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Unformatted text preview: California Water Plan Update 2005 Survey of Irrigation Methods in California By Morteza Orang, Richard Snyder and Scott Matyac, DWR and UC Davis Data and Analytical Tools 4 299 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Survey of Irrigation Methods in California in 2001 Morteza N. Orang1, Richard L. Snyder2, J. Scott Matyac3 Abstract This report discusses a statewide survey of irrigation methods conducted in California during 2002. The purpose of the study was to collect information on irrigation methods to determine which methods were used by growers to irrigate their crops in 2001. Reliable information on irrigation methods is an important factor for planning future water demand by agriculture irrigation based on trends. To conduct the survey, one-page survey form was developed to collect irrigated land (acres) by crop and irrigation method. Then a questionnaire was mailed out to 10,000 of the estimated 80,000 growers in California by the California Department of Food and Agriculture. The results from comparing earlier studies with 2001 indicated that the amount of land irrigated by drip irrigation method has increased by about 33%, while the amount of land irrigated by surface methods has decreased by about 31%. The area planted to orchards and vineyards has increased, while that planted to field crops has declined. The largest increase in sprinkler use has been in vegetable crops, an increase of 19% since 1972. The 1991 and 2001 statewide surveys exclude rice acreage. Introduction The application of water to soils for crop use is referred to as irrigation. Surface (gravity-driven surface irrigation), sprinkler, drip/micro, and sub-surface are types of irrigation methods that are used by growers to irrigate various crops in the state. The irrigation methods that growers use to apply water may affect the salt accumulation in the crop root zone (leaching), plant transpiration, soil evaporation, and runoff from soil surface. Irrigation performance is commonly measured by how much of applied water beneficially used for crop production. Irrigation (application) efficiency or consumed fraction is an index used to quantify the efficient use of water diverted to a field by an irrigation system and is defined as the ratio of that quantity of water stored in the root zone, which can be used in evapotranspiration to the amount of applied water as a percentage. Distribution uniformity (DU) is also an important element in irrigation water use efficiencies. DU is the measure of the uniformity of irrigation water distribution over a field. The most appropriate irrigation method for an area depends upon physical site conditions, the crops being grown, amount of water available, and management skill. The water management decisions strongly influence how uniform water can be applied through different irrigation methods to provide optimal soil water conditions for crop growth and marketable yields. The main objectives are to avoid water stress, achieve high yields and protect water quality. Water losses from irrigation vary with the type of irrigation method. In the absence of a reliable irrigation system, the water application is often non-uniform and is generally over applied, resulting in excess runoff and deep percolation below the root zone. If part of the Staff land and water use scientist, California Department of Water Resources Division of Planning and Local Assistance, PO Box 942836, Sacramento, CA 94236-0001 2 Biometeorologist, University of California, Atmospheric Science, Davis, CA 95616 3 Senior land and water use scientist, California Department of Water Resources Division of Planning and Local Assistance, PO Box 942836, Sacramento, CA 94236-0001 1 1 4 300 Survey of Irrigation Methods in California Volume 4 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 field is over irrigated, the crop roots near the soil surface will be exposed to water that has salinity near that of the irrigation water rather than an average root zone soil salinity value. As a result, crop yields are generally more affected by the irrigation water salinity level than by the soil water salinity in the lower part of the root zone. However, the use of a proper irrigation method that fits the crop, water, and site conditions will ensure that losses are held to a minimum and subsequently, will result in high irrigation efficiency and distribution uniformity. Runoff and deep percolation generally are greater for gravity systems than for well managed sprinkler and drip/micro irrigation methods. The combined losses of deep percolation and runoff for poor managed gravity irrigation system will lower consumed fraction