Agricultural Irrigation Water Demand
2008 Specialty Crop - Water Withdrawals

Vegetable, Fruit, and other specialty crops:

Georgia is blessed with a long growing season, easily worked soils, and abundant water resources that make possible production of a wide variety of fruits, vegetables, orchard, and specialty crops. Their proximity to major urban centers in the East and opportunities to partner with producers in Florida and other neighboring states, allows favorable marketing opportunities for fresh produce. Additionally, Georgia farmers have had long experience with producing and handling specialty crops like tobacco and food crops like peanut, peaches, and pecan. Their migration to more specialty crops was a logical development, one that may continue to make modest gains during the next 40 years.

Georgia specialty crops reported in the 2007 Farm Gate Reports prepared by the UGA Center for Agribusiness and Economic Development include Fruit and Nuts, Vegetables, and Ornamental (Green Industry) crops. Data below are Statewide totals of harvested area summarized from those Farm Gate reports. They highlights the diversity of Georgia crops. Most of these high value crops are produced with irrigation:

Eggplant (above), tomato and pepper are among several vegetables grown under plastic mulch and irrigated by drip systems.
Vegetables (ac)
Fruit & Nuts (ac)
Pepper6,620Pecan131,306
Tomato3,890Peach11,100
Eggplant1,100Apple622
Cabbage10,400
Greens19,700Blueberry10,700
Snap Bean20,400Strawberry277
Southern Pea5,300Other berries433
Sweet Corn25,800
Squash9,550
Green Industry (ac)
Cucumber10,700Sod Production50,600
Onion13,800Container Nursery4,820
Watermelon24,200Field Nursery9,240
Canteloupe4,910Greenhouse437
Okra320

Withdrawal Estimates for Specialty Crop Irrigation:

Every 3 to 4 years Georgia's Cooperative Extension Service surveys its county agricultural agents for their county's irrigation practices. Included in each agent's county summary are area calculations for most irrigated crops and average irrigation application depth, estimated by crop type for the survey year. The CES Irrigation Survey values can provide a starting point, a snapshot in time, of water withdrawals needed for specialty crop irrigation.
Which specalty crops are tracked?

Many vegetables that are produced under center pivots or other sprinkler systems are lumped as "Sprinkler-irrigated vegetables" in the survey. Similarly, vegetables produced with drip systems, often using plastic mulch, are grouped as "Drip-irrigated vegetables." Both of these include winter, spring, and summer multiple crops, and a field area would be counted two or three times if it was multicropped.

Other specialty crops are included in the CES Irrigation Survey individually. These include apples, peaches, grapes, and blueberries. Acreage of these orchard perennials change slowly over the years, and estimates tend to be quite accurate. For these crops water use can vary widely over years. For some part of the irrigation use includes water for frost protection needed for late season freezes.

Pecans may be considered a another specialty orchard crop, but acreage of pecans in Georgia is very large, and they are produced in most of the Coastal Plain counties in the same areas as major row crops. USDA tracks production of tree nuts nationally and makes predictions of their future production. Because of its extensive area, long-season of irrigation, and availability of long-term data and projections, pecan was included in the major crops of the Ag Water Demand study.

Although tobacco was grown more widely in past years, acreage has ben reduced since the tobacco buyout, and fewer growers are involved in its production. For purposes of the Ag Water Demand, it was included as a specialty crop.

The green industry that supplies turfgrass sod, shrubs and trees, container grown plants, and seedlings trees and plants is another important farm sector that involves irrigated production in a number of counties, including several in North Georgia. The CES Irrigation survey enumerates sod production, nurseries, and greenhouses separately.


Canteloupe (above), watermelon, squash, and cucumbers may be produced on large fields with overhead irrigation or may be produced on plastic mulch and irrigated by drip.

In container nurseries, limited rooting systems and small pot openings require irrigation several times per day so plastic mulch can be used to collect and reuse irrigation runoff.

Sod farming has moved to large fields irrigated by center pivots. With multiple harvests, the irrigation season can be quite long.

