\,A N'l.oO. <:,4 ~\ f1 (\0.3~ Irrigation Conservation Practices Appropriate for the Southeastern United States Robert 0. Evans2, Kerry A. Harrison1, James E. Hook1, Charles V. Privette3, William I. Segars1, W. Bryan Smith3, DanielL. Thomas1, and Anthony W. Tyson1 Edited by: Daniel L. Thomas University of Georgia College of Agricultural and Environmental Sciences Biological and Agricultural Engineering Department Tifton, GA 31793 Phone: 912-386-3377 Fax: 912-386-3958 E-mail: thomasdl@ tifton.cpes.peachnet.edu GEORGIA DEPARTMENT OF NATURAL RESOURCES Lonice C. Barrett, Commissioner ENVIRONMENTAL PROTECTION DIVISION Harold F. Reheis, Director GEORGIA GEOLOGIC SURVEY William H. McLemore, State Geologist Prepared in cooperation with the Georgia DNR, EPD under Proposal No. ES61135FC1; the University of Georgia, College of Agricultural and Environmental Sciences1; North Carolina State University, Cooperative Extension Service2; and Clemson University, Cooperative Extension Service3 Atlanta 1998 PROJECT REPORT 32 Irrigation Conservation Practices Appropriate for the Southeastern United States Robert 0. Evans Kerry A. Harrison James E. Hook Charles V. Privette WiJJiam I. Segars W. Bryan Smith Daniel L. Thomas Anthony W. Tyson Edited by: Daniel L. Thomas GEORGIA DEPARTMENT OF NATURAL RESOURCES ENVIRONMENTAL PROTECTION DIVISION GEORGIA GEOLOGIC SURVEY Atlanta 1998 PROJECT REPORT 32 . ! I \ TABLE OF CONTENTS ABSTRACT INTRODUCTION 2 General 2 Application Efficiencies 3 PROCEDURES 6 DESCRIPTION OF TABLES 7 COMPARISON OF IRRIGATION PRACTICES 9 Center Pivot and Lateral Move Systems (Table 1) 10 Improved Irrigation Practices for all Systems (Table 2) 15 Traveling Gun Systems Including Cable and Hose Tow (Table 3) 19 Drip{frickle/Mini/Micro Irrigation Systems (Table 4) 22 Solid Set Irrigation Systems (Table 4) 25 Changing to a Different System (Table 5)26 DESCRIPTION OF A NEWLY DESIGNED, PROPERLY MANAGED, WATER EFFICIENT IRRIGATION SYSTEM 26 IRRIGATION PRACTICES THAT MAY HAVE THE HIGHEST WATER-SAVING POTENTIAL 32 SUMMARY 32 REFERENCES 33 ACKNOWLEDGMENTS 33 LIST OF IRRIGATION PRACTICE IMPROVEMENT TABLES Irrigation Conservation Practices, Estimate of Water Savings from Improved Practices 1. Center Pivot and Linear Move Systems 2. Improved Irrigation Practices Appropriate for All Systems 3. Traveling Gun Systems Including Cable and Hose Tow 4. Drip{frickle/Mini/Micro Irrigation Systems 4. Solid Set Irrigation Systems 5. Comparisons Between Systems ii ABSTRACT Irrigation system efficiency and water conservation characteristics were investigated for the primary irrigation systems present in the southeastern United States and, in particular, Georgia. These recommendations take into account the humid region and the differences between this area and water conservation potential in arid regions. Although the most efficient irrigation systems are currently being used throughout the region, many systems have been in place for 20 years and are in need of upgrades and improvement. The potential for a tax incentive or regulatory program to encourage irrigation system upgrades to more efficient and conServation-oriented alternatives produced five (5) primary recommendations. Firstly, an irrigation audit is suggested for all systems considering a change to be sure recommended changes are appropriate. Although no direct water savings are associated with an irrigation audit, the characterization of needs is a primary consideration. Secondly, a properly operating end gun shutoff is recommended for the estimated 2,000+ center pivot systems that are in need of such repair/installation. .The estimated water savings are :::: 2,851 million gallons at a cost/benefit ratio of =$351/million gallons saved in an average year. Thirdly, repair of the water delivery system on 80 psi traveling gun systems (older ones still in use) is estimated to save =2,585 million gallons of water in an average year on the estimated 1600 systems in need of such repairs. The cost/benefit ratio of such repairs is estimated at :: $2,166 per million gallons saved in an average year. Fourthly, use of a preferred irrigation scheduling technique on orchard drip systems (estimated that :::: 500 systems, primarily on pecan, would benefit) would translate to = 1,996 million gallons of water saved in an average year. The cost/benefit ratio of such improvements is =$376 per million gallons saved. Fifthly, the replacement of old sprinkler packages with new, more efficient sprinklers is estimated to save =4,181 million gallons in an average year on the =4,400 systems in need of such replacement. The cost/benefit ratio of such replacement is =$631 per million gallons saved in an average year. The above scenarios represent less than IS% of the recommendations indicated in this report. The choice of particular improvements is based on the characteristics of individual systems and the desire to be more efficient and conservation minded. The suggestions in this report are not designed to be all inclusive, nor cover new alternatives which may be available in the future. However, water conservation in irrigation systems will continue to be a priority in considerations for existing and new irrigation systems (and permits) in Georgia. 1 INTRODUCTION General: Irrigation is an essential part of a full crop management program, whether in arid or humid areas. Irrigation in humid areas reduces part of the risks of growing crops by not relying totally on Mother Nature to supply plant water needs. In 1997 there were over 1.3 million acres of irrigated cropland in Georgia (Harrison and Tyson, 1997). The majority of irrigation in Georgia is associated with three primary classifications: center pivot and linear move, traveling gun, and drip/trickle/mini/micro. The number of systems associated with each type and the estimated land area under each classification are indicated in Figure l. This acreage is expected to increase in the future as profit margins on dryland crop production decrease and farmers attempt to reduce risks. Irrigation remains the life-blood of many of Georgia's agricultural operations and will continue to be require.d to meet future food arid fiber needs. Figure 1. Irrigation Systems in Georgia D Center Pivot .t Linear Move Traveling gun Drip/Trickle/Mini/Micro The prevalence of irrigation in Georgia and surrounding states and the amount of water associated with this practice has generated interest about the quantity of water used in irrigation. The estimation of how much water is actually used in agricultural irrigation became extremely important when the tri-state water dispute between Georgia, Alabama, Florida surfaced in the early 1990's. Since then, several projects have studied water use (including irrigation water use) in the major basins associated with Atlanta in order to estimate how changes in water allocation might impact Alabama, Florida and other parts of Georgia. Water use concerns associated with salt-water intrusion and pumping along the east coast have also increased the need for good quality data on agricultural water use. 2 ..,' . Unfortunately, agricultural water users have not been required to report their water use in Georgia, so current data and analysis are crude estimates at best. Whether these estimates are good or bad, they are, in fact, estimates. Since no frrm data were available to indicate how much water was being used, it was