The Geelong Botanic Gardens were established over a century and a half ago. In 1851 land was put aside for what is now Eastern Park and the Geelong Botanic Gardens.
The Geelong Botanic Gardens has historic and contemporary landscapes and large plant collections. The surrounding Eastern Park is an arboretum, or tree collection. Both landscapes have different water requirements.
The Botanic Gardens conserves plants from around the world. This means that they all have different water requirements based on the climate where they come from. Plants grown in the 21st Century Garden and the Eastern Park Arboretum have lower water requirements similar to indigenous plants adapted to local dry climate conditions.
To maintain the gardens important plant collection in the best condition irrigation can use up to 28 megalitres of water per year. This amount varies depending on the rainfall and temperature- particularly over the summer months.
Drought and the Geelong Botanic Gardens
In December 2006, along with majority of the Barwon Region, we went from Permanent Water Saving Restriction to Stage 4 Water Restrictions. There are provisions in the Water Restrictions By-Law to apply for an exemption to allow the use of potable (mains water) for gardens open to the public. This exemption was granted to ensure the survival of this historical garden which includes heritage trees and scientific plant collections.
The 21st Century Garden has been developed with sustainable use of water in mind requiring very small volumes of water even in the driest times. Other areas of the collection such as the 1851 Garden require more regular volumes of water particularly over the hotter summer months. The gardens irrigation was reduced during Stage 4 restrictions to reflect the minimum amount of water that could sustain the garden.
The impact of the 10 years of drought (and several dry years since) has had a negative impact on many of the trees within the Botanic Gardens and Eastern Park. There are over 30 trees listed in the Significant Tree register that were supported through the drought with supplementary tank watering.
Water management and the Geelong Botanic Gardens
In 2011 the City of Greater Geelong was successful in being awarded joint funding from the Australian Government’s Water for the Future program. This funding was to develop a stormwater storage and reuse facility in Eastern Park to enable the reuse of treated stormwater on the Geelong Botanic Gardens as well as trees within the park when available.
The project was supported by the Eastern Park and Geelong Botanic Gardens Strategic Plan Master Pan, adopted in January 2008. This plan identified the opportunity for reuse of stormwater and the development of a dam on the existing site of the 1860’s Bunce’s Lake with the removal of one of the sporting ovals.
The aim of the project is to reduce the reliance on potable water in the Geelong Botanic Gardens by replacing as much as possible from the treated stormwater. For greater detail refer to the information page on the Eastern Park Stormwater Harvesting Project.
Stormwater is captured from the 47 hectare suburban area of East Geelong. The dam water is treated thru sand and UV filters which is then pumped to storage tanks with a 250,000 lt capacity situated within the edge of the Geelong Botanic Gardens.
Linked to this project was the need to replace the irrigation system within the Geelong Botanic Gardens to maximize any water applied on the Geelong Botanic Gardens and in particular the treated stormwater.
The irrigation replacement was scheduled over a 4 year period commencing in late 2013. Detailed analysis of the soil, plant water requirements, impact of soil disturbance, and best practice for botanic garden irrigation was undertaken before the detailed design was developed.
Where either staff or members of the community have potential to come into direct contact with spray from water, potable water is used at all times. These areas include the nursery, glasshouses and the cool temperate rainforest. Unless we’re testing the system we water at night which minimises exposure and maximises water application.
Best practice principles are used in scheduling and managing the computer controlled weather-based irrigation system. The onsite weather station feeds the most current climatic conditions into the central controller to ensure effective irrigation. Factors such as soil-water holding capacity, rooting depths to maintain plant health and climatic conditions are all considered. Efficient irrigation scheduling means that the right amount of water is applied to the right time.
How the water is applied to garden beds and lawns varies depending on the individual plant requirements. The different methods include spray irrigation, hand watering and drip irrigation.
Horticultural staff at the Geelong Botanic Gardens have been trained in efficient irrigation management and best practice principals of water management for the gardens. Programmed regular independent water testing is conducted to ensure the treated water is “fit for purpose” and safe for reuse.