Sweet corn (above), snap bean, onion, and other vegetables may be produced in large fields irrigated by center pivots. 		2008 CES Survey Irrigated Area - Statewide:

Vegetable, Drip Irrigated22,200 ac
Vegetable, Sprinkler Irrigated 95, 600 ac
Tobacco11,900 ac
Apple 220 ac
Peach6,870 ac
Blueberry11,000 ac
Grape1,307 ac
.
Sod Production42,900 ac
Nurseries7,370 ac
Greenhouses240 ac
Computing withdrawals for specialty crops:

Within each county, the acres of each specialty crop was multiplied by the seasonal irrigation depth for that crop to give acre-inches applied. This was converted to million gallons, and that value was divided by 300 to get average million gallons per day (MGD) withdrawn for that crop for the months February through November. Irrigation application depths for each crop are reported as seasonal totals in the CES Irrigation Survey. However, for most crops the irrigation season only lasts two to three months. Because data is lumped as a class (e.g. vegetables - sprinkler irrigated), starting and ending months cannot be teased out of the data or assumed for the generic class. Instead, we have assumed that the irrigation withdrawals can be made anytime between February and November - about 300 days. We divide withdrawals evenly, although the total withdrawals may actually only occur in a few months in any given field. Withdrawal rates (MGD) calculated for individual specialty crops were summed across crops within a county. In the attached spreadsheet, counties are listed by WPR and sorted alphabetically. As a start to estimating withdrawals of all crops, specialty withdrawals can be added to predictions for February through November for major crops to get an estimate total irrigation withdrawals that includes specialty crops.

  • Average daily withdrawals, annualized, for all specialty crops in each county of Georgia. (Excel file).
    • Monthly Irrigation Depths from Ag Water Pumping Study:

    County agents did not attempt to break out estimates of irrigation depths by months. However, between 1999 and 2004, monthly irrigation application depths were measured by the "Ag Water Pumping" team. In this study funded by Georgia's Department of Natural Resources, UGA researchers and engineers installed meters on approximately 800 irrigated fields in Georgia. Locations were randomly selected from among permitted agricultural water users, and farmers participated voluntarily. Each month, a team member visited each field, noted the crop or crops being grown then, and recorded the water use for that past month. The same fields were observed month after month for five to six years regardless of crop rotation or irrigation use. (More details of the study, and a full report, can be found     HERE.)

    In the report below taken from Fact sheet 6 of the study, there are examples of irrigation application depths observed during the study years for 26 counties of southwest Georgia. This study region now includes most of the Lower Flint-Ocklockonee, Upper Flint, and Middle Chattahoochee Water Planning Regions. Average monthly irrigation was computed by crop type for all fields that were under observation in the region over all years. For example the average May irrigation to melons would involve all irrigation applied to observed melon fields during May of 1999, 2000, 2001, 2002, 2003, and 2004. The driest year irrigation would be the greatest monthly average application onto observed melon fields for the driest May. That driest May could have occurred in May, 2000, or May, 2001, for example. Similarly, the wettest year May could have occured in 2003 when the lowest average application was made to observed fields.

    In the Ag Water Pumping study, we noted that crops were rotated in individual fields over years, and fields may have been divided into more than one crop in a single season. While a field may have been planted entirely to cotton one year, in the next it could have had half of the area in peanut and the other half in corn. With the farmers' assistance we divided each month's irrigation to the portion of split fields that were actually irrigated that month. Specialty crops that we observed in monitored irrigation fields included vegetables Butterbeans, English peas, snap bean, southern pea, cucumber, squash, sweet corn, cabbage, collard, kale, mustard, carrot, onion, radish, egg plant, sweet pepper, staked tomato, "mixed" vegetables, canteloupe, and watermelon. Peach orchards, blueberry fields and grape vineyards were monitored in addition to many pecan orchards. We also tracked pine tree nurseries, ornamental plant nurseries and sod farms. Tobacco, sunflower, and even bird seed were among other minor row crops. In the spreadsheet, not all of those crops are shown becaust too few fields were observed to create long term averages. The solanaceous crops tomato, pepper, and eggplant are shown as one. canteloupe and watermelons were grouped as "melons." And zucchini and yellow squash were grouped as "summer squash." The two-hump appearance for graphs of sweet corn, snap bean, squash and solaneoceous crops reflects irrigation of separate spring and fall crops. Fall crops were usually planted on fewer acres than the spring crops. The diverse seasonal patterns visible in the graphs show the challenges associated with making generalizations over specialty crops and explain our decision to simply draw February through November daily withdrawal estimates for specialty crops.

  • Average and extreme monthly irrigation applications for specialty crops, as observed during 1999 through 2004 by the Ag Water Pumping Study. (Excel file).


    • Last updated 6/01/2009 James E. Hook