impossible to determine whether water was used wisely. Irrigation of agricultural crops has received "bad press" because problems in water application are usually easily identified. Traveler systems which are spraying water over roads, irrigation sprinklers which have failed and are shooting "geysers" of water into the air, and spray drift during high winds are occasionally observed and reported by the general public who travel near irrigation systems. Even though agricultural irrigation systems operate correctly most of the time, public opinion is often based on these rare events. The undeserved poor reputation for agricultural irrigation has created a need for better assessment of how well we are actually irrigating and what steps can be taken to improve those practices. The primary purpose of this report is to document the most prevalent irrigation practices currently being used in Georgia and indicate alternatives, which may be implemented to improve agricultural water use efficiency. Alternatives are suggested based on a particular type of irrigation system. Water savings and efficiency improvements associated with a change in irrigation type are also presented. Some improved management alternatives are suggested which can be applied to most agricultural irrigation situations. However, the scope of this report is limited in that only those practices most prevalent in Georgia and the southeastern United States are included. The practices in this report are also dated. New irrigation practices and management alternatives are being developed continuously. In all cases where older irrigation systems are replaced, new more efficient systems and/or components will hopefully be used. Irrigation practices discussed in this report relate to application efficiency and irrigation conservation. The application efficiency is the ratio of water being withdrawn from a particular resource to the water available for target plant production. Irrigation conservation is the process of improving the application efficiency. The term "improving" implies that an effort is made to reduce losses by a particular management or system change. In all irrigation systems, some water loss will occur (i.e., all water withdrawn from a source will not reach the target plant roots). However, some losses can be legitimately minimized or eliminated. When these losses have been minimized on a particular system, then the application efficiency is maximized for that system. Application Efficiencies: Application efficiency, as indicated above, is a term used to define the difference between the water taken from a water source and the water reaching a position where the target plants can use the water (usually at the plant roots). At this point the 3 differences between humid area irrigation and arid area irrigation diverge. In the application of water, if the water is not reaching the soil or remaining in the soil where roots are located, then this water is loSt. This loss directly reduces the efficiency of the irrigation system. Of course, there are other uses for irrigation besides meeting crop needs (seed bed preparation, seed germination, 'softening a soil crust during emergence, frost protection, salt removal, etc.; Burt, et al., 1997). In this report the primary use of irrigation in Georgia's humid region is ~ssociated with consumptive use, where the water is taken up by the plant. All other uses are either tied to arid conditions; or they are usually minor components of overall irrigation. applications in the southeast, and will not be extensively addressed in this report. In an irrigation system~ losses may occur at any position in the_ water's pathway. Application efficiencies are affected by system leaks, system water pressure (decreased droplet size), evaporation rate, wind speed and direction, uniformity of application, canopy interception, deep percolation, and other factors. Application efficiencies can vary widely by crop and the ,particular type of irrigation system. For the most part, irrigation systems that expose water to the atmosphere for a long period of time are . subject to decreased application efficiency. In the southeast, and particularly in Georgia, the majority of the irrigation systems being used are already the most efficient available for the particular crop and land conditions. Very little if any surface (including furrow, level basin, flood, ...) irrigation is used. Water table management (WTM, also know as sub-irrigation) is used extensively in North Carolina and Florida, but few systems have been installed in other states (Shirmohammadi, et al., 1992). Surface and WTM are usually less efficient irrigation alternatives. The predominate use of center pivot, drip/trickle, traveler, and solid set irrigation results in relatively high application efficiency potential. We say potential, because poor management and design of a particular system can result in poor application efficiency even though the average system is efficient. In irrigation system des~gn, application efficiency and uniformity are critical factors. Uniformity implies how consistently emitters/sprinklers apply water across the irrigation system. In most irrigation systems all the sprinklers or emitters do not apply the same amount of water. Those near a mainline tend to emit more water than those at the end of lines due to pressure los8es. Sprinklers and emitters may not wear evenly and some variation exists in manufacturing. As a result, water application oft~n varies significantly across a field. Obviously, a system with high uniformity is desirable to ensure the entire crop is receiving the same amount of water. In mariy irrigation system evalu.ations, the characteristics of application efficiency are based on the output from the low quarter emit.ters. The definition of low quarter . emitters or sprinklers is the quarter of the emitters or sprinklers producing the least amount of water in the irrigation system. The following are considered "reasonable" application efficiencies from two different sources. 4 ;... Keller and Bliesner (1990) state: "Average application efficiencies. are based on full crop canopies and systems that are well-designed and carefully maintained. The values are estimates and should be considered accordingly. Under conditions where poor management, poor design, or conditions are not suited for irrigation, values may be much lower ..." Allen (1991) reports the following potential application efficiencies of low quarter emitters/sprinklers: Sprinkler Solid Set Center Pivot Linear Move Big Gun Traveler Trickle Range(%) Average (%) 60-15 70 70-85 15 65- 85 15 55-65 60 60-80 70 70-95 Keller and Bliesner also (1990) provide the following other efficiency information: Efficiency % Moving or set systems with excellent uniformity in cool or humid climates and low winds. 85 Moving systems in most climates and winds; and set systems with medium to high application rates and good uniformity. 