Summary

Low Energy Spray Application (LESA) Irrigation

Irrigation: Low Energy Spray Application (LESA) vs. Mid-Elevation Spray Application (MESA)

Irrigation method that involves applying water below 12 inches above the ground surface for row crops. Energy savings occur due to reduced water pressure and increased water application effectiveness.

Synopsis:

LESA/LEPA technology can be applied to center-pivot or wheel-line irrigation systems and competes with mid-elevation spray application (MESA), and subsurface drip irrigation (SDI). LESA applies water below the crop foliage using applicators positioned about a foot above the ground surface. Nozzle pressures can be regulated to as low 6 to 10-psig. In contrast, MESA systems require water pressure of approximately 40 psig, which requires greater pumping energy and exacerbates any water leaks.

LESA is capable of using quad sprays, bubble emitters, drag socks or hoses to release water directly on the ground. LESA systems tested in the Northwest use water pressure of about 6-psig, and improve irrigation application efficiency to as high as 97% through reducing water losses due to wind drift and evaporation from the top of foliage. The technology is especially effective during periods of high temperatures, high winds, and low humidity. Energy savings are dependent upon the baseline irrigation technology, which is generally MESA in the Northwest, although much less efficient high spray systems are still used. Major factors that influence pumping costs for irrigated crops include energy costs, pumping lifts, pressure requirements of the application system, inches of water pumped and labor wage rates. By increasing irrigation efficiency, less total water has to be pumped to meet the crop water requirements and pumping occurs at a lower pressure. Results from the 2013 field tests in the Northwest documented a 15% to 20% reduction in water use accompanied by a 30% reduction in electrical energy consumption.

Because center pivot equipment life is approximately 30 to 50 years, irrigation equipment manufacturers and distributors have developed retrofit kits that can be used to convert existing pivots into LESA units.

Energy Savings: 29%

Energy Savings Rating: Extensive Assessment What's this?

Level	Status	Description
1	Concept not validated	Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.
2	Concept validated:	An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.
3	Limited assessment	An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline.
4	Extensive assessment	Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions.
5	Comprehensive analysis	Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.
6	Approved measure	Protocols for technology application are established and approved.

Simple Payback, New Construction (years): 2.6 What's this?

Simple Payback, Retrofit (years): 2.6 What's this?

Simple Payback is one tool used to estimate the cost-effectiveness of a proposed investment, such as the investment in an energy efficient technology. Simple payback indicates how many years it will take for the initial investment to "pay itself back." The basic formula for calculating a simple payback is:

Simple Payback = Incremental First Cost / Annual Savings

The Incremental Cost is determined by subtracting the Baseline First Cost from the Measure First Cost.

For New Construction, the Baseline First Cost is the cost to purchase the standard practice technology. The Measure First Cost is the cost of the alternative, more energy efficienct technology. Installation costs are not included, as it is assumed that installation costs are approximately the same for the Baseline and the Emerging Technology.

For Retrofit scenarios, the Baseline First Cost is $0, since the baseline scenario is to leave the existing equipment in place. The Emerging Technology First Cost is the Measure First Cost plus Installation Cost (the cost of the replacement technology, plus the labor cost to install it). Retrofit scenarios generally have a higher First Cost and longer Simple Paybacks than New Construction scenarios.

Simple Paybacks are called "simple" because they do not include details such as the time value of money or inflation, and often do not include operations and maintenance (O&M) costs or end-of-life disposal costs. However, they can still provide a powerful tool for a quick assessment of a proposed measure. These paybacks are rough estimates based upon best available data, and should be treated with caution. For major financial decisions, it is suggested that a full Lifecycle Cost Analysis be performed which includes the unique details of your situation.

The energy savings estimates are based upon an electric rate of $.09/kWh, and are calculated by comparing the range of estimated energy savings to the baseline energy use. For most technologies, this results in "Typical," "Fast" and "Slow" payback estimates, corresponding with the "Typical," "High" and "Low" estimates of energy savings, respectively.

