Transcript Sprinkler Irrigation System Planning and Evaluation

Center Pivot
Lateral Move
Solid set
Planning and Management
Considerations
Dale Heermann
ARS Retired Engineer
Planning Considerations
 Field Size
 Available water supply
 Management ability
 Labor availability
 Crops to be grown
 Soils characteristics
 Intake Rate
 Water holding capacity
Center Pivot
Planning Considerations
 Field Size – General needs large areas
 Available water supply – meets crop needs
 Management ability – Can manage multiple systems
 Labor availability – Low labor requirements
 Crops to be grown – must clear canopy
 Soils characteristics
 Intake Rate - runoff potential at outer end
 Water holding capacity – can apply small depths
Linear Move
Planning Considerations
 Field Size – General needs large rectangular areas
 Available water supply – meets crop needs
 Management ability – Can manage multiple systems
 Labor availability – Labor required to move hose
 Crops to be grown – must clear canopy
 Soils characteristics
 Intake Rate - Application rate constant along lateral
 Water holding capacity – can apply small depths
Solid set
Planning Considerations
 Field Size – Can be designed for irregular shapes
 Available water supply – meets crop needs
 Management ability – Can manage multiple systems
 Labor availability – Minimum Labor unless hand move
 Crops to be grown – Generally not a limitation
 Soils characteristics
 Intake Rate - Application rate function of spacing
 Water holding capacity – can apply small depths
Area is 4
times larger in
outer band
Discharge
must be 4
times as
large
50
200
Application
rate is also
higher
Application Rate Comparison at 1000'
7
6
60 hrs/rev
30 hrs/rev
App Rate - in/hour
5
4
3
2
1
0
0
1
2
3
4
5
Time - min
6
7
8
9
10
6
5
200 ft
1000 ft
4
Rate - inches/hour
Intake 1
Intake 2
3
2
1
0
0
5
10
15
Time - min
20
25
30
Sprinkler selection for center
pivot and linear move systems
High Pressure Impact- lower application rate
Low Pressure (sprays, rotators, wobblers)
 Spacing and pattern radii affect application rate
 In canopy
Truss height
 LEPA
 Must control runoff – limit to < 1%
 Plant in circle for center pivot LEPA
 Minimizes soil evaporation
 Low capacity – function of water holding capacity
Sprinkler System Capacity
Net Irrigation Capacity – Function of Crop ET and
precipitation which is function of local conditions
Example of reducing capacity by 25% of net
irrigation capacity based on soil water holding
capacity and Eastern Colorado climatic conditions.
 One inch maximum depletion would be
exceeded one out of two years.
 Five inch maximum depletion would not be
exceeded.
EVALUATION OBJECTIVES
Changes Over Time
Installed As Designed
Properly Designed
– Nozzle Wear
– Pumping Plant Efficiency
– Declining Water Table
CURRENT EVALUATION
PROCEDURES
ASAE STANDARD 436.1
NRCS PROCEDURE
EVALUATION PROCEDURE
PROVIDES AN ESTIMATE
OF UNIFORMITY
BUT
A POOR ESTIMATE OF
EFFICIENCY
EFFICIENCY ESTIMATES
• MUST CONSIDER
–IRRIGATION TIMING
–RUNOFF
–ERRORS IN CATCH CANS
• 6.2 m/s - 25% (Loss)
• 2.5 m/s - 5% (Loss)
FIELD PROBLEMS
CENTER PIVOT WITH SPRAYS
REQUIRES MANY CANS
WIND CAN CAUSE ERRORS
LABOR INTENSIVE
GROOVED OR SMOOTH PADS
TEST EXAMPLE
GROOVED PAD TEST
FOLLOWED BY
SMOOTH PAD TEST
Both tests with low wind
CU was 10% higher
for smooth pad test
SUGGESTED PROTOCOL
• INVENTORY IRRIGATION SYSTEM
– Sprinkler Model
– Nozzle Size
– Spacing
– Pressure
– Elevation of Each Tower
– Pipe Sizes
SUGGESTED PROTOCOL
FIELD MEASUREMENT
VERIFY INVENTORY
MEASURE
- PRESSURE
- DISCHARGE
OUTPUTS
APPLICATION DEPTH
NOZZLE PRESSURE
COEFFICIENT OF UNIFORMITY
CHRISTIANSEN - CU
LOW QUARTER - DU
SIMULATIONS
COMPARE SIMULATIONS
WITH
FIELD MEASUREMENTS
OF
PRESSURE AND DISCHARGE
SIMULATIONS
OTHER BENEFITS
Evaluate new designs.
Evaluate effect of topography.
Use pump curve for change in
elevation and drawdown in
water table.
CATCH CAN ADVANTAGES
VISUAL REAL FIELD DATA
SIMPLE TO INSTALL
ACCEPTED BY USERS
DOES NOT NEED A COMPUTER
DISADVANTAGES (CC)
Wind effects
Night testing is best
Evaporation
Grooved pads
Large number of cans
Labor intensive
Extreme care for setup
ADVANTAGES OF SIMULATION
• Less labor
• Wind not a problem
• Complete hydraulic analysis
• Eliminates catch can error
• Can be rerun easily for different
operating conditions
MULTIPLE RUNS
•
•
•
•
•
Evaluate multiple designs
Analyze effect of changes in drawdown
Effects of elevation changes
Effect of big gun operation
Identify potential problems with nozzle
wear, changes in pipe roughness,
pumping plant, and water table depth.
• Effect of pressure regulators
SIMULATION DISADVANTAGES
Need pattern shape and radius.
Additional data to trouble shoot.
Understand models.
Difficult to obtain pump data.
Difficult to obtain elevation data.
Need drawdown water level.
Labor to collect field data.
Final Decision Factors and
Evaluation
 Measurement is absolute necessity
 Scheduling is needed for efficiency
 Maximum depth to minimize evaporation
 Water holding capacity limits depth
 Applying more than needed reduces efficiency
 Consider differences in soils within field
 Crop requirements varies with season
 Crops have differing root zone requirements