Irrigation systems have come a long way since the first sprinkler was developed around 1900. Today, manufacturers offer a diverse mixture of products that not only maximize your control of irrigation, but also advise you how to best irrigate grounds. Some products will even keep an irrigation record that you can use as a reference point. The simplest irrigation system is one designed for residential use that is made up of a controller wired to several valves and applies water for a set amount of time. This automated set-up makes it easy to irrigate precisely with little attention.
Golf course irrigation systems, however, are much more complex than residential for a couple of reasons.
Low mowing height. Greens are grown at “near death” height. As a result, irrigation management requires precise amounts and frequency.
Various water requirements. Greens, tees, fairways and roughs all water on different schedules.
High volume of irrigated area. Golf courses water as much as a couple hundred acres of turf.
With the demands of maintaining high-quality turf under various growing conditions over such a large area, a complex irrigation control system has evolved. This has given the irrigation manager tremendous control and flexibility of where, when and how much water is applied.
Let's look at the components that make up golf course irrigation systems and how they've developed.
Due to its size and complexity, the irrigation system acts like a network of controllers. Of this network, the central control is the brain.
The central control system is often located in the maintenance facilities and has control over every irrigation sprinkler on the golf course. The system is software driven on a personal computer that can turn on or off any sprinkler on the course. The irrigation manager can point-and-click a sprinkler to turn it on or off. Changes can be made to individual sprinkler runtime or global changes to entire programs with a click of the button. All activities are recorded for historical reference.
This software allows for a great degree of flexibility and management of irrigation scheduling.
Real-time activity can be monitored on any sprinkler that is operating.
Flow management can be monitored at the pump station to maximize the pump efficiency and reduce hydraulic stress.
On-site weather station data can also be recorded and analyzed (temperature, humidity, evapotranspiration rate, soil moisture) to adjust programs.
Central control is not connected directly to each sprinkler. Instead, it sends directions to sub-components (field controllers) that are directly connected to sprinklers. Once directions are received from central control, the field controller sends the message to the sprinkler(s) to turn on or off.
Field controllers are often referred to as satellites. They are usually contained in a waist-high, metal box that is mounted to a concrete footing and require 110 volts to operate.
Golf courses utilize valve-in-head sprinklers, meaning that within the casing of each sprinkler is a valve. This is different than residential irrigation, where valves are installed on the pipe and control several sprinklers. For valve-in-head sprinklers, the satellites, or field controllers, are wired to each sprinkler controlling the encased valve. They have a large capacity and can control as many as 50 sprinklers or more. The irrigation manager also can go directly to the satellite rather than central control to manually turn the sprinklers on or off. Satellites can also be used as a stand-alone controller without being connected to a central control system.
In electrical systems, when the satellite receives the order to turn on a sprinkler, it sends a 24-volt “message” down a 12-gauge wire connected to the sprinkler to open the valve (in-head).
An alternative to electrical is a hydraulic system, where the satellite utilizes small tubing pressurized with water rather than electrical wire running to each sprinkler. When the satellite is directed to open a sprinkler, the pressure in the tubing is reduced that signals the valve to open.
With either system, adding new sprinklers requires you to install new wires or tubing from the new sprinkler to the satellite.
Manufacturers are now releasing wireless rotary sprinklers that eliminate the need to run wire out to new sprinklers, making expansion much less intrusive, and also reducing the risk of lightning damage because there are no wires to conduct electricity from nearby strikes.
Central control-to-satellite communication
Once the program is set on the computer at the central control, it sends directions to the satellites. The computer does not communicate directly with satellites, but rather through an interface. This is often a simple-looking box that is wired into the computer. The interface interprets the instructions and sends them out. There are a couple of ways this is accomplished.
- One-way communication
This is an older generation of system communication. With one-way communication, instructions are sent to the satellite where they are carried out. However, there is no communication back to the central control. Therefore, there is no way for you to monitor activities or be alerted to problems.
- Two-way communication
This is the most current form of system communication that allows satellites and other components of the system, such as the pump station or weather station, to communicate with central control. There are a couple of ways two-way communication is carried out.
A dedicated, direct burial line is connected from the central control to each satellite, pump station, weather station and sensor. This is a feasible set-up for new construction, where you can sink the line in ditches, but is disruptive in cases of expansion or retrofit.
