Irrigation Conversion Water Savings Destination Calculator

This is a rough estimate of how much water can be saved, where that water will be saved from, and where the lost water will go by converting from one type of irrigation system to another. This will help to make informed decisions on the impact to a drainage basin of converting large numbers of irrigation systems. For a comparison of the costs of various irrigation system technologies, go here. Select an irrigation technology to convert from and to to get default efficiency estimates as well as estimates of where the inefficiently used (lost) water came from. The irrigation systems are defined at the bottom of this page. This will bring in default irrigation system efficiencies that you can edit if you have better data. Please use actual numbers instead of the defaults if you have better data. Mouse-over the headings in blue to see more information about that value and how it is calculated.

Net Crop Water Requirement (ET):The amount of water the crop needs (Evapotranspiration or ET) in inches per year. Don't include irrigation system losses. in/yr
Total Area Applied to (optional):The field acreage. This number only gets used to calculate total water conservation as a volume (acre-ft) instead of a depth (inches of water). Note that sometimes system conversions will change irrigated areas such as when converting to a center pivot that can't irrigate corners as well. acres

Select Systems	Convert From	Convert To
Overall Irrigation Efficiency (%):Water stored in the crop root zone divided by water flowing onto the field.
Losses to Deep Percolation (%):The percent of the total lost water (short term irrigation water losses that are not stored in the crop root zone) that is lost to deep percolation.
Losses to Wind Drift and Evaporation (%):The percent of the total lost water (short term irrigation water losses that are not stored in the crop root zone) that runs off of the field.
Losses to Field Runoff (%):The percent of the total lost water (short term irrigation water losses that are not stored in the crop root zone) that runs off of the field.
Gross Water (in/yr): The depth of water that needs to flow onto the field (inches per year), including losses, in order to meet the total net crop water requirements. Calculated by dividing the net crop water requirements by the irrigation system efficiency and multiplying by 100.
Total Short Term Water Losses (in/yr): The depth of irrigation water per season that flows onto the field (inches per year) that is not stored in the crop root zone for later use (losses). This is calculated as the difference between the gross water (above) and the net crop water requirements (ET). Reducing short term water losses are especially important from an irrigation water delivery capability and irrigation system capacity standpoint. These water savings can reduce system delivery requirements and can reduce water requirements at times of year when water is least available. For example, reducing water requirements in the middle of the summer vs. winter water availability.
Deep Percolation Losses (in/yr): The depth of water (inches per year) that is lost to deep percolation. This model assumes that all deep percolation losses are eventually recoverable (i.e. a short term loss, but not a forever loss). Although deep percolation water losses can likely be recovered, it is difficult to predict the timing and location of this water recoverability. In addition the water quality can change. This value is calculated as the short term losses (above) multiplied by the % losses to deep percolation (above) divided by 100.
Wind Drift and Evaporation Losses (in/yr): The depth of water (inches per year) that is lost to evaporation and wind drift. This model assumes that all of these losses are both short term and forever (water vapor) losses. This value is calculated as the short term losses (above) multiplied by the % losses to wind drift and evaporation (above) divided by 100.
Field Runoff Losses (in/yr): The depth of water (inches per year) that is lost to runoff from the field. This model assumes that 90% of field runoff losses are eventually recoverable, while the remaining 10% are forever losses to the basin (water vapor) due to additional evaporation from drainage ditches and their vegetation. Although most runoff water losses can likely be recovered, it is more difficult to predict the timing and location of this water recoverability. In addition the water quality is often degraded. This value is calculated as the short term losses (above) multiplied by the % losses to field runoff (above) divided by 100.
Total Forever Losses (in/yr): Water losses (inches per year) that are converted to water vapor and are thus unlikely to be recovered in this drainage basin. Assumes all wind drift and evaporation losses are NOT recoverable (forever losses), but that all of deep percolation losses, and 90% of field runoff losses are eventually recoverable (not forever losses). This value is calculated as the sum of the wind drift and evaporation losses (above) plus 10% of the runoff losses (above).
Eventually Recoverable Losses (in/yr): Water losses (inches per year) that can be eventually recovered in the basin. This includes all of the deep percolation losses and 90% of field runoff losses. Calculated as the sum of the deep percolation losses (above) and 90% of the field runoff losses (above).
Total Depletion/Consumptive Use (in/yr): Total water consumptively used or depleted from the basin forever (inches per year). This includes water losses (forever losses as calculated above) and net crop water use (ET). Calculated as the gross water use minus the eventually recoverable losses. Or alternatively, the net crop water requirements plus the total forever losses.

