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Optimizing Water Conservation For Agricultural Irrigation

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Title:
Optimizing Water Conservation For Agricultural Irrigation
Creator:
Atyeo, Anthony
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
Agriculture ( jstor )
Cost estimates ( jstor )
Cost savings ( jstor )
Crops ( jstor )
Farms ( jstor )
Irrigated farming ( jstor )
Irrigation management ( jstor )
Irrigation systems ( jstor )
Irrigation water ( jstor )
Water conservation ( jstor )
Irrigation
Water conservation
Genre:
Undergraduate Honors Thesis

Notes

Abstract:
Fresh water is becoming a more limited resource and water management districts are looking for ways to conserve water. Agriculture, being a major consumer of fresh water in Florida, is a major in water conservation plans. This study attempts to maximize water savings for every dollar spent towards repairing irrigation systems that are not achieving best management practices. Previously completed farm audits and permit data were used to estimate the frequency of problems and their associated potential water savings occurring throughout the St. Johns Water Management District. These estimates, along with the cost to repair each issue, made it possible to create an optimizing tool to determine which repairs to make to yield the highest return on investment. The data showed the district can save 10MGD on the first $200,000 investment towards irrigation system repair. The marginal returns shrink as more money is invested with a maximum total savings of 40MGD if all issues are fixed costing between $10-25 million. These values are fairly significant because every four million gallons saved reduces agricultural daily consumption by 1%. ( en )
General Note:
Awarded Bachelor of Science in Civil Engineering; Graduated December 20, 2011 magna cum laude. Major: Civil Engineering
General Note:
College/School: College of Engineering
General Note:
Advisor: William Wise

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University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright Anthony Atyeo. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.

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Optimizing Water Conservation For Agricultural I rrigation By: Anthony Daniel Atyeo Graduating Fall 2011 Summa Cum Laude Bachelor of Science in Civil Engineering

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Optimizing Water Conservation For Agricultural Irrigation Page 1 Abstract : Fresh water is becoming a more limited resource and water management districts are looking for ways to conserve water. Agriculture, being a major consumer of fresh water in Florida, is a major in water conservation plans. This study attempts to maximize wa ter savings for every dollar spent towards repairing irrigation systems that are not achieving best management practices. Previously completed farm audits and permit data were used to estimate the frequency of problems and their associated potential water savings occurring throughout the St. Johns Water Management District. These estimates along with the cost to repair each issue made it possible to create an optimizing tool to determine which repairs to make to yield the highest return on investment. The data showed the district can save 10MGD on the first $200,000 investment towards irrigation system repair. The marginal returns shrink as more money is invested with a maximum total savings of 40MGD if all issues are fixed costing between $ 10 25 million. The se values a re fairly significant because every fo ur million gallons saved reduces agricultural daily consumption by 1%.

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Optimizing Water Conservation For Agricultural Irrigation Page 2 Introduction: As population continue s to grow, it becomes more challenging to balance the demand for fresh water supply with out negatively impacting the environment In the St Johns R iver Water Ma nagement District agriculture uses 413 million gallons per day (MGD) to irrigate 179,047 acres which accounts for 35% of all fresh water consumption in the district. Permit data estimates two thirds of the usages comes from the groundwater supply ( SJRWMD 2011 A ) Getting farms to achieve best management practices on their irrigation systems is one way to reduce the ir total demand on the fresh water supply Unfortunately, cost is a lways a limiting factor so I created a software tool using Microsoft Excel which determines the most effective combination of issues to address to achieve the greatest water savings per dollar spent on repairs. Currently, benchmark farms are the standard for water use and conservation potential, but this study aims to use account level data on a large scale to determine the potential for water savings in the area. The first aspect was to replicate Olmsted and Duke s Frequency of Residential Irrig a tion Management Problems study (2011) for agricultural irrigati on systems on Management District Then the frequency data can be used to determine the agricultural savings potential by mirroring a current project be ing done by the water management district (2011 B ) which uses account level data for residential properties to determine the potential water savings available. Finally, create a tool which calculates the ideal distribution of maintenance expenditures to ac hieve the greatest water savings. Methods The data were collected by the Florida Mobile Irrigation Lab which is a cooperative arrangement between The Natural Resource Conservation Service, Florida Department of Agriculture, and the water management distri ct, which provide irrigation audits on local farms. The farms audited in this study were all within the St Johns Water Management District and primarily in Lake and Volusia Counties. The data they collected contain the crop type, irrigation system the ir rigated acreage a list of the issues and the estimated potential water savings if all the problem s are fixed Some problem codes were left out of the analysis because, if corrected, those problems would not produce any water savings. These codes are grayed out on the problem code definition table in appendix A (Table 3 A ). Once the data had been compiled, similar crops and irrigation types were consolidated as outlined in tables 1A and 2A of Appendix A. Along with t he audit data t he St. Johns River Water Management District provided permit data to compare the total number of farms an d the acreage with in the district to the number of audited farms which can be used to extrapolate the audit data over the entire stud y area. Table 4A in Appendix A shows the sample sizes of each type of farm. The grayed out farms were used in the overall calculations, but not extrapolated over the district. T he potential water savings per acre were broken down by problem code for each c rop type and irrigation system This was done by assuming th e problems for each site had an equal contribution to the excess water being used and then averaging the volumes for each problem code for the set of condition The costs used in the calculations