and subsequently, will pollute the surface water and groundwater supplies. Sprinkler and drip/micro systems reduce runoff or deep percolation compared to gravity irrigation, because these type systems provide complete control over the amount of water applied to the field. As a result, water is distributed more uniformly within the intended root zone. Generally, more water is used with gravity and sprinkler irrigation on an annual basis than with drip/micro. According to the "Report on Evaporation from Irrigated Agricultural Land in California" by Charles Burt of CalPoly, gravity and sprinkler irrigation tends to wet larger fractions of the soil surface (0.6-1.0, or 60%-100%, of the soil surface is wet during a typical irrigation) than drip/micro systems. In addition, it is often difficult to control the application depth of irrigation water because of uniformity and scheduling constraints. Drip/micro has typical wetted fractions ranging from almost 0, for subsurface drip, to 0.8, for some micro spray on tree crops. A typical range for trees in California is 0.3-0.6 for surface drip/micro. Drip/micro is also considered to have more flexibility for irrigation scheduling. Water resources project planning requires reliable estimates of crop and irrigation system combinations, which are important components in a variety of water budget analysis. To update California's records on irrigation methods used within the state, a survey is conducted by the California Department of water Resources about every 10 years. The gathered survey data is analyzed and compared with earlier surveys to study how irrigation methods are changing and to make projections of future changes for long-term planning. The purpose of this report is twofold; (1) to demonstrate the reliability of the 2001 irrigation survey results on the number and type of irrigation systems used in California and (2) to present the results of our study comparing the earlier estimates to the 2001 estimates. Reliable information of current irrigation methods by various crops is extremely important for the California Department of Water Resources for planning its future water demand by agriculture irrigation based on trends. The absence of reliable information can severely limit its usefulness for long-term water planning purposes. Methodology Approximately every 10 years one-page irrigation survey forms are mailed out to many growers throughout California to conduct a statewide survey to update California's records on irrigation methods. A statewide survey of current irrigation methods was conducted during 2002 to determine which irrigation methods were used in California during 2001. The 1991 was chosen as the base year to keep a 10-year period between this survey and the previous study done during 1972. Earlier surveys of irrigation methods had been conducted by Ian Stewart in 1972 and by Robert Hagan with California Department of Water Resources in 1980. In these studies, irrigated crop acreage was estimated by UC Cooperative Extension specialists and county farm advisors in each county. The 1991 and 2001 studies were conducted by mailing questionnaires to growers who were randomly selected from a list of growers. A list 2 Data and Analytical Tools 4 301 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 of 58,000 of the estimated 80,000 growers in California from the California Department of Food and Agriculture (CDFA) was used to determine the mailing list. All rice-only growers were excluded from the list. Since valid data on the rice acreage for any given year is available and the irrigation method is flooding, collecting this information was unnecessary. Non-irrigated farms and large livestock ranches were also excluded from the survey. Growers were asked to state the main county in which they farmed and the acreages they had planted during 2001 to each of 20 possible crops by irrigation method within that county. Number and types of crops used in 2001 survey are slightly different from those used in 1979, 1980, and 1991. The 2001 survey of irrigation methods included a 20-crop category as opposed to 13-crop category used in 1991 survey. A list of crops used in 1972, 1980, 1991, and 2001 surveys are shown in Table 1. Note that the 1991 and 2001 surveys did not include rice, whereas 1979 and 1980 studies did include rice acreage (Table 1). Survey forms were mailed by the California Department of Food and Agriculture to an estimated 10,000 growers in 58 counties and there was a 35% useable return rate. A sample of the 2002 survey form is shown in Figure 1. Table 1. Crop types used in 1972, 1980, 1991, and 2001 2001 Crop Group Alfalfa Grain Corn Cotton Other Field Crops, Dry Beans, Safflower, Pasture, Turf grass and