Measurement of groundwater levels in the vicinity of lignite opencast mines
Remote monitoring with SENSECOM-HP series
Groundwater levels are monitored throughout the vicinity of opencast mines in order to avert early risks of landslides, drainage around the mine or, conversely, to prevent flooding.
How this was done in the past
Until recently, expert teams of hydrogeologists relied on capital- and operationally expensive electronic measurements at selected critical locations. At dozens of other sites, they went out to take manual readings of water levels, often in hard-to-reach locations. Automated systems required having a house built around the well with measuring equipment. Batteries had to be changed every 2 months, and once in a while the data collected on site had to be read-out. Electronic metering had to be provided, at least temporarily, during pumping tests.
What it looks like today
The situation at the North Bohemian mines has started to change since 2018 and today they have over 200 boreholes with daily data on rock level or pore pressure in two mining areas and a third one in the research. With the SENSECOM-HP series, several problems have been solved at once:
- the devices are low-power and consume battery power only when measuring and transmitting, in a very energy-efficient way.
- they communicate over a nation wide IoT network of LPWAN (supporting these low energy devices). Signal availability was 99% of the installed sites.
- A small 3.6V lithium battery, size C monocell, is sufficient to operate them for at least 5 years
- the device is capable of working with accurate and reliable vibrating wave (VW) type pressure transducers even with a battery of this size.
- Due to the low power consumption, the dimensions of the device are very small, the casing fits into a standard wellhead.
The Severočeské doly a.s. (North Bohemian mines, Inc.) now have a virtually on-line overview of groundwater levels and trends, which was not an option until recently, at a very favourable investment and operating costs. Most importantly, the costs are orders of magnitude higher, which are saved by early action when unrecognised changes in the geological bedrock are identified.
Use in different sectors
The SENSECOM-HP series is equally well suited for applications outside hydrogeology, e.g. in the construction industry (bridges, dams, tall buildings), where sensors using the same vibrating string (VW) principle are applied for accurate measurements of joint opening, expansion and tilting.