Details

Low Energy Spray Application (LESA) Irrigation

Irrigation: Low Energy Spray Application (LESA) vs. Mid-Elevation Spray Application (MESA)

Item ID: 288

Sector: Agricultural

Energy System: Irrigation--Irrigation Systems

Synopsis:

Baseline Example:

Baseline Description: Mid-Elevation Spray Application (MESA)
Baseline Energy Use: 103774 kWh per year per center pivot

Comments:

The baseline example is a 900 gallons/minute pivot irrigation system that is supplied with water from a well that is 100 feet to water. The pivot operates 2000 hours per year. The pivot currently has 20 psi pressure regulators. Converting the pivot to a LEPA sprinkler package would reduce the pivot flow to 800 gallons/minute with 6 psi pressure regulators. The lower flow also reduces the friction loss through the pivot piping resulting in a total head reduction savings of 16 psi or 37 feet. There could be additional friction loss savings through the distribution pipeline to the pivot that will not be calculated here. Assuming wire-to-water pump efficiency of 60%, demand is 51.9 kW with annual energy consumption of 103,774 kWh with the existing pivot package.

Manufacturer's Energy Savings Claims:

Comments:

Manufacturers don't make claims as the energy savings varies depending upon amount of water applied with the specified baseline irrigation technology, which in turn is dependent upon crop type, life stage, and soil type, plus is highly dependent upon pumping conditions (including required lift from surface or deep well sources) and pump efficiency itself. Irrigation equipment manufacturers and local equipment distributors and installers have developed retrofit kits that can be used to convert existing pivots into LESA units. A retrofit kit consists of a double goose-necked truss-rod hose sling, drop hose, weight, pressure regulator, and sprinkler nozzles or bubble emitters. Center pivot equipment life is approximately 30 to 50 years.

Best Estimate of Energy Savings:

"Typical" Savings: 29%
Low and High Energy Savings: 15% to 50%
Energy Savings Reliability: 4 - Extensive Assessment

Comments:

Energy savings are highly dependent upon the pump lift. Energy savings are also dependent upon the baseline spray application system and its efficiency, soil type, local climate, and in the total seasonal water application requirements for the crop being grown. Water savings are greatest during hottest days of the summer when high winds promote loss due to wind drift and evaporation. Energy savings are greatest when the energy costs to apply a fixed volume of water are the highest. For example, a pumping system that takes water from a canal and only requires 10 feet of lift (plus 22 feet of friction losses in piping, plus pressure drop across the regulator, plus regulated pressure) might require about 50,000 kWh/year per pivot. Energy savings from converting to LEPA arise from both reduced water application rates and from reductions in the pressure requirements. Savings are about 25,000 kWh/year or 50% of the baseline MESA energy use (assuming an application rate of 800 gpm versus 900 gpm for 2000 hours/year, a regulated pressure of 6-psig versus the 20-psig required with MESA, and with a 60% pumping plant efficiency).

For this analysis, we assume a 900 gallons/minute pivot that is supplied water from a well that is 100 feet to water. The pivot operates 2000 hours per year. The pivot currently has 20 psi pressure regulators. Converting the pivot to a LEPA sprinkler package would reduce the pivot flow to 800 gallons/minute with 6 psi pressure regulators. The lower flow also reduces the friction loss through the pivot resulting in a total head savings of 16 psi or 37 feet. There could be additional friction loss savings through the distribution pipeline to the pivot that will not be calculated here. Assuming wire-to-water pump efficiency of 60%, demand is 51.9 kW with annual energy consumption of 103,774 kWh with the existing pivot package. After changing to the LEPA pivot package and modifying the pump, demand would drop to 36.8 kW with an annual energy consumption of 73,677 kWh. This is a reduction of 30,097 kWh or a savings of 29% in energy consumption and demand.