Landscape Almond & Pistachio, Other Deciduous Subtropical Trees Sugar Beets Tomato (fresh), Tomato (process) Other Truck Crops, Onion & Garlic, Potato, Cucurbit Vineyard 1991 Crop Group Alfalfa Small Grains Corn Cotton Other Field Crops Pasture Deciduous Fruits and Nut Trees Subtropical Sugar Beets Processing Tomatoes Vegetables (Truck Crops) Grapes And Bush Berries 1980 Crop Group Alfalfa Grain Corn Cotton Miscellaneous Field Pasture Deciduous Fruits And Nut Trees Subtropical Sugar Beets Tomatoes Miscellaneous Truck 1972 Crop Group Alfalfa Small Grains, Misc. Hay Corn Cotton Other Field Crops Pasture Peaches & Nectar./Prunes/ Almonds/Walnuts Citrus & Avocado/Other Orchard Sugar Beets Tomatoes Beans, All Types/Potatoes/ Lettuce/Other Veg. Crops Grapes Rice Vineyard Rice 3 4 302 Survey of Irrigation Methods in California Volume 4 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Figure 1. A sample of the irrigation survey form to gather irrigated acreages by crop and by irrigation method in 2001 ACERAGE IRRIGATED BY CROP AND BY IRRIGATION METHODS IN 2001 What is the name of the main county where you farm? _____________________________. Please fill in the number of acres of each crop irrigated by each method in 2001 (include only those acres in the main county where you farm). In the shaded cell, below the number of acres, enter the main water source for that irrigation system and crop: S = surface water, G=ground water, or B = both IRRIGATION METHOD CROP (not including rice) SUBSURFACE DRAIN PIPE WILD OR DITCH FLOOD (NOT DRIP) SURFACE BORDER BASIN FURROW SURFACE/SPRINKLER FURROW FURROW SIDEHANDROLL MOVE SPRINKLER HANDPERMANENT MOVE LINEARMOVE SIDEROLL MICROMINI HOSEPULL CENTER PIVOT DRIP ABOVE GROUND BURIED DRIP CORN COTTON DRY BEANS GRAINS (1) SAFFLOWER SUGAR BEETS OTHER FIELD CROPS (2) ALFALFA PASTURE (3) CUCURBITS (4) ONION & GARLIC POTATO TOMATO (FRESH) TOMATOES (PROCESSING) OTHER TRUCK CROPS (5) ALMOND & PISTACHIO OTHER DECIDUOUS (6) SUBTROPICAL TREES (7) TURFGRASS & LANDSCAPE VINEYARD 1 Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source Acres Source wheat, oats, barley, etc; 2sorghum, sunflower, sudangrass, etc; 3excluding grass hay; 4melons, squash, cucumbers, etc; 5carrots, celery, cauliflower, broccoli, strawberries, asparagus, etc; 6apples, peaches, prunes, pears, etc; 7olives, avocados, citrus, dates, etc. Table 2 includes the individual and total irrigated land in acres by each 20 crops and by each 16 different irrigation methods in California during 2001 irrigation survey. The total irrigated land from 1991 and 2001 surveys are 539,875 and 509,400 acres, respectively. The variation between 1991 and 2001 surveys is only 5.6%. This indicates an insignificant difference in irrigated land between the 1991 and 2001 surveys. The sample of 509,400 irrigated acres in the state was used to determine which irrigation methods growers used to irrigate their crops in 2001. The sample represents nearly 5.6% of the irrigated land in the state surveyed. 4 Data and Analytical Tools 4 303 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Table 2. - Statewide irrigated land (acres) by crop and irrigation method in 2001 Irrigation Method SUBSURFACE WILD FLOOD BORDER BASIN FURROW SIDE-ROLL HAND- MOVE PERMANENT HAND-MOVE LINEARMOVE SIDE-ROLL MICRO-MINI HOSE-PULL CENTER PIVOT ABOVE GROUND BURIED DRIP Corn 4,183.00 1,842.50 4,672.00 65.00 23,092.50 0.00 341.00 50.00 2.00 0.00 0.00 0.00 0.00 220.00 2.00 0.00 Cotton 381.00 0.00 700.00 0.00 32,456.00 2,000.00 100.00 652.00 1,265.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Dry Beans 0.00 20.00 69.00 120.00 1,119.00 0.00 385.00 0.00 895.00 0.00 0.00 0.00 0.00 400.00 0.00 0.00 Grains 583.00 1,926.30 17,505.00 70.00 3,360.00 72.00 148.00 80.00 1,403.00 50.00 715.00 0.00 30.00 505.00 5.00 0.00 Safflower 315.00 258.60 247.00 85.00 650.00 0.00 0.00 0.00 600.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Sugar beet 0.00 0.00 0.00 0.00 1,708.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.50 Other Field Crops 24.00 200.50 3,425.00 0.00 2,923.00 0.00 0.00 15.00 555.00 5.00 292.00 6.50 0.00 125.00 122.00 0.00 Alfalfa 1,545.00 1,278.50 48,076.50 225.00 5,310.00 0.00 468.50 47.00 2,419.00 2,345.00 4,323.00 0.00 40.00 2,844.00 0.00 0.00 Pasture 1,505.00 11,118.74 10,255.40 242.00 849.00 1,120.00 321.00 859.00 2,537.50 2,025.00 580.00 0.00 202.50 223.80 0.00 0.00 Cucurbit 0.00 17.00 15.00 0.00 274.00 0.00 139.00 6.17 200.00 0.00 25.00 0.00 0.00 0.00 49.13 256.00 5 4 304 Survey of Irrigation Methods in California Volume 4 California Water Plan Update 2005 Survey of Irrigation Methods in California in Table 2. - Statewide irrigated land (acres) by crop and irrigation method in 2001 (continued) Irrigation Method SUBSURFACE