| More than 10 years ago the Glen Eira Council put in a Motorola Irrinet centralised control system to computerise the watering of their public playing fields making it easier to manage their overhead sprinkler system and reducing the requirement for manual sprinkler management which was both water and staff intensive.
As water restrictions came into place technology was pursued further in an effort to further reduce water consumption and electric pulse meters were installed to measure
and manage water flow.
High and low flow expectations were able to be entered and in the event of these flows being greater than anticipated the station recording the anomaly would shut down within a minute and a message be sent via SMS to the irrigation manager. If more than 3 stations recorded an anomaly within 3 minutes the system would shut down until reset by the irrigation manager removing the incident of leaks and sprinkler ‘blow outs’ spouting water for hours on end.
Moisture sensors were installed at each of the grounds to identify when the watering systems needed to be activated to maintain healthy turf as well as minimising the incidence of over-watering.
Under 3a restrictions water authorities allowed only one in four playing fields and parks to be watered. In 2005 the City of Glen Eira, Victoria, decided to explore other options to minimise water use on its sports fields with a view to operating more efficiently on more grounds. They hoped that this ‘best practice irrigation’ approach would help them to secure a ‘bucket’ of water to enable them to water more area with the same amount of water they had used the year previously.
With potable water becoming scarce and restrictions becoming tighter, it appeared that drip irrigation may support the future for sports turf. They discussed the pros and cons of a conventional sprinkler system compared against subsurface drip irrigation (SDI) and felt that the advantages offered by SDI offered significant
water saving and management benefits.
Benefits identified included:
Watering efficiency of up to 99% – sub-surface drip systems radiate water throughout the soil profile, delivering water directly to the plant root zone.
Water savings of up to 50% in comparison to volume required for spray irrigation.
Ready for Recycled water – The ability to apply water sub surface provides an opportunity to use alternate water resources (i.e.: recycled water, stormwater, etc) and minimises the requirement for potable water.
No overspray therefore less staining, slippery surfaces and wasted water.
Less vandalism of watering systems as they are predominantly underground.
Even water distribution throughout playing field, no pooling and no sprinkler heads to trip over.
Reduced weed germination.
Reduced compaction of playing field.
The ability to irrigate while people are playing on the surface.
Fertigation through the drip tube making it easy to apply and ensuring less opportunity for chemical contact with the general public.
While at the moment SDI is still more expensive than traditional spray systems, the Glen Eira Council felt that with water savings, reduced maintenance and management costs along with less possibility of vandalism, the system would pay for itself very quickly. It would also help the Council supply high quality amenities to rate payers improving the general quality of life in the area. In 2007 Marlborough Reserve soccer ground was identified as a surface that required a complete reconstruction and could become a model of water conservation for future projects in Glen Eira and the State of Victoria.
A Netafim subsurface drip irrigation system was installed.
|
Glen Eira Council completed a comparison of two sites similar in soil structure and grass variety; Marlborough Reserve (SDI) and McKinnon Oval 1 (Above ground sprinklers). In the current climate, Glen Eira Council requires approximately 6-7 ML/ Hectare per annum to keep cool season turf alive during the summer. Gradually the existing turf varieties will be changed to warm season grasses, which will reduce these figures to approximately 4-5 ML/Hectare per annum, a total water saving across all their ovals of around 50 ML/per annum.
With current water prices of $1.22/KL it is equivalent to savings of approximately $61,000/year. By installing SDI systems in all grounds they estimate additional savings of between 30-40 ML/annum (up to $48,800/year). These savings will be amplified by any increases in water prices in the future.
Glen Eira Council will be changing sprinkler irrigation to drip line whenever any of the sports grounds are renewed or redeveloped. This approach to water management has helped redefine how water is allocated to sport grounds during water restrictions – rather than being on an oval basis, it is on a water volume basis effectively rewarding good irrigation practice.
Currently Glen Eira Council is able to irrigate 18 of the 43 playing fields, where previously only 11 could be irrigated with the same amount of water used the previous year. The results from the Marlborough reserve drip irrigation made it an easy decision for Glen Eira Council to decide to install a second Netafim drip irrigation system at Murrumbeena Park Oval 1.
The reconstruction at Murrumbeena Park was completed in December 2008. Murrumbeena Park Oval 1 will also recapture run off from the water and pump it into tanks next to the oval. The irrigation system will be connected to these tanks which utilising float
valves to monitor the water level.
When there is water within the tank system the irrigation will draw on the recaptured water held in these tanks. Once the tank float level registers that there is no water available within the tank system it will turn off and the mains backup will turn on and irrigate the oval utilising the potable water supply under the current 3a water restrictions. This tank could also be filled with recycled water fit for this purpose as an alternative water source.
During wet periods the oval drainage system will also capture excess water and store it within the tank system. It has been estimated that the process of rain water harvesting from the oval and recapturing excess irrigation water will save Glen Eira Council approximately 30% of their water allocation for this ground.
Glen Eira Council will continue to work in partnership with Netafim implementing sub-surface drip irrigation systems as the opportunities arise. It is hoped that eventually all 60 of the Glen Eira sports grounds will utilise drip irrigation systems to provide lush green sports grounds and water savings of between 30 to 60%.
Currently in the pipeline is a $30 million swimming pool complex for East Bentleigh where they hope to utilise recycled water from the pool complex to irrigate the surrounding 3.5 hectares of playing fields without utilising a single drop of potable water!
For further information please contact Terry Cole (Netafim Pty Ltd) on 0409 793 886 or tcole@netafim.com.au or Peter Todd (Glen Eira Council) on ptodd@gleneira.vic.gov.au
Extract from ReWater, a publication by Arris Pty Ltd. www.recycledwater.com.au
Terry Cole talks about the subsurface advantage.
|
