Agricultural irrigated land-use inventory for the counties in the Suwannee River Water Management District in Florida, 2015

Abstract

A detailed inventory of irrigated crop acreage is not available at the level of resolution needed to accurately estimate agricultural water use or to project future water demands in many Florida counties. A detailed digital map and summary of irrigated acreage during the 2015 growing season was developed for 13 of the 15 counties that compose the Suwannee River Water Management District. The irrigated areas were delineated using land-use data, orthoimagery, and information obtained from the water management district consumptive water-use permits that were then field verified between May and November of 2015. Selected attribute data were collected for the irrigated areas, including crop type, primary water source, and type of irrigation system. Results indicate that an estimated 113,134 acres were either irrigated or had potential for irrigation in all or part of the 13 counties within the Suwannee River Water Management District during 2015. This estimate includes 108,870 acres of field-verified, irrigated crops and 4,264 acres of irrigated land observed as (1) idle (with an irrigation system visible but no crop present at the time of the field-verification visit), (2) acres that could not be verified during field visits, or (3) acres that were located on publicly owned research lands. Of the total field-verified crops, 83,721 acres were field crops; 20,962 acres were vegetable crops (sometimes referred to as row crops); 3,089 acres were in tree nurseries, ornamentals, and sod production; and 1,098 acres were fruit crops. Specific irrigated crops included 32,468 acres of corn (primarily for silage); 28,170 acres of peanuts; and 10,331 acres of hay. About 40 percent of the vegetable acreage (8,340 acres) was double cropped (planted with both a spring and a fall crop on the same field). Beans, carrots, and watermelons were the most commonly grown vegetable crops in these 13 counties in 2015. Sprinkler irrigation systems including center pivots, portable or traveling guns, and permanent or solid overhead fixtures accounted for nearly 91 percent (102,874 acres) of the total irrigated acreage in the Suwannee River Water Management District, whereas microirrigation systems including drip irrigation accounted for 9 percent (10,260 acres) of the irrigated acreage. A total of 1,466 center pivots were observed during field verification in 2015 and accounted for 93,093 irrigated acres (which represents 82 percent of the total irrigated acreage). Most center pivots were in use at the time of the field verification, although about 3 percent appeared idle. No flood irrigation systems were observed during field verification in 2015. Overall, groundwater was used to irrigate nearly all of the field-verified acreage (99.8 percent). Dairy wastewater effluent was used on many fields during 2015; however, a quantitative estimate of acreage using effluent could not be determined. Irrigated cropland totaled 26,927 acres in Suwannee County; 16,511 acres in Madison County; 14,862 acres in Hamilton County; and 14,155 acres in Gilchrist County; these four counties accounted for nearly two-thirds (64 percent) of the acres irrigated within the Suwannee River Water Management District during 2015. Corn (primarily for silage) and peanuts were the primary irrigated crops, accounting for 48, 70, and 71 percent, respectively, of the total irrigated acreage in Suwannee, Madison, and Gilchrist Counties; vegetables accounted for 52 percent of the total irrigated acres in Hamilton County. Other counties with substantial irrigated acreage included Levy (10,122 acres), Alachua (9,547 acres), and Lafayette (8,110 acres); these three counties, combined with Suwannee, Madison, Hamilton, and Gilchrist Counties, accounted for 88 percent of the irrigated acreage in the Suwannee River Water Management District. The irrigated acreage that was field verified in 2015 for the 13 counties in the Suwannee River Water Management District (113,134 acres) is about 6 percent higher than the estimated acreage published by the U.S. Department of Agriculture (107,217 acres) for 2012; however, this 2012 value represents acreage for the entire portion of all 13 counties, not just the Suwannee River Water Management District portion. Differences between the 2015 field-verified acreage totals and those published by the U.S. Department of Agriculture for 2012 may Open-File Report 2016–1111 2 Agricultural Irrigated Land-Use Inventory in the Suwannee River Water Management District in Florida, 2015 occur because (1) irrigated acreage for some specific crops increased or decreased substantially during the 3-year interval due to commodity prices or economic changes, (2) calculated field-verified irrigated acreage may be an overestimate because irrigation was assumed if an irrigation system was present and therefore the acreage was counted