Sub-surface Drip Irrigation (SDI), the troublesome child of the irrigation industry. Managed well it is a show stopper, quiet, efficient, inexpensive to operate and unobtrusive. Badly managed or designed a disaster. The stories of its success defy belief, likewise the stories of its failures.
The secret of the successful installations are:
All this attention to detail but, to put this in perspective we are looking at a finely tuned irrigation system that, like a high performance vehicle, needs to be handled with respect to draw from its full potential.
With SDI, the full potential is:
What is required to make a viable SDI system?
With any irrigation system, what is really being irrigated is the soil. Knowing the makeup of the soil to be irrigated, what its chemical composition is and how it relates to the water that is going to irrigate it is of primary importance.
Irrespective of whether the oval is a premier league field or a suburban multi use field, with SDI there is only one standard, first rate. This is because the purpose of SDI is to irrigate the soil. What may vary between ovals with and SDI system is the emitter flow rate and the lateral spacing.
This variance is purely based on how the water travels through the soil and at what rate it travels.
The first step in the SDI process is a comprehensive soil/water analysis to establish the emitter flow and spacing and the lateral spacing.
The comprehensive water analysis establishes how the soil to be irrigated responds to its water supply. Do they respond well to each other or do they repel each other?
Design of an SDI system calls for a differing set of skills than those that are required. For a start we are operating at a much lower pressure, between 70 – 200 kPa so the margin for error is much lower than a system operating at 500 kPa.
Because SDI is laid down 200mm – 300mm below the finished level of the oval, attention to how air and vacuums is managed in the system is important. On start up for instance, air in the SDI system is purged out into the soil via the emitters. On shut down, air needs to be drawn back into the system so that vacuums don’t develop and draw soil into the emitters. This blocks them up.
Then there is the flushing main infrastructure. This is important in that it is used to flush clean the SDI tubes during maintenance cycles. What tends to build up in the SDI tubes are particles smaller than 100 micron in size, such as clay sediment, fertilizer carrier and some algae.
Once installed, SDI readily lends itself to the injection of fertilizers and chemicals into the root zone of the turf. If required, SDI can be irrigating while play is going on above.
Dependent upon the flow and pressure available, pumps may not be necessary.
Another major difference to traditional irrigation system is the irrigation efficiency of the system. Traditional systems often struggle to meet an 80% Distribution Uniformity. With SDI, the minimum Distribution Uniformity is 90% with the norm being between 93% and 95%. This is time and money. For instance two systems a traditional pop up system operating at 650 kPa and the second SDI system operating at 300 kPa, each with a flow rate of 6 litres per second. The difference in kilowatts given a pump operating efficiency of 70% is:
Sub-surface drip irrigation is a viable alternative to traditional oval irrigation systems. Life expectancy is 20+ years with the correct maintenance.
We at JP WATER have been designing SDI since 1989 and have systems that are 20+ years old still operating and saving their owners money.
Talk to us today and let us show you the difference.
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