WILD FLOOD BORDER BASIN FURROW SIDE-ROLL HAND- MOVE PERMANENT HAND-MOVE LINEAR-MOVE SIDE-ROLL MICRO-MINI HOSE-PULL CENTER PIVOT ABOVE GROUND BURIED DRIP Onion & Garlic 0.00 0.00 0.00 0.00 303.50 0.00 585.00 826.17 319.00 0.00 0.00 0.00 0.00 0.00 1.25 0.00 Potato 0.00 0.00 0.00 0.00 37.50 0.00 0.00 41.17 2,731.00 0.00 0.00 0.00 0.00 0.00 230.63 0.00 Other Deciduous 156.80 1,309.05 4,537.48 586.50 6,041.57 57.00 37.25 7,974.44 2,488.08 80.00 80.00 Subtropica l Trees 358.00 169.40 215.50 1,103.30 2,288.33 112.00 102.00 3,626.80 368.20 5.00 464.00 Turf grass & landscape 2.00 0.00 5.00 0.00 1.00 0.00 0.00 43.00 206.14 0.00 600.00 Vineyard 151.50 182.00 759.00 551.50 15,093.8 2 64.50 120.00 6,749.00 262.00 0.00 0.00 Tomato (fresh) 0.00 0.00 0.00 0.00 1,825.50 307.00 2,017.50 2.00 0.00 0.00 0.00 0.00 0.00 0.00 402.31 2,216.00 Tomato (process ) 0.00 0.00 0.00 0.00 3,809.00 493.00 863.00 0.00 2,299.00 0.00 0.00 0.00 0.00 0.00 75.00 74.00 Other Truck Crops 0.00 0.00 0.00 29.00 5,609.00 0.00 6,987.50 273.60 12,883.0 0 10.00 0.00 245.00 105.00 12.00 6,498.25 2,300.00 Almond & Pistachio 159.30 1,631.65 9,968.60 1,249.50 510.00 155.00 1,810.00 7,908.60 819.83 0.00 9.00 273.61 0.00 5,504.60 773.00 100.00 6,979.50 566.50 25,388.34 422.59 57.00 4,378.57 604.00 25.00 25.00 0.00 74.00 1.00 1,045.20 0.00 30.00 52,866.52 2,602.50 34,514.80 18,894.60 1,880.00 Data and Analytical Tools 4 305 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Percentage of statewide acreage reported for each crop was then calculated by each irrigation method. Table 3 illustrates the percentages of irrigated land by each of 20 crops and by four irrigation methods in 2001. Table 3. Percentages of irrigated land area by crop and irrigation method in California in 2001 Crop 1 2 3 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Gravity 87.1 93.9 56.9 87.3 57.6 99.9 85.1 80.3 75.1 45.3 43.7 1.2 61.3 67.8 36.1 19.2 33.7 10.1 0.6 20.8 49.4 Sprinkler 0.8 5.1 43.1 10.5 27.8 0.0 12.9 17.4 20.2 23.6 56.3 91.2 0.0 30.2 38.0 11.3 30.8 12.5 89.0 8.7 15.6 Drip/Micro 0.0 0.0 0.0 0.0 0.0 0.1 1.7 0.0 0.0 31.1 0.1 7.6 38.7 2.0 25.9 69.3 35.0 76.6 10.2 70.2 33.1 Other 12.1 1.0 0.0 2.2 14.6 0.0 0.3 2.2 4.7 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.4 0.9 0.2 0.2 1.8 Corn Cotton Dry beans Grains Safflower Sugar beet Other Field crops Alfalfa Pasture Cucurbit Onion & Garlic Potato Tomato (fresh) Tomato (process) Other Truck Crops Almond & Pistachio Other Deciduous Subtropical Trees Turfgrass & landscape Vineyard Total Tables 4 and 5 show the irrigated land area by each of 13 crops and by each 16 different irrigation methods in California during 1991 and 2001, respectively. 7 4 306 Survey of Irrigation Methods in California Volume 4 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Table 4. Statewide irrigated land (acres) by crop and irrigation method in 1991 Irrigation Methods Wild flood Border Basin Furrow Furrow and wheel line Furrow and hand move Solid set sprinkler Hand move sprinkler Linear move sprinkler Wheel line sprinkler Micro and mini sprinkler Hose pull sprinkler Other sprinkler methods Surface drip Burried drip Drip and sprinkler Subsurface total Total ALF 4,616 49,793 566 4,362 SGR 1,265 22,662 452 8,717 CRN 563 4,587 35 11,313 CTN 0 13,360 0 40,451 OTH 1,815 9,025 1,944 8,983 PAS 9,282 9,364 165 2,626 DEC 4,288 20,869 981 12,911 SUB 259 249 558 3,238 SBT 0 178 0 8,630 TOM 0 336 0 13,318 VEG 309 538 151 13,135 VIN 1,299 3,021 781 17,409 Total 23,697 133,983 5,632 145,093 0 168 44 400 353 0 417 0 781 1,650 2,141 469 6,424 0 1,929 1,359 11,784 721 158 1,077 235 1,420 16,934 10,260 477 46,354 44 0 0 469 689 504 28,546 3,460 116 74 8,141 6,210 48,254 3,162 1,855 0 3,848 412 1,998 8,028 291 1,566 1,492 3,604 277 26,533 0 99 0 0 0 44 121 40 0 0 2,438 0 2,742 2,974 2,035 0 0 1,089 175 7 242 0 689 0 0 7,212 299 0 0 0 42 0 9,327 25,416 0 0 2 37 35,123 516 0 0 0 0 170 2,388 2,065 0 0 0 89 5,229 1,998 25 0 299 0 0 0 0 0 249 0 161 133 22 168 274 0 0 442 8,687 3,762 170 2,947 143 0 0 0 0 0 299 0 2,719 4,182 0 21,610 299 3,567 36,010 9,013 0 0 0 0 0 0 1,210 22 0 0 499 153 1,885 650 69,004 165 39,646 161 18,061 0 70,724 121 25,520 1,630 26,392 257 103,318 0 39,337 0 12,691 0 34,792 0 48,121 141 52,270 3,125 539,875 8 Data and Analytical Tools 4 307 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Table 5. Statewide irrigated land (acres) by crop and irrigation method in 2001 Irrigation SUBSURFACE WILD FLOOD BORDER BASIN FURROW SIDE-ROLL HAND- MOVE PERMANENT HAND-MOVE LINEAR-MOVE SIDE-ROLL MICRO-MINI HOSE-PULL CENTER PIVOT ABOVE GROUND BURIED DRIP Total ALF 1,545 1,279 48,077 225 5,310 0 469 47 2,419 2,345 4,323 0 40 2,844 0 0 68,922 SGR 583 1,926 17,505 70 3,360 72 148 80 1,403 50 715 0 30 505 5 0 26,452 