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Optimizing Water Conservation For Agricultural Irrigation Page 3 represent a high and a low estimate for what may actually be experienced, but is left up to the software user to adjust to make the program more flexible and provide users more accurate results. Using the potential water savings for each scenario the tota l number of acres affected by the problem and a cost per acre to fix the issue excel can maximize the volume of water saved per dollar spent on repairs or minimize the cost that would be incurred to achieve a water savings goal. Example calculations for all steps can be seen in Appendix B. Results: The graphs below depict the diminishing returns of money spent towards getting farms up to bes t management practice standards, as well as the marginal returns. The second marginal returns graph shows a clos e up on the tail end to get a better image of the later returns. Figure 1: Dimi nishing returns on investment for agricultural water conservation in the SJRWMD. 0 5 10 15 20 25 30 35 40 45 0 5 10 15 20 25 PWS (MGD) Cost (Million $) Diminishing Water Savings On Agricultural Irrigation Repairs High Cost Low Cost

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Optimizing Water Conservation For Agricultural Irrigation Page 4 Figure 2: Marginal returns on investment in agricultural water conservation in the SJRWMD Figure 3: Tail end of marginal returns on investment in agricultural water conservation in the SJRWMD. 0 50 100 150 200 250 300 350 400 450 500 4 6 8 10 12 14 16 18 20 Gallons per day per dollar Water Savings (MGD) Marginal Savings On Agricultural Irrigation Repairs High Cost Low Cost 0 1 2 3 4 5 6 7 8 9 10 15 20 25 30 35 Gallons per day per dollar Water Savings (MGD) Marginal Savings On Agricultural Irrigation Repairs (Cont.) High Cost Low Cost

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Optimizing Water Conservation For Agricultural Irrigation Page 5 The following tables are an example report the tool will produ ce for a user with a savings goal of 10MGD. Water Savings Goal Savings Goal (MGD) 10 Cost $193,777.08 Crop System Code Repair s Cost Water S aving (Acres) ($) (gpd) B.Berries Micro Spray 4 38 570.00 7036 B.Berries Micro Spray 6 38 570.00 7036 B.Berries Sprinkler 4 254 3816.00 39898 C.Nursery Micro Spray 4 880 13202.00 224957 C.Nursery Micro Spray 20 393 11780.57 99966 C.Nursery Sprinkler 55 1920 76800.00 8570339 Citrus Micro Spray 50 931 13970.96 156865 Nursery Drip 4 24 360.00 5237 Nursery Micro Spray 4 11 170.00 1618 Nursery Sprinkler 3 2 29.73 762 Nursery Sprinkler 4 14 208.09 8305 Nursery Sprinkler 6 3 39.64 2521 Nursery Sprinkler 20 12 356.73 5643 Nursery Sprinkler 21 1 39.64 726 Nursery Sprinkler 22 4 237.82 2911 Nursery Sprinkler 23 7 198.18 6068 Nursery Sprinkler 30 2 99.09 1646 Nursery Sprinkler 31 1 19.82 726 Nursery Sprinkler 33 9 386.45 3715 Nursery Sprinkler 34 10 594.55 5172 Nursery Sprinkler 55 21 845.58 13822 Nursery Enclosed Sprinkler 20 66 1968.00 26035 Nursery Enclosed Sprinkler 23 87 2624.00 44488 Nursery Enclosed Sprinkler 32 22 656.00 7369 Nursery Open Field Center Pivot 55 44 1760.00 22655 Nursery Open Field Micro Spray 4 158 2364.00 38113 Nursery Open Field Sprinkler 4 39 587.25 30469 Nursery Open Field Sprinkler 22 235 14094.00 158919 Nursery Open Field Sprinkler 23 352 10570.50 120974 Nursery Open Field Sprinkler 32 117 3523.50 88087 Nursery Open Field Sprinkler 55 783 31320.00 297768 Peach Micro Spray 3 1 15.00 154 Totals 193777.08 10 Figure 4: Example output report generate d by the tool