Given a deep well turbine pump with a 700 foot lift, the same baseline center pivot would require about 475,000 kWh/year to operate. Energy savings from converting to LEPA increase to about 73,000 kWh/year but the savings are only 15.4% when expressed as a percentage of baseline energy use. This is an important observation; in this example the savings are more than doubled but the percent savings are roughly halved. Costs to modify the center pivot are unchanged, but pump modifications would be required to efficiently capture the portion of the savings due to a reduction in operating pressure. Some irrigation system designers specify adjustable speed drives (ASD) for their low voltage 700 hp and below motor driven deep well turbine pumps. The presence of an ASD simplifies system optimization.

Energy Use of Emerging Technology:

73,679.5 kWh per center pivot per year What's this?

Energy Use of an Emerging Technology is based upon the following algorithm.

Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))

Comments:

See calculations above.

Technical Potential:
Units: center pivot
Potential number of units replaced by this technology: 6,173
Comments:

According to the 2008 Farm and Ranch Irrigation Survey put out by the National Agricultural Statistics Service (NASS) there are 3.2 million acres under center pivots in the Pacific Northwest Water Resource Region. Ongoing research at the IAREC in Prosser, WA will help determine which of those acres are amenable to LEPA, but for the purposes of this estimate it is assumed that only about 1/3 of these acres or about 1 million irrigated acres that have the potential for conversion to LEPA. Using the assumptions above, and assuming a 1500 foot long pivot that irrigates about 162 Acres, results in an estimated 6,173 center pivots within the region that can be converted to LEPA.

Regional Technical Potential:
0.19 TWh per year
21 aMW
What's this?

Regional Technical Potential of an Emerging Technology is calculated as follows:

Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)

First Cost:

Installed first cost per: center pivot
Emerging Technology Unit Cost (Equipment Only): $7000.00
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.00
Baseline Technology Unit Cost (Equipment Only): $0.00

Comments:

Center pivots with LEPA designs can be purchased new, or existing center pivots can be converted to LEPA. Water outlets on older center-pivot mainlines are typically spaced 8.5 to 10 feet apart. LEPA drops are placed between every other crop row, so additional outlets are necessary. Because every other row is irrigated, drops are needed every 60 inches (or 5 feet) for a crop spacing of 30 inches. For 36-inch row spacing, drops are needed every 6 feet. Outlets can be added to a mainline by drilling holes and inserting a coupler into the hole. Alternatively, tees, plumbing and clamps can be used to connect with existing mainline outlets. Retrofitting mainline outlet spacing typically costs $10,000 more than when spacings are specified with an initial purchase. (Assume $30 per drop and 288 hose drops per pivot plus installation). Newer pivots often come with the additional outlets available, but plugged. The pumping system would also have to be modified (i.e., stages removed from a vertical turbine pump, impeller trimming, or use of a variable frequency drive) to reduce pressure drops across regulating valves. Note that VFD use is increasing in the irrigated agriculture sector.

The remainder of the existing sprinkler system must be replaced below existing furrow arms or goosenecks. The LEPA retrofit application system components include flexible hose drops, any rigid pipe used on the drop, pressure regulators, gate values (if needed), nozzle bodies or bracket assemblies, and sprinkler or bubble-type nozzles, drag socks or surface hoses. Only the weights may be re-used (NRCS, 2005).

Cost Effectiveness:

Simple payback, new construction (years): 2.6

Simple payback, retrofit (years): 2.6

What's this?

Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.

Comments:

The BPA-supported "Multi-State LEPA/LESA Demonstration Project" will result in a publication that provides LEPA conversion cost information. Estimates of power and energy savings will also be included in the publication (BPA, 2014).

Detailed Description:

LESA involves irrigating with a center-pivot, wheel line or lateral move mechanism with attached hoses spaced only 5 to 6 feet apart. Water is applied with applicators located no higher than 18 inches above the ground surface, which applies water in bubble patterns, or by drag socks or hoses that releases water on the ground.