Telephone lines are used with modems located at central control and satellites. Once central control sends instructions, the modem dials the assigned number of each satellite modem to access it. This set up allows for remote access of the central control. An irrigation manager can dial-up the central control via modem at home and change programs or monitor activities.
This became the ideal option for upgrading irrigation systems because it requires no trenching.
Radio communication utilizes a transmitter at central control that sends out directions to satellites that are equipped with receivers. The central control is also equipped with a receiver for communications to be sent back from satellites.
Cellular communication operates similar to a hardwire telephone setup. A company called IrriDigital utilizes a nationwide wireless carrier as a means of communicating from central control to satellites. Confirmation messages can be sent back to central control or to a phone, pager or e-mail.
- Decoder systems
A system that has long been used in Europe and is now gaining acceptance in America is the use of decoders. In this system, there are no satellite controllers. Because satellites are very accessible, they are easy targets of vandalism. Decoders are small, weatherproof modules that are buried 12 to 24 inches below grade (ground?). The decoder contains a microprocessor that receives power (24 VAC) and control signals along a two-wire line directly from central control. Therefore, all communication with the irrigation system is done through central control. Each decoder has it's own identification number that is logged at central control. Future expansion is easy: just wire a valve-in-head to a new decoder that simply taps into the two-wire line.
In the past, the downside of decoders was accessing the irrigation system in the field when away from central control. This was done by using remote keyboards that could be plugged into access points along the two-wire line in the field. However, with the development of handheld remotes, communication with central control can be done from anywhere.
- Handheld remote controls
With the development of radio modem communication, remote access to the central control was created through a hand-held radio. This often comes in the form of a “walkie-talkie” with a keypad. The keypad is used to send instructions to central control to turn sprinklers on or off or make other adjustments to the system, while the radio can be used to communicate with others on the course. This gives the irrigation manager control of the system from anywhere on the course.
- Personal digital assistants (PDAs)
Manufacturers are now integrating PDAs into their central control systems. Connected to some form of wireless communication, they can offer easier control from the field. They also store changes that you enter while out in the field, which are transferred to the central control computer when you return to the office.
Weather stations and sensors
On-site weather stations have been around for a while, but the data they provide is becoming more integrated into central control irrigation. The advantage of on-site weather stations is getting exact conditions, rather than readings from the regional weather service. These can be greatly different with microclimate effects on humidity and temperature and especially rainfall. Some of the data that can be collected from weather stations include wind speed, rainfall, soil moisture and humidity.
Evapotranspiration is the total loss of water to the atmosphere through evaporation and transpiration (the loss of water from the plant). ET is at its highest during hot, sunny, low humidity conditions, and at its lowest during cool, cloudy, high humidity days. The most efficient irrigation practices only replace the soil moisture that is lost through ET.
Data can be automatically downloaded and utilized by central control to calculate evapotranspiration (ET). Some central control software can use ET values and rainfall to automatically adjust irrigation times to provide the most efficient irrigation practices.
- Sensor decoder
You can also use decoders with sensors in the same way you would use them with valves. You can connect soil moisture or temperature sensors to a sensor decoder so that data can be downloaded to central control.
Regardless of what type of control system you use, it's wise to also opt for storm protection. One of the most common damages to the irrigation system is a power surge that results from lightning strikes. Lightning can cause electrical surges to run through field wire and damage equipment and sprinklers.
Lightning protection systems can be installed to electrically isolate components of the irrigation system, such as central control, satellites, pump station and weather station. This will prevent damage whenever lightning is detected within a few square miles. Although this will not protect from direct strikes, it prevents the most common damage that results from surges.
Tony Bertauski is a horticulture instructor at Trident Technical College (Charleston, S.C.).
AS A MATTER OF FACT
The first remote controls were developed to operate military machines. The German navy developed radio-controlled motorboats that they used to ram enemy ships during World War II. During the war, bombs and some other weapons were also operated by remote control. After the war, scientists in the United States used this technology to develop nonmilitary uses for the remote control. They introduced remote-controlled garage door openers in the 1940s, and by the 1950s, they had developed the remote's most popular use — television remote controls!
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