CRN 4,183 1,843 4,672 65 23,093 0 341 50 2 0 0 0 0 220 2 0 34,470 CTN 381 0 700 0 32,456 2,000 100 652 1,265 0 0 0 0 0 0 0 37,554 OTH 339 479 3,741 205 4,692 0 385 15 2,050 5 292 7 0 525 122 0 12,857 PAS 1,505 11,119 10,255 242 849 1,120 321 859 2,538 2,025 580 0 203 224 0 0 31,839 DEC 316 2,941 14,506 1,836 6,552 212 1,847 15,883 3,308 80 89 40,019 1,047 100 25,874 2,447 117,056 SUB 358 169 216 1,103 2,288 112 102 3,627 368 5 464 25,388 423 57 4,379 604 39,663 SBT 0 0 0 0 1,708 0 0 0 0 0 0 0 0 0 0 2 1,710 TOM 0 0 0 0 5,635 800 2,881 2 2,299 0 0 0 0 0 477 2,290 14,383 VEG 0 37 84 149 7,343 0 8,097 1,147 17,028 10 25 245 105 412 6,779 2,556 44,017 VIN 152 182 759 552 15,094 65 120 6,749 262 0 0 1,045 0 30 52,867 2,603 80,478 9 4 308 Survey of Irrigation Methods in California Volume 4 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Irrigation Methods Irrigation methods are separated into four groups, surface (gravity), sprinkler, drip/micro, and subsurface. These types of irrigation methods are used by growers to irrigate their crops in the state. Sub-Surface Irrigation In sub-surface irrigation, underground pipe or open ditches are blocked to back up water and force it into a crop root zone. Surface Irrigation Surface irrigation includes wild flood, border, basin, furrow irrigation without sprinklers, wheel line sprinklers followed by furrow irrigation, and hand move sprinklers followed by furrow irrigation. Acres that are irrigated with both sprinklers and furrows are included under the surface irrigation column. Sprinkler Irrigation Sprinkler methods include solid set, hand move, linear move, wheel line, hose including center pivot, gun-type, etc. Drip/Micro-Sprinkler Irrigation Drip/micro-sprinkler irrigation includes surface and buried and micro- or mini-sprinklers. The method used to separate irrigation methods into four groups in 2001 is slightly different from those used in 1991 study. Micro- or mini sprinklers are combined with surface and buried drip in 2001, while they were listed as sprinklers in 1991 study. To be consistent with 2001 estimates, micro sprinklers in 1991 were separated into surface and buried drip as done in 2001. Table 6 and 7 show the breakdown of irrigated land in percentage by each of 13 crops and four irrigation methods during 1991 and 2001. Table 6. Percentage of irrigated land planted by crop and irrigation method in 1991 Irrigation Method Gravity Sprinkler Low Volume Subsurface Total Irrigation Method Gravity Sprinkler Low Volume Subsurface Total pull, and other types ALF 86.0 12.6 0.5 0.9 100.0 SGR 88.8 10.8 0.0 0.4 100.0 CRN 99.1 0.0 0.0 0.9 100.0 CTN 93.3 6.5 0.2 0.0 100.0 OTH 89.5 9.1 0.9 0.5 100.0 PAS 81.8 12.0 0.0 6.2 100.0 DEC 39.2 38.3 22.2 0.2 100.0 SUB 11.5 15.9 72.5 0.0 100.0 SBT 86.7 13.3 0.0 0.0 100.0 TOM 92.7 6.5 0.9 0.0 100.0 Table 6. Percentage of irrigated land planted by crop and irrigation method in 1991 (continued) VEG 55.1 29.5 15.4 0.0 100.0 VIN 44.9 12.6 42.3 0.3 100.0 Total 66.9 17.3 15.2 0.6 100.0 10 Data and Analytical Tools 4 309 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Table 7. Percentage of irrigated land planted by crop and irrigation method in 2001 Irrigation Method Gravity Sprinkler Low Volume Subsurface Total SUB 10.1 12.5 76.6 0.9 100 SBT 99.9 0.0 0.1 0.0 100 TOM 64.8 16.0 19.2 0.0 100 VEG 35.7 42.5 21.8 0.0 100 VIN 20.8 8.7 70.2 0.2 100 ALF 80.3 17.4 0.0 2.2 100 SGR 87.3 10.5 0.0 2.2 100 CRN 87.1 0.8 0.0 12.1 100 CTN 93.9 5.1 0.0 1.0 100 OTH 73.9 22.5 1.0 2.6 100 PAS 75.1 20.2 0.0 4.7 100 DEC 23.8 17.5 58.4 0.3 100 Total 49.6 15.7 32.9 1.8 100 To compare the earlier estimates with those of 2001, it was also necessary to aggregate the 1991 and 2001 crops into four crop groups. The breakdown of irrigated land in percentage by four crop groups and four irrigation methods during 1991 and 2001 are shown in Tables 8 and 9, respectively. Table 8. Percentages of irrigated land by four crop categories and irrigation methods in 1991 Irrigation Method Gravity Sprinkler Low Volume Subsurface Total Field 89.3 9.4 0.3 1.0 100.0 Vegetable 70.9 19.8 9.3 0.0 100.0 Orchard 31.6 32.1 36.1 0.2 100.0 Vineyard 44.9 12.6 42.3 0.3 100.0 All Crops 66.9 17.3 15.2 0.6 100.0 Table 9. Percentages of irrigated land by four crop categories and irrigation methods in 2001 Irrigation Method Gravity Sprinkler Low Volume Subsurface Total Field 83.6 12.3 0.1 4.0 100.0 Vegetable 42.9 36.0 21.1 0.0 100.0 Orchard 20.3 16.2 63.0 0.4 100.0 Vineyard 20.8 8.7 70.2 0.2 100.0 All Crops 49.6 15.7 32.9 1.8 100.0 Results and Discussion A comparison of early studies with those conducted in 2001 indicated that irrigated land planted to vineyards and orchards has increased, while the percentage of land planted by field crops has decreased. Table 10 and figure 2 illustrate the estimated irrigated land in percentage by four crop categories in California since 1972 and how the percentage of acreages planted by various crop categories has changed from 1972 to 2001. Table 10. Percentage of irrigated acreages by four crop categories in 1972, 1980, 1991, and 2001 Year 2001 1991 1980 1972 Field crops (%) 42 49 68 67 Vegetable (%) 11 15 10 12 Orchard (%) 31 26 15 15 Vineyard (%) 16 10 7 6 Total (%) 100 100 100 100 11 4 310 Survey of Irrigation Methods in California Volume 4 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Figure 2. Percentages of irrigated land planted by four crop categories in California between 1972 and 2001. 