Description and conclusions of the pilot “measuring water level with the Staal radar measurement” carried out by the Brabantse Delta Water Board.
A concrete reason for the Brabantse Delta Water Board to look for a solution 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 gauging sections where the water level can only be measured occasionally and manually. Based on the task 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 constructed to improve the evaluation of water level decisions.
According to an initial evaluation by the Brabantse Delta Water Board, current measurement techniques appear to be too expensive for this, mainly because of the installation and management costs.
The Brabantse Delta Water Board was therefore open to setting up and implementing an extensive pilot project together with Staal Instruments to test a new measuring technique. This concerns the Staal wireless radar measurement. The combination of a non-contact radar level measurement, integrated telemetry, battery powered, price, ease of installation and maintenance aroused the interest.
Pilot setup and Locations
The new measuring technique has been compared by Brabantse Delta with the current measuring techniques. For 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 standalone pressure transducer (submersible hydrostatic pressure sensor) was also installed so that the same reference measurement technique was used at both locations.
Markiezaatsmeer Bergen op Zoom: Several meters were already present at this location: A gauge and an “E + WATER L” pressure sensor. An extra pressure sensor and the Staal radar measurement have been added to this for the pilot. In addition, manual measurements were taken. The Staal radar measurement is attached to the weir with a bracket directly above the gauge (see figure 1).
At Stuw Markiezaatsmeer, measurements were taken with a gauge, reference manual measurement, two pressure sensors and one radar measurement. Every six weeks, the pressure transducers were manually read to retrieve data, including the level scale. The radar measurement automatically discloses the data to the Staal portal.
Dongedijk's Gravenmoer: At this location, in addition to a gauge, a TSX-100 pressure transducer in a protective tube is already present. An extra pressure sensor has been added to this. The Staal radar measurement is attached to the existing wooden measuring pole to which the other measuring equipment is also attached (see figure 2).
At Dongedijk's Gravenmoer, measurements were taken with a gauge, two pressure sensors and one radar measurement. Every month, the pressure sensors were read to collect data, including the level scale. The radar measurement automatically discloses the data to the Staal Portal.
Results of the comparison of Staal radar and pressure sensors by the Brabantse Delta Water Board:
- At the Markiezaatsmeer, the average difference between the Staal radar measurement and the pressure sensor is 5.4 mm.
- The average difference between the Staal and the E + WATER L is only 2.7mm.
- The e + WATER L uses the local air pressure.
- Noticeably higher differences in March. This could be the result of a blocked air pressure gauge in the e + WATER L.
- There is no noticeable course or deviation in any of the measuring instruments.
Conclusion & Recommendations
The conclusion & Recommendations of the Brabantse Delta Water Board:
The Staal radar gauge appears to be an instrument that meets the requirements of the Water Board in terms of accuracy and reliability of the measurements.
In view of its accuracy, it can not only be used for monitoring water levels, but may even be used for measuring overflow levels at weirs to determine flow rates. However, this requires further research.
In addition, the Staal radar level sensor is a measuring instrument that can easily be installed and, if desired, easily moved: it is a matter of unscrewing the device, installing 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 sooner detected by a user who can view the data at any time. For example, the pressure sensor must first be read before the data is available and then compensated with the air pressure.
The only criticism is that the Staal radar measurement is less robust than the way the current pressure transducers are mounted, making it more susceptible to vandalism. Because the Staal is installed 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 a somewhat greater fluctuation occurs in the measurement series.
However, this does not affect the mean values. The water level remains the same based on average hourly or daily values.
All in all, the Staal radar measurement for monitoring surface water levels scores better than the current standard of the Water Board, the hydrostatic / pressure sensor.
NOTE: This Testimonial is fully based on the description, measurement results and conclusions from the report “Surface Water Monitoring” by the Brabantse Delta Water Board, delivered on 9 October 2019, by authors: Rutger van Ouwerkerk and Jens Vloedgraven, and reviewers: Luc Rouws, George Corman , Mark Janssen, Arjan Segeren, Linda Lauwerijssen and Ben Willemsen.