80 Average set system in most climates and winds 15 Travelers 70 Gun or boom sprinklers 60-75 Periodic-move laterals 70-85 Fixed lateral 70-88 In defining application efficiencies which correspond to crop type in Georgia, the predominate irrigation system used for crops such as corn, cotton, peanut, soybean, sorghum, and wheat is the center pivot system. For tobacco, the predominate system type is traveler. For peaches, the systems are split between drip/trickle and traveler. For 5 pecan, the systems are split between drip/trickle and sprinkler. For vegetables, the predominate irrigation system used is drip/trickle. Watermelon and Vidalia Onions, two of Georgia's largest acreage horticultural crops, are predominately under center pivot. In practically all cropping situations, a different type irrigation system than mentioned above is probably being used on some acreage. Therefore, recommendations for improvement need to b.e' addressed . for each individual system. It is important to note that all recommendations indicated below will not work for every situation. The ranges and averages imply that the savings and efficiency increases are not the same for every system. Care should be taken to evaluate each system independently and determine the best alternatives for water savings. The overall goal of this report is to encourage our producers to improve irrigation efficiency. "Poor" systems can be improved greatly while our "good" systems may only require minimal improvements. PROCEDURES A workshop approach was used to develop these irrigation conservation practices. Irrigation specialists from the southeast region were brought together to evaluate each individual alternative as a group in two sets of workshops. Initial categories and characteristics were defmed in the first workshop and fmal numbers and ranges were consolidated in _the second. The . combined "professional years" of design, recommendation, or other irrigation activity (following graduation) of the report authors is well over 100 years. The desire was to obtain the best input possible on the recommendations to be sure. tlie values presented are reasonable. In some cases extensive discussion occurred in order to determine an alternative range of water savings. Published resources from other states and related activities from the participants were also used in developing the information. The fmal results are based on a "compendium of opinion" from those participating. The qualifications of the individuals participating only implies that these values are reasonable, but do not imply that they are "absolutely right" in all cases. . The documentation for this report was reviewed by the authors twice, followed by submission to the following list of irrigation specialists and interested parties both i~side, see following listing of individuals, and outside Georgia for their comments and input. James Lee Adams, Farmer and Member, Southwest Georgia Agribusiness Association Gary Black, Georgia Agribusiness Council, Norcross. Jimmy Bramblett, Agricultural Economist, NRCS, Athens. 6 . : I. Cecil Burke, Georgia Farm Bureau, Macon. Lamar Ortega, Lindsay Manufacturing, Dothan, Alabama Elton Sharp, Sharp Systems, Leslie, Georgia Garland Mears, Garland Mears Irrigation, Americus, Georgia Allen Smajstrla, Professor and Extension Specialist, Agricultural and Biological Engineering, University of Florida, Gainesville. Specialist in irrigation applications in Florida. Glenn Smith, Georgia Cattleman's Association, Macon. Ted Tyson, Extension Agricultural Engineer and Associate Professor, Auburn University, Alabama. Specialist in irrigation design and management and liquid animal waste management. Kurt Webster, Suwanee River Water Management District, Live Oak, Florida The base information in this report is designed to apply across the southeast region. The tables and numbers are directed toward Georgia. It is anticipated that reports will be developed with similar specific recommendations for potential water savings in the other states in the region. These anticipated reports will provide a reference/resource for the most logical approaches to improving efficiency of water use in agriculture and potential for water savings through conservation. The final reports from these efforts are designed to be working documents, with changes and recommendations occurring in the future. The authors welcome input from anyone who has knowledge or information for improvement. DESCRIPTION OF WATER EFFICIENCY TABLES Tables 1 through 5 summarize estimates of water savings associated with different changes in irrigation practices. Below is a description of the categories in the tables. Comparison: Each Comparison is "labeled" for reference purposes. The text will describe reasons for the indicated differences based on these Iabeled comparisons. 7 Current Base Svstem: This category indicates a summary of the baseline system configurations in the comparison. For each change/improvement in irrigation, the system used before the change must be identified. Proposed System Change: This category is a summary of the potential changes which may or may not provide a water savings. Proposed system changes are presented for the majority of the categories which may have been considered in the past for water or energy savings. Estimated water savings range: This column describes the range in potential savings for a proposed system change. Water savings are positive, while increased water usage would be indicated by a negative value. The range is provided because the proposed changes will not be as effective for all systems. While negative responses indicate an increase in total water usage, water use efficiency is improved so that overall, the change has net benefits. The units of "%" imply percent of total water usage during irrigation. Estimated water savings average: This is an arithmetic average within the water savings range. In some cases the average may be ""skewed" to indicate more systems may benefit from a change than others (or vice versa). Potential number of irrigation systems affected: This number is only associated with Georgia at this time. Similar numbers are expected to be included for neighboring states in future reports. The number reflects input from irrigation specialists and irrigation dealers about the number of systems which are "eligible" for the indicated system change. Average system size: This number is the average size for the particular irrigation system of interest in the state of Georgia (rounded to the nearest 5). The average system size is used to estimate the total potential water savings and the estimated cost per system. Average Year. total potential gallons saved if fully implemented (million gallons): This number is an estimate of how much water will be saved if all systems suitable for improvement were to implement the proposed system changes. Average year is based on 7 inches of annual water application. Irrigation amounts indicated are not specific for a particular crop or type of irrigation system. Obviously, vegetables with plastic mulch would use more than 7 inches of water in an average year. The calculation is based on the average system size, 7 inches of water applied, and the average estimated water savings. I . j 8 . I ,,',.:. ~- .""" ':";:- ...._-,:. ... ,)'-"'~'- ....~.. to~-~ Dry Year. total potential gallons saved if fully implemented (million gallons): This number estimates how much water will be saved if all systems suitable for improvement were to implement the proposed system changes during a dry year. An "average dry" year criteria (12 inches of water application) is designed to provide estimated conservation effects during those periods when water availability may be critical. Obviously, other dry year criteria can be determined with higher values of water application. The long-term impact of water conservation practices is based on long-term average application values. Estimated cost for implementation on an average system (1998 $): This is an estimate of the cost per system based on the average size for implementing the indicated change in 1998 dollars. Statewide costs for full implementation (Million $. 