1972 1980 1991 2001 75 70 Percentage of Irrigated Acres by Four Crop Categories 65 60 55 50 45 40 35 30 25 20 15 10 5 0 Field crops Vegetable Crop Categories Orchard Vineyard As it is evident from the table and figure, the percentage of land area planted to orchard has increased from about 15% to 31% and acreages planted by vineyard has increased from about 6% to 16%, while the amount of land planted by field crops has decreased from about 67% to 42% since 1972. To validate the information of the irrigation survey conducted in 2001, we compared 2001 estimates to the 1972, 1980, and 1991 estimates to see if a shift toward drip/micro irrigation method is a positive trend for orchards and vineyards. To increase the benefits from more precise water application to soils for crop use, it is expected to see a shift from sprinkler and gravity irrigation toward drip/micro by growers. Drip/micro irrigation allows growers to distribute water more uniformly within the intended root zone than sprinkler and gravity irrigation. Table 11 shows the percentage of irrigated land by irrigation methods for 1972, 1980, 1991, and 2001. We used the information in Table 11 to see if there is a consistent trend in shifting irrigation methods from gravity to drip/micro between 1972 and 2001. The results confirm the trend of decreased acreage in gravity and the increased acreage in drip/micro irrigation from 1972 to 2001. The comparison demonstrates that the amount of land irrigated by gravity irrigation has declined from 80.5% in 1972 to about 49.6% in 2001, while the amount of land irrigated by micro/drip irrigation has increased from 0.3% to 32.9% over the period of the data sets. Although different methodologies were used to conduct these studies, results show a very consistent trend in the use of specific irrigation methods when plotted on a time series graph (Figure 3). 12 Data and Analytical Tools 4 311 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Table 11. Percentage of irrigated land by different irrigation systems for 1972, 1980, 1988, 1991, 1994, 1995, and 2001 survey results in California Irrigation Method Gravity Sprinkler Drip Other Total 1972 80.5 18.1 0.3 1.1 100 1980 76.5 19.7 2.4 1.3 100 1988 70.3 23.7 4.9 1.0 100 1991 66.9 17.3 15.2 0.6 100 1994 61.7 25.0 12.6 0.8 100 1995 60.6 25.2 13.2 1.0 100 2001 49.6 15.7 32.9 1.8 100.0 Since the 1972 and 1980 surveys were mainly based on farm advisors estimates rather than direct grower responses, there was no information available on data variability to determine changes in the use of irrigation methods. Using data from the seven surveys, non-linear trendlines of the percentage of land versus time were determined to evaluate changes in the usage of the irrigation methods from 1972 to 2001. Figure 3 shows the percentage of irrigated land by irrigation methods versus time and it shows trends in irrigation methods based on the information collected from variety of sources (e.g., decreasing use of gravity irrigation and increasing use of drip/micro irrigation). The results of this analysis confirm that the irrigation method survey conducted during 2001 is valid and reliable for long-range water planning in California. Figure 3. Comparison of irrigated land by different irrigation method in percentage within the state Gravity Poly. (Sprinkler) Sprinkler Poly. (Drip) Drip Poly. (Other) Other Poly. (Gravity) Poly. (Gravity) 100.0 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 1968 Acres Irrigated by Various Irrigation Methods (%) 1971 1974 1977 1980 1983 1986 Time (year) 1989 1992 1995 1998 2001 2004 13 4 312 Survey of Irrigation Methods in California Volume 4 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 While there has been a slight decrease in acreage irrigated with sprinklers, there has been a shift towards more irrigated acreage with drip/micro irrigation in 2001. The decrease in sprinkler irrigation method in 2001 was mainly due to changes in orchard and vineyards irrigation technology, shifting from sprinklers to drip/micro irrigation. For