as irrigated, when in fact that may not have been the case as some farmers may not have used their irrigation systems during this growing period even if they had a crop in the field, or (3) the amount of irrigated acreages published by the U.S. Department of Agriculture for selected crops may be underestimated in some cases. Introduction Water withdrawals for agricultural irrigation generally are estimated in counties throughout Florida because most irrigators do not meter or report their usage, or the metered information obtained does not provide a cumulative total. The most common procedure used to estimate water withdrawals for agricultural irrigation in Florida is to multiply the reported or published number of acres of each crop irrigated by a cropspecific net irrigation requirement, also known as an application rate (Marella, 2014). The acreage irrigated and the application rates are estimated by each of five water management districts (WMD) for the counties within their boundaries. Many assumptions must be made to estimate water withdrawals using irrigated acreage data and application rates. Some of the problems associated with obtaining and using reported or published irrigated acreage data include • variations in definitions, data-collection procedures, and reporting levels between agencies that compile such data, and differences in years published; • inadequate documentation of accuracy and detail; • missing data due to incomplete compilations or privacy restrictions or disclosures; • inability to differentiate between irrigated and nonirrigated crop data at the county level; • lack of information about irrigation method and water source; and • lack of spatial data describing the location of irrigated crop lands. Accurate and detailed estimates of irrigated acreage are not available at the level needed to improve current wateruse estimates or to project future demands. The results of this study will increase the accuracy of water-use estimates and provide a more detailed summary of the irrigated crops within the 13 counties of the Suwannee River Water Management District (SRWMD) than the values published in the past for these counties. Information on crop type, irrigation system, and water source enables water managers and planners to better estimate current and future water needs. An accurate assessment of the spatial distribution of irrigated lands will allow better identification of water use at the local and regional level, and facilitate more reliable assignment of withdrawals for use in predictive hydrologic models. Background In 1998, the five Florida WMDs each prepared a detailed regional water supply plan for areas or counties within their jurisdiction to determine whether existing sources of water were adequate for current and future water needs (Florida Department of Environmental Protection, 2013). Water needs include water for public supply, domestic/small public supply, commercial/industrial/institutional self-supplied, power generation, agricultural irrigation, and recreational irrigation (mainly golf courses). The primary objective of these water supply plans was to project future water demands and develop alternative water supplies to help meet these projected demands. In 2013, the Florida Legislature mandated that future water demand projections for the agricultural irrigation part of WMD water supply plans be provided by the Florida Department of Agriculture and Consumer Services (FDACS) for consideration by the WMDs (Marella and Dixon, 2015). The water supply plans typically project 20 years into the future and are updated by the WMDs on a 5-year cycle. Generally, all water supply plans are approved and adopted as policy guides by the governing board of each WMD. Water withdrawals for agricultural irrigation refer to water used for crop irrigation and for non-irrigation uses associated with agricultural and farming operations (Marella, 2014). Crop irrigation includes the application of water on lands to assist in cultivation of crops or to prevent crop damage caused by harsh weather. Non-irrigation uses include withdrawals for livestock watering, washing of dairy and farm equipment, augmentation of ponds used for fish farming, and other farm uses (Marella, 2014). Purpose and Scope The purpose of this report is to present the results of a cooperative study between the U.S. Geological Survey (USGS), FDACS, and the SRWMD designed to provide a detailed digital map and summary of field-verified irrigated acreage within all or part of 13 of the 15 counties located within the SRWMD boundary for the 2015 calendar year. These 13 counties include Alachua, Bradford, Columbia, Dixie, Gilchrist, Hamilton, Jefferson, Lafayette, Levy, Madison, Suwannee, Taylor, and Union (fig. 1). The small areas of Baker and Putnam Counties located within the SRWMD were not included in this study. Four of the 13 counties inventoried (Alachua, Bradford, Jefferson, and Levy) are only partially within the