Grass Roots Irrigation

The Grass Roots irrigation system is divided into two distinct irrigation methods. The sections labelled ‘A’ are irrigated by sprinklers, with the remaining sections watered by three different types of sub-surface, or underground, drip irrigation systems. Each of these systems are run and monitored separately.

What is Sub-Surface Drip Irrigation?

Traditional drip irrigation is found above ground. Now with the invention of sub-surface drip irrigation or SDI, drip lines can be buried 10-20cm below the ground. Sub-surface drip irrigation applies water and nutrients directly to the root zone of plants through small holes in the drip line called emitters. This allows the user to manage and optimise water use. The depth and placement of drip lines depends on the soil and need of the plants being irrigated. Water spreads through the soil, forming a uniformly wetted area.

There are several types of SDI products available, three of which are being used for the Grass Roots project.

Irrigation Methods

Sprinklers

Sprinklers have traditionally been the most common method of irrigation in Canberra. In order to establish the most efficient watering schedules using a sprinkler system, a commercial, low profile pop-up sprinkler was selected to irrigate Section A of the project site.

Section A includes a control area that is irrigated to a schedule that reflects a watering regime commonly applied turfed areas in Canberra. The rest of Section A is irrigated using a schedule that will apply less water to the various turf varieties in order to determine minimum watering requirements using sprinklers.

Sprinklers have been spaced 'head to head' 15 metres apart, so that the distance reached by one sprinkler hits the housing of the adjacent sprinkler. This assists with irrigation efficiency, especially in times of high wind.

Full circle and part circle sprinklers have been grouped into separate valve combinations, each with identical nozzles. When the sprinklers are scheduled for irrigation, the full circle sprinklers run for twice as long as the half circle sprinklers, resulting in the same volume of application.

Sub-surface In-Line Drip Irrigation

Sections B, E, F, G and H have all been installed with an in-line drip product at a depth of 125mm. The drip lines are spaced 40cm apart, with drippers emitting 2.4 litres per hour (l/h) spaced at 30cm to provide the various turf sections with a total wetted root zone.

This type of in-line drip system is protected from root intrusion by emitters that are impregnated with a herbicide. The herbicide is slowly released to prevent root growth around the emitters.

Each section of the oval installed with this product will have varying irrigation schedules and application rates to establish the minimum watering requirements for each turf variety using this irrigation method.

Sub-surface (Wrap) In-Line Capillary Irrigation

Section C has been installed with an in-line capillary irrigation system (CIP). Whilst the flow rate and spacings are the same as the in-line drip system, this product is wrapped in a specialised fabric that enhances the lateral spread of water in the soil.

So in the case of in-line drip systems, wet circles of soil are formed around the emitters. A capillary system wets the fabric along the length of the line, acting as one large emitter wetting a larger volume of surrounding soil using the same volume of water.

Sub-surface (Flat) In-Line Capillary Irrigation

Within Section D is another in-line capillary irrigation system. This product uses 1 l/h emitters spaced at 20cm along the drip line and is also covered with fabric on the upper side to increase the lateral spread of water in the soil. This allows the drip lines in this section to be spaced at 60cm as opposed to 40cm.

What distinguishes this system from other products is a flat polyethylene strip attached to the underside of the drip line. This prevents the downward movement of water away from the root zones.