vineyards and orchards, the amount of land irrigated by gravity and sprinkler irrigation has declined, while the amount of land irrigated by drip/micro irrigation has increased. Figures 4-6 display the changes in irrigation method by four crop categories for 1972, 1980, 1991, and 2001 surveys. In the analysis of the 2001 survey, it was observed that gravity-driven surface irrigation methods were used to irrigate 83.5% of the field crops with an additional 12.4% irrigated by sprinkler methods. For the orchard crops, 63% were irrigated by drip irrigation methods and 20.3% irrigated using surface methods. Most of the vegetable crops were irrigated by gravity methods (42%) and 36% were irrigated by sprinkler methods. The majority of the vineyard crop land was irrigated by drip irrigation (70%) whereas 21% was irrigated by surface irrigation methods. The largest change in irrigation methods from 1972 to 2001 was the increase in drip irrigation, particularly in vineyard and orchard crops (Figure 4). In 1972, 0.6% of the vineyard crops and 1.9% of the orchard crops were under drip irrigation. In 2001, 70.2% of the vineyards and 63% of the orchards were irrigated with drip irrigation methods, an increase of 69.9% for vineyards and 61.1% for orchards. The increase in drip irrigation in vineyards corresponds with declines in both surface (down 62.6%) and sprinkler (down 7.1%) methods from 1972 to 2001. Drip irrigation also increased 21% in vegetable and 1.8% in orchard crops as well. For all crops combined, drip irrigation increased from 0.3% in 1972 to 15.2% in 1991 to 32.9% in 2001. Figure 4 illustrates the increase in drip irrigation in vegetable, orchard, and grape crops. There has been a large increase in sprinkler irrigation with vegetable crops. Sprinkler irrigation increased from 16.9% in 1972 to 36.2% in 2001, while sprinkler use in most crops appeared to have declined slightly from 1972 to 2001. It declined dramatically in orchards from 59.3% in 1972 to 20.3% in 2001, a decrease of 39%. The large increase in sprinkler use in vegetables corresponds with declines in surface methods from 1991 to 2001, a decrease of 39.7%. Sprinkler irrigation increased 26.4% in vegetables since 1991. For all crops combined, sprinkler use decreased from 18.1% in 1972 to 17.3% in 1991 to a low of 15.7% in 2001 (Fig. 5). It is important to note that the reduction in sprinklers in 2001 was due to a shift from sprinklers to drip because of changes in orchard and grapevine irrigation practices. 14 Data and Analytical Tools 4 313 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Figure 4. Comparison of irrigated land by micro/drip irrigation by various crops from 1972, 1980, 1991, and 2001 1972 1980 1991 2001 75 70 65 Percentage of Statewide Acreage by Drip 60 55 50 45 40 35 30 25 20 15 10 5 0 1972 1980 1991 2001 Field Crops Vegetable Orchard Vineyard All Crops 0.0 0.3 0.3 0.1 0.0 2.1 9.3 21.1 1.9 10.0 36.1 63.0 0.6 10.4 42.3 70.2 0.3 2.4 15.2 32.9 Figure 5. Comparison of irrigated land by high-pressure sprinkler irrigation by various crops from 1972, 1980, 1991, and 2001 1972 1980 1991 2001 50.0 45.0 Percentage of Statewide Acreage by Sprinkler 40.0 35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0 1972 1980 1991 2001 Field Crops Vegetable Orchard Vineyard All Crops 13.9 16.4 9.4 12.3 16.9 16.8 19.8 36.0 38.8 37.3 32.1 16.2 15.8 20.0 12.6 8.7 18.1 19.7 17.3 15.7 15 4 314 Survey of Irrigation Methods in California Volume 4 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 The results from comparing the surveys conducted in 1972, 1980, 1991, and 2001, show that surface irrigation has declined for all crops from 80.5% in 1972 to 49.6% in 2001 (Figure 6). There has been a dramatic decrease particularly in vineyards. In 1972, approximately 82.5% of the land area planted to vegetables, 59.3% planted to orchards, and 83.6% planted to vineyards were under surface irrigation methods. In 2001, 42.8% of the vegetables, 20.3% of the orchards, and 20.8% vineyards were irrigated with surface irrigation methods. The study shows a decrease of 39.7% for vegetables, 39% for orchards, and 62.8% for vineyards. Figure 6. Comparison of irrigated land by gravity-driven surface irrigation by various crops from 1972, 1980, 1991, and 2001 1972 1980 1991 2001 100 90 80 70 60 50 40 30 20 10 0 1972 1980 1991 2001 Percentage of Statewide Land by Gravity Field Crops Vegetable Orchard Vineyard All Crops 84.6 81.6 89.3 83.6 82.5 81.1 70.9 42.9 59.3 52.7 31.6 20.3 83.6 69.6 44.9 20.8 80.5 76.5 66.9 49.6 The reductions in surface methods are due to the reductions in field crop acreages. The percentage of land area planted to orchard has increased from about 15% to 31% and acreages planted by vineyard has increased from about 6% to 16%, while the amount of land planted by fields crops has decreased from about 67% to 42% since 1972. Table 12 displays percentage change per year of percentage of acreages irrigated by gravity, sprinkler, and drip methods for four crop categories between 1972 and 2001. There has been a large increase in drip irrigation, particularly in vineyards. The table below shows that the drip irrigation in vineyards has increased at an average rate of 2.4% per year over the period of the data sets (Table 12 and Figure 7). 