1998): This is the potential number of systems multiplied by the estimated cost for improvement. The potential tax loss, for the indicated tax incentive value, is reflected in this figure ( 1998 $). Cost per unit water saved in an average year (1998 $/Million gallon): This value is calculated from the estimates for water saved and total statewide cost figures (in 1998 $). This number provides a value to represent the cost/benefit ratio. Obviously, practices with a lower cost per unit of water saved are more desirable. One important aspect of this value is that no amortization is used. All costs are indicated within one year. Essentially, the cost/gallons saved values are presented for amortization in the first year. Obviously, the cost in the second year for similar water savings may be greatly reduced if all outlays were for capital expenses and no yearly charge is required. COMPARISON OF IRRIGATION PRACTICES The following narrative comparisons are associated with Tables 1-5. As indicated above, all cost figures are in 1998 dollars. The benefit of the narrative descriptions is to find a comparison, which has application to a particular system of interest. The ,narrative comparison will then help explain what irrigation system conditions contribute to the different levels of water savings within a particular range. As in any of the analysis, columns to the right are based on the average savings values. For an individual system, the water savings may be more or less than the average. Cost figures do not include changes that may be necessary to improve water supplies (i.e., weJJ re-working, new pumps or power units, etc.) if the recommended system change requires a different 9 flow rate. These type changes could increase the cost for potential modification. The reader needs to be aware that these average cost figures will not apply to all systems; Center Pivot and Lateral Move Systems (Table 1): The following comparisons are listed in Table 1 and are associated with center pivot and lateral move systems. In Georgia, the average system size of this type is 100 acres. There are approximately 8,500 systems in this category. Comparison 1: From No end gun shutoffto end gun shutoff The base system is a center pivot or lateral move system. Typically, the system will have an end gun. The end gun will apply water outside the target area and not be equipped with a working mechanism to turn the end gun on-and-off at desired locations. Estimated water savings are between 5 and 10%. The low end is associated with systems which are already using good practices and throwing little water into off-target areas. The high end is associated with systems which operate continuously through 24 hours in very open areas and a large percentage of the water is thrown in off-target areas. The average estimated water savings is =7.5%. Of the 8,000+ center pivot systems currently in the state of Georgia, 2000 are estimated to be candidates for this type improvement. The potential water savings from this practice alone would be =2,851 million gallons duringan average year. The cost to implement such a change is =$500 per system. The estimated statewide costs for full implementation is $1.0 million. The cost per unit water saved is estimated to be = $351 per million gallons of water saved. Comoarison 2: From poorlv uniform system to new sprinkler package (same as original) The base system is a center pivot or lateral move system with a sprinkler package performing below the accepted standard of 80% uniformity. Typically, the system will_ have an end gun. The suggested alternative is to install a new sprinkler package that is the same as the original package. Estimated water savings are between 0 and 10%. No savings are associated -with systems which are already using good practices and have uniformity coefficients that will not improve significantly. The high end savings are associated with systems which have uniformity coefficients well below the standard and are therefore over-applying water in some areas. The average estimated water savings is =5%. Of the 8,000+ center pivot systems currently in the state of Georgia, 4400 are estimated to be candidates for this type improvement. The potential water savings from = this practice alone would be 4,181 million gallons during an average year. The cost to 10 ..... ' ' ~ . .))" -: ........ ' Jo "'"":_, ;:>.'"'$ <(.J' ',~-.I, I implement such a change is between $0 and $1,000 per system. The low end cost is associated with a system that needed only sprinkler adjustments that used farm labor available at no cost. The high end cost is associated with a complete sprinkler change. The average cost for this comparison is $250 per system. The estimated statewide costs for full implementation is $2.2 million. The cost per unit water saved is estimated to be = $526 per million gallons of water saved. - Comparison 3: From 23 degrees impact sprinklers on top of boom to reduced angle sprinklers on top The base system is a center pivot or lateral move system operated with 23 degree angle impact sprinklers on the top of the pivot. The operating pressure is in the high range (> 80 psi). Typically, the system will have an end gun. The new alternative is reduced angle impact sprinklers on top of the pivot. Estimated water savings are between 5 and 15%. The low end savings is associated with systems which are already operating at night and using good practices. The high end is associated with systems which operate continuously through 24 hours in very open areas. The average estimated water savings is = 10%. Of the 8,000+ center pivot systems currently in the state of Georgia, 850 are estimated to be candidates for this type improvement. All systems with 23 degree impact sprinklers on top of the pivot are not candidates for the change due to the limitation on soil intake rates. The reduced angle impact sprinklers will apply slightly more water in a smaller area than the impact sprinklers at a higher pressure. If the soil is not capable of handling the additional input rate, irrigation water would runoff and be ineffective. This is also the sprinkler package recommended for wastewater application so those systems will remain 23 degree impact sprinklers. The potential water savings from this = practice alone would be 1,616 million gallons during an average year. The cost to implement such a change will range from $500 to $2,000 per system depending on the outside labor required. The estimated statewide costs for full implementation is $1.02 million (using a $1,200 average). The cost per unit water saved is estimated to be = $631 per million gallons of water saved. Comparison 4: From 23 degree impact sprinklers on top of boom to low pressure sprinklers on top The base system is a center pivot or lateral move system operated with 23 degree angle impact sprinklers on the top of the pivot. The operating pressure is in the high range(> 80 psi). Typically, the system will have an end gun. The suggested alternative is to change to low pressure spray nozzles on top of the pivot boom with a reduction in water pressure ( 15- 25 psi). 