LEPA systems are in wide scale use in Texas, Kansas, and Oklahoma, although the driving force for their adoption is water savings over energy savings. They have been adapted for use in the Northwest, but are not in common use here. They are suitable for row crops like carrots and onions. They can also be used with corn and alfalfa. Drag hoses are used with mint crops as growers don’t want sprinklers to wash the mint oil off of the leaves. A future demonstration project will test the compatibility of the LEPA system with potatoes. The unknown with this crop is whether the drop hoses would pull through the above ground portion of the vines.

The WSU Irrigated Agriculture Extension Center in Prosser, Washington, started a two-year, BPA-funded LEPA demonstration project in Washington, Idaho and Nevada in 2012. LEPA requires management attention because a good deal of water is applied in a short time, presenting infiltration and runoff issues if the soil is not sandy or the ground flat. To prevent runoff, more drops (sprinklers or emitters) must be added to the pivot, tillage practices changed, and dams or dikes employed.

The researchers found that LEPA is used in Texas and Oklahoma as a “supplemental” source of water --- i.e. it supplements rainfall by meeting about 50% of crop water requirements. In the Northwest, the LEPA technology was reconfigured into LESA and modified to be able to provide the total water needs of the crop. Center pivots were modified to a drop hose spacing of about 5 feet to irrigate every other furrow.

The retrofit involves purchase of components from multiple component suppliers. A retrofit kit may consist of a double goose-necked truss-rod hose sling, drop hose, weight, pressure regulator, and sprinkler nozzles, bubble emitters or drag socks. Each component can be supplied by multiple small manufacturers. The local irrigation shop assembles the components and then drills holes for more drop tubes in the existing pipe and completes the retrofit. Therefore, no product suppliers are provided in the Product Information section.

Standard Practice:

Irrigation accounts for 85 percent of the region’s (Northwest) total agricultural electrical energy use. Overall, agricultural irrigation uses 5% of the region’s electric energy, representing a $335 million annual cost. As of 2008, there was a total of 8,701,486 irrigated acres in the Pacific Northwest (Washington, Oregon, Idaho and Montana). Of these:

2,768,899 acres are irrigated by gravity systems,
5,940,010 acres are irrigated by sprinkler systems (68.3%), and
243,986 acres are irrigated with irrigation water supplied by drip, trickle or low-flow micro sprinklers (USDA, Census of Agriculture, National Agricultural Statistics Service).

Center-pivot systems are used to irrigate about 3,733,249 acres (about 62.8% of acres served with sprinkler systems); low-pressure center pivots (under 30 psig) are used for 1,420,457 acres.

The center-pivot system is the system of choice for agricultural irrigation due to low labor and maintenance requirements, convenience, flexibility, performance, and easy operation. The center-pivot system saves water, energy and time (New, et. al., 2000 Pg B-6096). LEPA technology has not been applied in the Northwest where center pivots are frequently used; instead, impact sprinklers, mid-elevation spray application (MESA), or low-elevation spray application (LESA) techniques are used.

Development Status:

In the early 1980s, Low Energy Precision Application (LEPA) systems were developed for the southern plains states. They have been widely used in Texas, Oklahoma and Kansas, where water is scarce and application efficiency (not energy efficiency) is of huge importance. A "quad" applicator has been developed to deliver a bubble spray pattern that can be set to deliver optimal sprays for germination, chemigation and other in-field requirements.

Non-Energy Benefits:

LEPA features application efficiencies of 95 to 97%. Because water droplets are applied directly to or near the soil surface, this practice eliminates water losses due to wind drift and evaporation. Water sprays that wet the underside of leafy vegetation does not incur rapid evaporation from leaf tops. A dry canopy may lead to less crop diseases (Peters, et. al., 2014).