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Optimizing Water Conservation For Agricultural Irrigation Page 6 Discussion : The graph of diminishing returns (Figure 1 ) shows the first $ 200 ,000 spent toward fixing these issues can ac hieve a high return, saving about 10 MGD or about 2.5% of the total daily use From this point the high and low cost estimates begin to depart. An investment of two million dollars should return between 15 and 20 MGD. To achieve the maximum return of 41 MGD an investment between $10 and $26 million would be needed depending on cost of repairs. Fixi ng all of the issues would reduce agricultural consumption by 10% and reduce total consumption by 3.3% T hese values may be conservative estimates because the bulk of the surveyed farms were in Lake and Volusia Counties, and the Survey of Estimated Annual Water Use mentions these counties have a significant representation of be nch mark farms ( SJRWMD, 2010) T he marginal return graph (Figure 2 & 3 ) show s the major break point s o n the rate of return on investment Initial investments less than $ 200,000 are capable of returning over 100 gallons per day per do llar. Investing up to $2 million steadily decreases the returns to about 10 gallons per day per dollar and flattening out under 10gpd per dollar for larger inputs. These graphs show that a reasonable inv estme nt used optimally could return fairly large savings, but the returns drop off sharply ; thus large investments may not be economically desirable. Figure 4 shows an example of a report that th e tool will generate for a user with a savings goal of 10 MG D. The left columns define the type of farm and the problems needing to be addressed The right columns show the number of acres to repair along with the cost and water saving s associated with those repairs, giving a total cost of approximately $194,000 to achieve the 10 MGD of water savings goal. The results show there a re large potential water savings available, although these numbers may not be entirely accurate. The cost s associated with fixing the problems is also a re rough estimate s use to show how the tool works. The costs are designed to be updated by the user in the problem code definition tab. This will help users get more accurate results accounting for future price changes, variability in labor cost and other differences that may occur Also several of the crop types present did not contain a representative sample of the farm in the area or had questionable data which could arise from consolidating certain crops and irrigation systems In these cases the audited farms were in cluded in the optimization tool but were not extrapolated to the study area to avoid error propagation These are noted by grey highlighting in the main table, which include berries, peanuts, potatoes, nurseries with sprinklers, as well as a few others These issues hig hlight a potential to refine the future auditing process to get more comprehensive data across the study area. On e of the major sources of error in this project is in the calculation of the potential water savings for each problem code. T he mobile irrigation lab calculated the potential water saving for e a ch site as a whole so getting the potential savings per code required backing in t o the savings based on the problems that were present and o nce the data were so rt ed by crop and irrigati on type the number of similar sites left were relative ly small and had very similar issues. This made it difficult to determine the effect each problem had on the total water loss. Especially since the problem codes are not distinguished by the severity o f the problem. Two farms may have broken valves, but one could be producing a slow leak while the other is leaking severely Averaging the savings would reduce the error,

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Optimizing Water Conservation For Agricultural Irrigation Page 7 but g iven the data there was no way to account for outliers Assuming that each code contributes equally to losses experienced at each site is inaccu rate, but when averaging the saving for each code across enough similar farms the weight each code begins to move to a closer estimate of reality. It may be feasible to improve these estimates with out collecting more data, by normalizing the potential water savings by the crops annual irrigation requirements, so all farms with similar irrigation systems could be solved simultaneously. Although the methods for determining the potential water sa vings per problem code provide only a rough estimate, the errors are not so significant that they cloud the big picture of the potential this tool could have. The n ext step in development is to include irrigation system replacement or upgrades into the cal cu lation. In some instances it may b e more economical to replace an entire irrigation system with a new system or a mor e efficient type of irrigation rather than fixing all of the p roblems associated with a site. T he cost structure could also be improved b y providing cost adjustments on multiple codes being fixed at a single site as well as, a time function to determine the duration these saving can be achieved Getting multiple problems resolved at one location would save money on travel cost and time whi ch would yield a higher savings on the dollar. Ideally this model will eventually be integrated with similar tools for residential, commercial and industrial lands to provide a comprehensive tool to determine the maximum savings across all major types of w ater use

