Agricultural Irrigation Development in Georgia
Jim Hook and Kerry Harrison

Crops are irrigated by Georgia farmers for several reasons: increasing overall profitability, stabilizing income over dry as well as wet years, and insuring they can meet contractual obligations including marketing agreements, operating loan and other farm indebtedness. Irrigation allows farmers to enter new enterprises such as vegetables or other produce for fresh and processing markets. Turfgrass sod can be grown for sale, and ornamental plants may be grown in-ground or in containers for wholesale markets. Irrigation increases the overall efficiency of crop land and investments that must be made annually for crop production. Expensive land preparation, seed and seed technology fees, fertilizers, fuel, and agrichemicals can be wasted when drought lowers crop yield or crop quality. Beginning in the 1970s, Georgia farmers began a conversion of their farming practices from dryland to irrigated.
When farmers convert fields from non-irrigated to irrigated production, they have several options for irrigation equipment, but also several limitations. In many areas of the world, in the western US, and even in the Mississippi Delta as well as Florida flatwoods, the first choice of irrigation is often surface irrigation. For surface irrigation, water is distributed by flooding the field or channeling water down long furrows. These distribution techniques typically require an infrastructure of canals or very large pumps to deliver enough water to spread across a practical-sized field. Often, extensive land-levelling work is needed to plane or terrace fields for this use. Heavy showers and tropical storms may add unwanted, excess water that must be removed from fields. A system of tail-water drainage also becomes a necessity. Water delivery and drainage require coordinated efforts among land holders.

In Georgia, the agricultural rolling topography and sandy topsoils, as well as small land holdings, made surface irrigation impractical. As a result of these difficulties, flood and furrow irrigation, so common in the Western US and elsewhere around the world, never became established in this state. That was fortunate since these methods typically have a low water use efficiency.


Portable pipe removed from fields after final irrigation. 		Portable Pipe Systems

Early irrigation in Georgia was accomplished with portable pipe and impact sprinklers. Portable pipe usually involved 20 ft sections of aluminum pipe latched together. Sprinklers were often attached on vertical riser pipes on every 2nd to 4th section. Parallel rows of pipes left risers in square or diamond patterns with overlapping patterns to effectively cover the crop. When pipe was limited, it had to be moved after each irrigation set - each part of the field. It was very labor intensive to set up irrigation in the field after the the crop was established. For tractor operations like spraying pipe had to be moved, and then pipe had to be completely dismantled and removed before harvest could begin. Large fields were impractical to irrigate, so most crops that were irrigated were high value crops like tobacco. Despite the labor requirements, almost any field shape, soil, or crop could be irrigated this way. Portable pipe still finds some use in plant and tree nurseries.

Solid Set Sprinkler Systems

While portable pipe is seldom found on Georgia farms today, their successor - solid-set sprinklers - remain in use in certain orchard, vegetable, and ornamental applications, especially where frost protection may be needed (blueberries, strawberries, etc.) In modern solid set systems, water is distributed by buried plastic pipe and a manifold of distribution pipes carries water from pumps to different zones within a field or orchard. Like their counterparts in home lawns, the system lends itself well to automation. Timers or other automation will assure that irrigation is regularly applied. Any size or shape field can be irrigated with these systems. These systems are expensive; materials cost $1500/ acre and installation is labor intensive. Their use is limited today to high cash value crops. Solid set systems accounts for fewer than 4% of all systems in Georgia, and because those systems commonly irrigate smaller areas their aerial extent in Georgia is even less.(CES, 2009)
Solid set sprinklers on a turf farm.

Peach orchard equipped with solid-set sprinklers on tall risers for frost protection. In-season irrigation is accomplished by micro-sprinklers (blue & red sprinklers fed from black plastic tubes).
Pecan orchards with solid-set impact sprinklers are still common in Georgia, but new orchards use drip and micro-irrigation technologies.
Traveler Systems

As farm labor shortages grew, farmers looked for other tools for irrigation. Portable systems, generally classified as "travelers", were a common entry-level irrigation system. Travelers included several designs that dragged a cart with a large water cannon, as well as a large hose, through the field. Large sprinklers delivered water over 100 feet, but they required pumps capable of delivering 200 to 500 gallons per minute at high pressure. The high pressure spray to spread water over large areas used considerable energy, and the resulting high trajectory spray was subject to water losses by evaporation and drift. Typically, application efficiency over the course of a day was 50% or less. The high pressure sprays precluded their use on large tree crops, except for initial establishment, and soil splash, compaction and potential runoff limits their use in vegetable crops. Most tied up a tractor for power and anchor, and they required an alley of cropland be cut out for the hose and cart. Once a run was started, the irrigation could proceed several hours unattended, but shutdown for pumps and travelers was not reliably automated.