Growers have found that precision application of water keeps it out of the center pivot wheel tracks. This prevents formation of ruts which can ultimately result in wheels getting stuck. Another benefit occurs during chemigation as the drops can be raised slightly and a chemigation plate used to spray the water to the underside of leaves. This is where the pests are located, so a more effective application is possible. The LESA approach also leads to more uniformity (in corn) and less “lodging” or losses due to the inability of a heavy and wet plant to support itself (Peters, et. al., 2014).

LEPA/LESA saves water. Water left in rivers can benefit fish and wildlife habitats and dilute in-stream pollutants, and it can be diverted through existing power-generation turbines. Application uniformity improves between day and night and windy and calm days (Peters, et. al., 2014). Maintenance is easier, requiring no ladders, and workers stay drier (Peters, et. al., 2014).

End User Drawbacks:

A LESA package uses low-pressure (6 to 10 psig) bubblers or drag socks that are suspended from a drop tube located up to 18 inches above the soil surface. Crop rows must be planted to follow the circular path of the center-pivot system or in rows for a lateral rolling irrigation system.

Previous short-term LEPA trials in the Northwest were unsuccessful due to lack of knowledge regarding the LEPA system. Fields must be properly prepared and growers must apply best management practices to mitigate excessive runoff. LEPA and LESA systems typically have high application rates that often exceed the soil infiltration rate. Water management techniques must be employed, particularly in soils with high clay content. The land slope for a LEPA or LESA system should not exceed 1.0%. LEPA and LESA systems should employ some method of providing surface water storage such as furrow diking, pitting, tillage or implanted reservoirs. One study in Idaho found that the increase in application efficiency was offset by increased runoff (King, et. al. , 1997).

Some of the changes farmers will have to make are as follows. Crop row spacing has to be modified (possibly resulting in a slight decrease in crop size), and pumping plants would have to be modified to capture the energy savings potential given the reduced pressures required by the LEPA system. For deep well pumping systems, this means removing stages or use of an adjustable speed drive. For operating flexibility, some irrigation system designers include adjustable speed drive control for deep well turbine pumps (up to 700 hp).

Early sprinkler designs could be clogged by buildup of debris from pumped surface waters --- that could result in the need for filtering. Redesign has eliminated this problem, and users of the LESA equipment have found that nozzle cleaning or replacement is easy due to the easy access to the ground level equipment. Changing out to smaller nozzles (due to reduced water use due to improved application efficiency) could lead to additional plugging (Peters, et. al., 2014).

Operations and Maintenance Costs:

Comments:

Maintenance costs would be comparable to those encountered with MESA systems. Maintenance costs would increase compared to costs of operating flood irrigation systems. It is expected that increases in maintenance costs would be small compared to the significant energy savings available with the LEPA technology. Energy requirements are proportional to both pumping pressure and the volume of water pumped. Improved application efficiencies result in reduced water requirements. Pumping pressures are typically reduced from 40 psig to as low as 6 psig.

Effective Life:

Comments:

Assume 15 to 20 years. Project components will be repaired and/or replaced as needed.

Competing Technologies:

LESA technology is one of many techniques that can be applied to center-pivot irrigation systems and competes with mid-elevation spray application (MESA). The BPA-supported "Multi-State LEPA Demonstration Project" will result in a side-by-side comparison of LEPA and MESA in the same soils, on the same irrigation schedule and with identical application rates. The evaluation will consider application uniformity, measure moisture content over time as a function of soil depth, compare crop yield and, determine water application efficiency.