11 r----------,----,---------~~~~~------------~------- Estimated water savings are between 5 and 15%. The low end savings is aSsociated with systems which are already operating at night and using good practices. The high end savings is associated with systems which operate continuously through 24 hours in very open areas. The average estimated water savings is = 10%. Of the 8,000+ center pivot systems currently in the state of Georgia, 200 are estimated to be candidates for this type improvement. All systems with impact sprinklers on top of the pivot are not candidates for the change due to the limitation on soil intake rates. The spray nozzles will apply more water in a smaller area than the higher pressure sprinklers. If the soil is not capable of handling the additional input rate, irrigation water would run off and be ineffective. The potential water savings from this practice alone would be = 380 million gallons during an average year. The cost to implement such a change is =$3,500 per system if a booster pump is required. The estimated statewide costs for full implementation is $0.7 million. The cost per unit water saved is estimated to be = $1,841 per million gallons of water saved. Comparison 5: From 23 degree impact sprinklers on top of the boom to low pressure sprinklers on drops The base system is a center pivot or lateral move system operated with 23 degree angle impact sprinklers on the top of the pivot. The operating pressure is in the high range (> 80 psi). Typically, the system will have an end gun. The suggested alternative is to change to low pressure spray nozzles on drops with a reduction in water pressure ( 10- 20 psi). Estimated water savings are between 5 and 25%. The low end savings is associated with systems which are already operating at night and using good practices. The high end savings is associated with systems which operate contiimously through 24 hours in very open areas. The average estimated water savings is = 15%. Of the 8,000+ center pivot systems currently in the state of Georgia, 200 are estimated to be candidates for this type improvement. All systems with impact sprinklers on top of the pivot are not candidates for the change due to the limitation on soil intake rates. The spray nozzles will apply more water in a smaller area than the higher pressure sprinklers on top. If the soil is not capable of handling the additional input. rate, irrigation water would ruri off and be ineffective . The potential water savings from this practice alone would be = 570 million gallons during an average year. The cost to implement such a change is = $4,000 per system if a booster pump is required. The estimated statewide costs for full implementation is $0.24 million. The cost per unit water saved is estimated to be =$421 per million gallons of water saved. Comparison 6: From reduced angle impact sprinklers on top of boom to low pressure sprinklers on top 12 I ' '! . - *' __ . .;_.., ~. . r-~ --: .; .,..,...-J,. .~~-... 'l.t"--!'..1--: .. The base system is a center pivot or lateral move system operated with reduced angle impact sprinklers on the top of the pivot. The operating pressure is in the medium range (20-50 psi). Typically, the system will have an end gun. The suggested alternative is to change to low pressure spray nozzles on top of the pivot with a reduction in water pressure (15- 25 psi). Estimated water savings are between 0 and 5%. No low end is associated with systems which are already operating at night and using good practices. The high end is associated with systems which operate continuously through 24 hours in very open areas. The average estimated water savings is :::: 2.5%. Of the 8,000+ center pivot systems currently in the state of Georgia, 700 are estimated to be candidates for this type improvement. All systems with reduced angle impact sprinklers on top of the pivot are not candidates for the change due to the limitation on soil intake rates. The spray nozzles will apply more water in a smaller area than the impact sprinklers at a higher pressure. If the soil is not capable of handling the additional input rate, irrigation water would run off and be ineffective. The potential water savings from this practice alone would be :::: 333 million gallons during an average year. The cost to implement such a change is :::: $1,000 per system. The estimated statewide costs for full implementation is $0.7 million. The cost per unit water saved is estimated to be :::: $2,105 per million gallons of water saved. Comparison 7: From reduced angle impact sprinklers on top of boom to low pressure sprinklers on drops The base system is a center pivot or lateral move system operated with reduced angle impact sprinklers on the top of the pivot. The operating pressure is in the medium range (20-50 psi). Typically, the system will have an end gun. The suggested alternative is to change to low pressure spray nozzles on drops with a reduction in water pressure ( 10- 20 psi). Estimated water savings are between 0 and 10%. No low end is associated with systems which are already operating at night and using good practices. The high end is associated with systems which operate continuously through 24 hours in very open areas. The average estimated water savings is :::: 5%. Of the 8,000+ center pivot systems currently in the state of Georgia, 700 are estimated to be candidates for this type improvement. All systems with impact sprinklers on top of the pivot are not candidates for the change due to the limitation on soil intake rates. The spray nozzles will apply more water in a smaller area than the higher pressure sprinklers. If the soil is not capable of handling the additional input rate, irrigation water would run off and be ineffective. The potential water savings from this practice alone would be :::: 665 million gallons during an average year. The cost to implement such a change is :::: $4,000 per system if an end gun booster pump is required. 13 The estimated statewide costs for full implementation is $2.8 million. The cost per unit water saved is estimated to be = $4,209 per million gallons of water saved. Comparison 8: From reduced angle impact sprinklers on top of boom to LEPA nozzles on drops The. base system is a center pivot or lateral move system operated with reduced angle impact sprinklers on the top of the pivot. The operating pressure is in the medium range (20-50 psi). Typically, the system will have an end gun. The suggested alternative is to change to LEPA (low energy precision application) type spray nozzles with a reduction in water pressure (5- 10 psi). Es.timated water savings are between 0 and 10%. No low end is associated with systems which are already operating at night and using good practices. The high end is associated with systems which operate continuously through 24 hours in very open areas. The average estimated water savings is =5% .. Of the 8,000+ center pivot systems currently in the state of Georgia, 50 are estimated to be candidates for this type improvement. All systems with impact sprinklers on top of the pivot are not candidates for the change due to the limitation on soil intake rates. The spray nozzles will apply more water in a smaller area than the higher pressure sprinklers. If the soil is not