Any shaped field could be irrigated by travelers, but the pattern of cart movement was always in a straight line or gentle curve. With a sprinkler spraying an even pattern on both sides of the travel path, the wetted path of a single run looked like a hot-dog stretched throughout a field. To cover all areas of an unevenly edged field meant that some water had to be directed out of the field into surrounding vegetation, buildings, or highways. Alternatively, only part of a full crop field would receive water. Farmers who used travelers regularly and repeatedly during the growing season set up rows of risers connected by underground pipe to the pump. They preferred rectangular fields where a riser could be used for irrigation runs in two directions perpendicular to the row of risers.

Travelers are sometimes used for drought rescue irrigation, including pastures. With drought rescue, a farmer doesn't plan a full-season control of the crop's water needs. Instead, irrigation will be set up to save a crop that is severely threatened by long rainless periods. With their portability, they can be dragged into fields that have a nearby water source like a pond. Portable pumps, often on wheeled trailers, and portable pipe can be brought in quickly to supply the traveler. This temporary setup requires considerable labor for each travel run.

In general, fields described and labeled as irrigated by travelers are not irrigated every year. In a five-year field monitoring study, fields described as traveler-irrigated typically received water only 50 to 75% of the time even in drought years. In a wetter than normal year, as many as 85% of monitored traveler sites were not irrigated at all. (AWP, 2005). Traveler systems reached their peak use in 1982 when 4,900 systems were in use in Georgia. By 2008, their use had dropped to 2,100 as farmers found more permanent and reliable solutions for field crop irrigation. (CES, 2009)



Aerial views of other traveler-irrigated fields.
Big gun (traveler) irrigating a tobacco crop.

Hose-reel traveler parked at edge of field ready for its next use.

Heavy spray from the sprinkler temporarily knocked down leaves of this crop, showing the pattern of spray and movement of this traveler.

Traveler set on fourth run in the field pulling to the north (top, near pond) in the field. Areas wetted in earlier runs are visible in the soil of the emerging crop.
Center Pivot Systems

The real growth in irrigated area in Georgia began in the early 1970's as center pivots began to move here. These systems were first used in the west in places like Nebraska, Kansas, and Texas, on areas underlain by the Ogalala Aquifer. These areas were agriculturally marginal praries where the topography and soil was unsuitable for flood irrigation used elsewhere in the west. Pivot circles turned sandy praries into corn, sorghum, wheat, and cotton fields. But as the market for new pivots slowed in the west, manufacturers looked for other areas to market their designs. The Dougherty Plain and other areas in Georgia had marginal dryland agriculture on sandy soils. Much of the land had been left in trees. These seemed logical areas for pivots. Pine forests could be cleared to make way for the large circles. Wells could be conveniently drilled into the Floridan aquifer to supply water at the pivot point. As pivots turned sandy lands into highly productive fields where multiple cropping of row crops, and even vegetables, were possible, the advantages of pivots became obvious to growers on other areas of the Georgia Coastal Plain.

Center pivots are well engineered structures that effectively deliver water to large fields. A main water delivery pipe is suspended over the field out of the way of the crops. Sprinklers or spray nozzles can be spaced along that pipe to apply water wherever the pipe is traveling. At each tower pipe sections are connected with a flexible joint. The joint allows the pipe to move through a limited range without twisting or breaking. This flexibility also allows vertical bending that allows pivots to climb moderate hillslopes.

When operating, most systems turn a motor on at the end tower (at the circumference of the circle) for set periods of time. Set at "100%" that tower would run continuously, and the pivot would move at its fastest rate. At faster speeds less water is applied. Usually the fastest speed is used only when moving the pivot out of the way of field operations. Then no water is applied while it is moving. At "50%" the motor is cycled, half on and half off, e.g. 30 seconds running then 30 seconds stopped. This gives time for more water to be applied. During normal irrigation, pivots operate at 10% to 20% allowing about an inch to be applied in one pass. While the end tower is controlled by timing circuitry at the pivot control panel, the inside towers are controlled by switches located at each tower. As the pipe bends at the flexible joints, switches are tripped turning on the tower motors to run forward or reverse to straighten the pipe. The process creates a long straight pipe that may extend one-half mile in length allowing the whole pipe to move together as a radius for the pivot circle.


