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Improving Efficiency in Your Flood or Pivot Irrigation
Irrigation
Caleb CarterUW Extension Hay Workshop, Pinedale, WY February 20, 2015
Web Soil Survey
Obtain info on:• Soil type• H2O capacity• infiltration
http://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm
Strategies• Experience/observation
• Field leveling
• Lining ditches
• Gated pipe
• Improving irrigation
management
Boulder watershed study• Producer findings:
o Allows lengthened sets
o Can irrigate larger area
o More even distribution
o Increased yields
o Less labor intensive
o Feel that it is more efficient and has increased yields
Other considerations…
• Reduced return flows?
o Study in Laramie Basin
• Identified 74 wetlands
• Found that 65% of inflows were from irrigation
• Majority of that from subsurface flows
o Powell, WY example
Stream size
𝑠𝑡𝑟𝑒𝑎𝑚 𝑠𝑖𝑧𝑒 =𝑝𝑢𝑚𝑝 𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒 (𝑔𝑝𝑚)
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑓𝑢𝑟𝑟𝑜𝑤𝑠 𝑓𝑙𝑜𝑤𝑖𝑛𝑔
• Considerations
oLeaks minimal in delivery system?
oKeep stream size smaller than max
non-erosive stream size: 12.5 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑠𝑙𝑜𝑝𝑒 𝑜𝑓 𝑓𝑖𝑒𝑙𝑑
Gross depth
𝐺𝑟𝑜𝑠𝑠 𝑑𝑒𝑝𝑡ℎ:
=1,155 𝑥 𝑠𝑡𝑟𝑒𝑎𝑚 𝑠𝑖𝑧𝑒 𝑔𝑝𝑚 𝑥 𝑡𝑖𝑚𝑒 𝑤𝑎𝑡𝑒𝑟 𝑎𝑝𝑝𝑙𝑖𝑒𝑑 (ℎ𝑟𝑠)
𝑓𝑢𝑟𝑟𝑜𝑤 𝑙𝑒𝑛𝑔𝑡ℎ 𝑓𝑡 𝑥 𝑤𝑒𝑡𝑡𝑒𝑑 𝑓𝑢𝑟𝑟𝑜𝑤 𝑠𝑝𝑎𝑐𝑖𝑛𝑔 (𝑖𝑛)
Soil Texture Ideal GrossApplication
Sandy 1.5 – 2 inches
Medium to Fine 2.5 – 3 inches
Cutoff ratio
𝑐𝑢𝑡𝑜𝑓𝑓 𝑟𝑎𝑡𝑖𝑜 =𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑎𝑑𝑣𝑎𝑛𝑐𝑒 𝑡𝑖𝑚𝑒
𝑠𝑒𝑡 𝑡𝑖𝑚𝑒
Target cutoff ratio per soil/system considerations.Sandy Soils Loamy Soils Clayey Soils
Without Reuse 0.5 0.70 0.9With Reuse 0.20 0.40 0.5Blocked Ends 0.7 0.85 0.95
Example• Soil = sandy
• Pump discharge =
760 gpm
• Furrow length =
2,600 ft.
• Set time = 24 hours
• System = no reuse
• Set size = 80 gates flowing
• Watered furrow spacing = 30 inches
• Observed advance time = 15 hours
Example (cont.)
• 𝒄𝒖𝒕𝒐𝒇𝒇 𝒓𝒂𝒕𝒊𝒐 =15 ℎ𝑟𝑠
24 ℎ𝑟𝑠= 0.63
• 𝒔𝒕𝒓𝒆𝒂𝒎 𝒔𝒊𝒛𝒆 =760 𝑔𝑝𝑚
80 𝑓𝑢𝑟𝑟𝑜𝑤𝑠= 9.5 𝑔𝑝𝑚 𝑝𝑒𝑟 𝑓𝑢𝑟𝑟𝑜𝑤
• 𝑮𝒓𝒐𝒔𝒔 𝒂𝒑𝒑𝒍𝒊𝒄𝒂𝒕𝒊𝒐𝒏 =1,155 𝑥 9.5 𝑔𝑝𝑚 𝑥 24 ℎ𝑟𝑠
2,600 𝑓𝑡 𝑥 30 𝑖𝑛= 3.4 𝑖𝑛
• Cutoff time: 0.63 > 0.5
• Gross application: 3.4 inches
Example (cont.)
Parameter Calculation Method Example
Desired cutoff ratio
Table 1 0.5
New Advance Time
Desired Cutoff Ratio x New set time
0.50 x 12 hrs = 6.0 hrs
Advance Time Ratio
New Advance Time ÷Original advance time
6 hrs ÷ 15 hrs = 0.40
Furrow Ratio Figure 2 0.6
New Number of Gates
Original Number of Gates x Furrow Ratio
80 x 0.60 = 48 gates
New Stream Size Equation 1 760 ÷ 48 = 15.6 gpm
New Gross Application
Equation 2(1155 x 15.6 x 12)
÷ (2600 x 30) = 2.8 in
Surge Irrigation Trials
• 26 trials
• No trial was less efficient
• Only half significantly decreased advance time
• Better for high infiltration soils
• First irrigation shows the most benefit
Surge irrigation – Cycles
Fraction of FieldCycle No.