	DifferencesThe differences, in inches of water per year, when converting 'from' the selected irrigation system or technology 'to' the selected technology. Calculated as the 'To' values minus the 'From' values.	% of PreviousThe differences when converting 'from' the selected irrigation system or technology 'to' the selected irrigation system or technology. Calculated as the Total Water value (just above) divided by the gross water requirement of the 'from' system or technology.	Total WaterThe total acre-ft per year of water savings when converting 'from' the selected irrigation system or technology 'to' the selected irrigation system or technology. Calculated as the total water differences (in inches) multiplied by the acres (entered above) divided by 12 in/ft.	% Savings From:Shows what percentage of the total short term water savings will come from the different categories of wind drift and evaporation, runoff, or deep percolation.
Wind Drift and Evaporation Losses The difference in the water that goes to wind drift and evaporation losses. Calculated as the wind drift and evaporation losses (above) of the 'To' system or technology minus that of the 'From' system or technology.
Field Runoff LossesThe difference in the water that runs off of and leaves the field. Calculated as the runoff losses (above) of the 'To' system or technology minus that of the 'From' system or technology. Although most runoff water losses can likely be recovered, it is difficult to predict the timing and location of this water recoverability. In addition the water quality is often degraded.
Deep Percolation LossesThe difference in the water that goes to deep percolation (leaching) past the bottom of the crop root zone. Calculated as the deep percolation losses (above) of the 'To' system or technology minus that of the 'From' system or technology. Although deep percolation water losses can likely be recovered, it is difficult to predict the timing and location of this water recoverability. In addition the water quality can change.
Total Short Term Water LossesThe total water savings. Calculated as the difference between the gross irrigation water requirements of the 'To' technology minus that of the 'From' technology. Short term water losses are important from an irrigation water delivery capability and system capacity standpoint. These water savings can reduce system delivery requirements and can reduce water requirements at times of year when water is least available. For example, reducing water requirements in the middle of the summer vs. winter water availability.
Total Forever Water LossesWater losses that leave the drainage basin as water vapor. Calculated as the wind drift and evaporation losses plus 10% of the deep percolation losses.
Depletion/Consumptive UseDifferences in the total long-term consumptive use. Calculated as the Total Depletion/consumptive use of the 'To' system minus that of the 'From' system.

* A Negative value is a reduction in water use (a savings). A positive value is an increase in water use.

Technical Notes and Assumptions

These efficiency estimates, and the assumptions on where the losses go comes from the table below for various irrigation systems. The variables and terms used are defined below.

Assumptions: This information was compiled from a wide variety of publications (Alam, 1997; Irrigation Association, 2010; Hanson, 2004; Brouwer et al., 1989; Burt, 1995; Burt et al., 2000; Hanson, 1994; Irmak et al., 2011; Kisekka et al., 2016; Kranz, 2020; Sadeghi et al., 2015; S. H. Sadeghi et al., 2017; Solomon, 1988a, 1988b; Stetson & Mecham, 2011; Melvin & Martin, 2018). These efficiency estimates assume no water losses due to imperfect irrigation scheduling, which is difficult to achieve. The non-included water losses due to imperfect irrigation scheduling usually end up as deep percolation water losses.