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Optimizing Water Conservation For Agricultural Irrigation Page 8 Appendix A: Reference Tables Irrigation consolidation Center Pivot Center Pivot Drip Drip Irrigation Micro Drip Microdrip Sprinkler Micro Spray Micro Jet Micro Spray Sprinkler Linear Move Sprinkler Fixed Impact Sprinkler Linear Move Spray Head Sprinkler Table A 1: Description of irrigation system consolidation Crop consolidation B. Berries Blueberries C. Nursery Container Nursery Citrus Citrus Cut Foliage Asparagus Fern Liriope Aspidistra Lirirope Coontie Fern Pittosporum Leatherleaf Tree Fern Ligustrum Fruit Cantaloupe Melon Grapes Strawberries Mangos Watermelon Nursery Nursery Nursery Enclosed Greenhouse Nursery Nursery Open Field Field Nursery Other Broccoli Cucumber Mustard greens Pumpkin Cabbage Cucurbits Onions Radishes Cauliflower Eggplant Oriental Vegetables Red Peppers Chestnuts Grass Cover Crop Paddies Sod Collard Greens Green cover crop Peas Sorghum Corn Greens Pecans Spinach Cotton Hay Persimmons Sugarcane Crucifers Mixed Vegetables Pine Zucchini Peaches Peach Peanut Peanut Potato Potato Table A 2: Description of crop consolidation

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Optimizing Water Conservation For Agricultural Irrigation Page 9 Code Count Problem Definition PRESSURE AND IRRIGATION RATE 3 12 Higher pressure than manufacturer's specifications 4 72 Lower pressure than manufacturer's specifications 6 49 Different pressure between manifolds 7 3 Wetted area not adequate for crop requirement 11 80 Pressure variation due to elevation differences 12 7 Missing/malfunctioning pressure gauge/regulator/filter 13 5 Mixed Crops or container with different water requirements in the same zone EMITTERS AND/OR SPRINKLERS 20 154 Mixed sprinkler/emitter sizes & unmatched precipitation in the same zone 21 39 Mixed sprinkler/emitter brands or types in the same zone 22 87 Poor emitter/sprinkler uniformity due to worn orifice 23 68 Poor overlap due to improper sprinkler/emitter alignment or spacing 24 23 Various riser heights in same zone 25 13 Emitter/sprinkler spacing varies in same zone 26 71 Missing/malfunctioning emitters or sprinklers 27 49 27 End Gun is out of adjustment or not operating MAINTENANCE 30 111 Leaks and broken valves, pipe, laterals lines (Poly tubing), emitters, sprinklers 31 19 Clogged filter or filter screen 32 5 Sprinkler heads not properly adjusted, causing overflow on paved areas 33 165 33 Clogged emitters/nozzles (due to biological, chemical or physical factors) 34 24 Leaning sprinklers/emitters causing non uniform distribution 35 1 Malfunctioning valves 40 19 Stream of water blocked by vegetation 41 2 Variable crop spacing and stage of growth 44 1 Uncatagorized 45 2 Uncatagorized OPERATION AND/OR MANAGEMENT 50 1 Operating time too long 51 1 Operating time too short 52 10 Operating time too frequent 53 94 No rain shut off device 54 94 No soil moisture measuring device or rain gage 55 278 No irrigation water management plan 63 1 Uncatagorized Table A 3: Problem code definitions

