Water Efficiency Through Turf Irrigation Management

City of Melville Western Australia

Synopsis

The City of Melville, a Water Campaign™ participant since 2004, has been progressively addressing water conservation through its irrigation practices in a water efficiency project that began in 1989.

Through this project the City of Melville has developed a wealth of knowledge and is recognised as a leader in irrigation management, winning the 2006 WA Water Award for Local Government Water Efficiency.

The City of Melville’s approach to irrigation management involves;

An Irrigation Asset Register which records information required to assign a water “budget” to each site.
Utilising an irrigation monitoring system to provide continuous weather and system performance data and adjusting the irrigation schedules for each site accordingly.
Utilising a number of other water saving initiatives such as soil amendment with flyash/soilwetting agent, stormwater substitution, water efficient species selection, drip and subsurface irrigation to reduce water and fertiliser use.
Carrying out comprehensive system performance monitoring at each site through - groundwater bore metering, flow testing, soil moisture monitoring, irrigation system audits, Enviroscan units, lysimeters and leaf tissue analysis to calibrate the irrigation monitoring system and allow adjustments to be made to the water and fertilising regimes.

: Weather Station Source: City of Melville

Motivation for Installation of Water Efficiency Measures

As with most local governments in the Perth metropolitan region the City of Melville utilises groundwater to irrigate areas of open space and playing fields.

In Western Australia, the current drying climate means that the amount of water being recharged to the groundwater aquifer is declining. In addition the widespread use of groundwater by commercial and private users has meant that groundwater levels are rapidly falling causing changes in wetland hydrological regimes, acid sulphate soils and saline groundwater intrusion.

Groundwater resources in Western Australia are regulated by the Department of Environment who set a sustainable groundwater allocation by local government area. Many local governments are close to reaching the maximum allocation and therefore need to look at using their water more efficiently in order to address these environmental problems and maintain the current condition of their parks and gardens.

It is for these reasons that the City of Melville has taken steps to ensure it’s irrigation systems are as efficient as possible.

Approach Undertaken

The City of Melville has adopted irrigation management practices which involve constant monitoring and feedback in order to adjust watering schedules to the specific weather and irrigation systems at specific sites. Irrigating to the specific requirements of the site reduces wastage of water. The City of Melville achieves through a number of processes outlined below.

: Installation of sub-surface irrigation Source: City of Melville

Irrigation Asset Register

The City of Melville maintains an irrigation assets register which contains the following information on each site;

Irrigated area (ha)
Source water type – bore, scheme or stormwater
Types of usage – active or passive
A rating of desired condition – gold (best condition for playing fields and highly visible areas), green or brown.Types of irrigation system – eg. sprinkler, drip or subsurface
The collection of this information provides an excellent way of assessing the required volumes at each site and which systems require replacement.

Irrigation Monitoring System

The City of Melville’s irrigation systems are controlled and monitored by a central control system. This system controls all watering scheduling for all sites via a weather station. This system was installed in 1989. Since 1994 this system has been replaced and developed to control 117 sites out of a possible 179 irrigation systems. The system measures and stores information on a number of parameters including site specific characteristics, weather data and the water consumption and performance of the system.

Amongst other functions the controller performs the following tasks;

Check it’s own communications and report failures back to the host computer
Examine and display each controller’s status and watering schedules
Collects and stores a range of weather data
Calculates the daily Evapotranspiration (E.T) value
Controls each individual site on an E.T. based schedule or a manual program (an application rate of 50-60% net pan evaporation is considered best practice1)
Adjusts the E.T. rate at each E.T. controlled site with the following input factors.
o Site water budget
o Default E.T
o Minimum E.T. value (estimates short nightly irrigation times)
o Maximum daily E.T. value (puts a “cap” on the E.T. to ensure programs do not run too long)
o Crop coefficients – to adjust for type of turf and seasonal changes
o Soil moisture-holding capacities
o Soil moisture refill percentages
o Soil infiltration rates
Measures the precipitation rate of each sprinkler block
Measures the flow rate
Cancels or pauses all programs automatically if certain specified rainfalls occur
Allows the operator to adjust the earliest and latest time the schedule will be allowed to operate

The controller can also provide graphical displays of weather data, system flow, pressure and amps.

The sensitivity of this system allows irrigation according to the exact conditions and requirements of the site ensuring the water is used as efficiently as possible and therefore delivering significant water savings.

Other Water Saving Initiatives

In addition to ensuring that turf areas are watered as efficiently as possible through the irrigation monitoring system the City of Melville has trialled and implemented a number of additional water saving initiatives.

Stormwater Use

The City of Melville waters 14.8 hectare over 4 reserves with stormwater from two water runoff or drainage lakes.

Soil Amendment

The City of Melville often use soil wetting agents and in some circumstances fly ash, for their retention properties.

Design

The City of Melville has utilised water efficient design principles, such as sub-surface irrigation and water efficient native plants.

: Lysimeter collection vessel Source: City of Melville

Monitoring

Aside from the constant monitoring occurring through the Irrigation Monitoring System a number of other monitoring techniques are used to test the system performance against a number of indicators.

Flow Testing

Flow tests are completed on all 143 bores and 154 pumps each year. This is a very important part of the monitoring program, as it provides an accurate record on the performance of each installation. The City of Melville uses this information to make informed decisions on the maintenance or replacement of these installations. This is an important part of the irrigation system as the system design can be very inefficient if the performance drops to such a level that it effects the uniformity with which the water falls across the irrigated area (coefficient of uniformity), therefore increasing the length of time the area must be irrigated in order to ensure all parts of the irrigated area receive enough water.

Soil Moisture Monitoring

The City of Melville has ten soil moisture probes around the City to monitor the total percentage of soil moisture each fifteen minutes throughout the day. Parameters are set to warn the operator when the soil moisture reaches a maximum or minimum level. These provide vital information on the volume and frequency of watering events that are sufficient.

Lysimeters

Lysimeters are also used in various locations with differing soil conditions to monitor leaching. These devices are able to determine whether fertilisers are leaching through the soil profile (and therefore possibly too much fertiliser is being applied). It is also used to measure the amount of water leaching through the soil profile (and therefore indicate whether too much water is being applied and not being used by the turf).

Leaf Tissue Analysis

Leaf tissue analysis reports are undertaken by a private company to enable the City of Melville to make informed decisions on the correct Nitrogen Phosphorus and Potassium to apply, to avoid over fertilizing the reserves. Monitoring is undertaken twice a year and recorded in a database for future use.

Irrigation System Audits

Audits are carried out on all reserves every year as a part of the winter maintenance program. This is a very important part of the maintenance schedule as it allows the operator to tune the systems to operate at their optimum.

Savings and Benefits

Reduced water and energy use and reduced nutrient leaching.

The Western Australian Department of Environment has set a sustainable groundwater allocation rate of 7500kl of water per hectare per annum for turf irrigation. From 1999 to 2008 the City of Melville has maintained their water use at an average of 11per cent below their allocation.

Costs

The City of Melville budgets over $413,000 each year to upgrade irrigation systems. There are ten staff directly involved in irrigation at the council.

References

Sports Turf Technology (2004) Final Report Irrigation Benchmarking Project (Unpublished)

ICLEI Oceania would like to acknowledge the assistance of Kelton Hincks and the City of Melville in the production of this case study.

For further information about this project contact:

Kelton Hincks
Facilities and Services Manager
City of Melville
Civic Centre 10 Almondbury Road
ARDROSS WA 6153
Tel: (08) 9364 0274
Email:kelton.hincks@melville.wa.gov.au

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