This tool is meant to be used as a comparison between irrigation systems. The literature-based values for sprinkler irrigation efficiency are almost exclusively based on surface-placed catch can tests and rarely include the unavoidable water losses to deep percolation (leaching) due to imperfect irrigation system uniformity, while surface-irrigation estimates of efficiency from research are almost totally based on deep percolation water losses. Because of this the literature-based efficiency estimates were reduced by 5% for all the sprinkler irrigation systems except for LEPA and Microsprinklers, which were adjusted down by 10% and 15% respectively based on research reports.

Also, based on this research and similar research reports, attempts were made to allocate the fraction of the water losses that end up as deep percolation, wind drift and evaporation, or field runoff. These terms are defined below.

Caveats: To have usable tools we need them to be simple and not require large numbers of inputs that users won't know. However, using a single number for efficiency estimates is always going to be problematic since efficiency can depend on so many other things! These include factors such as:
• Weather! We know that efficiency is strongly a function of wind speed and vapor pressure deficit (aridity) and thus irrigation efficiencies change drastically over the year, especially wind drift and evaporation losses!
• Sprinkler system operating pressure (both for wind drift and evaporation losses and proper uniformity to reduce deep percolation losses)
• Sprinkler wetted radius
• Sprinkler design (rotator plate design, spinners, wobblers, rotators, impacts vs rotators, etc.)
• Sprinkler height above ground level
• How things change as the rows close vs. a bare soil, perennial vs. annual crops, etc.
• Inter-row cover crops in perennial crops such as tree-fruit and vineyards
• Row spacing for furrow irrigation
• Whether furrows are irrigated in every row, vs. every-other row
• Subsurface drip irrigation burial depth (sometimes the surface is wetted, sometimes it isn’t)
• Irrigation frequency! More frequent irrigations result in comparatively more water losses to evaporation from a wet soil surface.
• Soil type (this affects soil surface evaporation rates and duration, and the soil water holding capacity affects irrigation frequency)
• Tillage and surface residue management (can effect infiltration and runoff)
• Crop canopy type (affects water interception)
• Irrigation system maintenance (most estimates assume better maintenance than is common)
• Grower behavior and skill! Especially as related to irrigation scheduling, maintenance, and controlling runoff. Irrigator skill is especially important and variable for surface irrigation methods.

However, in order to help guide decision making, this table and conversion estimate tool contains our best research-based estimates of what might be expected, on average, over time, in a large drainage basin. If you are aware of better research data please contact us!