Reference and Citations:

Stephen Amosson, et. al., 01/11/2002. Economics of Irrigation Systems
AgriLife Extension, Texas A&M University

Traxco, 11/26/2010. Low Energy Precision Application, LEPA
Traxco Center Pivot Irrigation Components

Andrew Tarantola, 06/15/2011. Center Pivot Irrigation: How to Grow Food in the Middle of the Sahara
Gizmodo

Blaine Hanson, et. al., 09/01/1988. Uniformity of Low-Energy Precise-Application (LEPA) Irrigation Machines
California Agriculture , 42

Paul Colaizzi, et. al., 02/22/2011. Corn Production with Spray, LEPA, and SDI
Proceedings of the 23rd Annual Central Plains Irrigation Conference, Burlington, CO., February 22-23, 2011

Paul Colaizzi, et. al., 02/25/2009. Comparison of Grain, Sorghum, Soybean, and Cotton Production Under Spray, LEPA, and SDI
Proceedings of the 21st Annual Central Plains Irrigation Conference, Colby Kansas, February 24-25, 2009

Mark Nielson, et. al., 05/16/2012. Retiming Benefits Analysis for Conservation in the Walla Walla, Horse Heaven Hills and Southern Franklin County Study Areas
Pacific Groundwater Group, Presentation to Columbia River Basin Water Management

Freddie Lamm, et. al., 02/21/2012. Erraticity of Sprinkler Irrigated Corn in 2011
2Proceedings of the 24th Annual Central Plains Irrigation Conference, Colby, Kansas

Richard Smith, et. al., 03/01/1991. Subsurface Drip Produced Highest Net Return in Westlands Area Study
California Agriculture , 45

Navigant, 04/15/2013. Northwest Agricultural Irrigation Market Characterization and Baseline Study
Northwest Energy Efficiency Alliance

Bradley King, et. al. , 12/01/1997. Optimal Performance from Center Pivot Sprinkler Systems
University of Idaho, College of Agriculture

Leon New, et. al., 07/19/2000. Center Pivot Irrigation
Texas Agricultural Extension Service, Texas A&M University System

NRCS, 05/27/2005. Utilizing Center Pivot Sprinkler Irrigation Systems to Maximize Water Savings
Natural Resources Conservation Service, U.S. Department of Agriculture

USDA, 02/11/2013. Farm and Ranch Irrigation Survey
Census of Agriculture, U.S.Department of Agriculture

Dan Berne, 02/10/2015. Agricultural Irrigation Initiative: Overview of Center Pivot Irrigation Systems
Northwest Energy Efficiency Alliance

BPA, 2014. BPA Emerging Technologies for Energy Efficiency: Industrial & Agricultural Technology
Bonneville Power Administration

Troy Peters, et. al., 2014. Low Energy Precision Application (LEPA) in the Pacific Northwest
Washington State University Extension, Idaho State University Extension, Bonneville Power Administration

Rank & Scores

Low Energy Spray Application (LESA) Irrigation

There is no TAG available for this technology.

Market Potential

Low Energy Spray Application (LESA) Irrigation

Last Edited:

1/4/2013 6:08:57 PM by JackZ

Market Segment:

Agricultural Sector. Growers of field crops with a slope of less than 1%.

Regional Fit:

LEPA has a water application efficiency of about 95% versus the 85% obtained with MESA. Use of the technology can save both water and energy. Irrigation predominately is used east of the Cascade Mountains in Washington and Oregon, plus in the states of Idaho and Montana.

Zones:

Cooling Zone 2, Cooling Zone 3

Load Shape:

The LEPA technology would have the "Agricultural--Irrigation" load shape (load factor =0.54, coincidence =0.33). Water applications and energy savings occur during the irrigation season which runs from April through September. The quantity of water applied is dependent upon type of crop and life stage, soil type, solar insolation, and rainfall. Peak irrigation requirements occur in July and August.

Performance Trajectory:

LEPA is a mature and highly efficient sprinkler technology, and few changes in performance are expected over the next 5 years. As LEPA systems have not been installed in the Northwest, efforts are underway to introduce and demonstrate the effectiveness of the technology.

Cost Trajectory:

No significant change is expected in the costs of this technology over the next 5 years.