capable of handling the additional input rate, irrigation water would run off and be ineffective. Another problem with the adoption . I of this sprinkler package is the growers requirement to adopt a different tillage practice called "furrow diking". Not all individuals will adopt this tillage change. The potential water savings from this practice alone would be =48 million gallons during an average year. The cost to implement such a change is =$4,500 per system if a booster pump is required. The estimated statewide costs for full implementation is $0.225 million. The cost per unit water saved is estimated to be =$4,735 per million gallons of water saved. Comparison 9: From low pressure sprinklers on top of boom to low pressure sprinklers on drops The base system is a center pivot or lateral move system operated with low pressure sprinklers on the top of the boom. The operating pressure is in the medium range (20-50 psi). Typically, the system will have an end gun. The suggested alternative is to change to low pressure sprinklers on drops with a reduction in water pressur.e ( 1020 psi). Estimated water:savings are between 0 and 10%. No low end is associated with systems which are already operating at night and using good practices. The high end is associated with systems which operate continuously through 24 hours in very open areas. The average estimated water savings is = 5%. 14 Of the 8,000+ center pivot systems currently in the state of Georgia, 2,550 are estimated to be candidates for this type improvement. The potential water savings from this practice alone would be :::: 2,423 million gallons during an average year. The cost to implement such a change is :::: $1,500 per system. The estimated statewide costs for full implementation is $3.83 million. The cost per unit water saved is estimated to be :::: $1,578 per million gallons of water saved. Comparison 10: From low pressure sprinklers on drops to LEPA nozzles on drops The base system is a center pivot or lateral move system operated with low pressure sprinklers on drops. The operating pressure is in the low range ( 10-20 psi). Typically, the system will have an end gun. The suggested alternative is to change to LEPA type spray nozzles with a reduction in water pressure (5- 10 psi). Estimated water savings are between 0 and 3%. No low end is associated with systems which are already operating at night and using good practices. The high end is associated with systems which operate continuously through 24 hours in very open areas. The average estimated water savings is = 1%. Of the 8,000+ center pivot systems currently in the state of Georgia, it is estimated that none will be candidates for this type improvement. The spray nozzles on drops at ground level will apply more water in a smaller area than the spray nozzles mounted at truss rod height. If the soil is not capable of handling the additional input rate, irrigation water would run off and be ineffective. Another problem with the adoption of this sprinkler package is the growers requirement to adopt a different tillage practice called "furrow diking". Not all individuals will adopt this tillage change. Improved Irrigation Practices for all Systems (Table 2): The following comparisons are listed in Table. 2 and are associated with all irrigation systems. In Georgia, the average system size assumed for this analysis is 100 acres. There are approximately 13,000 irrigation systems that may be affected. Comparison 11: From no cu"ent method of irrigation scheduling to irrigation scheduling The majority of irrigation systems do not use a consistent irrigation scheduling method. Typically, irrigation is the last "crop need" met following nutrients and pest control. Many crops are not receiving as much water as the crop actually needs, while in other cases, the crops are being over-irrigated to reduce the potential for droughtrelated stress (high value crops in particular). Estimated water savings are between -10 and + 10%. Improved irrigation scheduling on many row crop applications will actually indicate more water is needed by the crop. On the average, the estimated water savings are = 0%. 15 . An estimated 11,700 systems could benefit from an irrigation scheduling method. The average cost for implementation is = $700 which may be as convenient as watching local weather and calculating.water needs (book-keeping approach) to installation of soil moisture sensors in the field. Services are also available to help manage crop water requirements. Although this recommendation does not achieve water savings, the benefits of more efficient water application can be directly tied to improved and/or more consistent crop yields. In addition, the potential for improved water and chemical management can benefit water quality, reduce potential runoff, and reduce potential leaching of nutrients and chemicals. Comparison 12: From no cu"ent method of irrigation scheduling to irrigation scheduling with a Class A Evaporation Pan This proposed practice has the same potential benefits as Comparison 11. The only difference is the use of a Class A evaporation pan for irrigation scheduling. The evaporation pan provides a method of converting irrigations and water losses almost directly to crop needs (with calculations). The cost of a pan is slightly higher, but if well maintained, the pan can provide an excellent method of determining evaporation losses on a scheduled basis. Estimated water savings are between -10 and + 10%. Improved irrigation scheduling on many row crop applications will actually indicate more water is needed .bY the crop. On the average, the estimated water savings are =0%. An estimated 11,700 systems could benefit from an irrigation scheduling method. The average cost for implementation is =$1,500 which includes a pan and hook gage (for accurately reading the water level). Although this recommendation does not achieve water savings, the benefits of more efficient water application can be directly tied to improved and/or more consistent crop yields. In addition, the potential for improved water and chemical management can benefit water quality, reduce potential runoff, and reduce potential leaching of nutrients and chemicals. Comparison 13: From no uniformity test performed in last 5 vears to uniformity test performed This proposed practice does not directly "save" or "waste" water in itself. The "modifications to the system" to improve uniformity will result in the change in water use. A uniformity test is a procedure to measure the output and distribution of sprinklers, emitters, etc. to determine whether the amount of water estimated to be reaching the crop is actually reaching the crop. Poor uniformity (< 80% Christiansen's 16 1, ~. 