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Irrigation Introduction

Even though a quality irrigation system may seem to be expensive, it is probably a golf club's most important single purchase other than the land. Because the entire golf operation depends on this system, it is critical to stress that the irrigation system be designed and installed properly.

An irrigation system should not be considered an expense. Rather it is a long-term investment in healthy green grass and is as much a part of a top quality golf course as the architect's design and construction of the course. Further, a quality irrigation system has lower long-term costs because of less maintenance and repair and greater irrigation efficiency.

Selecting the right irrigation system for a golf course need not be as complex as the task may appear. A multitude of factors must be considered: terrain, climate, course design, types of grass, operating labour requirements, and others, including cost. But if properly done using a systematic approach, the task can be accomplished much easier.

Seven Key tasks of a Quality Irrigation System

It grows healthy green grass where required.
It results in a course that looks good and plays well.
It irrigates outside of playing hours and does not interfere with play.
It minimises long-term maintenance costs.
It minimises long-term maintenance problems
It accomplishes all the above for the smallest possible investment.
It conserves water and power, and extends the life of the pumping plant.

Guide for readily Available Moisture based on Feel or Appearance of Soil

Percent available moisture remaining	Loamy sands and sandy loams (coarse textured)	Very fine sandy loam and silt loam (med. textured)	Silty loams and clay loams (fine textured)
0 - 25	Dry, loose, flows through fingers	Powdery, sometimes slightly crusted, easily broken down to a powdery condition.	Hard baked, cracked; difficult to break down into a powdery condition.
25 - 50	Appears to be dry, will not form a ball with pressure.	Somewhat crumbly but holds together with pressure.	Somewhat pliable, balls under pressure.
50 - 75	Tends to ball under pressure, but seldom holds together.	Forms a ball, somewhat plastic, sticks slightly with pressure.	Forms a ball, ribbons out between thumb and forefinger, has a slick feeling.
75 - 100	Forms a weak ball breaks easily when bounced in hand.	Forms a very pliable ball, sticks readily.	Easily ribbons out between thumb and forefinger, has a slick feeling.
100 (at FC)	Upon squeezing no free water appears on soil, but wet outline of ball is left in hand; soil sticks to thumb when rolled between thumb & forefinger.	Same as sandy loam.	Same as sandy loam.
Saturated	Free water appears on soil when squeezed.	Same as sandy loam.	Same as sandy loam.

Guidelines for Interpretation of Irrigation Water Quality

Potential problem		Degree of problem
Potential problem		Problem	Increasing problem	Severe problem
SALINITY (affects crop water availability)
SALINITY (affects crop water availability)	Ecw (mmhox/cm)	<0.75	0.75 - 3.0	3.0
PERMEABILITY (affects infiltration rate into soil)
	Ecw (mmhos/cm)	>0.5	0.5 - 0.2	0.2
	adj. SAR	<6	6 - 9	9
SPECIFIC ION TOXICITY (affects sensitive crops)
	Sodium (adj SAR)	<3	3 - 9	9
	Chloride (meg/I)	<4	4 - 10	10
	Boron (mg/I or ppm)	<0.5	0.5 - 2.0	2.0 - 10.0
MISCELLANEOUS EFFECTS (affects susceptible crops)
	NO3N(NH4-N)(mg/l)	<5	5 - 30	30
	NCO3 (meg/l)(overhead sprinkling	<1.5	1.5 - 8.5	8.5
pH	Normal range 6.5 - 8.4

Refer to a qualified hydraulics engineer for design assistance.

Estimated Maximum Water Application Rates for Design

Soil groups based on texture and profile	Slopes* 0 - 8		Slopes** 9? - 12.5?		Slopes*** over 12.5?
Soil groups based on texture and profile	mm/h	in/h	mm/h	in/h	mm/h	in/h
Sands and light sandy loams uniform in texture to 1.82m (6ft) pumice	31.8	1.25	25.4	1.00	20.3	0.80
Sandy loams to 0.61m (2ft) overlaying a heavier subsoil	20.3	0.80	16.5	0.65	12.7	0.50
Medium loams to sandy clays over a heavier subsoil	16.5	0.65	12.7	0.50	10.2	0.40
Clay loams over a clay subsoil	12.7	0.50	10.2	0.40	10.2	0.40
Silt loams and silt clays	10.2	0.40	7.6	0.30	5.1	0.20
Clays	6.4	0.25	5.1	0.20	3.8	0.15
Peat	16.5	0.65	-	-	-	-

* 0 - 8? slope level to undulating.
** 9? - 12.5? slope undulating to low hills.
*** Over 12.5? slope low to steep hills.

NOTE 1 - The above figures are intended for guidance only.

Where detailed soil surveys and infiltration experiments have been carried out, or where reliable application rate data are available for a similar soil, the figures so established should be used.

NOTE 2 - For bare cultivation such as under tree watering, the above rates should be reduced by up to 50% (to avoid loss or damage to structure).

NOTE 3 - Lighter application rates should be used when fairways are being established.

NOTE 4 - In areas where very high evapo = transpiration rates frequently occur, when application rates below 6mm per hour, consideration should be given to -

(a) The practicability of designing the system from late evening through the night until morning when, generally, hot windy conditions that would adversely affect efficiencies will not apply; or

(b) The use of surface irrigation. If the topography is not suitable for surface irrigation, and it is not practical to restrict irrigation to night-time operation, due allowance should be made for water application efficiencies.

PVC Pipe Size & Classes

Size
15, 20, 25mm	Minimum Class E
32, 40mm	Minimum Class D
50mm	Minimum Class C
65mm and above	Minimum Class B	Not for turf use

PVC Pressure Pipe Classes

Class	Working Pressure			Marking Colour
B	600 kPa	60m head	87 psi	Red
C	900 kPa	90m head	129 psi	Blue
D	1200 kPa	120m hea	173 psi	Green
E	1500 kPa	150m head	217 psi	Brown
F	1800 kPa	180m head	260 psi	Yellow

Pipe Size	Maximum Flow at 1.6m/sec		Optimum Flow at 1.0m/sec
Pipe Size	Flow (l/s)	Headloss/100m	Flow (l/s)	Headloss/100m
25mm E PVC	0.97	9.30	0.60	4.00
32mm D PVC	1.65	6.80	1.05	2.90
40mm D PVC	2.20	5.70	1.35	2.45
50mm C PVC	3.60	4.20	2.25	1.80
65mm C PVC	5.70	3.15	3.55	1.40
80mm C PVC	7.90	2.60	5.00	1.10
100mm C PVC	13.00	1.90	8.10	0.82