Product Supply and Installation Risk:

No production shortages or manufacturing, distribution, or installation barriers are expected. Growers have time to modify their equipment during the fall and winter, so production is not impacted due to sprinkler system upgrading. Crop row spacing would have to be modified (possibly resulting in a slight decrease in crop size) and pumping plants would have to be modified to capture the energy savings potential given the reduced pressures required by the LEPA system. For deep well pumping systems, this means removing stages or use of an adjustable speed drive. For operating flexibility, some irrigation system designers include adjustable speed drive control for deep well turbine pumps (up to 700 hp).

Technical Dominance:

Sprinkler systems can be categorized as "good, better, best" with respect to both energy consumption and water application efficiency. Irrigation systems include Mid-Elevation Spray Application (MESA—good) and Low Elevation Spray Application (LESA-better) and LEPA-best. LEPA provides improved application efficiency through eliminating high pressure spraying and applying the water directly to the ground with bubble emitters, drag socks or hoses.

Target Customer:

The market segment for Low Energy Precision Application (LEPA) irrigation systems are growers of row crops (onions, potatoes, carrots, corn, and perhaps alfalfa) that currently use high, medium, or low pressure center pivots, lateral move or side roll systems, or Mid-Elevation Spray Application (MESA) systems. LEPA may be successfully applied in fields with a slope of less than 1%. Google Earth can be used to ascertain terrain slop and other features. Typically, a grower would identify the type of irrigation system desired. A system designer would verify field dimensions, design the circle, then acquire, modify, and install the irrigation equipment. Software tools are available to assist in mainline sizing, setting span lengths, nozzle sizing and spacing, and system design. Design practices size for lowest purchase price and operating cost.

Market Channels:

LEPA sprinkler equipment would be sold through the existing network of irrigation equipment distributors and installers. These equipment suppliers can also handle installations and, in retrofit scenarios, provide pumping system modifications. While LEPA equipment has not been used in the northwest, equipment and design aids can readily be obtained from users. Many of the components, including pressure regulators, connectors (sledges), hose drops, sprinklers etc are common to MESA, LESA, and LEPA designs.

Regulatory Issues:

No regulations exist that dictate irrigation system selection. Irrigators are, however, awarded water rights which carry a "use it or lose it" aspect. Water that is "freed up" due to improved application efficiency may be used to grow additional crops (but at an improved metric of energy use per unit of production), transferred to junior water rights holders (if water is taken from an irrigation canal or river), or left in the river to provide additional instream flows that result in improved fish spawning and rearing habitat.

Other risks and barriers:

Growers are most interested in production (yield or quantity of crop per irrigated acre) and crop quality. The forthcoming BPA demonstration project will use soil moisture sensors to ensure that crops receive enough water, and document water application efficiency and yield, as well as providing for visual comparisons. Evaluations and sprinkler system design will ensure both water application uniformity and efficiency. Part of the demonstration project will involve the application of best management practices to mitigate LEPA runoff issues.One barrier is current design practice. Irrigation system designers like to provide 50-psig water to the circle. They cite a small "margin for error" in low pressure systems. Energy savings due to reduced operating pressures will only partially materialize if delivered pressures are maintained with nozzle pressures dictated by pressure regulators. Adjustable speed drives may have to be incorporated into pumping systems to provide growers with the confidence that water will be delivered as needed.

Basis of Savings:

The standard protocol for measuring energy savings is appropriate for center pivots or lateral move (side roll) systems using MESA and LEPA sprinkler technologies. Energy use is dictated by the input kilowatts to a pump drive motor and the pump run time. Input kilowatts is reduced when the required pumping flow rates and discharge pressure are reduced by using LEPA rather than MESA. It is assumed that pump run or irrigation times will remain constant, so energy savings can easily be documented through taking "before and after" power readings at the electrical panel serving the pump. One component of LEPA system optimization will be matching of new pumps to the modified load requirements or changing pump performance (through removal of stages in a multi-stage pump) to match pump output to sprinkler system requirements. This does not include any additional savings related to costs of water procurement.