Center Pivot irrigating peanut.

The center or pivot tower anchors the system and supplies water and power.

A pipe span is supported by a truss rod structure and nozzles are attached to openings on the top.

The last tower drives the system and often supports an over-hang pipe or end gun that extends the range of the circle.

Interior towers are controlled by levers or wires that trip switches to start their motors.

Towable center pivots have the main tower on wheels, but they are anchored in use. The small diesel powered generator under the tower supplies electricity. Water arrives at the pipe riser from a pond pump at the edge of the field.

Diesel engines can be used to drive well pumps directly and produce electricity needed for pivot motors and controls (left). Alternatively, electricity from utility companies or farmers' generators can power those pumps and pivots.

Large impact sprinklers - end guns - extend the reach of the pivot. Together with overhang pipes, they can add irrigation to areas where the pivot towers cannot travel.
At the center of the circular field, an anchored tower holds up the end of system and provides flexible joints that allow both water pipe and electrical wires 360 degrees of movement. Water and power are supplied to the system at the pivot point. In many cases in Georgia, water is derived from wells that are drilled within a dozen feet of the tower. In other cases it is delivered by buried pipe from a nearby pond, river, or other source. Power may be delivered from electric utilities by means of buried wires, or it may be generated on-site by a generator attached to a diesel, propane, or gas fueled motor. That motor may also drive the well pump by a drive shaft or it may supply electricity to an elecric well pump. In early years of pivots, some were driven by water powered gears or hydraulic fluid driven motors. Today, almost all systems require electricity for controls and for power to drive the towers.

Each pivot is designed specifically for the field in which it is constructed. This is a process of matching design criteria to available natural resources. One of those is the reliable supply of water. It takes a large water supply to add water to an entire field before the water you applied at the start is evaporated. At the other side of the equation, soil can only take in water at a certain rate, a rate reduced when the soil is packed or crusted over. It does no good to apply water faster at any given point in the field than the intake rate because the extra will just run off. A well designed system creates a field size and a sprinkler package that optimizes for these limits, but that still allows a little down time for repairs, even during peak irrigation periods.

After it is designed, the system is manufactured from standardized parts in plants in the mid-west, and sub-assemblies are trucked directly to farm fields. A few companies in the Southeast specialize in erecting these systems in the field. Once erected and connected to water and power, little maintenance is required. With proper flushing, draining for freeze protection, and minimal replacement of gaskets and sprinklers, a center pivot can remain operable for as much as 30 years. With their long life, the number of pivots have grown since 1970. By 2008, there were more than 16,000 in operation in the state of Georgia.

In the West where pivots were first installed, fields were carved out of praries by mandates that created mile-square farm plats. Most of that mile square could be used for farming. A typical "quarter-circle" field would hold a 125-acre full-circle pivot, and four of those could be placed uniformly in a mile square. The first pivots in Georgia were sized to take advantage of these existing designs. While fields that are cleared out of woodlands of the Dougherty Plain or Flatwoods regions in Georgia might be arranged in convenient and uniform circular fields for center pivots, that proved to be the exception to the rule in agricultural regions of the Coastal Plain. Most fields are located on upland areas dissected by the numerous streams, tributaries, and drainage ways that developed in this rainfed climate. Usually these streams lie in broader lowlands that themselves are too wet to farm. The remaining uplands are irregular in shape, and they are further divided into fields by animal fencing, property boundaries, roads, and existing structures. To make most effective use of their existing crop fields, farmers have had to use a wide variety of sizes of pivot circles, and frequently part circle systems are used. Currently only 60% of Georgia's center pivots can complete a full circle; 24% of pivots are blocked in ways that make partial circles from 3/4 to nearly full. The other 16% are arranged in rectangular fields where a half circle pivots work better. The average area covered by pivots in Georgia is 85 acres, but the fields range in size of less from than 10 acres to more than 400 acres under individual pivots.