1 coefficient of uniformity) implies that a sufficiently large section of the field is not receiving the "average" water application. As a result, the water that is being applied may be higher in some areas than is expected (encourages deep percolation and runoft) or lower (not meeting crop needs). This practice also affects the efficiency of water use. Estimated water savings are between -10 and + 10% if improvements are made. Additional water may be required if uniformity is affected by clogged emitters in a drip system. Water savings may be associated with worn sprinklers with larger orifices than in the original new sprinkler. On the average, water savings are =0%, but water will be used more efficiently. An estimated 11,700 systems are considered to be at least 5 years old and have not had a uniformity test in the last 5 years. The average cost for a uniformity test on a 100 acre system is = $250. Obviously, the changes in the system to improve uniformity would have associated costs depending on the system needs. Although this recommendation does not achieve water savings, the benefits of more efficient water application can be directly tied to improved and/or more consistent crop yields. In addition, the potential for improved water and chemical management can benefit water quality, reduce potential runoff, and reduce potential leaching of nutrients and chemicals. Comparison 14: From no uniformity test. calibration. or major maintenance check in past 5 years to performance of an irrigation audit This proposed practice, as in 13 above, does not directly "save" or "waste" Wdter in itself. The "modifications to the system" to improve uniformity, calibrate operating pressures and supply components, and repair significant leaks, will result in the change in water use. The "irrigation audit" is a full analysis of the entire irrigation system. An audit is essential to determine the most effective and needed recommendations for reducing water use. Estimated water savings are between -15 and +50% if improvements are made. Additional water may be required if uniformity is affected by clogged emitters in a drip system or operating pressures have not been sufficient (too many zones in a drip system operated at one time). Water savings may be associated with worn sprinklers with larger orifices than in the original new sprinkler, fixing major leaks, better zone management in a drip system, or end gun shut-offs and sprinkler package changes in sprinkler systems. On the average, the estimated water savings are :: 5%, but water and energy wiJI be used more efficiently. An estimated 11,700 systems are considered to be at least 5 years old and have not had a complete irrigation audit in the past 5 years. The average cost for an irrigation audit on a 100 acre system is = $1000. The statewide costs for full 17 implementation is estimated at $11.7 million. Obviously, the changes required to improve irrigation systems would have additional costs, but this audit provides essential information to determine what, if anything, needs to be changed. Although this recommendation does not achieve water savings, the benefits of more efficient water applicat~on can be directly tied to improved and/or more consistent crop yields. The implementation of a program to encourage ir..rigation audits across all systems in Georgia where necessary would provide additional information on the efficiency of current irrigation practices and systems. Understanding how much water can potentially be saved is essential to future recommendations on agricultural water use. Comparison 15: From no major maintenance checks performed in last 5 years to major maintenance check perfOrmed This proposed practice also does not directly "save" or "waste" water in itself. The "modifications to the system" for a more efficient pumping plant, and supply system which does not leak will result in the change in water use. A major maintenance check is a check of fuel use efficiency; meeting pressure requirements, and checking water losses throughout the system. This practice also affects the efficiency of water use but should save water on the average. Estimated water savings are between 0 and 10% if improvements are made. The largest improvements are based on fixing leaks, repairing gaskets, and so forth. The average estimated water savings is 5%. An ~stimated 11,500 systems are considered to be at least 5 years old and have. not had a major maintenance check in the last 5 years. The potential water savings from this practice alone would be = 10,929 million gallons in an average year if changes were implemented. The cost to perform a inajor maintenance check on a 100 acre syste~ is = $500. The estimated statewide costs for major maintenance checks for all appropriate systems is $5.75 million. The cost per unit water saved is not directly applicable, since the costs for improvements have not been added (i.e., the maintenance check does not save water by itself). Comparison 16: From pressure gages not operating to pressure gages repaired/replaced . A system operating at the correct pressure will operate more efficiently. As in several scenarios above, this proposed practice does not directly ."save" or "waste" water in itself. The "modifications to the system" required to ensure proper pressure throughout the system is important. . Estimated water savings are between -5 and + 5% if improvements are made. The largest improvements are based on systems which have been over-pressured. The average estimated water savings is 0%. 18 An estimated 6,500 systems are considered to not have correctly operating pressure gages, and therefore are most likely not being operated at the correct pressure. The cost to repair/replace gages on a 100 acre system is :::: $50 on the average. The estimated statewide costs for pressure gage replacement/repair is :::: $0.33 million. Traveling Gun Systems Including Cable and Hose Tow (Table 3): The term "Traveler Irrigation System.. refers to either cable tow or hard hose traveling sprinkler systems. The cable tow traveler consists of a single gun sprinkler mounted on a trailer with water being supp1ied through a collapsible, flexible hose that ranges in length from 330 to 1,320 feet. A steel cable, anchored at one end of the field, is used to guide the gun cart. As the machine moves through the field, dragging the hose behind it, the cable winds around the cable drum. The cable tow traveler was very popular during the early to mid 70's. As a result, many of the machine still in use are old and need repairs. The hose-drag traveler became popular in the late 70's and consists of a hose drum, a medium-density polyethylene (PE) hose and a gun type sprinkler. The hose drum is mounted on a multi-wheel trailer or wagon. The gun sprinkler is mounted on a wheel or sled type cart referred to as the gun cart. The hose supp1ies water to the gun sprinkler and also pulls the sprinkler cart toward the drum. The hose drum is rotated by a water turbine, water piston, water bellows, or by an internal combustion engine. Regardless of the drive mechanism, systems should be equipped with speed compensation so that the sprinkler cart travels at a uniform speed from the beginning of the pull until the hose is fully wound onto the hose reel. Many older systems were not equipped with speed compensation and will apply about 30% more water on one end of the field than the other. Nozzle sizes on gun type travelers are typically 1/2 to 2 inch diameter and require high operating pressures of 75 to 100 psi at the gun for uniform distribution. On most older systems, the gun discharge trajectory angle is 27 degrees. With high discharge angle and operating pressure, water can be thrown as much as 30 feet high and 250 feet from the gun. Compared to other types of systems, travelers have slightly poorer uniformity than center pivots but much better than non-overlapping stationary sprinklers (app1ication uniformity is a measure of the uniformity of water reaching the soil throughout the application area). Travelers tend to have poor app1ication efficiency due to high evaporative losses during app1ication because of their high operating pressure and distance water is thrown. The primary advantage of traveler systems is that they can be easily moved from field to field and are well suited to irregular sized and shaped fields. While travelers tend to have the poorest overall water use efficiency there are numerous applications where they are the system of choice (i.e., more practical than other system options). 