0 Irrigation of Sports Turf

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Irrigation of Sports Turf

By Rob Lucas, Reaseheath College, Cheshire.

Module: National Diploma Sports Turf (Turf Irrigation & Drainage)
Module Tutor: P Sharples
Submission date: 15th May 2004
Marks Awarded: Merit

Introduction

For this assignment I was required to write about irrigation systems used on golf courses, the first task is an explanation of the component parts of an automatic pop up irrigation system. The second task is an explanation of the factors involved and the importance of best management and correct scheduling of irrigation water with timing and frequency, record keeping and an example of record keeping given. The third task is an explanation of how to go about gaining an extraction licence for irrigation water. The fourth task is an explanation of the common problems with pop up irrigation systems.

Firstly I researched irrigation systems, I used books I found in the college library and my lecture notes, I used brochures I collected from the Harrogate Turf Show for my pictures and appendices. I searched the internet to find information regarding the extraction licence. Before I started the assignment I thought the assignment was a good one, I could see how it would make me more knowledgeable about irrigation systems.

The grass plant uses water to survive, the plant absorbs the water when in the soil and through its leaves and stem entering in liquid and vapour through the epidermal cells rather than the stomata. The majority of the absorbed water is taken in by the roots. The roots have root hairs, these root hairs increase surface area so more liquid can be taken out of the soil. The amount of root hairs increases as the soil gets drier. The grass plant must continually absorb water because it can't hold it for along time.
Only 1-3% of the absorbed water is used in metabolic processes, water is lost through evapotranspiration. Evapotranspiration is a mixture of the words evaporation which refers to the loss of water from the soil, and transpiration which refers to the loss of water from the plant, the stomata which are on the underside of the leaf are responsible for transpiration. They close up in darkness and light causes the stomata to open, when the stomata are closed evaporation occurs from the epidermal cells of the plant. Evapotranspiration is influenced by:

1/ Light intensity
2/ Temperature
3/Atmospheric vapour pressure
4/ Humidity
5/ Wind
6/ Water absorption rate
7/ Soil moisture tension

Because natural rainfall can't be relied upon for irrigation, golf courses are designed to use an irrigation system to provide water. The irrigation system can be turned on when no rainfall is occurring naturally, doing this stops the plants wilting and loosing rigidity and elasticity. It is a very important tool for turf maintenance especially in summer when no rainfall can occur for months.

The term field capacity refers to the maximum amount of water that a soil will hold against the force of gravity. At field capacity the soil stops loosing water to drainage and no evapotranspiration loss has occurred. It is the ideal amount of soil moisture for the grass plant to grow in. Water is only available to the plant when the soil is at or very close to field capacity, to reach FC the soil must be saturated, when a soil is saturated all air pores are full of water, the excess water soon drains out of a sandy soil. When at field capacity all small pores are full of water and the large pores contain air with water residue over the particle surface. When a soil loses a lot of its water from evapotranspiration most of its pores fill with air, this stage is called permanent wilting point, the plant can't use the water because it is held too tightly. If the soil becomes any drier the soil is air dry, in air dry soil there isn't enough moisture for a plant to survive. An important term for irrigation is soil moisture deficit, this is the amount of water required to restore the soil to field capacity. (P. Sharples 2004)

Task 1- Parts of an Automatic Irrigation System:

Pump System
The pump system pressurises the water and extracts it from a lake, pond, underground stream etc.

The various pump types are:

  • Centrifugal pump, this design takes in water using a rotating impeller, speeds up the water via a centrifugal force and discharges at specific flow and pressure.
  • Submersible pump, found in underground aquifers, less efficient than centrifugal due to small size and cost more in servicing and repair costs because must be removed from underground location.
  • Vertical turbine, is the most efficient type of irrigation pump and requires the least maintenance but is the most expensive.

Pump Controls:

Controlled by pressure switches and limit switch on the pressure regulating valve. The limit switch signals when the pressure regulating valve is opened or closed. When the limit switch senses no flow the pump system is shut off, a drop in pressure activates a jockey pump which increases pressure. The main pump turns on and off according to various pressure points. A different control type is computerised with a programmable logic controller (PLC). It uses pressure transducers and flow meters installed on the discharge manifold. The computer decides which pumps should be on or off and monitors the safety circuits, it can display information on a user interface display.
The most energy efficient control is using variable frequency drive (VFD). VFD's control the frequency of the electricity going to the pump motor, which increases or decreases the power of the motor. Controlling the power of the motor allows the discharge pressure from the pump system to be constant, other controls have to have a pressure regulating valve to do the same thing. With VFD the electricity bill is lower because it is more efficient and is less damaging to the pipes because there are less surges from pumps turning on and off.