The vast majority of pivots in Georgia are permanently anchored at the pivot, i.e. the center tower is mounted on a concrete pad and left attached to the water source. However, in early pivot development in Georgia, towable pivots were seen in most counties. Towable pivots sometimes offered better coverage in a long rectangular field than part circle pivots. A towable pivot has a center tower that is itself a movable cart with wheels. Temporary tie-downs hold it place while it is in operation. However, after an irrigation, or an irrigation season, the tie-downs can be removed and water pipes disconnected. Wheels on each of the towers are rotated through 90 degrees, and the whole pivot is then towed by tractor to a nearby field. At the new field the water is reconnected to a new riser, or hydrant, connected to a buried pipe, wheels are rotated for circular movement and the system is ready to go again. Needless to say, this process is labor intensive, and it is not common to move between locations within a single season. Still hundreds of these remain in use in Georgia.

Farmers usually try to build out the pivot hardware as far as possible in a field. Fences, property lines, highways, houses and barns, wooded areas, power poles, and ponds are common obstructions that limit the length of the pivot pipe. These rarely surround the field in a circular pattern. End guns allow water to be thrown beyond the pipe length into outlying parts of the field where crops can be grown. In these cases, an "end gun shutoff device" may be used to turn off water to the end gun when it would spray out into uncropped areas.

End guns are a common feature on most pivots in Georgia. The guns themselves are large impact sprinklers. They may throw water as far as 130 ft beyond the pivot hardware, although the effective watering radius would only be about 100 ft of that. Adding 100 ft to the radius of the circle substantially increases the field area that can watered by the pivot. For small pivot circle, say 25 acres, this would increase area 36%, providing another 9 acres of irrigated cropland. On a large pivot of 200 acres the increase is only 12%, but 24 acres of irrigated land are added using this single end gun. End guns are not without their problems. The angle of operation must be carefully set to deliver water unbiformly. Many require a booster pump to raise pressure to the desired nozzle pressure. If the water pressure at the end of the pipe is sufficient, this booster can be omitted, but operating a pivot at higher pressure increases pumping costs, and it may require pressure regulation on some or all of the other sprinklers on the pivot.


Center pivots are most efficient and cost effective when centered in square or rounded fields, but when necessary other field areas can be irrigated with pivots operating in a partial circle.
Center pivots owe their popularity to their convenience and durability. During the growing season, a single worker can go to the field, throw a few switches or set automated control panels to power and operate the unit and its attached pumps. A pivot is usually left in unattended mode after that, while the systems safeties will keep the unit operating within design limits or shut it down it something fails. Center pivots are easily automated, tracked by remote monitors, or even controlled remotely.
Drip and MicroSprinkler Spray Systems

While center pivots now apply most of the irrigation to farm lands in Georgia, drip and other micro-irrigation systems have many advantages in vegetable, fruit, and other specialty crops. Their use in Georgia is increasing as more specialty crops are produced. Features common to these systems are partial root zone wetting and minimal evaporative loss during irrigation.

In some applications a micro-sprinkler is placed under a tree and a portion of the soil in the orchard where the tree roots are located is sprayed. Water may spray out a few feet or a dozen or more feet, depending on the size of the tree and its canopy. In other micro-irrigation applications, emitters are very thin tubes. During the irrigation cycle, water drips out of the ends of the tube like a leaky faucet. The small tubes allow the water to be placed a few feet from water delivery lines. Interior diameter and length control the flow rate. Weights may be added at the ends to keep them in the right place. Both micro-sprinkler and tubing emitters are found where plants like trees and shrubs will be in place for several years.

With annual plants it is more common to use drip lines where water delivery and emitters are combined. Emitters are built directly into the distrbution tube wall. Drip tubes with in-line emitters are the type used most often in vegetable fields where plastic mulch is in use. Tubes are usually placed a few inches below the soil surface, even under the plastic mulch. This keeps tubing in place instead of moving around as heat from the sun lengthens the tube, and it reduces the problems from thirsty rodents.


Drip tubing is exposed where the plastic mulch is cut and pulled back on these beds of staked tomatoes.

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.
Drip and other micro-irrigation systems often require complex distribution and control systems. Although the slow drip of emitters and weak streams from micro-sprinklers give the appearance that little water is being applied, a quick calculation shows the combined application of emitters to a field or orchard is quite large. For example to apply as much as 0.35 inch of water a day during peak use times would require 6.5 gallons per minute for each acre, and the pump would have to run all day and night. For a 50 acre orchard, this would mean pumping continuously at 325 gallons per minute. Water pressure would have to be carefully managed as pressure is stepped down from pump operating pressures to the 10 pounds per square inch that drip and distribution tubes require. Because water pressure decreases as it travels along the drip/distribution tubes, the length of these drip tubing sections must be considered. The result of these hydraulic considerations is that each drip system must be carefully engineered and installed to operate effectively. Usually zones - smaller field or orchard areas - are irrigated separately. This allows for down time of pumps and infiltration and drying cycles for soils. Electronic controls allow swithching between zones and they control the length of time each zone is irrigated.

