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Irrigation systems are a crucial investment for the production of high yielding quality produce.
Therefore, keeping to a maintenance program will ensure the investment continues to pay off for years to come.
Drip irrigation is an efficient way to maintain soil moisture, apply fertiliser and reduce weed growth to grow a productive crop. However, just like your car, the long-term functionality of a drip line will depend on how well you service it.
An efficient irrigation system is reliant on regular maintenance. This includes the periodic flushing of pipelines to remove potential blockages and keep water flowing evenly through the entire system.
What is flushing?
Contaminates like minerals or organic material can be found in any water source. When water is travelling quickly through a pipeline this isn’t an issue as it stays suspended in the water, but when it slows down or stops, it can begin to settle out and build up over time.
Flushing, as it sounds, sends a larger volume of water through the system to push out any contaminates that have built up over time. They are then released through an open ended source such as flush valve, in order to keep the pipeline and emitters clean of debris. Chemicals can also be used during this process to break down any mineral or organic build-up of materials and clean the pipeline.
To provide some perspective, a 17mm (15.2mm ID) dripline lateral that has been designed with 200 drippers at one metre apart, will on average require 200 litres of water per hour during system operation. When the system is flushed it requires an additional 320 litres per hour, totalling 520 litres per hour.
To develop an effective flushing program, a grower must first understand what is the quality of the water source and what is the irrigation demand of the crop.
An optimal flushing program begins at the initial design of the system. Manufacturers work closely with their customers to develop and deliver a system that takes into account the terrain, water quality and source, crop water requirements and the type of pipes, emitters and filtration required.
Water velocity and flushing
Basically, velocity is the speed at which the water is travelling through the pipeline and is measured in meters per second (m/s). Getting the velocity right is critical to the effectiveness of the flush. An irrigation system should aim to get the minimum velocity requirements for efficient system operation.
In a perfect world, flushing velocity should be 0.5m/s, but in most cases this can be difficult due to the different requirements between irrigation and flushing, the amount of water needed to achieve this velocity, and the irrigation infrastructure itself.
Drip manufactures Rivulis Irrigation recommend a minimum flushing velocity for dripline laterals of 0.35m/s. Anything below 0.35m/s won’t adequately flush out contaminates as the water moves too slowly through the system.
Water quality and its impact on flushing
According to Rivulis hydraulic designers, it is not wise to develop a generalist approach to flushing as there are too many variables. That is why each flushing program is custom designed and starts at understanding the water source quality.
Aquifer water for example, is generally quite clean and contains mineral contaminates, rather than organic contaminants in suspension. A system that draws water from a river or dam where there can be high quantities of organic material that encourage algae growth in the pipeline.
Crop water requirements
The next part to planning a flush is to understand the needs of your crop. For, vineyards where drip lines are expected to last many years, flushing becomes very important.
It’s also imperative to look at the plant water requirements as this will vary the amount of flushing required. For example, a vineyard crop may require 6ML of water per hectare per season, while an almond crop will require 12ML/Ha. With more water flowing through the almond system due to longer irrigation times, it’s more likely for contaminates to build up and flushing will be needed more frequently than the vineyard.
To discuss flushing, or any other drip irrigation need, contact Rivulis at This email address is being protected from spambots. You need JavaScript enabled to view it. or Rivulis.co.nz. ν
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