical Low O & M High Reliability Central Delivery Point. Applying Irrigation Water in Circles (vs. squares). Why it’s a little trickier?. In a circular system the area increases as the radius increases - PowerPoint PPT Presentation
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Applying Irrigation Water in Circles (vs. squares)
1) Economical
2) Low O & M
3) High Reliability
4) Central Delivery Point
Why (briefly)
Applying Irrigation Water in Circles (vs. squares)
Why it’s a little trickier?
In a rectangular system eachsprinkler applies water to an Identically sized Area (A)
In a circular system the areaincreases as the radius increasesHence, each sprinkler applies water to a differently sized Area (A)
1 2 43
1 432
A1 = A2 = A3 = A4 A1 < A2 < A3 < A4
Circle Area Computations
Area = π R2
Radius
(ft.)
Total Area
(acres)
Spoke Area
(acres)
Flow Required
(gpm)
130 1.2 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 11.0 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
How Does this Weigh up on a Typical System?(System Capacity = 6 gpm / acre)
Sprinklers are sized appropriatelyalong length of pivot to maintainuniform applications along linear length of the center pivot machine
How Does this Weigh up on a Typical System?
High Pressure
How Does this Weigh up on a Typical System?
Medium Pressure
How Does this Weigh up on a Typical System?
Low Pressure
0.2 0.3 0.4 0.50.1
Time (hrs)
0.0
1.0
2.0
3.0
4.0
0.0
Inta
ke R
ate
(in
/ h
r)
Soil / Water Intake Curves
1.0 Family
0.5 Family
0.3 Family
Sprinkler Pressure vs. Intake CharacteristicsTimed Rain Gauge Analysis Thunderstorm Intensity
Sprinkler Pressure vs. Intake CharacteristicsTimed Rain Gauge Analysis Thunderstorm Intensity
Low
High
Medium
Low Medium High
CPNozzle ProgramNew 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
RUN CPNOZZLE
.
GIS – Toolkit Applications
Family 0.3 Family 0.5 Family 1Acres Potential Weighted Acres Potential Weighted Acres Potential Weighted
Spoke # Runoff % Runoff Runoff % Runoff Runoff % Runoff123456789
10
Total Weighted Runoff ____________Total Acres ____________Potential Runoff ____________
CPNOZZLE Example Composite Worksheet
Irrigation System Design (Some Basic Concepts)Don’t Over - Complicate
FIELD
We Want To Get ThisUp Here
WATER
Irrigation System Design (Some Basic Concepts)Don’t Over - Complicate
FIELD
We Want To Get ThisUp Here
WATER
Irrigation System Design (Some Basic Concepts)2 Important Parameters
1)Flow (most commonly given in gpm)
2)Pressure or Head (given in psi or ft. of water)
Bucket–Fulls Per Unit Time
SquirtingDistance
FLOW DETERMINATION
1) Crop / Soil Requirementsa) effective root zoneb) soil texture
2) Field Size
3) Water Source Limitationsa) physicalb) by permitc) other
Table 1. System Capacity in gallons per minute per acre (gpm/acre) for different soil textures needed to supply sufficient water for each crop in 9 out of 10 years. An application efficiency of 80% and a 50% depletion of available soil water were used for the calculations. ------------------------------------------------------------ Root Coarse Loam Zone Sand Fine and Depth and Loamy Sandy Sandy Silt Crop (ft) Gravel Sand Sand Loam Loam Loam ------------------------------------------------------------ POTATOES* 2.0 8.2 7.5 7.0 6.4 6.1 5.7 DRY BEANS 2.0 7.9 7.1 6.4 6.1 5.7 5.4 SOYBEANS 2.0 7.9 7.1 6.4 6.1 5.7 5.4 CORN 3.0 7.3 6.6 5.9 5.5 5.3 4.9 SUGARBEETS 3.0 7.3 6.6 5.9 5.5 5.3 4.9 SMALL GRAINS 3.0 7.3 6.6 5.9 5.5 5.3 4.9 ALFALFA 4.0 6.8 5.9 5.6 5.1 5.0 4.5 ------------------------------------------------------------ *Adjusted for 40% depletion of available water
Crop Requirements (gpm / acre)From NDSU: “Selecting a Sprinkler Irrigation System”
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 HEAD4 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
Elevation Difference between water source and point of distribution
Vertical distance between pumping water surfaceand the field delivery point
(for center pivots use the highest point in the irrigatedfield for conservative calculations)
Surface Water
Ground Water
Example 50 feet
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 butIs usually calculated and included as part of the
operational pressure requirements)
Transmission PipelineMost 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
H = 10.44LQ1.85
C1.85d4.87
Friction Losses
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.)