In most vegetable applications, drip tubing, and plastic mulch, if used, are replaced with each crop. When possible some farmers retain the mulch and drip tubing for two cycles, often when one vegetable crop is planted in spring and a second planted in mid-summer for fall harvest. Most of these reuse applications are on high value vegetables that are planted by hand or manually fed planters. The drip tubing can last longer than a single crop or year, and equipment is available to extract, roll up and reuse it. However, gradual damage from rodents and insects, tears caused by planting or staking, and clogging of emitters eventually reduce the drip tubing's utility. Rather than face non-uniform irrigation or high labor costs for drip tube maintenance, most growers will discarded tubing annually. Disposal of plastic is often a problem for drip irrigated fields, although recycling of plastic materials is now reducing the long term impact of plastic wastes.


Eggplant (above), tomato and pepper are among several staked vegetables grown under plastic mulch and irrigated by drip systems.
Subsurface Systems

Subsurface drip irrigation (SDI) is one form of micro-irrigation that can be used in row crops.With SDI, a drip tube with in-line emitters is buried to depths of 8 to 16 inches. Because of the weight of soil on it, tensile strength needed to pull it down deeper with installation equipment, and expectation of many years use, heavier weight, more expensive, drip tubing is used for subsoil applications than typical for drip tubing installed near the surface. To keep emitters and tubing clear of bacteria and algae and debris pumped from water sources, a flushing system and careful operating regimen is required. As with other drip applications, water filtration, irrigation zones, manifolds distributing to zones, valves, and controls are necessary. However, the costs of supplies and installation are amortized over a life expectancy of 10 to 20 years. In orchards one or more lines are used with each row of bushes or trees. In typical applications for row crops, one drip line is placed midway between two crop rows, with every other row middle empty. Roots from plants adjacent to the drip rows get their water from the nearest drip line. Most deep-rooted crops - corn, cotton, peanut, soybean, etc. are suitable candidates for SDI. While SDI has been installed in the past in orchards and other places with permanent crops, many have failed as roots intrude the emitter openings. Although herbicide treated plastics can be used to slow this intrusion, long term applications may best avoid SDI.

Subsurface drip usually requires installation of buried laterals to which subsurface drip tubes are attached. Controls for each zone include pressure regulators, and filters plus timing circuits are required for the entire field. Once installed only controls and flush valves are above ground and they are usually outside of the crop areas.
The real strength of SDI for row crops is that small and irregular shape fields common in most of Georgia's Coastal Plain can be irrigated efficiently. No water is lost to direct evaporation. These factors make SDI effective in fields where center pivots are impractical or too expensive. Despite these advantages, SDI has not been adopted much in Georgia. Because tubing remains in the field, deep tillage needed to loosen compacted soils is limited. This can be mostly overcome by precision guidance and steering now becoming available on many farm tractors. Tubing is placed by quidance equipment, and subsequent deep tillage is limited to areas between the tubing. However, small farms that might benefit most from SDI are the least likely to have precision guidance equipment. Perhaps even more limiting is the inability of SDI to wet the soil surface. While established plants have no problem reaching water from SDI tubes, seed zones can be too dry in some planting conditions. Emergence may be uneven or delayed, and herbicides needed to control weeds until the crop is established may be ineffective. With other irrigation systems, emergence may be aided by one or more light irrigations just before or just after planting. Even the inherent water application efficiency can be doubted. Although no water is lost to direct evaporation, water can drain out of the root zone if time and duration of irrigation are not matched to soil conditions and plant needs.


Sweet corn (above), snap bean, onion, and other vegetables may be produced in large fields irrigated by center pivots.
2008 CES Survey Irrigation Systems
Average field size and number of systems statewide


Portable Pipe24 ac243 systems
Solid Set45 ac642 systems
Cable-tow traveler56 ac1193 systems
Hose-reel traveler62 ac243 systems
Center Pivot *90 ac13,010 systems
Drip & Micro56 ac1630 systems

* Recent statewide mapping of irrigation in Georgia has confirmed more than 15,000 center pivots
Hook, et al. 2009. Georgia Water Resources Conference.


Last updated 6/01/2009 James E. Hook