Reason for the tests
A concrete reason for Brabantse Delta to look for a solution to be able to realize additional measurements of the surface water level is the more intensive monitoring of water level areas. At the moment there are still a large number of water level sections where the water level can only be measured incidentally and manually. From the point of view of complying with the water level decisions, this is no longer sufficient and it has been determined that at least 70 new measuring points must be installed in order to improve the evaluation of water level decisions.
According to an initial evaluation by Brabantse Delta, current measuring techniques appear to be too expensive for this, mainly because of the installation and management costs.
Brabantse Delta was therefore open to setting up and executing an extensive pilot project together with Staal instruments to test a new measurement technique. This concerns the Staal wireless radar measurement. The combination of non-contact radar level measurement, integrated telemetry, battery powered, price, ease of installation and maintenance sparked interest.
Pilot setup and locations
The new measuring technique has been compared by Brabantse Delta with the current measuring techniques. During six months, two Staal wireless radar sensors were placed next to existing measurement techniques. Two measurement locations have been selected for this. After this measurement period, the results were compared and assessed.
Measuring equipment was already present at both locations and, in addition to the Staal radar measurement, a pressure transducer (submersible hydrostatic pressure sensor) was also installed, so that the same reference measurement technique was used at both locations.
Conclusions comparison of STAAL radar and pressure transducers by Brabantse Delta:
• At the Markiezaatsmeer, the average difference between the Staal radar measurement and the Pressure transducer is 5.4 mm.
• The average difference between the Staal and the E+WATER L is only 2.7mm.
• The e+WATER L uses local air pressure.
• Strikingly higher differences in March. This could be the result of a clogged air pressure gauge in the e+WATER L.
• There is no noticeable variation or deviation in any of the measuring instruments.
Conclusion & Recommendations Water Board Brabantse Delta
The Staal radar meter appears to be an instrument that meets the requirements of the Water Board in terms of accuracy and reliability of the measurements. Given its accuracy, it can not only be used for monitoring water levels, but may even be used for measuring overflow heights at weirs to determine discharges. However, this requires further research.
In addition, the Staal radar measurement is a measuring instrument that can be easily installed and moved if required: it is a matter of unscrewing the device, hanging it in the new location and within a few minutes the device is fully operational again.
Furthermore, the measurement data of the Staal radar measurement is available in real-time. This means that in real-time an error or defect is detected earlier by a user who can view the data at any time. The pressure sensor, for example, must first be read before the data is available and then be compensated with the air pressure.
The only criticism is that the Staal radar measurement is less robust than the way current pressure transducers are mounted, making it more susceptible to vandalism. Because the Staal hangs above the water surface and the pressure transducers are installed in a stilling well, the Staal also has more external influences, such as wave action, and there is a somewhat larger fluctuation in the measurement series.
However, this does not affect the mean values. Based on average hourly or daily values, the water level remains the same. All in all, the Staal radar measurement for monitoring surface water levels scores better than the current standard of the Water Board (the pressure sensor).