Safety monitoring on pump system:

  • Phase, incoming power monitors voltage.
  • High and low pressure, for possible pipe burst pumps shut down so no more damage is done.
  • Low water, used in underground water supply such as wells, pump is turned off when water level gets below a set level, it stops pumps pumping air which would damage seals.
  • Loss of prime, protects centrifugal pump from pumping air by sensing water pressure on suction side of pump is too low.
  • High temperature, the flow of water cools the heat caused by mechanics, when no water is flowing the temperature rises very quickly.
    (Barrett et. al. 2003)

Valves:

  • Pressure relief valve is a safety device which protects the piping system from high pressure, it senses the pressure in the pump system and if pressure is too high the valve opens so no damage is done, the opening pressure is usually 15psi.
  • Mainline isolation valves, responsible for shutting down the entire irrigation system, positioned at the water source and on the mainline. Used when the system needs to be repaired or serviced.
  • Lateral/Sub main isolation valves, responsible for shutting down sections of the irrigation system, so damage can be repaired, they isolate remote control valves.
  • Air release valves, eliminate trapped air from pipes, positioned on the high points of the irrigation system mainline.
  • Drain valves, used to empty water from the system, needs to be done for winterisation, service and repairs. Drain valves are fitted to underside of pipelines are accessible via a valve box and reach tube they are manually operated. Water must drain away from course so valves must be located for water to do this, gravel sumps can be used. Positioning drain valve between two mainline isolation valves gives a lot of flexibility because parts of the system can be drained separately.
  • Check valves, allows water to pass through pipes in one direction, prevents damage from flow reversal.
  • Remote control vales, electric or hydraulic, allow water to flow through to activate a sprinkler or a group of sprinklers. Manual isolation valves are installed upstream of each valve so servicing is easier.
  • Quick coupling valves, used to connect aboveground sprinklers or hose to belowground pipelines, also used to flush pipes, drain pipes and for air to escape when empty pipes are filled with water.
  • Valve boxes and reach wells, provide a home for valves protecting them and making them easily accessible for use and servicing.
    (Barrett et. al. 2003)

Pipes:

The most used material for piping is PVC and polyethylene (PE). They are used because they resist corrosion and chemicals, have a high tensile strength, light weight, long life, good at insulating, smooth inside of pipe, easy to install. The thickness of the pipe shows how much pressure it can take, also the diameter of the pipe shows how much pressure it can take. The amount of pressure pipe can take decreases as the diameter increases, thick pipe can take more pressure than thin pipe. PVC pipe is available in a range of lengths with a gasket joint or solvent weld ending. PE pipe is more flexible than PVC which makes it easier to work with it is also more tolerant to freezing water and resistant to UV light so can be used above ground.

Fittings:

A fitting is a connection to a pipeline, there are lots of different connections such as:

  • Connection of different piping materials, use a deep bell push on or gasket fitting.
  • Connection of pipes of same size, use a solvent weld or threaded fitting
  • Pipes of different sizes, use a deep bell push on gasket fitting
  • Different components to pipelines, use a saddles fitting
  • Changing direction of pipeline, use a deep bell push on gasket fitting
    (Barrett et. al. 2003)

Swing Joints:

A swing joint is used to connect a sprinkler or quick coupling valve to the piping system. Its purpose is to protect the pipeline from damage caused by maintenance equipment, it is height adjustable so allows the pipes to be installed at a range of heights. Made out of PVC, made to withstand 1000psi without leaking, they are attached at an angle of 30 to 45 degrees.

Sprinklers:

A sprinklers job is to water its diameter of throw uniformly, golf course sprinklers pop up from the ground when turned on and go back down when turned off, this is so mowers can work over not around them.
The sprinkler consists of a rotating head and a fixed casing which is attached to the swing joint. Old design sprinklers are called impact sprinklers, the force of the water coming out of the nozzle hits a spring loaded swing arm which makes the sprinkler rotate, they are made from cast bronze. They can rotate a full 360 degrees or be adjusted to rotate less than 360 degrees, one or two nozzles can be used per sprinkler it depends on the required diameter of throw. A short throw can be made with a single nozzle, a large throw must have two nozzles one for long range and the other for short range. A long throw with only one nozzle would provide poor water coverage because there is not much water being delivered to the grass close to the sprinkler.

Modern sprinkler design is called gear drive sprinklers, (see appendix 1) they work by using gears and turbines in the sprinkler casing which converts the water entering from the pipe into a rotational force which turns a casing containing the nozzle. They also can rotate fully or be adjusted to turn only 30 degrees. The gears are protected in oil or water filled casing. Impact sprinklers are made in only one size and shape, gear sprinklers are made in several sizes from small to large, smaller ones provide a radius of 30-50ft, larger ones provide a radius of up to 115ft.

