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.
in/yr acres
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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 from poor uniformity. 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. Thus the irrigation efficiency estimates of sprinklers might be lower than you have used in the past.
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 do not typically 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 and Climate! 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 and even over a single day, 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 crop type and condition 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 from research assume better maintenance than is common in practice) • Total water requirements, rainfall, and irrigation applied to the field • 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 replace the defaults in the calculator, and 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 about 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. 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. 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. Microsprinkler: Emit water at lower pressures and low flow rates and have smaller wetted radii (3-10 ft). Most often used in orchards or vineyards. Under-tree 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. Big Gun – Traveler: A large, usually singular sprinkler with a large nozzle size and operates at high pressure such that it has a large wetted radius. These are usually attached to a hose that reels the sprinkler in slowly to irrigate a strip. 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. 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. Furrow w/ Surge: Furrow irrigation where the water is controlled such that it applies water in pulses. This wetting and settling affects the infiltration rate of the previously wetted soils such that it results in improved irrigation uniformity, and thus efficiency. It usually requires an automated valve and gated pipe to work effectively. Furrow w/ Tailwater Reuse: Furrow irrigation where the runoff water is collected in a small pond or basin and pumped back up to the top of the field for re-use. This limits runoff. 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. Border: A surface irrigation method where water flows evenly (ideally) accross a field as restricted by borders on each strip of land. Contour 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. Corrugation: A surface irrigation method where corrugates (small rills) are plowed in to help the water flow more evenly accross the soil surface. This is more common in forage production. Wild Flood: A surface irrigation method where water is turned out without grading, furrows, or corrugations to guide its flow accross the soil. More common in forage production in mountain valleys. Subsurface Drip: Drip irrigation with the drip tubing or emitters buried beneath the soil surface. Surface Drip: Drip irrigation with the drip tubing or emitters placed on the surface, or just above the surface of the soil. Mobile Drip Irrigation: A center pivot or linear move irrigation system that drags drip tubing with integrated emitters. Irrigation Application Efficiency of the Low Quarter (Ealq): 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 (Equation 1) x 100. 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. This is reasonably adjusted for uniformity (see details about the edits for sprinkler surface and drip below) for typical season-long non-uniformity issues. Primary Destination of Water Losses: No system is 100% efficient. The water losses from different systems go primarily to various destinations including wind drift and evaporation (WDE), deep percolation (DP), and runoff (RO). Irrigation Efficiency Range: Irrigation application efficiency ranges considerably depending on a wide variety of factors, fields, system characteristics, operating conditions, weather, maintenance, timing, and irrigator. The named ranges are what is typical. 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 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. Percent Losses to DP: Percent of the losses (100 – Ealq) that go to deep percolation (DP). Calculated as losses to DP / total irrigation water flowing onto the field x 100. Deep percolation losses stay in the basin and are thus sometimes referred to as “return flows”. Percent Losses to WDE: Percent of the losses (100 – Ealq) that go to wind drift and evaporation (WDE). Calculated as: losses to WDE / total irrigation water flowing onto the field x 100. Wind drift and evaporation losses leave the basin and are thus part of “consumptive use”. Percent Losses to RO: Percent of the losses (100 – Ealq) that go to field runoff (RO). Calculated as: losses that go to field runoff / total irrigation water flowing onto the field x 100. Run off losses stay in the basin and are thus sometimes referred to as “return flows”. Total Consumptive Use (%): The percentage of the total gross irrigation water required that is consumptive use (evaporation and transpiration). Calculated as the Ealq + [(100 – Ealq) x (WDE + 0.1 x RO) / 100]. Or it can be calculated as 100 – Return Flow %. This assumes that all of the irrigation water requirements and all wind drift and evaporation losses, and 10% of field runoff (additional evaporation from tailwater ditches and weed growth) is consumptive use (converted to water vapor). Return Flow (%): The percentage of the total gross irrigation water required that is return flow. Calculated as (100 - Ealq) x [(DP + 0.9 x RO) / 100] or as 100 – total consumptive use %. This assumes that all deep percolation and 90% of runoff losses are eventually recoverable (return flow).