The automatic irrigation system used in the grounds features a series of drippers, overhead sprinklers, micro-sprayers and ground-level low volume emitters.
Each horticulturist sets the parameters for the automatic watering of their sections using the computerised irrigation software program, Irrinet. They set the days of the week to water, the volume of water to be used, and the "cycle and soak" timing periods. Watering is between 5:00 pm to 8:00 am for short periods (around an hour) to allow the water to soak in and to avoid run-off.
If the automatic weather station registers more than 20 mm of rain, then the irrigation program cancels all watering until further notice. The irrigation officer manually restarts the program when watering needs to recommence.
In hot weather the horticulturists water by hand early in the day to supplement the evening watering. Watering at this time helps minimise evaporation.
Monthly water usage reports for each section help the horticulturists manage their water usage and significant water savings have been made in recent years.
Under the café bridge at the top end of the Tasmanian rainforest is a fogging system purchased by the Friends of the ANBG. It has a series of small nozzles that emit a mist of water at an average rate of only 17 litres / minute. The misters usually come on every day at 11:00 am, 12:00 pm, 1:00 pm, 2:00 pm and 3:00 pm and run for 30 minutes each time. The system has a rain-switch that turns off after 15 mm of rain and remains off until the switch dries out.
The fogger mainly has a pleasing aesthetic effect although it does affect the microclimate for the Tasmanian rainforest plants in the vicinity. The humidity is increased and plants are moistened by the fog. The fogging system will be extended in late 2009 to the Eastern Australia rainforest.
The horticulturists hand water in the propagation and production areas of the nursery. With such a wide variety of plants that have differing water requirements, overhead watering systems are not well-suited to the Gardens nursery. Fungal problems can develop with too much water, especially when watering over-head. Low emission drippers directed at plant level have also been trialled.
Water run-off from the nursery is captured in storage tanks below the nursery. This water can then be used for watering outdoor garden beds.
- propagation houses in the nursery - once a day (all year)
- production area of the nursery - twice a day in summer
- production area of the nursery - once or twice a week in winter
Watering in the glasshouses is by hand using a water-wand and by micro-irrigation - drippers and spray from micro-jets. A misting system increases the humidity in the glasshouses. This system comes on several times a day in summer and less often in winter.
The plants receive additional hand watering as required. Each glasshouse simulates a different environment e.g. sub-tropical, montane, Papua New Guinea - so watering varies.
A general guide to hand-watering in the glasshouses is:
- once or twice a day (summer)
- once or twice a week (winter).