Many different nozzles are available, (see appendix 2) each has its own radius of throw and flow rate at a certain pressure. The nozzle size and pressure determine the gpm (gallons per minute) output of a sprinkler. The largest sprinklers can have a gpm of 65.
Nozzles are colour coded so can be easily identified, the top of the sprinkler shows the colour of the nozzle, number or size and direction for easy identification.
The gpm rate is important data because it is used to calculate how long the sprinkler needs to be turned on for with regard to field capacity.

It is possible to run a single sprinkler or a group of sprinklers, single sprinklers are operated by electric valve in head (EVIH), the valve is run by a solenoid which is also an electronic device.
A pressure regulator is fitted to the sprinkler so the correct pressure is maintained, the pressure is preset by the manufacturer but can be changed on the course by adjusting a regulator spring located in the pilot assembly and by a screw on top of the sprinkler. Pressure settings are 60,65,70,80,100 or 120 psi, a selector switch allows the sprinkler to be turned on manually the switch can also be used so the sprinkler does not operate electrically, otherwise it will operate from the solenoid.
Sprinklers are designed so valve parts and electrical components are serviceable without having to remove the sprinkler casing from the ground, snap rings allow the internal drive, nozzle and lower valve to be lifted out form the casing. Pressure must be shut off before doing this to prevent injury.
Hydraulic sprinklers are available (HVIH) hydraulic valve in head, they are very similar to the EVIH they don't use the solenoid instead use a hydraulic module which activates the control valve. The whole sprinkler is a closed case which seals any debris from entering the sprinkler, a debris screen is accessible from the top of the sprinkler and can be cleaned and replaced in case the casing gets damaged. Pop up height can be adjusted from 2cm to more than 10 cm, this allows nozzle clearance over long grass.The old impact design can be replaced with the modern gear design without having to excavate down to the swing joint, gear drive retrofit can be fitted inside the impact casing.

Control Systems:

Computers control modern irrigation systems, before modern technology sprinklers were turned on and off manually, so modern technology has made golf course irrigation much simpler and given a greater range of control.
A PC allows greenkeepers to store and use schedule and program information, this information is then passed on by the PC to field controllers or a decoder system.
Field controllers are located on the golf course, they communicate with the central controller (the PC) by underground cable or radio. A field controller has 5 components: (see appendix 3)

1/ Face plate, data is entered and viewed here
2/ Outpost terminal strip, this accepts the value field wiring
3/ Transformer, it turns high voltage from the power supply into a reduced level of voltage which can be safely used for the electrics and valve solenoids
4/ Enclosure, made of plastic or metal it protects other parts.
5/ Communication with central controller, an antenna for radio control or a communication module for underground cable.

Field controllers (see appendix 4) can also be used to activate sprinklers, without the command coming from the central controller first, a digital screen displays information about programming such as run times and operational status. To prevent water run off several light applications instead of one heavy application can be programmed with the FC, faults are displayed on the faceplate, the FC automatically sends messages back to the central controller about which sprinklers are operating and fuse status.

In a decoder system all parts are underground, better than having field controllers if vandalism is a problem or members of the golf club think FC's look bad.
Basically a decoder is a circuit board located in a valve box or close to the valve it is to activate, each decoder has an individual address but share communication paths. When the decoder is activated by the central or FC it turns the sprinkler on or off by opening or shutting the valve.
A decoder can be a single address or multiple addresses, multiple addresses have up to six addresses, multiple solenoids per address is another option so a decoder can be used to control several individual sprinklers.
The decoder accepts power and signal from the communication wire, its output goes to a solenoid, so it is a bridge between communication and solenoid. The communication wire runs to the central or field controller, it is possible to have an irrigation system which uses both the field controller and decoder systems in the same system. Each decoder address is recognised by the central controller so each decoder can be identified, operated and monitored, the central can trouble shoot the entire decoder system, it tests for electrical operation of every decoder and solenoid and reports if each are functioning correctly.

Remote Control:

Radio remote control allows greenkeepers to turn sprinklers on and off by using a hand held portable radio, data stored in the field or central controller can be accessed and activated, the features of radio remote control are:

  • Central base receiver, this receives commands from the portable radio sends commands to the central controller, which sends commands to activate sprinklers, it is located with the computer.
  • Portable radio, it has a keypad so commands can be translated and understood by computer. Can turn sprinklers on or off with a selected run time, pause and resume, can turn programs on or off.