Defintion of Terms

Center Pivot/Linear MESA: Mid-elevation spray application. A center pivot or linear move irrigation system with sprinklers mounted at a mid elevation of abouit 5-12 ft from the soil surface. This is currently the most common sprinkler configuration on center pivots.
Center Pivot/Linear LEPA: Low-energy precision application. A center pivot or linear move irrigation system with emitters mounted close together and close to the soil surface such that water dribbles directly onto the soil surface. These systems are very efficient, but can require additional tillage and planting management for uniform irrigation and avoid surface runoff.
Center Pivot/Linear LESA: Low-elevation spray application. A center pivot or linear move irrigation system with sprinklers mounted close together and close to the soil surface (6-24 inches) but with spray emitter device on each sprinkler. These systems are very efficient, but can sometimes exacerbate runoff problems due to the sprinkler's reduced wetted radius.
Mobile Drip Irrigation: A center pivot or linear move irrigation system that drags drip tubing with integrated emitters. These have been used successfully and are very efficient. Contact your irrigation extension specialist for more information.
Pivot/Linear Top of the Pipe: A center pivot or linear move irrigation system with high pressure impact or rotator sprinklers mounted on the top of the pipe. Although the application rate is slower, these systems lose a tremendous amount of water to wind drift and evaporation and inefficient.
Surface Drip: Drip irrigation with the drip tubing or emitters placed on the surface, or just above the surface of the soil.
Subsurface Drip: Drip irrigation with the drip tubing or emitters buried beneath the soil surface.
Micrsprinkler: Emit water at lower pressures and low flow rates and have smaller wetted radii (3-10 ft). Most often used in orchards or vineyards.
Undertree orchard: Sprinklers (often impact or rotating type sprinklers) that operate below the canopy in orchards.
Solids Set Sprinklers: Sprinkler irrigation systems with larger wetted radii (10-40 ft) where the sprinklers are not moved throughout the irrigation season.
Hand Move: Sprinkler irrigation systems with larger wetted radii (10-40 ft) where there is usually one sprinkler per span of pipe, and the pipe is disconnected and moved by hand throughout the season.
Wheel Line: Sprinkler irrigation systems with larger wetted radii (10-40 ft) where there is usually one sprinkler per span of pipe, but the pipes have a wheel mounted such that the entire line can be moved simultaneously with a mover at the center of the line.
Basin: A surface irrigation method used in very level fields where irrigation flows onto the field and fills it up like a bathtub. Runoff is restricted.
Boarder: A surface irrigation method where water flows evenly (ideally) accross a field as restricted by borders on each strip of land.
Graded Furrow: A surface irrigation method where water flows through furrows or rills where the land has been graded to make the water flow more evenly across the soil surface to increase the infiltration uniformity.
Countour Border: A surface irrigation method where water flows onto a field that has been contoured with built up borders such that, on the overall slope, each countour is level.
Furrow: A surface irrigation method, common in cultivated row crops, where water flows accross the field in furrows or rills that are tilled into the soil, usually between every crop row, or every-other crop row.
Corrugation: A surface irrigation method where corrugates (small rills) are plowed in to help the water flow more evenly accross the soil surface. More common in forage production.
Wild Flood: A surface irrigation method where water is turned out without grading, furrows, or corrugations to guide it's flow accross the soil. More common in forage production in mountain valleys.

Irrigation Efficiency (Ea): Water that is stored in the soil for evaporation or transpiration (evapotranspiration or ET) by the crop divided, by the overall water that flows onto the field. The water that is not stored in the root zone for later ET by the crop includes water lost to deep percolation, wind drift and evaporation (primarily from sprinklers), and field runoff.
Deep Percolation (DP): When more water is applied than the soil can hold in the crop's root zone, the excess water drains through the soil and out past the reach of the crop's roots and enters the groundwater. Much of this water can be eventually recovered, albeit often with changed water quality, by pumping the groundwater from wells.
Wind Drift and Evaporation (WDE): Sprinklers lose large amounts of water to wind drift and evaporation. Although this humidifies and cools the air and thus can decrease crop water demand down-wind, these changes in water demand have been shown in research to be minimal. Thus nearly all of this water leaves the basin as water vapor and can be considered to be forever losses.
Runoff (RO): Irrigation water runs off of a field when water is applied faster than it can be absorbed by the soil or used by the crops. Much of this water is often captured and used downstream.
Short Term Losses: Much of the water losses to deep percolation and field runoff can be eventually recovered in the basin. How much and when the water can be recovered depends on the local topography, geology, groundwater hydrology, and irrigation and drainage systems. The recovered water can also have degraded water quality that is less suitable for irrigation.
Forever Losses: The irrigation water from wind drift and evaporation losses that leaves the drainage basin as water vapor. Although this water may eventually fall as rainfall somewhere else, it cannot be eventually recovered by anyone in the area of interes.
Fraction Losses to DP: Fraction (% of total irrigation water flowing onto the field / 100) of the losses that go to deep percolation (DP).
Fraction Losses to WDE: Fraction (% of total irrigation water flowing onto the field / 100) of the losses that go to wind drift and evaporation (WDE).
Fraction Losses to RO: Fraction (% of total irrigation water flowing onto the field / 100) of the losses that go to field runoff (RO).
Fraction of Short Term Losses: Fraction (% of total irrigation water flowing onto the field / 100) that is lost to the irrigator, but stays in the basin. Is calculated as (100 - Irrigation Efficiency of the System) / 100.
Fraction of Forever Losses: Fraction (% of total irrigation water flowing onto the field / 100) that leaves the basin and is unrecoverable. Is calculated as the Fraction of Short Term Losses x (Fraction of Losses to Wind Drift and Evaporation + 10% of the Fraction of the Water Losses to Runoff). This assumes that all wind drift and evaporation losses are forever losses and 10% of field runoff is long term losses (due to additional ET along drainage ditch banks), but all deep percolation is eventually recoverd. Rounding errors can make is seem like they don't all add up, but the do if exact calculations are used.