4 advance stages
5 advance stages
6 advance stages
On-time factor
1 1/4 1/5 1/6 1.02 1/2 2/5 1/3 1.93 3/4 3/5 1/2 2.64 1.0 4/5 2/3 3.15 ― 1.0 5/6 3.46 ― ― 1.0 3.8
Advance cycles
C𝒖𝒕𝒐𝒇𝒇 𝒄𝒚𝒄𝒍𝒆 =0.65 𝑥 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑎𝑠𝑡 𝑎𝑑𝑣𝑎𝑛𝑐𝑒 𝑐𝑦𝑐𝑙𝑒
Example
Cycle Type and Number
On-Time Factor x First Cycle On-Time
On-Time for Each Cycle
Advance Cycle 1 1.0 x 20 =20 minutes per
side
Advance Cycle 2 1.9 x 20 =38 minutes per
side
Advance Cycle 3 2.6 x 20 =52 minutes per
side
Advance Cycle 4 3.1 x 20 =62 minutes per
sideEach Cutback Cycle 0.65 x 62 =
40 minutes per side
• 1,000 ft field• 4 advance stages: 250 ft per stage
Surge Irrigation Limitations
• Surge valve cost: $1500 to
$2500
• Varied results
• Depends on soil type,
topography, management
• Lower infiltration rates may
lead to less water in root
zone
• Field leveling very important
Flood irrigation
• Efficient flood
irrigationoAlmost filling root
zone
o Utilizing or minimizing
runoff
Pivot characteristics
Span
Span end(ft)
Area withinthe span (acres)
Discharge from span
(gpm)
1 180 2 14
2 360 7 42
3 540 12 71
4 720 16 99
5 900 21 127
6 1080 26 156
7 1260 30 184
OH 1310 9 56
Total 124 750
7 x 180 ft. spans
Span1 2 3 4 5 6 7
Potential problems in the field
• Sprinkler installation or maintenance problems
• Inadequate pressure at pivot point to provide
desired flow rate and uniformity
• System capacity is not appropriate
• Sprinkler placement that decreases uniformity an
does not provide evaporation savings that many
expect
• Runoff due to inappropriate sprinkler selection or
system operation
• Inappropriate monitoring of systems to ensure
proper operation
How much water are you applying?
System capacity (gpm/ac)
System flow rate for land acres of:
Depth applied (in/day)
Depth applied (in/wk)
Time to apply one
inch (days)120 130 160 2403.0 360 390 480 720 0.16 1.1 6.33.5 420 455 560 840 0.19 1.3 5.44.0 480 520 640 960 0.21 1.5 4.74.5 540 585 720 1080 0.24 1.7 4.25.0 600 650 800 1200 0.27 1.9 3.85.5 660 715 880 1320 0.29 2.0 3.46.0 720 780 960 1440 0.32 2.2 3.16.5 780 845 1040 1560 0.34 2.4 2.97.0 840 910 1120 1680 0.37 2.6 2.77.5 900 975 1200 1800 0.40 2.8 2.58.0 960 1040 1280 1920 0.42 3.0 2.48.5 1020 1105 1360 2040 0.45 3.2 2.2
Sprinkler spacing• Follow manufacturer
recommendations
• Keep sprinklers out of canopy if possible
• If in canopy, reduce spacing
• Narrow spacing for expensive sprinklers may not be advisable
• Get in field to see how good the coverage is when the crops are tall
• Check runoff when lateral aligns with row direction
Runoff potential
0.0
0.5
1.0
1.5
2.0
2.5
0.00 0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 1.05 1.15 1.25 1.35
Rat
e (i
nch
es/h
ou
r)
Time (hours)
Infiltration rate-How fast soil takes in water
Application rate-How fast water is applied
Runoff potential
0.0
0.5
1.0
1.5
2.0
2.5
0.00 0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 1.05 1.15 1.25 1.35
Rat
e (i
nch
es/h
ou
r)
Time (hours)
Infiltration rate-How fast soil takes in water
Application rate-How fast water is applied
Surface storage amount ponded
Surfacesaturates
Runoff potential
0.0
0.5
1.0
1.5
2.0
2.5
0.00 0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 1.05 1.15 1.25 1.35
Rat
e (i
nch
es/h
ou
r)
Time (hours)
Infiltration rate-How fast soil takes in water
Application rate-How fast water is applied
Surface storage amount ponded
Surfacesaturates
Runoff PotentialWater that can move in or leave the field
Runoff begins
Reducing runoff• Short term:
o Speed up the pivot
• Long termo Increase wetted diameter
o Reduce gpm into pivot – be careful to meet crop needs
o Increase surface storage
• Special tillage – dammer dike
• Increase residue on soil surface
o Increase soil infiltration rate
• Tillage
• No-till
Hard to manage what you don’t measure
• Schedule irrigations
• Measure soil water
• Monitor pivot
• Control
Summary• Get sprinkler chart & ensure package is properly installed
• Determine if system capacity is adequate for your
location
• Ensure that pump and pivot are properly matched
• Buy good pressure gauge and operate system at design
pressure
• Operate system when crops are small and look for broken,
plugged sprinklers or pressure regulators, other leaks
• Observe water application in the outermost span on the
steepest portion of the field to see if you have runoff, if
problems exist:o Reduce the application depth
o Use reduced tillage to enhance surface storage and infiltration
o Eventually evaluate if different sprinkler package would help
o Select devices with large droplet size when renozzling
• Routinely maintain mechanical/electrical components
Questions?
Caleb CarterExtension Educator, Goshen County(307) [email protected]
Web: www.uwextension.org/highplainscropsite