The central records water use which occurred from commands send by the portable radio so accurate water usage records are kept.

Pocket PC Remote Control:

This technology allows the greenkeeper to view a map of the irrigation system overlaid onto the golf course. Individual sprinkler locations are marked on a map showing tees, fairways, rough, bunkers, water hazards, out of bounds and greens. They are basically a PC in the palm of your hand, irrigation system information can be downloaded onto it from central controller, also information gathered while using it on the golf course such as adjustments to run times due to shade, soil type, compaction and slope can be saved and uploaded to the central controller at a later date. The pocket PC communicates commands to turn sprinklers on or off with radio, the commands are sent to the central which activates the sprinklers, when the sprinklers have been activated their locations on the map start flashing to show that the command has been successful. (see appendix 5)

Weather Stations:

The irrigation system requires an on site weather station to record:

  • Wind speed, done by anemometer records in mph and a vane which records direction.
  • Air temperature, done with a temperature and relative humidity probe records in Celsius and farenheight and % humidity.
  • Solar radiation, done with a solar pyranometer.
  • Rainfall, done with a tipping bucket rain gauge.

The data gathered is used to work out the evapotranspiration rate (ET), the ET is the most important piece of data when scheduling irrigation because it shows how much water has been lost so helps greenkeepers decide on how much water needs to be put back. The weather station automatically calculates the ET rate, this data can be downloaded to the central controller and used from here. (see appendix 6)

Lighting Protection:

Irrigation systems get damaged by lightning because there is a lot of metal wire underneath the soil which attracts the lightning.
There are two types of protection available for golf courses the active and passive systems.
The active system reacts to the threat of lightning, it senses the lightning using radio waves and disconnects the central controller, field controllers, pump station and weather station from all attached wires such as power source and communication cables. Wires are automatically reconnected when threat is over, the detection device is placed in the same building as the central controller.
The passive system reacts to the effects of lightning when it has entered the wiring, a surge protection device is placed with the communication cable and power supply cable, it is connected to an earth so can direct lightning to safety. (Barrett et. al. 2003)


Task 2 - Best Management & Scheduling of Irrigation Water

Timing & Frequency:

Barrett et. al. (2003) states that to properly schedule irrigation timing and frequency to prevent run off and puddles, the intake rate of the soil is important. Intake rate is calculated by soil texture, soil structure, turf cover and thatch. A sandy textured soil which has the ideal mix of 50% soil, 25% water and 25% air will have a high intake of water, but a clay soil which is compacted will have a much lower intake of water. Turf cover and thatch decrease the intake rate because they are barriers between the soil and atmosphere.
Therefore a soil with a high intake rate will need to be irrigated heavily and frequently to keep it at field capacity and a soil with a low intake rate would need to be irrigated lightly and infrequently. Rainfall which has fallen effects the scheduling because it reduces the need for irrigation water, a lot of rainfall means no need for irrigation until the soil is less than field capacity.


Record Keeping:

Weather records can be kept by recording data from weather stations, tension meters (a probe which is in the rootzone it records the tension of the soil to show how much water is in it), weather web pages such as weather.com, the met office can provide data about evapotranspiration rate for specific locations in the country. Soil moisture deficit sheets can be used to record precise amounts of rainfall, irrigation, evapotranspiration, daily loss or gain and soil moisture deficit of the rootzone for any day of the year. The weather station is the best way to record the evapotranspiration rate, the data can be sent from the weather station directly to the computer, it is the most accurate method because the weather station is located on the golf course.
The purpose of record keeping is to find out how much irrigation water is needed, the best way is to use an on site weather station to provide data on rainfall and evapotranspiration rate, this data can be recorded in a daily water balance sheet to calculate the daily soil moisture deficit of the rootzone, the soil moisture deficit shows how much water is needed to restore the rootzone to field capacity.

The following page shows a water balance sheet for July 2004, irrigation is done to keep a low soil moisture deficit.


Task 3 - Extraction Licence for Irrigation Water

England and Wales have extraction licence for irrigation water controlled by the Environment Agency (EA), it is responsible for making sure water resources are managed in the correct way. It is a law under the Water Resources Act of 1991 to obtain a licence from the EA to take water from a surface or underground water source. In Scotland there are no abstraction licences in existence.
An abstraction licence gives the holder a right to take water from the stated source every year, until the licence expires or until the holder wishes to give up that right by cancelling the licence. A licence guarantees that no one else who would require a licence can lawfully take the share of water allocated to the holder.
The licence states:

  • How much water can be taken.
  • What the water can be used for.
  • The land where the water can be used.
  • The name and address of the licensed abstractor.
  • The duration of the licence.
  • The source of supply.
  • The means of abstraction.
  • Conditions to protect other interests and the water environment.
  • The means by which abstraction is measured and records kept.