References

• Alam, M. (1997). Surface irrigation efficiencies. Kansas State University Extension Publication.
• Irrigation Association. (2010). Principles of Irrigation. . Retrieved from Irrigation Association Education Foundation:
• Hanson, B., L. J. S., Allan Fulton. (2004). Scheduling irrigations: when and how much water to apply.
• Brouwer, C., Prins, K., and Heibloem, M. (1989). Irrigation Water Management: Irrigation Scheduling. Retrieved from http://www.fao.org/tempref/agl/AGLW/fwm/Manual4.pdf
• Burt, C. M. (1995). The surface irrgation manual. Retrieved from http://irrigationtoolbox.com/IrrigationToolBox/Section%201%20-%20Soil%20Water%20Plant%20Relationships/Publications/Surface%20Irrigation%20Manual.pdf
• Burt, C. M., Clemmens, A. J., Bliesner, R., Merriam, J. L., and Hardy, L. (2000). Selection of Irrigation Methods for Agriculture: American Society of Civil Engineers.
• Hanson, B. R., and W. Bowers. . (1994). An analysis of mobile laboratory irrigation system evaluation data. Retrieved from Final report to the California State Department of Water Resources
• Irmak, S., Odhiambo, L. O., Kranz, W. L., and Eisenhauer, D. E. (2011). Irrigation efficiency and uniformity, and crop water use efficiency. Retrieved from https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1455&context=biosysengfacpub
• Kisekka, I., Oker, T., Nguyen, G., Aguilar, J., and Rogers, D. (2016). Mobile drip irrigation evaluation in corn. Kansas Agricultural Experiment Station Research Reports, New Prairie Press, 2(7). doi:https://doi.org/10.4148/2378-5977.1253
• Kranz, B. (Producer). (2020, 2020). Irrigation Chapter 8 - Irrigation Efficiencies. Retrieved from https://passel2.unl.edu/view/lesson/bda727eb8a5a/8
• Sadeghi, S.H., Peters, R.T., Amini, M.Z., Malone, S.L., and Loescher, H.W. (2015). Novel approach to evaluate the dynamic variation of wind drift and evaporation losses under moving irrigation systems. Biosystems Engineering, 135, 44-53. doi:https://doi.org/10.1016/j.biosystemseng.2015.04.011
• Sadeghi, S.H., Peters, T., Shafii, B., Amini, M.Z., and Stöckle, C. (2017). Continuous variation of wind drift and evaporation losses under a linear move irrigation system. Agricultural Water Management, 182, 39-54. doi:https://doi.org/10.1016/j.agwat.2016.12.009
• Solomon, K. H. (1988a). Irrigation systems and water application efficiencies. Irrigation Notes.
• Solomon, K. H. (1988b). Irrigation systems selection. Irrigation Notes.
• Stetson, L. E., and Mecham, B. Q. (2011). Irrigation, 6th Edition: Irrigation Association.
• Melvin, S.R. and Martin, D. L. (2018). In-Canopy Vs. Above-Canopy Sprinklers, which is better suited to your field? Paper presented at the Proceedings of the 30th Annual Central Plains Irrigation Conference, Colby, Kansas.