Hazen Williams Equation
H = 10.44LQ1.85
C1.85d4.87
Friction Losses
ExampleIf 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 packagespreadsheet
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 alignment2) Extra losses through pump and suction pipe3) Friction loss incurred in well tubing4) Other
In large pipeline networks minor losses can be a substantialportion 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 tosimply add 5 to 10 feet to the final head calculation as an adjustmentfor 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)
4)Minor losses estimate = 10 ft.
Total Dynamic Head = 176 ft.
PUMP SELECTION
Flow (gpm)
To
tal D
yn
amic
He
ad
(ft
.)
Full Impellor
30% Trim
20% Trim
10% Trim
85%
82%
79%
176
7500 1250
225
PUMP SELECTION
Flow (gpm)
To
tal D
yn
amic
He
ad
(ft
.)
20% Trim 85%
82%
79%
0 1250
225
PUMP STUFF1) 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
1) Rewritten for use by NRCS in EQIP program2) Evaluates sprinkler package coefficient of
uniformity (must be at least 85% according to NRCS sprinkler standard)
3) Uses pump input parameters to give an entire system evaluation
4) Sprinkler inputs set up similar to OUTLETS program
RUN CPED
IRRIGATION WATER MANAGEMENT
By the Checkbook Method
1) Treats soil profile as a checkbook2) Water is the $3) Inputs and outputs are measured or estimated and
the balance is tracked throughout the growing season
4) Can be tracked by hand, in a spreadsheet or with other software
Checkbook Account Transfers
Deep Percolation (Withdrawal)
Rain(Deposit)
Irrigation(Deposit)
Evapotranspiration(Withdrawal)
So
il P
rofi
le(A
cco
un
t B
alan
ce)
IRRIGATION SCHEDULING by the CHECKBOOK METHOD
NDSU software1) Baled Lotus spreadsheet which tracks soil
depletion throughout growing season2) Estimates crop water use based on daily high
temperature input and days past emergence of particular crop
3) Soil available water inputs are entered at setup4) Contains historical weather record for several
sites in ND and MN.5) Actual soil water measurements can be entered to
keep record closer to actual
RUN IRRIGATION
EQIPIrrigation 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.
2) System Capacity / Field Information
Flow(gpm) 750 Total Area(acres) 132 System Efficiency(%) 75
Daily Application Rates at ____ efficiencyDaily 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
3) Soils Information
Soil NameFarland Grail Stady Bryant
Field Acreage 46 44 38 2
Field Percentage 35.4 33.9 29.2 1.5
Irrigation Group 8c 10c 6i 8cCumulative Available Water to depth (in.)
Top 1 foot 2.5 2.5 2.5 2.5
Top 2 feet 4.5 4.5 4.5 4.5
Top 3 feet 6.5 6.5 5.5 6.5
Top 4 feet 8.5 8.5 6.0 8.5
Top 5 feet 10 10.5 6.5 10.0
4) Crop Data
Year2006 2007 2008
Crop Corn Potato Wheat
Full Rooting Depth (ft.) 4.0 2.0 3.5
Suggested MAD (%)* 50 40 50
Avg. Annual Water Use 25.9 23.2 18.8Est. annual no. days crop water
use exceeds system capacity25 23 18
Robinson, ND Corn Crop Water Use 2000-2004 averages vs. 5.8 GPM / Acre
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
5/1
5
5/2
9
6/1
2
6/2
6
7/1
0
7/2
4
8/7
8/2
1
9/4
9/1
8
Date
Co
rn E
T (
in. /
da
y)
Rain or Soil WaterDependant
System can meet CropRequirements @ 80% eff.
5) Water Management Plan
Year2006 2007 2008
Crop Corn Potato Wheat
Managed Soil Farland Stady Farland
Managed Crop Rooting Depth (ft.) 4.0 2.0 3.0Managed 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 0.50
Managed Soil Water (in.) 3.75 1.7 2.75Minimum Soil Available Water
(in., %)4.25,50 2.70,60 3.25,50
CSP Irrigation Water Management
Evaluation Sheet
1) Evaluates an irrigation system and management scheme for placement/eligibility in the CSP program
RUN CSP program
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)
Cnty SoilsLink
CH 1link
CH 2link
Electrical Center Pivot Operation
1) 3 Phase Electric Power so that motors can be easily reversed and consequently the machine will reverse directions
2) Motor power is 480 V 3Ph, Control power is 120 V 1Ph
3) 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
4) 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
Electrical Center Pivot Operation
Electrical Center Pivot Operation
Last Tower Controlled By Percent Timer
Electrical Center Pivot Operation
Next Tower Follows When Micro-switch
Triggers
Electrical Center Pivot Operation
All Other Towers Follow Similarly
Center Pivot 10 Conductor Span Cable
Power
Power PowerGround
Forward
Neutral
Reverse
Safety
Timer
End Gun
THE END