How to get an abstraction licence, applicants must be the occupier or prospective occupier of the land on which the abstraction point is located, a right of access may be adequate. First the Environment Agency must be contacted, application forms will be sent and returned, a decision on the success of the application and the conditions to which it may be subject is usually made within 3 months, all applications will need to be advertised in the local press and London Gazette before being submitted.
When land is sold the new owner may use the abstraction licence, the EA must be informed within 15 months of occupation, if not the licence is cancelled.

Charges for an abstraction licence, there is a fixed application fee for the EA's work, also licence holders pay an annual charge based on the amount of water licensed for extraction, the source of water, the time of year water is taken and the purpose the water is used for.
(www.waterexchangeuk.com) accessed 22nd May 2004.

Task 4 - Common Problems with Irrigation Systems:

There are many problems with irrigation systems, most problems stem from surges in pressure, these surges cause pipes, seals and fittings to burst. Pipe work is also damaged by maintenance machinery, aeration is a common cause of damage, if the aeration is done too deeply or the pipes have not been set deep enough pipes will get damaged. Sprinklers are commonly damaged by aeration, it is easy to damage a sprinkler because it is on the surface. Incorrect installation of the pipes can make they easily damaged, if they are installed too low they get damaged by machinery, if the fittings and glue is not done correctly the pipes are more susceptible to surge damage.

Soil particles can get into the irrigation system, eventually they get into the sprinklers which blocks the nozzles, so there is a disruption in sprinkler performance. The cause of the problem is a faulty filter when the water is taken from the water source.

Because the computer side of irrigation systems is so complicated there is a lot of opportunity for problems. The computer can become damaged by computer virus, this may cause a complete shutdown of the irrigation system. As there are thousands of wires there are a lot of problems with faulty electric circuits, the electric circuits get very badly damaged when there is a lightning strike with no lightning protection. Corrosion can happen on metallic parts of the system because metal gets damaged by the weather and being underground. The valves are important to the irrigation system because they control the flow of water and set the correct pressure and release pressure. There are many valves on an irrigation system, a common problem is for these valves to become faulty, when a valve becomes faulty the pressure is too high or too low which pits stress on the pipes. Sprinklers will not work correctly if their valve is faulty.

The pumps can be damaged because they are under a massive amount of stress with the work they do, parts of the pumps can become faulty with overuse which may cause the whole pump to stop working.

The weather station can cause problems if it becomes faulty and produces incorrect data which leads to an incorrect calculation of the evapotranspiration rate. The instruments to record the weather such as the wind vane and solar pyranometer can be damaged by corrosion and faulty manufacture.

Repair methods:

  • Burst pipes and seals are difficult to repair because the location of the burst must be found which is time consuming, then the pipe must be excavated from the ground which is also time consuming and a lot of damage to the turf is done. When the pipe has been found it must be replaced, the section must be shut of with the appropriate valves and fully drained.
  • Filters on the water source may need to be cleaned or replaced if soil particles are getting into the system. Sprinkler nozzles are easy to replace as the whole sprinkler doesn't need to be excavated for this.
  • Problems with the computer hardware and software can be repaired by a computer technician, better virus protection can be purchased. Trouble with the wiring and weather station has the be repaired by a specialist from the irrigation manufacturer because it is very complicated.
  • The majority of valves are underground so repairing these has similar problems associated with repairing pipes.
  • Pumps are very complicated so a specialist may need to fix these also.

Summary:

From doing this assignment I increased my knowledge of the parts of an irrigation system, I already had knowledge of sprinklers and how they operate however I had little knowledge of valves, pumps, lightning protection and control systems. I learned a lot in the second task also, I now know the most effective time and the correct amount of water to apply thanks to researching timing and frequency and the water balance sheets. I had no knowledge of extraction licence's, now I could apply for one if I needed to. I am aware of the common problems with irrigation systems and how to repair them.
I will use this assignment as a reference in my future career as a greenkeeper, irrigation systems are very complicated so having this assignment will be a help when I forget some of the information.


BIBLIOGRAPHY

Barrett J, Vinchesi B, Dobson R, Roche P & Zoldoske D., 2003., Golf Course Irrigation : John Wiley & Sons

www.waterexchangeuk.com

Sharples P, 2004 lecture notes

OCMIS 2003 Trade Brochure

Toro 2003 Trade Brochure

Rainbird 2003 Trade Brochure

Hunter 2003 Trade Brochure













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