19 . Water conservation alternatives for traveler systems are listed in Table 3. There 'are currently about 4,000 trav~ler irrigation systems in use in Georgia. System sizes . range from 40 to 100 acres with the average system being capable of irrigating about 85 acres per year. Total system replacement cost is approximately $30,000 for a system capable of irrigating 70 to 100 acres.. Comparison 17: Repair the water delivery system for travelers. A typical traveler irrigation system has a 1,000 ft hose and is operated at 80 psi at the gun. The system is operated about 2,000 feet from the w~ter supply. Many systems have been in operation more than 15 years and continue to use a portable, above ground, aluminum pipe water delivery system. The aluminum pipe is typically in 20 foot lengths with. worn or decayed rubber gaskets resulting in significant mainline leakage. On older systems, it is also common to find several repairs in the flexible hose , I that are also leaking. Water conservation options range from minor repairs to the water delivery system such as replace gaskets and/or fittings .to more costly repairs including replacement of pipe and/or hoses. Water conservation will range from none to over 20% with smaller savings associated.with less severe leakage. Simply replacing gaskets in 20 foot aluminum mainline pipe (at a cost of $5/gasket, $500 total for 2,000 ft system) could save about 5% on many older systems. In some cases, total replacement of the aluminum mainline with buried PVC would equate to savings of up ~o 20%, but the cost of this repair could approach $6,000 (2,000 ft X $3/ft). On very old systems, the flexible hose should be replaced which could also approach $6,()00, It is estimated that 1,600 traveler systems would benefit from major maintenance to repair the water delivery system with an average water savings of ::: 10%. If all potential systems were repaired, the total annual water savings in an average year would be 2585 million gallons. In a dry year, water savings would approach ::: 4,431 million gallons. The average cost of these repairs is estimated at $3,500 per system. The . i' I statewide co~s for full implementation are ::: $5.6 million. The cost benefit ratio is ::: $2,166 per million gallons saved. Comparison 18: Add Speed Compensation to Hard Hose Travelers The typical hard hose traveler irrigation system has a 1,000 foot hose and is operated at 80 psi at the gun. Many older systems do not have speed compensation. As the hose is wound onto the reel, the effective diameter of the reel changes, thus changing the travel speed of the gun. Most systems are managed to apply the target irrigation amount at the "faster" speed in the cycle. At the slower speed, up to 30% more water is applied, thus wasting 15% on average. 20 Addition of speed compensation for an existing system would involve retrofitting with a small, 3-5 horsepower, gasoline or dieSel engine and subsequent modifications to the drive train (gears, sprockets and pulleys). The average costs of a speed compensation retrofit is :::l $5,000 and would result in an average water savings of = 10%. It is estimated that 1,300 hard hose traveler irrigation systems would benefit from the addition of speed compensation. If fully implemented, the statewide water savings would be 2,100 million gallons per year. In a dry year, statewide water savings would approach 3,600 million gallons. The estimated cost for full implementation is = $6.5 million with a water savings cost benefit ratio of = $3,095/million gallons. Comparison 19: Conversion from standard to low angle gun: The base system for this comparison includes a traveler system with a 1,000 ft hose. The base system has speed compensation and an efficient water delivery system. A standard 27 degree trajectory gun with a ring nozzle is in use. The suggested alternative is to replace the gun assembly and change to an 18 degree trajectory taper bore nozzle. The lower trajectory will not throw water as high resulting in less evaporation during application. A taper bore nozzle must be used to provide the same overlap and uniformity of coverage at the lower discharge trajectory angle. Estimated water savings for this alternative range from 0 to 10% with an average . of 5%. Greater savings will result if larger nozzles with higher operating pressure are converted. Time of day application would also affect savings with greater savings realized on those systems operated predominately during daylight hours. Of the 4,000 traveler systems currently in use, approximately 1,200 could benefit from this modification. The potential water savings would be 969 million gallons annually on average, and 1,662 million gallons in a dry year. The average system costs fo~ this modification is $1,500. With full statewide implementation, the total cost for 1,200 systems wo~ld be = $1.8 million with a water savings cost/benefit ratio of= $1,857 per million gallons. Comparison 20: Adjustment to Proper Operating Pressure: The base system for this comparison includes a traveler system with a 1,000 ft hose. The base system has speed compensation and an efficient water delivery system. The suggested alternative is to determine and adjust, where necessary, the operating pressure. Similar results would be expected for either the standard 27 degree trajectory gun with a ring nozzle or a low angle, 18 degree trajectory gun with taper bore nozzle. System design including determination of lane spacing for proper overlap is based on manufacturers specifications. These specifications give discharge and wetted diameter specifications for operating pressures at the gun. Many systems do not have functional 21 pressure gages at the gun, instead, the operator relies on a pressure gage at the reel or in some cases at the pumping plant. The result is that many systems are not being operated at design specifications which results in improper overlap and poor application uniformity. System performance should be adjusted to design and manufacturers specifications. In some cases this will require decreasing the operating pressure which will result in less water loss to evaporation (lower pressure results in larger droplets which are less susceptible to evaporation and wind drift). But, in many cases, the operating pressure will need to be increased, resulting in greater water losses. Thus, water savings are estimated to range from -5 (more water use) to + 5%. The costs of this modification may range from as little as $25 to simply install a pressure gage on the gun to over $6,000 if the pump or pipe needs to be replaced to achieve higher operating pressures. There are no net water savings estimated for this practice. While total water savings from this practice may be small, water use efficiency will improve because operating the system at the proper pressure will result in better applicati