Evaluation Plan:

The grower will apply water as needed to ensure that soil moisture requirements are met at the plant's root zone. Assuring uniformity of application and providing the needed amounts of water should ensure crop quality. Pumping savings will occur due to improved application efficiency and reduced pressure requirements. Energy savings would be determined through monitoring annual "before and after" energy use for pumps serving one or more center pivot or side roll sprinkler systems. Savings would vary with respect to crop type (due to varying irrigation requirements, uptake, and evapotranspiration) and before and after trends could be expressed as energy use per unit of production (of a particular crop). Water applications would vary depending upon rainfall that occurs during the irrigation season so the energy use data would have to be corrected to account for rainfall as well as temperature and humidity.

Citations:

Texas A&M University, Economics of Irrigation Systems, December, 2001. http://itc.tamu.edu/documentsBradley King and Dennis Kincaid, "Optimal Performance from Center Pivot Sprinkler Systems", University of Idaho College of Agriculture, Bulletin 797, December, 1997. Texas Agricultural Extension Service, "Center Pivot Irrigation", Texas A&M University System, B-6096.USDA, Natural Resources Conservation Service, "Utilizing Center Pivot Sprinkler Irrigation Systems to Maximize Water Savings". Dick Stroh, BPA, Troy Peters, WSU IAREC, and Howard Neibling, Extension Irrigation Engineer, University of Idaho, "Multi-State LEPA Demonstration Project" Proposal to BPA, February, 2011.

Additional Information:

Texas A&M University, Economics of Irrigation Systems, December, 2001 http://itc.tamu.edu/documentsURL last accessed 9/26/12 Traxco Center Pivot Irrigation Components - Low energy precision application, LEPA - November 2010 http://www.traxcoirrigation.com/ low-energy-precision-application-lepa URL last accessed 9/26/12 Gizmodo - Low Energy Precision Application - Center Pivot Irrigation: How to Grow Food in the Middle of the Saharahttp://gizmodo.com/Low-Energy-Precision-Application URL last accessed 9/26/12California Agriculture - Uniformity of low-energy precise-application (LEPA) irrigation machines - September-October 1988 http://ucce.ucdavis.edu/files/ repositoryfiles/ca4205p12-68794.pdf URL last accessed 9/26/12 USDA Agricultural Research Service - CORN PRODUCTION WITH SPRAY, LEPA, AND SDI - February 2011 http://www.cprl.ars.usda.gov/wmru/ pdfs/Colaizzi%20et%20al%20%20(2011)%20Corn%20production%20with%20spray-LEPA-SDI_CPIC%20meeting.pdf URL last accessed 9/26/12 USDA Agricultural Research Service - COMPARISON OF GRAIN SORGHUM, SOYBEAN, AND COTTON PRODUCTION UNDER SPRAY, LEPA, AND SDI - February 2009 http://www.cprl.ars.usda.gov/Wmru/ pdfs/Colaizzi%20CPIC%202009.pdf URL last accessed 9/26/12 State of Washington Department of Ecology - Pacific Groundwater Group - Retiming Benefits Analysis for Conservation in the Walla Walla, Horse Heaven Hills and Southern Franklin County Study Areas http://www.ecy.wa.gov/programs/ wr/cwp/images/pdf/RBA-PAG-5-16-12.pdf URL last accessed 9/26/12 Proceedings of the 24th Annual Central Plains Irrigation Conference - ERRATICITY OF SPRINKLER IRRIGATED CORN IN 2011 - February 2012 http://www.cprl.ars.usda.gov/wmru/ pdfs/Erraticity%20of%20Sprinkler%20irrigated%20corn%20in%202011.pdf URL last accessed 9/26/12 University of California - Subsurface drip produced highest net return in Westlands area study http://ucanr.org/repository/cao/ landingpage.cfm?article=ca.v045n02p8&fulltext=yes URL last accessed 9/26/12

Completed:

1/4/2013 6:08:57 PM by Jack Zeiger