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Optimizing Water Conservation For Agricultural Irrigation Page 10 Percentage of Farms Center Pivot Drip Micro Spray Other Sprinkler Total Acres Farms Acres Farms Acres Farms Acres Farms Acres Farms Acres Farms All B Berries 58 8 38 3 1272 48 1368 59 MIL B.Berries 18 1 48.5 5 66.5 6 Percent 0 0 47.1 33.3 3.8 10.4 4.9 10.2 All C. Nursery 45 1 2016 378 943 167 13 4 1920 911 4937 1461 MIL C.Nursery 39.3 15 1 2 40.3 17 Percent 0 0 0 0 4.2 9.0 0 0 0.1 0.2 0.8 1.2 All Citrus 150 8 72649 1250 458 26 416 46 73672 1330 MIL Citrus 1925 78 1925 78 Percent 0 0 2.6 6.2 0 0 0 0 2.6 5.9 All Cut Foliage 10 4 9 5 10 1 8002 1249 8031 1259 MIL Cut Foliage 0 0 644.8 80 644.8 80 Percent 0 0 0 0 0 0 8.1 6.4 8.0 6.4 All Fruit 61 1 185 31 9 5 917 26 34 11 1206 74 MIL Fruit 188 9 6 1 194 10 Percent 0 0 0 0 2079.9 180 0 0 17.5 9.1 16.1 13.5 All Nursery 24 4 6 10 30 14 MIL Nursery 0.55 2 51 18 21.8 33 73.37 52 Percent 2.3 50 376.3 330 247.0 371.4 All Nursery Enclosed 164 107 318 257 0 2 328 273 810 639 MIL Nursery Enclosed 3.6 4 10 2 11.38 15 24.98 21 Percent 2.2 3.7 3.1 0.8 0 0 3.5 5.5 3.1 3.3 All Nursery Open Field 1860 153 1576 132 473 39 783 177 4693 501 MIL Nursery Open Field 44 3 76.2 20 85.05 20 205.25 43 Percent 0 0 4.8 15.2 0 0 10.9 11.3 4.4 8.6 All Other 4501 41 532 43 290 24 50545 937 3338 105 59206 1150 MIL Other 2.5 2 0 0 2.5 2 Percent 0 0 0.5 4.7 0 0 0 0 0 0 0.0 0.2 All Peach 48 2 48 2 MIL Peach 1 1 1 1 Percent 2.1 50 2.1 50 All Peanut 26 1 26 1 MIL Peanut 248 2 248 2 Percent 0 0 952.3 200 All Potato 18165 286 18165 286 MIL Potato 161 1 161 1 Percent 0 0 0.9 0.3 MIL Berries 50 2 59.2 3 109.2 5 MIL Tomato 0.5 1 0.5 1 MIL Trees Ornamental 15.3 4 15.3 4 Table A4: Percent of Audited Farms

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Optimizing Water Conservation For Agricultural Irrigation Page 11 Appendix B: Sample Calculations Extrapolation equation: PWS per code calculation: PWS Calculation Code contribution to site Irrigation Crop PWS PC 4 23 55 Sprinkler B.Berries 208 55 208 Sprinkler B.Berries 314 4 55 157 157 Sprinkler B.Berries 104 23 55 52 52 Sprinkler B.Berries 89 23 55 45 45 Sprinkler B.Berries 45 23 55 22 22 Average code contribution 157 39.7 96.8 Step 1: Average the site PWS for each problem code Step 2: Average all values for each code Total Cost equation: Total Estimated Water Savings:

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Optimizing Water Conservation For Agricultural Irrigation Page 12 Solver Inputs: Case 1: Fixed Budget Maximize: Total PWS By varying: Fix Quantity Constraint 1: Total Cost <= Budget Constraint 2: Fix Quantity <= Total Acres Case 2: Savings Goal Minimize: Total Cost By varying: Fix Quantity Constraint 1: Total PWS >= Savings Goal Constraint 2: Fix Quantity <= Total Acres

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Optimizing Water Conservation For Agricultural Irrigation Page 13 References: [SJRWMD] St. Johns River Water Management District. 2011 A 2010 Survey of Estimated Annual Water Use Technical Fact Sheet SJ2011 FS1. Palatka, Fla.: St. Johns River Water Management District Thomas R. Olmsted & Michael D. Dukes. 2011. Frequency of Residential Irrigation Maintenance Issues, 2011. Universit y of Florida IFAS Extension Document AE472. Gainesville, Fla.: University of Florida Institute of Food and Agricultural Science. [SJRWMD] St. Johns River Water Management District. 2011B. W ater C onservation P otential For The D istrict W ater S upply P lan 2010 Special Publication SJ2011 SP2. Palatka, Fla.: St. Johns River Water Management District Acknowledgements: Max Castaneda & Tom Blush Thank you for helping me get involved in this project and helping me through with any problems. Dr. Wise I thank you for putting me in contact with the St. Johns River Water Management District and getting this internship started.