The Karsten Group has several farms along the Orange river. Previously, we have focused on installing water meters at the pump stations of individual irrigation units on these farms. The water meters helped us to accurately monitor how much irrigation water goes to the different blocks. The meters also helped us to apply the correct dosages of liquid fertiliser.
The legislation that DWS introduced in 2018 has shifted our focus to installing water meters at withdrawal points along the river. Some of the farms already have meters at their withdrawal points, but it will still be expensive to install meters at all other withdrawal points. We have asked DWS for an extension so that we can distribute the cost of installation over a longer period.
We work closely with Andrag Agrico and have decided to install Arad’s mechanical meters for all pipelines with a diameter of 300mm and smaller. For pipelines larger than 300mm, we have selected Flowmetrix’s Safsonic ultrasonic meters. We wanted to install Netafim’s Octave ultrasonic meters but decided against it because of the cost of these meters.
According to legislation, the accuracy of the meters should be verified every five years. We are uncertain about the verification process. Should we send the meters to the suppliers or will the suppliers come to the farms to test the accuracy of the meters? If the meters are sent to the suppliers, we will not be able to measure the water during that time. Plus, irrigation systems with flanged meters will not be able to run while the meters have been taken of the system. This will put pressure on crops that must be irrigated during this time.
We are not aware of a platform on which you can upload the water meter data directly to DWS. We would like more information on this, as well as in which format the data should be.
We’ve had a few practical challenges with the installation of water meters. For example:
- DWS does not prescribe or recommend any water meter brands. We had to do our own research and after we’ve made some mistakes, we decided to stick to the brands recognised by the market.
- Correct installation is critical to getting accurate readings.
- We encountered different problems with the different types of pipes (fibre glass, asbestos, PVC and steel). For example, the clamp-on ultrasonic meters cannot be used on fibre glass and asbestos pipes. We had to install a piece of steel pipe on which the meter could be placed.
- Sometimes it is difficult to install meters according to the supplier specifications. For example, you might not have the prescribed distances of straight pipe length available before and after the meter. Or, for underground pipes, the pipes have to be excavated and a cement case has to be built around the pipes so that the meter can be installed according to the specifications.
- Ultrasonic meters installed on the outside of pipes are very sensitive and correct installation is therefore critical. In, older irrigation systems with galvanised steel pipes, it was necessary to replace part of the pipe, because these pipes were rusted on the inside. Rust has an effect on the inner diameter of a pipe, and this impairs the accuracy of ultrasonic meters.
- During lightning strikes when the power supply is uneven (dips and spikes), ultrasonic meters tend to give faulty readings. Precautions must therefore be taken to protect the meters from lightning damage. Battery-driven meters like Netafim’s Octave ultrasonic meter could be considered as a solution to this problem. The batteries of these meters last up to 15 years.
- Meters at withdrawal points must be protected against vandalism, theft and sabotage.