16 Data and Analytical Tools 4 315 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Table 12. Percentage change per year of percentage of land area irrigated by various irrigation methods by four crop categories assuming a linear change between 1972 and 2001. Crops Irrigation Method Change per Year (%) Field crops Gravity Sprinkler Drip -0.04 -0.05 0.01 -1.37 0.67 0.72 -1.34 -0.78 2.11 -2.16 -0.78 2.40 -1.07 -0.08 1.12 Vegetable Gravity Sprinkler Drip Orchard Gravity Sprinkler Drip Vineyard Gravity Sprinkler Drip All crops Gravity Sprinkler Drip There was a small increase in the use of the drip irrigation for vineyards between 1972 and 1980, an increase of 9.8%. But a dramatic increase in drip irrigation was observed between 1980 and 2001, an increase of 59.8%. The rate of increase calculated between 1980 and 2001 is about 3% per year. The increase in drip irrigation is mostly due to a 2.16% per year decrease in surface irrigation and 0.75 % decrease in sprinkler to vineyards. The uses of drip irrigation in orchards and vegetable crops have also increased at about 2.1% and 1.1% per year, respectively. For all crops, drip irrigation increased at about 1.1% per year during the period of record. For vegetable crops, drip irrigation increased at a rate of 0.72% per year. Although use of sprinkler irrigation in most crops declined slightly from 1972 to 2001, it increased at about 0.67% per year for vegetable crops (Table 12 and Figure 7). For vineyard and orchard crops, surface irrigation has declined approximately 2.16% and 1.3% per year from 1972 to 2001, respectively. For vegetables and all crops, surface irrigation declined at about 1.37% and 1.07% per year, respectively. There have been no changes in irrigation methods for field crops. Results indicate that field crops are still mainly irrigated by surface irrigation methods and the land area planted to field crops is reduced by small percentage. 17 4 316 Survey of Irrigation Methods in California Volume 4 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Figure 7. Percentage change per year of land irrigated by various irrigation methods versus years from 1972 by crop categories Percentage change per year of land irrigated by various irrigation methods Gravity Sprinkler Drip 3.00 2.50 2.00 1.50 1.00 Change/Year (%) 0.50 0.00 -0.50 -1.00 -1.50 -2.00 -2.50 -3.00 Gravity Sprinkler Drip Field crops Vegetable Orchard Vineyard All crops -0.04 -0.05 0.01 -1.37 0.67 0.72 -1.34 -0.78 2.11 -2.16 -0.78 2.40 -1.07 -0.08 1.12 Conclusions The results of 2001 survey demonstrate consistent trends in crop acreages as well as the irrigation methods used in the various crops based on the information collected from variety of sources. A decrease in use of surface irrigation and an increase in use of drip/micro irrigation have been observed. The largest increase in drip irrigation use occurred in orchards and vineyards. The largest increase in sprinkler use was in vegetable crops. The results of this survey seem to be consistent with the information collected from other sources on trends in crop acreage and irrigation methods. References Burt, C.M., Mutziger, R.J., Allen, R.G., Howell, T.A. (2004). "Evaporation Research A Review and Interpretation." Unpublished CalPoly report. Edinger-Marshal, S., and Letey, J. (1996). "Irrigation shifts toward sprinklers, drip and microsprinklers." California Agriculture, Volume 51, Number 3: 38-40. Hagan, R. M., and Wagner, R. J. (1983). Irrigation methods in California: an update. California Dept. of Water Resour. Div. of Plng., Sacramento, Calif. Snyder, R. L., Plas, M. A., Grieshop, J. I. (1996). " Irrigation Methods Used in California: Grower Survey" ASCE J. of Irrig. & Drain. Engr. 122(4): 259-262. 18 Data and Analytical Tools 4 317 California Water Plan Update 2005 Survey of Irrigation Methods in California in 2001 Stewart, J. I. (1975). "Irrigation in California: a report to the State Water Resources Control Board." Standard Agreement No. 2-2-65 between State Board and Univ. of California, California Water Resour. Control Board, Sacramento, Calif. 19 4 318 Survey of Irrigation Methods in California Volume 4 ...
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