Irrigation Frequency
Three high probes are provided with Measured Irrigation: 2 litre probe, 1.5 litre probe and 1 litre probe.
The following table is an approximate guide to the irrigation frequency under various weather conditions assuming that it does not rain.
If it rains then the start of the next irrigation interval will be delayed.
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probe selection
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frequency in hot sunny weather
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frequency in cool overcast weather
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frequency with zero evaporation
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2 litre probe
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2 to 3 days
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4 to 5 days
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6 days
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1.5 litre probe
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1 to 2 days
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2 to 3 days
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4 to 5 days
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1 litre probe
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daily
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2 days
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3 days
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Whenever you change probes, the annual rate of water consumption remains approximately the same. If you increase the length of the high probe, the irrigation frequency will increase and the amount of water used during the irrigation interval will decrease. On the other hand, if you decrease the length of the high probe, the irrigation frequency will decrease and the amount of water used during the irrigation interval will increase. If you want the amount of water used during the irrigation interval to remain the same, you will need to reselect the control nozzle to ensure that each sector and each plant within each sector receives the desired volume of water during the irrigation interval.
Scalability
The principles of Measured Irrigation are completely scalable to very large irrigation systems or to small irrigation systems.
For very large irrigation systems, you may need many flow splitters in a hierarchical configuration. Each flow splitter can be as large or as small as required and each flow splitter can have as many outlets as required. Each outlet on the top level flow splitter may deliver water to a second level flow splitter, and each outlet on a second level flow splitter may deliver water to a third level flow splitter.
Using a single control nozzle on the top level flow splitter, it is a straightforward calculation to determine the volume of water delivered by every nozzle on every flow splitter. The top level flow splitter may have an overflow outlet; however, all the other flow splitters should not have an overflow outlet so that all the water entering the flow splitter leaves the flow splitter via one of the irrigation nozzles.
The choice of power supply and the choice of pump depend on the number of litres per hour required by the top level flow splitter.
An example of a small irrigation system is one to water all your indoor plants when you go on holidays (the flow splitter can hang over the shower screen in your bathroom, and the pump can be connected to the bottom of your toilet cistern). Because indoor plants require less water, a larger control nozzle is preferred.